Graphene and MXene fibers: rising stars for emerging smart textiles

Mechanical properties

Mechanical property testing parameters: Unless otherwise noted, the GFs described here were tested for tensile strength, Young’s modulus, and toughness under conventional laboratory circumstances (temperature: 23-25 °C, relative humidity: 45%-55%). A universal testing machine with a gauge length of 10-20 mm and a crosshead speed of 1-5 mm·min^-1 was used for the testing. Any departures from normal settings (such as high-temperature or wet-state testing) are specifically noted in the associated original publications. These standard testing protocols are in line with techniques frequently used in the literature.

The size and orientation of graphene sheets, interfacial interactions between sheets, structural defect density, and the microscopic assembly mode of the fibers are the main multiscale structural factors that control the macroscopic mechanical properties of GFs. Figure 3A displays atomic force microscopy (AFM) pictures of graphene nanosheets. Even though single-layer graphene has an incredibly high intrinsic strength (~150 GPa), there are many obstacles in the way of successfully transferring this strength to macroscopic fibers. The sheet size of GO, the basic component of fibers, has a significant impact on their mechanical characteristics. Since pure graphene is naturally insoluble in water, it cannot be directly dissolved in solvents or transformed into fibers using standard solution-based techniques. As a result, GO, an oxidized derivative abundant in functional groups that include oxygen, is frequently used as a processable precursor for the production of GFs. GO easily dissolves in polar solvents and water, and after spinning, it regains its conductive graphitic network structure after reduction treatment. Therefore, as the primary fibrous component, the size of GO flakes has a major impact on the mechanical characteristics of the material. High-orientation sheet alignment along the fiber axis during spinning is made possible by large-sized GO sheets that easily form a liquid crystal phase in the spinning solution. By drastically lowering the overlap density at the fiber’s sheet ends, this method efficiently improves macroscopic mechanical characteristics by reducing stress concentration spots. Using this GO-based platform, Li et al. filled the concentric skeletal voids created by large-sized GO with small-sized GO to create fibers with a Young’s modulus as high as 901 GPa^[52]. Moreover, another crucial strategy for improving performance is to optimize the intrinsic chemical structure of GO precursors. Similarly, exploiting the chemical tunability of GO, Tang et al. used tighter stacking and stronger interlayer π-π interactions to achieve a high toughness of 24.0 MJ·m^-3 and a tensile strength of 791.7 MPa in hydrospun fibers without additives^[50].

Figure 3. (A) AFM image of f-GO nanosheets. Reproduced with permission^[50], Copyright © 2022 John Wiley and Sons; (B) Schematic illustration of the traditional disordered crystalline-amorphous structure (left) and the naturally occurring crystalline-amorphous superstructure (right); (C) SEM image of a GAZP fiber viewed along the axial section and schematic diagrams showing the evolution of microstructure of the fiber with the stretching process. (B and C) are reprinted with permission from Ref.^[61], Copyright © 2022 Elsevier; (D) POM snapshots showing different tensile fracture behaviors of GOFs with and without the addition of Ca²⁺ in a 50% EtOH plastic-stretching bath, highlighting the simultaneously improved plastic deformation and load-bearing capacity by CMP; (E) Tensile curves. (D and E) are reprinted with permission from Ref.^[51], Copyright © 2025 Elsevier; (F) Tensile strength and modulus of the PBIA; Dynamic modulus of PBIA fibers under (G) different loading frequencies and (H) different strain rates; Loading-unloading cyclic curves of (I) 0.075-HrGO/PBIA fibers. (F-I) are reprinted with permission from Ref.^[62], Copyright © 2022 John Wiley and Sons; (J) 50-filament GOFs with yellow color collected on a reel; (K) The multiscale structures of high-quality GFs. As a comparison, all the multiscale defects have been suppressed by full scale defect engineering approach. These GFs have smooth surface with regular aligned wrinkles up to macroscopic scale, homogenous and compact sections without voids (SEM), and highly crystalline laminates of high-quality graphene sheets (HR-TEM). Scale bars from left to right are 2 μm, 500 nm, 100 nm, and 2 nm, respectively. (J and K) are reprinted with permission from Ref.^[17], Copyright © 2016 John Wiley and Sons. AFM: Atomic force microscopy; GO: graphene oxide; SEM: scanning electron microscope; GAZP: GO@amorphous-ZrO₂-polyvinyl alcohol; POM: polarizing optical microscope; GOFs: graphene oxide fibers; CMP: crosslink-modulated plasticity; PBIA: poly(p-phenylene-benzimidazole-tetraphthalamide); HrGO: holey reduced graphene oxide; GFs: graphene fibers; HR-TEM: high-resolution transmission electron microscopy; PVA: polyvinyl alcohol; EDA: ethylenediamine; rGO: reduced graphene oxide.

Traditional disordered crystalline-amorphous structures and naturally occurring crystalline-amorphous superstructures, as seen in Figure 3B, indicate how adding ordered nanostructures can synergistically improve mechanical properties in fiber structural design. Li et al. created graphene-based fibers with high strength and high toughness by in-situ growing an amorphous coating over crystalline GO sheets, drawing inspiration from the “brick-and-mortar” structure of nacre^[61]. During tensile loading, the micro-wrinkled surface structure efficiently releases energy through a “wrinkle extension” process, allowing the fiber to attain a high toughness of 10.6 MJ·m^-3 and a high strength of 935 MPa. Figure 3C illustrates how the fiber microstructure changes during stretching. By controlling the size of liquid crystal domains, another “domain folding” technique reduces structural flaws brought on by layer curling and inadequate stacking at the source by causing GO sheets to form highly folded yet densely interconnected nanostructures^[19]. Many interface enhancement techniques have been used extensively to improve stress transfer between nanosheets. Fiber ductility and load-bearing capacity can be greatly increased by ionic crosslinking, such as by adding Ca²⁺ or ethylenediamine, which can improve interlamellar contacts during plasticization^[51]. Covalent crosslinking uses chemical interactions, such as amidation reactions between aromatic amines and carboxyl groups at GO edges, to connect layers [Figure 3D and E]. By creating extended conjugated systems, this method not only increases the tensile strength of the fiber but also greatly improves electrical conductivity^[63]. Moreover, topological limitations act as a mechanism for physical reinforcement. Polymer chains create physical crosslinking networks that efficiently improve stress transfer by passing through the pores of porous graphene sheets [Figure 3F-I]^[62].

A crucial post-treatment step for improving the performance of GFs is high-temperature thermal reduction. By efficiently eliminating oxygen-containing functional groups, reestablishing the sp²-hybridized carbon network, and decreasing interlayer spacing, this procedure enhances the fiber’s mechanical and electrical conductivity. High-performance GFs with tensile strengths up to 2.2 GPa and Young’s moduli of 400 GPa have been successfully manufactured by optimized thermal reduction techniques^[17], as shown by their macroscopic and microscopic morphologies in Figure 3J and K. However, compared to commercial high-performance carbon fibers, the strength and modulus of modern GFs are still typically lower. Grain boundaries that are challenging to totally eradicate, sheet creases, and intrinsic structural flaws in the GO precursor are important limiting constraints. Notably, the majority of current research has concentrated on attaining exceptionally high modulus and tensile strength. However, it is essential to give nanosheets exceptional toughness, fatigue resistance, and long-term durability while retaining high strength for wearable smart textile applications. Three-dimensional graphene networks’ toughening and reinforcing methods could serve as an inspiration for future studies. It may be possible to improve the strength, flexibility, and service stability of one-dimensional dense fibers by investigating how to apply these principles which allow for superelasticity, high fatigue life, and exceptional toughness to the production process^[64,65].

Electrical properties

Conductivity testing conditions: Unless otherwise noted, the four-probe method was usually used to measure conductivity values presented in this section at ambient temperatures (25 °C, 40%-60% relative humidity). The associated circumstances are described in detail in the original sources and quickly summarized in the pertinent discussion sections for fibers measured under particular conditions (such as vacuum, post-doping, or cryogenic settings).

The capacity of graphene-based fibers to carry out circuit connectivity, signal transmission, sensing, and energy storage tasks is largely dependent on their high electrical conductivity. The conductivity of macroscopic graphene-based fibers is limited by interlayer contact resistance, structural flaws, and orientation, despite the exceptionally high intrinsic conductivity of single-layer graphene (~10⁸ S·m^-1). Significant progress has been made in addressing this through synergistic regulation using techniques including chemical doping, efficient reduction, and structural optimization.

It is essential to establish effective seamlessly interconnected electronic channels. Grain boundaries and electron scattering can be decreased by using large-sized GO precursors and producing well orientated nanosheets. Tensile stress, for example, causes sheets to align axially during wet-spinning, and a 1.3 draw ratio increases conductivity by 56%^[12]. Through extreme shear stress, technologies such as microfluidic spinning achieve ultra-high sheet orientation [Figure 4A], producing fibers with conductivities as high as 1.04 × 10⁶ S·m^-1[16]. Additionally, a crucial stage in improving and restoring conductivity is reduction treatment. In order for GO to become conductive, its sp² network structure must be restored by reduction. Chemical reduction techniques work in mild conditions, although they usually have limited structural defect correction and conductivity of 10⁴-10⁵ S·m^-1. High-temperature thermal reduction (> 1,273 K) improves graphitization and allows for a more complete elimination of functional groups containing oxygen. Electrical conductivities of up to 8 × 10⁵ S·m^-1 are seen in fibers treated at 3,273 K^[17]. Qi et al. created GF fabrics with porous architectures, superior conductivity, and flexibility at the fabric level by combining a “plasticization-swelling” technique with comprehensive thermal reduction^[53]. A material basis for smart textile integration is provided by the scanning electron microscope (SEM) image of the fiber cross-section [Figure 4B].

Figure 4. (A) Morphology of columnar fiber produced from a tubular and Morphology of layer structure fiber produced from a flat channel. Reproduced with permission^[16], Copyright © 2019 Springer Nature; (B) SEM images of the rGOAF cross section swelling in solvent with different ratios of water and ethanol. Reproduced with permission^[53], Copyright © 2023 Springer Nature; (C) Electrical conductivity of nanofibers annealed at different temperatures. Reproduced with permission^[54], Copyright © 2021 Springer Nature; (D) Time-dependent temperature variation of GQFF under different voltages; (E) Electrothermal temperature of GQFF under different voltages. (D and E) are reprinted with permission from Ref.^[66], Copyright © 2020 American Chemical Society; (F) The enhancement factor in electrical conductivities of reduced RGG-Ag fibers as a function of the feed AgNWs weight percentage in original GGO-AgNWs fibers. Reproduced with permission^[67], Copyright © 2013 John Wiley and Sons; (G) Photothermal reaction of the microfiber under irradiation of 0.63, 1.42, and 3.20 W·cm^-2; (H) Temperature changes of the microfiber during cyclic photothermal heating and natural cooling with different irradiance; (I) Schematic showing the microstructure of the graphene-coating microfiber during the heating period. (G-I) are reprinted with permission from Ref.^[55], Copyright © 2022 Elsevier; (J) Schematic illustrations on heat allocation. Reproduced with permission^[68], Copyright © 2022 Springer Nature. SEM: Scanning electron microscope; rGOAF: reduced graphene oxide aerogel fibers; GQFF: graphene quartz fiber fabric; RGG: reduced giant graphene oxide; AgNWs: silver nanowires; GGO: giant graphene oxide; HOPG: highly oriented pyrolytic graphite; rGNF: reduced graphene nanofiber; VC: vitamin C; HI: hydroiodic acid; SA: sodium alginate; HGAF: holey graphene aerogel fiber.

Novel approaches to preparation have created new opportunities. By using polymeric carriers to electrospin GO, Han et al. produced graphene nanofibers with diameters ranging from 100 to 900 nm^[54]. As seen in Figure 4C, these fibers demonstrated electrical conductivities as high as 2.02 × 10⁶ S·m^-1 after annealing at 3,000 °C. Moreover, layer stacking problems are avoided when graphene coatings are grown in situ on fiber substrates using chemical vapor deposition (CVD). As seen in Figure 4D and E^[66], the resultant textiles have exceptional electrothermal characteristics and tunable sheet resistance. One important tactic for getting over the inherent conductivity limit is chemical doping. By adding high-concentration dopants like K, FeCl₃, and Br₂, Cao et al. greatly enhanced carrier concentration and boosted conductivity to the 10⁷ S·m^-1 region^[69]. Interestingly, K-doped fibers’ conductivity (2.24 × 10⁷ S·m^-1) even outperformed metallic nickel. In order to improve interlayer forces and carrier concentration through N doping, Kim et al. used a bio-inspired poly(dopamine) (PDA) modification and pyrolysis technique^[70]. As seen in Figure 4F, composite architectures containing metals, such as silver nanowires (AgNWs), also successfully increased conductivity and carrier capacity^[49]. Interestingly, calcium intercalation doping has shown promise for flexible superconducting devices by inducing a superconducting transition (Tc ≈ 11 K) in macroscopic GFs for the first time^[71]. For practical applications, the doped fibers’ environmental stability is still a problem.

The electrical properties of graphene-based soft conductive fibers have consistently outperformed those of conventional carbon fibers (0.1-1.4 × 10⁵ S·m^-1) and CNT fibers (~5 × 10⁵ S·m^-1) through multidimensional synergistic optimization, providing a strong basis for their use in flexible electronics and smart textiles^[72].

Thermal properties

Graphene is a perfect material for creating extremely thermally conductive fibers because of its exceptionally high intrinsic thermal conductivity, which can reach up to 5,300 W·m^-1·K^-1 in a monolayer^[73]. However, weak interlayer tensions, grain boundaries, and defects seriously hinder phonon transport in macroscopic fibers, resulting in a considerable drop in thermal conductivity as structural disorder increases^[74]. As a result, there are two main approaches to thermal management research on graphene-based fibers: the first is to maximize axial thermal conductivity through multiscale structural engineering, and the second is to go beyond pure heat conduction by building active thermal regulation systems that incorporate energy conversion and storage.

The orientation, size, and stacking structure of graphene flakes must be optimized in order to improve the axial heat conductivity of fibers. Phonon transit can be efficiently promoted by building a continuous network with large-flake GO and attaining highly orientated alignment by liquid crystal spinning. Jalili et al. used large-flake GO with an average size of 37 μm to produce a fiber thermal conductivity of 1,435 W·m^-1·K^-1[14]. Additional high-temperature heat treatment improves graphitization and fixes flaws. Fiber thermal conductivity can be raised from 607 to 1,025 W·m^-1·K^-1 following optimization and high-temperature treatment, according to research by Xin et al.^[15]. All of this indicates that the key to producing high thermal conductivity fibers is structural ordering and crystallinity tuning.

Automation, flexibility, and multifunctional integration are the next steps in the evolution of intelligent thermal management. By adding functional units like photothermal, adsorption, or phase-change capabilities, graphene-based fibers exhibit special benefits. For example, Yu et al. created core-shell hydrogel fibers coated with GO, whose GO layer demonstrates exceptional photothermal effects [Figure 4G and H], allowing them to serve as flexible, light-controlled, localized heating sources^[55]. As shown by the microstructure in Figure 4I, combining graphene’s highly conductive network with phase change materials simultaneously greatly increases thermal cycling response speeds during heating. Das et al. created phase change core-shell fibers using rGO as the thermal conduction framework^[75]. In order to achieve effective “heat conduction-heat storage” synergy, the rGO network speeds up heat transmission within the phase change material. As seen in Figure 4J, Hou et al. created hygroscopic graphene aerogel fibers that store and redistribute thermal energy through enthalpy changes during water molecule adsorption/desorption, exhibiting a unique thermal management method independent of high axial thermal conductivity^[68]. Interestingly, the inter-fiber contact thermal resistance represents a barrier limiting overall thermal management efficacy when integrated into fabrics. Thus, it is essential to build a three-dimensional thermal conduction network across various scales. By growing graphene on the surface of fiber fabrics and vertically aligning CNTs, Liu et al. were able to create “thermal bridges” between fibers that reduced the out-of-plane thermal resistance by more than 70%^[76]. This method offers a fresh approach to efficient fabric-level heat management.

The focus of research on the thermal characteristics of graphene-based fibers is now on functionalization, integration, and systematization rather than excessive thermal conductivity. Future research is anticipated to concentrate on two areas: (1) deepening “structure-function” integrated design by combining multiple mechanisms such as thermal conduction, photo/electrothermal conversion, and phase change energy storage, to develop adaptive smart thermal management textiles that dynamically respond to environmental and human signals; and (2) further improving the intrinsic thermal conductivity of fibers through grain boundary engineering and precise orientation control to serve high-power device heat dissipation. This covers a wide range of applications, such as energy-efficient buildings, wearable electronics thermal management, and customized thermal comfort.

Other performance

GFs’ density, specific surface area, and structural flexibility are important factors that determine their appropriateness for smart textiles in addition to their mechanical, electrical, and thermal characteristics. In line with the “light-weight and high-strength” design goal, GFs usually have a low density (about 1.4-1.9 g·cm^-3), similar to commercial carbon fibers (1.7-1.9 g·cm^-3). Drawing, heat treatment, or changing the size ratio of graphene flakes can all be used to accurately alter density^[15]. When it comes to particular surface area, GFs show notable advantages. For instance, porous GO fibers with a specific surface area of up to 2,605 m²·g^-1 were produced by Suter et al. using controlled coagulation kinetics^[77]. Compared to fibers made by freeze-drying, which had a surface area of about 884 m²·g^-1, they preserved a surface area of 2,210 m²·g^-1 after reduction. This lays the groundwork for their use in high-loading electrodes, adsorption, and catalysis.

Alongside fibers like cotton and polyester, GFs can be integrated with traditional textile processes (like knitting and weaving) due to their exceptional flexibility and weavability. This offers a material basis for the functional realization and structural design of smart textiles. However, because to structural flaws, improper orientation, and insufficient density during the manufacturing process, their macroscopic mechanical and electrical properties typically stay below theoretical values and those of some commercial carbon-based fibers. Thus, by optimizing graphene building blocks, controlling the fiber’s “tertiary structure” (layer orientation, pore distribution, and interfacial bonding), enhancing spinning methods, and perfecting post-treatment techniques, current research aims to improve the overall performance of GFs. The goal of this strategy is to effectively convert graphene’s microscopic nanosheet benefits into macroscopic fiber assembly performance.

Wet spinning

The most scalable method for creating continuous, high-performance graphene-based fibers is wet spinning. By extruding a GO dispersion with nematic liquid crystal behavior into a coagulation bath, phase separation solidification, drawing, and reduction post-treatment enable continuous fiber manufacturing^[11]. Figure 5A shows a constant wet spinning configuration. The dual diffusion and phase separation processes are essential to the core quality of fiber production. Solvent outward diffusion and coagulant inward diffusion happen at the same time when a fine stream of GO solution is injected into the coagulation bath. The microstructure and compactness of the fiber are directly determined by the kinetic rate of this process. Studies show that the development of fibers with more homogeneous architectures and fewer flaws is facilitated by relatively slow diffusion processes. Effective fiber solidification is only possible in certain thermodynamic zones, and this process adheres to the phase diagram principles of a ternary system (GO, solvent, coagulant). By enhancing the dual-diffusion mechanism, Martinez et al. showed that this method is scalable, allowing for flexible control over fiber diameter and high-speed spinning [Figure 5B]^[42]. GF filament bundles with a significant length and consistent structure were successfully produced by Shi et al. using a 100-hole spinneret for continuous spinning at speeds up to 75 m/h^[78]. As seen in Figure 5C-E, their morphology creates a process foundation for practical smart textile applications.

Figure 5. (A) Continuous wet-spinning apparatus of GOFFs. Reproduced with permission^[78], Copyright © 2024 Elsevier; (B) Actuation stress curves of graphene/LCE composite filaments characterized across increasing applied strain for various diameters. Reproduced with permission^[42], Copyright © 2024 John Wiley and Sons; (C) A close-up snapshot of 100-hole spinneret; (D) 100-filament GO fibers in the plasticization bath; (E) Collection of GOFFs onto the graphite collector. (C-E) are reprinted with permission from Ref.^[78], Copyright © 2024 Elsevier; The POM images and surface and cross SEM images of the three typical phases, including random isotropic phase (F), concentric roll (G), and spiral coil (H). (F-H) are reprinted with permission from Ref.^[52], Copyright © 2024 Springer Nature; (I) Schematic of the process to assemble GO sheets into a macroscopic fiber with belt-type morphology with highly oriented and ordered stacking structure by selective edge linkage. Reproduced with permission^[63], Copyright © 2024 Springer Nature; (J) Density and orientation degree of rGOFFs with different SRs. Reproduced with permission^[78], Copyright © 2024 Elsevier; (K) Overall properties of the fabricated GFs, including thermal and electrical conductivities, tensile strength, and Young’s modulus. Reproduced with permission^[52], Copyright © 2024 Springer Nature; (L) Current signal response under different pressure loads; (M) Response and recovery time. (L and M) are reprinted with permission from Ref.^[56], Copyright © 2026 Elsevier. GOFFs: Graphene oxide fiber filaments; LCE: liquid crystal elastomer; GO: graphene oxide; POM: polarizing optical microscope; SEM: scanning electron microscope; rGOFFs: reduced graphene oxide fiber filaments; SRs: stretching ratios; LC: liquid crystalline; RI: random isotropic; CR: concentric roll; SC: spiral coil.

The spinnability and ultimate performance of the fibers are significantly influenced by the characteristics of the spinning solution, specifically the size and concentration of GO sheets. Nematic liquid crystals, which are essential for obtaining highly ordered macroscopic layer assembly and creating high-performance fibers, can be formed by GO dispersions over the critical concentration. Researchers frequently use GO’s liquid crystal characteristics to direct wet spinning in real-world applications. Ma et al. established the groundwork for creating high-performance fiber electrodes by using rheological tests to confirm the exceptional spinnability of liquid crystal mother liquors^[79]. With the structural history shown in Figure 5F-H, Li et al. further mapped the structural phase diagram of GO liquid crystals at various concentrations and shear forces, offering theoretical direction for precisely managing the ordered state of spinning precursors^[52]. Another crucial element in controlling the double diffusion rate and fiber structure is the solidification bath’s composition. The solidification bath’s purpose has grown beyond simple solidification in recent years. In order to facilitate the co-assembly and simultaneous solidification of functional nanomaterials with GO sheets, it is now used to incorporate active components. Using the solidification bath as a chemical reactor is one noteworthy invention. In order to facilitate amidation interactions with carboxyl groups at the margins of GO, Ding et al. used an amine compound solution as the solidification bath^[63]. As seen in Figure 5I, this method concurrently created a strong covalent network during shaping, accomplishing integrated “solidification-crosslinking”. In order to create very uniform composite fibers with a consistent composition, Guo et al. used a microfluidic spinning technique to instantly combine reactants at the minuscule scale^[80]. This is the process’s most advanced level of precision. Additionally, post-processing methods are essential for figuring out the fibers’ final characteristics. By decreasing porosity and greatly increasing the alignment of GO layers along the fiber axis, the drawing process simultaneously increases mechanical strength and electrical conductivity. This procedure can be applied either in the gel form or following drying through “plastic stretching”. By applying intercalation plastic stretching to GO gel fibers, Shi et al. greatly enhanced the orientation and density of decreased fibers [Figure 5J]^[78].

Wet-spinning is now a programmable framework for structural modulation, having progressed from creating individual structures. By using coaxial spinning and flow field design to gain continuous control over lamellar arrangement, Hao et al. laid the groundwork for functionally configurable smart fibers^[81]. As seen in Figure 5K, the multi-shear flow field-assisted spinning method created by Li et al. allows for the programming of different ordered textures such as concentric and helical patterns within the fiber cross-section, resulting in synergistic advances in mechanical and thermal properties^[52]. Zhi et al. used substrate-assisted drying techniques to create fibers with distinctive heterogeneous structures in terms of fiber morphological innovation^[56]. Their unique morphologies give devices wide detection ranges and great sensitivity [Figure 5L and M].

Wet spinning is a very adjustable method of precision preparation to fabricate GFs. It is possible to precisely regulate the microstructure, mechanical, electrical, and functional properties of graphene-based fibers by methodical optimization and creative design of the spinning solution, coagulation bath, spinning process, and post-treatment techniques. This creates an ideal fabrication platform for the widespread application of soft graphene-based conductive fibers in high-performance smart fabrics.Several interrelated processing parameters control the conversion of GO’s inherent characteristics into macroscopic fiber performance. Throughput and orientation efficiency are directly influenced by spinning speed: Shi et al. used a 100-hole spinneret to achieve continuous production at 75 m·h^-1[78], while Martinez et al. used a high-speed dual-diffusion strategy to push the limits of graphene/liquid crystal composite fibers to 4,500 m·h^-1[42]. However, extreme speeds require some trade-off in mechanical properties. A moderate draw ratio of 1.3 times improves electrical conductivity by 56%^[12], while plastic drawing at 2.0 to 3.0 times simultaneously increases density, orientation, and elastic modulus^[78]. Draw ratio also plays a significant impact. Large flakes (> 20 μm) favor high orientation and modulus (reaching 901 GPa when paired with small-flake filling^[50]), whereas small flakes (< 5 μm) increase processability but decrease mechanical strength. GO flake size determines liquid crystallinity and defect density. Solvent exchange kinetics are controlled by the solidification bath’s composition: functional baths, such amine solutions, allow for in situ cross-linking, whereas retarding agents, like ethanol/water mixes, create denser structures^[63]. Post-treatment factors have a significant impact on modulus retention and electrical conductivity (up to 1.2 × 10⁶ S·cm^-1), especially thermal reduction temperature (≥ 3,000 °C for graphitization)^[17]. These factors are still closely related, and a major obstacle to converting lab discoveries into commercial GF manufacturing is precisely optimizing their synergistic effects.

Other fabrication methods

In order to meet the specific requirements of various applications for fiber structure, characteristics, and preparation procedures, a number of alternative spinning techniques have been developed in addition to conventional wet-spinning techniques. Every technique has its own unique features; some concentrate on increasing production efficiency, others on creating distinctive morphologies, and yet others on optimizing process flows. However, they typically struggle to achieve balanced overall performance, cost management, or continuous manufacturing. Their development can be seen as a useful extension and potent supplement to the conventional wet-spinning method.

Dry and dry-to-wet spinning
In dry spinning, a high-concentration spinning solution is extruded straight from the spinneret, where the solvent evaporates in the air to solidify and produce the fiber. Figure 6A depicts a schematic of the dry spinning procedure. This process permits solvent recovery, does not require a coagulation bath, and is comparatively eco-friendly. However, mechanical strength is usually low and porous fibers may result from solvent evaporation. By twisting and stretching GO films into fibers made of graphene nanorolls, Zheng et al. used a twist-spinning assembly technique^[83]. Figure 6B and C show the fiber structure, while Figure 6D shows how layered entanglement improves mechanical properties. Organic-inorganic composite fibers can also be prepared by dry spinning. For example, Zhang et al. used covalent crosslinking to create photothermal-responsive smart actuator fibers by combining surface-modified GO with liquid crystal elastomers^[82]. Figure 6E and F illustrates the connection between driving strain and time under light/heat stimulation.

Figure 6. (A) Schematic diagram of the preparation process of GO@LCE fiber actuators. Reproduced with permission^[82], Copyright © 2025 Elsevier; (B) and (C) SEM pictures of various LGF locations; (D) Stress-strain curves of c-LGF (red) and t-LGF (black). (B-D) are reprinted with permission from Ref.^[83], Copyright © 2019 Elsevier; (E) The relationship between actuation strain and time under thermal stimulation; (F) The relationship between actuation strain and time under light stimulation. (E and F) are reprinted with permission from Ref.^[82], Copyright © 2025 Elsevier; (G) Electrospinning fPAANFs to synthesize fPINFs; (H) SEM images of electrospun fPAANPs or NFs under various solution concentrations with scale bars indicating 10.0 μm. (G and H) are reprinted with permission from Ref.^[84], Copyright © 2025 John Wiley and Sons; (I) The 3D geometric structures of GFs; (J) Photograph of GF network embedded in PDMS matrix. (I and J) are reprinted with permission from Ref.^[85], Copyright © 2012 John Wiley and Sons; (K) The cumulative pore volume of rGO fibers obtained using different drying conditions from the same rGO hydrogel fibers; (L) The comparison of volumetric and gravimetric capacitances of rGO fibers determined at 2 mv·s^-1. (K and L) are reprinted with permission from Ref.^[86], Copyright © 2020 Elsevier; (M) Schematic illustration of the fabrication process for porous GFs. Reproduced with permission^[87]. Copyright © 2025 Elsevier. GO: Graphene oxide; LCE: liquid crystal elastomer; SEM: scanning electron microscope; LGF: ultralight graphene fiber; fPAANFs: fluorinated poly(amic) acid nanofibers; fPINFs: fluorinated polyimide nanofibers; NFs: nanofibers; GFs: graphene fibers; PDMS: polydimethylsiloxane; rGO: reduced graphene oxide; UV: ultraviolet; NIR: near-infrared; 6FDA: 4,4′-(hexafluoroisopropylidene)diphthalic anhydride; TFB: 2,2′-bis(trifluoromethyl)benzidine; fPAA: fluorinated poly(amic) acid; SSA: specific surface area.

The orienting benefits of dry spinning and the solidification features of wet spinning are combined in dry-wet spinning. In order to prepare structurally thick, highly orientated fibers, the spinning solution is subjected to air-gap stretching prior to entering the solidification bath. This technique was used by Xiang et al. to create GFs with high orientation and smooth surfaces^[88]. However, the procedure’s complicated process control restricts its widespread use, and it frequently depends on extremely corrosive solvents like chlorosulfonic acid to create the liquid crystal spinning solution.

Electrospinning
As seen in Figure 6G, electrospinning is a popular method for creating nanofibers by applying ultrafine stretching via high-voltage electrostatic forces to polymer solutions or melts. This method has been effectively expanded to produce graphene-based nanofibers in recent years. By adding transient polymer additives, Han et al. invented the electrospinning of continuous, pure graphene nanofibers and achieved noticeably improved electrical conductivity following graphitization^[54]. This technique makes it easier to build three-dimensional networks of porous fibers, which makes it appropriate for uses like flexible electrodes. Park et al. created porous graphene nanofibers in a single step by combining electrospinning and laser photothermal treatment to further enhance the structure^[84]. Figure 6H displays SEM images at various solution concentrations, showing noticeably improved electrochemical performance. However, controlling the macroscopic mechanical characteristics of the fibers is difficult since electrospinning usually necessitates the use of polymer spinning aids and entails several following processing steps.

Method of confined hydrothermal assembly
Constrained hydrothermal assembly operates on the basis of thermally induced self-assembly under spatial confinement instead of shear flow orientation, which is a major difference from wet spinning. Typically, a glass or polytetrafluoroethylene capillary with an inner diameter of tens to hundreds of micrometers is injected with a high-concentration GO aqueous solution (2-10 mg·mL^-1 at pH ≈ 6-7)^[85]. Under self-generated pressure, the sealed capillary is heated to 80-230 °C, which sets off a sequence of interconnected physicochemical changes. Three synergistic processes take place simultaneously under hydrothermal conditions: capillary-induced confinement, where the cylindrical geometry of the capillary imposes one-dimensional spatial constraints, guiding randomly oriented layers into highly aligned fibrillar morphologies during hydrogel curing; π-π stacking drives self-assembly, where restored conjugated domains promote face-to-face stacking of layers, minimising interfacial energy and forming a three-dimensional hydrogel network; and partial reduction of GO, where thermal energy eliminates some oxygen-containing functional groups, restoring conjugated sp² domains and increasing the hydrophobicity of GO sheets [Figure 6I and J].

The initially fluid GO sol gradually changes into structurally unique hydrogel fibers as the hydrothermal reaction continues, and their morphology accurately mimics the capillary’s internal features. By using capillaries with non-circular cross-sections or multi-channel designs, it is easy to create fibers with hollow, helical, or multi-channel structures^[85]. The GO dispersion’s pH and concentration are crucial factors in this method’s success. Dispersions that are too diluted (less than 1 mg·mL^-1) do not create continuous hydrogel networks; instead, they produce fragmented microgels instead of whole fibers. On the other hand, excessively high viscosity in highly concentrated dispersions (> 15 mg·mL^-1) makes capillary injection more difficult and increases blockage susceptibility. Strongly alkaline circumstances encourage excessive reduction and aggregation of GO before orderly assembly, therefore a pH that is slightly acidic or almost neutral is ideal.

Restricted hydrothermal assembly’s main selling points are its ease of use and capacity to create unusual microstructured fibers that are challenging to do using wet spinning. Extended reaction durations (usually ranging from several hours to days), batch-operated methods limited by capillary length, and a high sensitivity of the final fiber quality to the drying process are some of the technique’s inherent drawbacks. The difficulty of attaining repeatable process control was highlighted by a systematic study by Wang et al. that showed how various drying protocols (such as ambient-temperature drying and supercritical CO₂ drying) drastically change the pore structure and volumetric properties of the fibers [Figure 6K and L]^[86]. In order to get over the limits of batch production, Ding et al. suggested a hybrid approach that involves hydrothermally treating porous graphene microgels first, then combining them with GO spinning slurry for continuous wet spinning^[87]. As shown in Figure 6M, this method effectively combined the scalability of wet spinning with the structural benefits of hydrothermal assembly (high specific surface area, porous architecture).

Film twisting and template-assisted CVD
Although the goal of both of these essentially different processes is to create GFs from premium graphene sheets, their working principles are completely different and they function separately.

Twisting technique for films. This method uses mechanical twisting and winding to convert existing two-dimensional graphene assemblies into one-dimensional fibers. There are several ways to manufacture the first film, including growing it directly by chemical vapour deposition on a metal substrate and then transferring it, or chemically rGO after vacuum filtration. In order to create hybrid fibers, Zhang’s group^[89] used a two-step process, first depositing GO onto CNT fiber scaffolds and then decreasing it. Low interlayer bonding strength frequently leads to low tensile strength and restricted preparation efficiency, even when highly extensible fibers can be produced. The scalability and mechanical qualities of film twisting technology continue to be major obstacles, despite the fact that it provides flexibility in film sourcing.

Chemical vapour deposition with the use of a template. Graphene is grown directly on one-dimensional templates (such as copper wires or quartz optical fibers) using CVD. After growth, the template can either be kept to create composite fibers or removed to produce hollow GFs [Figure 7A]. Recent developments have greatly improved mechanistic knowledge and process scalability. Li et al. demonstrated the feasibility of roll-to-roll manufacturing and proposed a novel “gas-surface-solid”growth mechanism by achieving low-temperature, high-speed graphene synthesis on alumina fiber fabrics [Figure 7B]^[90]. Chen and Dai created porous GFs for fiber-based solar cells using copper wires as templates^[96]. Graphene was grown on glass fibers by Yuan et al. to create high-performance infrared electrothermal textiles [Figure 7C]^[57]. Although the procedure usually entails template removal steps and lacks the continuity of wet spinning methods, these examples demonstrate the potential of template-assisted CVD approaches for the synthesis of structurally controlled, high-quality GFs.

Figure 7. (A) Schematic of GAF prepared via CVD process; (B) SEM images of GAF obtained with the growth time of ~20 and ~70 min (top), and graphene-skinned quartz fiber obtained with the growth time of ~60 and ~120 min (bottom). Scale bar, 1 μm. (A and B) are reprinted with permission from Ref.^[90], Copyright © 2024 Springer Nature; (C) Flexible GGFF with length and width of 350 and 50 cm, respectively. Reproduced with permission^[57], Copyright © 2022 American Chemical Society; (D) Capacitance retention and coulombic efficiency over 15,000 charge/discharge cycles at 0.05 mA·cm^-2 and 30 kPa. Reproduced with permission^[91], Copyright © 2024 Springer Nature; (E) Charge/discharge profiles. Reproduced with permission^[92], Copyright © 2022 John Wiley and Sons; (F) Photo image of the fabricated TENG device. Reproduced with permission^[93], Copyright © 2020 Elsevier; (G) Schematic diagram of diversified applications enabled by the 3D t-TENG. Reproduced with permission^[94], Copyright © 2022 Elsevier; (H) The robot wears fiber sensors at movable joints (elbow, waist, and knee). Each sensor is marked in the red box at specific joint position. Responsive curves of wearable sensors during the robot’s dance “Gangnam Style”: elbow (black line), waist (red line), and knee (blue line). Reproduced with permission^[95], Copyright © 2015 John Wiley and Sons; (I) The photographs (i) and SEM images (ii) of GFF; (J) Images of the GFF-PB-based sensing patch on a volunteer’s wrist. Enlarged view of the sensor and iontophoretic anode in (i). In vivo invasive blood glucose measurement by using a finger-prick glucometer (ii). (I and J) are reprinted with permission from Ref.^[1], Copyright © 2021 Elsevier. GAF: Graphene-skinned alumina fiber; CVD: chemical vapor deposition; SEM: scanning electron microscope; GGFF: graphene glass fiber fabric; TENG: triboelectric nanogenerator; GFF: graphene fiber fabric; PB: Prussian blue; AF: alumina fiber; PET: polyethylene terephthalate.

These works show great potential for high-end applications and expand the selection of templates. In conclusion, the aforementioned techniques offer a variety of technological approaches for the fabrication of GFs, each with unique benefits in the areas of orientation control, porosity design, nanostructure construction, and high-efficiency graphene production. Continuous production, cost management, process stability, and attaining balanced comprehensive performance are still difficult tasks, nevertheless. In order to overcome the drawbacks of individual procedures and advance the creation of high-performance, functionalized GFs, current trends favor integrating various methods or combining spinning with post-treatment technologies.

Adaptable energy harvesting and storage

Fiber-based energy storage and harvesting devices have arisen in response to the pressing need for flexible, lightweight, and integrated power supply systems in wearable electronics. Graphene-based conductive fibers are now the perfect electrode materials for building high-performance fiber-based energy devices because of their intrinsic high conductivity, huge specific surface area, superior mechanical flexibility, and customizable electrochemical activity. Their main uses are fiber-based batteries, fiber-based triboelectric nanogenerators (TENGs), and fiber-based supercapacitors. They push the development of smart textiles toward self-powered, multipurpose integration by integrating into textile processes.

GFs can directly function as core electrodes in fiber-based supercapacitors. Micro/nano-structural design and interfacial engineering optimization are critical for improving performance. For example, Wu et al. used interfacial chemical bonding and microfluidic self-assembly to create MoS₂/porous graphene core-shell microfibers^[97]. Strong interfacial interaction and hierarchical pore architecture allowed these fibers to attain high areal capacitance and exceptional cycling stability. Additionally, fibrous electrodes’ mechanical robustness is essential for useful wearable applications. As seen in Figure 7D, the GO/carbon fiber composite electrode created by Zhang et al. showed remarkable mechanical-electrochemical coupling stability, retaining a high capacitance retention of 99.58% after withstanding a 30 kPa surface load and 15,000 cycles^[91].

GFs are mostly used as flexible, highly conductive scaffolds or current collectors in the field of fiber-based batteries. Performance can be further improved by optimizing structural design and compositing with other active materials. For example, carbon nanofibers (CNFs) vertically enter graphene sheets in a three-dimensional interpenetrating network created by Liu et al.^[98]. This produces high specific capacity and exceptional rate performance by successfully preventing graphene stacking and offering continuous electrical and ionic transport channels. Huang et al. greatly improved reaction kinetics and cycling stability in lithium-sulfur batteries by implanting active materials into GF cavities and enhancing polysulfide anchoring by interfacial engineering^[92]. At high sulfur loading, the constructed pouch cell reached an areal capacity of 5.8 mAh·cm^-2 [Figure 7E]. Additionally, GFs are a great catalytic support for metal-air batteries. Zeolitic imidazolate framework (ZIF)-derived bimetallic doped Co nanoparticles were enclosed in pleated graphene nanoroll fibers by Zhang et al.^[99]. The built zinc-air battery was able to accomplish stable cycling for up to 1,140 h with good low-temperature adaptability thanks to the special tubular channels and pleated construction that avoided active component agglomeration and optimized electronic structure.

Beyond energy storage, extracting mechanical energy from the environment is another essential component of self-powered devices. Because of their flexible material and structural design, TENGs have become an important energy harvesting technology. Graphene-based conductive fibers are suited for building high-performance electrodes in fiber-shaped TENGs. For example, Xiong et al. achieved direct integration of TENGs into textiles via a scalable spinning-knitting process, enabling dual functions of energy harvesting and motion sensing^[94], and Shi et al. showed that a composite nanofiber membrane TENG fabricated via electrospinning could output high voltages, directly powering small electronic devices as shown in Figure 7F^[93]. Graphene can be used with natural polymers or elastomers to improve a device’s mechanical adaptability or environmental friendliness, opening up new possibilities for personalized electronic textiles. Figure 7G illustrates a variety of application concepts. In a TENG with graphene electrodes and cellulose nanocrystals as the friction layer, Alghamdi et al. showed long-term output stability^[100]. Chen et al. used 3D-printed graphene/polydimethylsiloxane (PDMS) core-sheath fibers to create stretchy, washable smart textiles, providing new methods for creating self-powered personalized healthcare electrical textiles^[101].

Integrated, self-powered fiber systems are the direction of future trends. By carrying out “segment-selective functionalization” on individual fibers, Yao et al. produced tiny integrated devices that allowed for the integration of energy conversion and storage units across several segments^[102]. A more sophisticated approach is creating “structure-function integrated” smart composites by directly incorporating energy storage capabilities into structural fibers. Graphene soft conductive fiber exhibits great potential as a crucial active and reinforcing component in these smart textiles.

Smart actuation and health monitoring

GFs have become the perfect material platform for creating smart textiles that combine “sensing” and “response” functions due to their extremely sensitive electrical response to external physical and chemical stimuli and programmable deformation capabilities that can be achieved through structural design. Their primary application is to connect the intrinsic electrical characteristics of the fibers to mechanical deformation, environmental changes, or biological signals. This allows for the detection of different signals or the execution of particular activities.

GFs have exceptional flexibility and integrability in the realm of health monitoring sensors. Cheng et al. created a “compression spring” strain sensor based on graphene-coated elastic fibers for tracking human motion. Tensile, bending, and torsional deformations can be distinguished with this structure’s high sensitivity (detection limit of 0.2% strain) and broad detection range (up to 100% strain)^[95]. As seen in Figure 7H, it has been effectively used to monitor robotic actions and human joint movements. Cai et al. used hydrospinning to create GF textiles for biochemical sensing^[1]; Figure 7I displays photos and SEM images. They created a flexible electrochemical glucose sensor with great sensitivity (1,539.53 μA·mM^-1·cm^-2) after immobilizing glucose oxidase and modifying it with Prussian blue. This allowed for non-invasive monitoring of glucose in sweat on the skin’s surface [Figure 7J]. Multi-sensing integrated multimodal smart textiles are an important area of research to enable more thorough physiological state assessment. A fabric based on graphene/Fe₂(MoO₄)₃/thermoplastic polyurethane (TPU) micro-nano porous fibers was created by Zhang et al. The simultaneous, interference-free real-time detection of temperature and pressure (e.g., pulse) is made possible by these fibers’ thermoelectric and triboelectric response properties. This integrated solution provides a promising method for monitoring cardiovascular health with a high temperature sensitivity coefficient β of 4,994.55 K^[103].

GFs in smart actuation go beyond “sensing” to “responding”. To create bionic “artificial muscle” fibers, one important strategy is to combine them with stimulus-responsive polymers like liquid crystal elastomers (LCEs). Inspired by skeletal muscle, Kim et al. created graphene/LCE composite fiber bundles that, when stimulated by near-infrared light, show around 45% contraction strain and 1.22 MPa stress, which is comparable to the performance of genuine muscle^[104]. Figure 8A depicts the schematic of the fiber shape deformation mechanism. Importantly, during actuation, the internal graphene network experiences reversible “permeation-depermeation” transitions that cause systematic axial resistance variations up to ten times. This provides essential components for closed-loop control by enabling self-sensing actuation without the need for external sensors [Figure 8B]. For large-scale applications, scalable continuous fabrication methods are crucial. A high-speed “dual-diffusion” wet spinning method that can continuously produce graphene/LCE composite fibers with adjustable diameters at 4,500 m·h^-1 was developed by Shi et al.^[78]. They proved its promise for scalable, weavable applications by demonstrating its capacity to drive biomimetic joints. Alternative actuation mechanisms have also been investigated, such as creating rGO/poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) composite fibers for electro-bending via electrostatic repulsion or designing actuator fibers based on the differential humidity response between GO and rGO^[109], providing a variety of motion solutions for soft robotics.

Figure 8. (A) Schematic of a G-LCF composite fibre for shape deformation mechanism with reversible percolation. Schematic of a composite fibre for shape deformation mechanism with reversible percolation; (B) Actuation strain and concurrent electrical current change at the single-fibre level of G0.3-LCF induced by different NIR intensities under a constant stress. (A and B) are reprinted with permission from Ref.^[104], Copyright © 2022 Springer Nature; (C) The CNF/G composites as wearable sensors with excellent performance, such as thermal management, EMI shielding, health monitoring, and Joule heating; (D) TC values of CNF/G composites at different contents of mGNPs; (E) Schematic diagram of the heat transfer model for CNF/G composites. (C-E) are reprinted with permission from Ref.^[105], Copyright © 2024 John Wiley and Sons; (F) Thickness evolution of GF-TIM after compressive cycles under the same compressive strain. Reproduced with permission^[106], Copyright © 2024, American Chemical Society; (G) EMI SE of CNF/G composites with different mGNPs contents; (H) Photographs of EMI shielding ability of paper and CNF/G28 composite for wireless charging of smartphones. (G and H) are reprinted with permission from Ref.^[105], Copyright © 2024 John Wiley and Sons; (I) PN0.85GC-900’s reflection loss presentation in the frequency range of 2-18 GHz with varying thicknesses (1-5 mm). Reproduced with permission^[107], Copyright © 2022 Springer Nature; (J) Demonstration of the EMI shielding performance of GNF@tCu. A piece of non-shielding paper is taken as comparison (middle); (K) EMI SE and specific shielding effectiveness of GNFs with a thickness of 20 μm under different electroless plating duration. (J and K) are reprinted with permission from Ref.^[108], Copyright © 2025 Elsevier. G-LCF: Graphene liquid crystal elastomer fibre; NIR: near-infrared; CNF/G: cellulose nanofibers/graphene nanoplatelets composite; EMI: electromagnetic interference; TC: thermal conductivity; mGNPs: modified graphene nanoplatelets; GF-TIM: graphene fiber-based thermal interface material; SE: shielding effectiveness; GNFs: graphene nanofibers; LCE: liquid crystal elastomer; G-LCE: graphene liquid crystal elastomer; LC: liquid crystalline; EM: electromagnetic; RL: reflection loss.

Electromagnetic shielding and thermal management

Because of their exceptional thermal and electrical conductivity, graphene-based conductive fibers and their composites have substantial application value in thermal management and electromagnetic shielding for smart textiles, as shown in Figure 8C. Through passive heat dissipation or active heating mechanisms, these materials allow the wearable microenvironment to be effectively regulated for thermal management. Zhu et al. created a composite fiber with high in-plane thermal conductivity (136.2 W·m^-1·K^-1) by electrostatically self-assembling modified graphene nanosheets with cellulose nanofibers [Figure 8D]^[105]. As shown by the heat transfer model in Figure 8E, this material is appropriate for heat dissipation interfaces in wearable electronics, improving wear comfort without sacrificing device functionality. Additionally, Lu et al. created vertically oriented GF arrays with an in-plane thermal conductivity of 82.4 W·m^-1·K^-1 while preserving structural stability at low compressive moduli by using a mechanical-electric field co-alignment technique [Figure 8F]^[106]. This method provides new information for high-power microelectronic devices’ integrated thermal management. Graphene-based fibers have extremely effective electrothermal conversion capability in active heating applications. For example, graphene/glass fiber textiles function as dual-emitter infrared radiators, combining high emissivity with quick electrothermal response, which makes them appropriate for outdoor heating clothing and medicinal treatment^[57]. Rapid heating and de-icing capabilities under low-voltage drive are made possible by graphene sheets reinforced with ground paper fiber (GPFC), which shows promise for wearable technology in cold climates^[110]. Additionally, in the 0.3-1.2 V low-voltage range, graphene/copper core-shell nanofiber textiles (GNF@tCu) show quick, consistent electrothermal reactions, offering effective heating solutions for portable wearable devices that are power-sensitive^[108].

By creating highly conductive networks and multiscale structures, graphene-based fibers efficiently block or absorb electromagnetic interference (EMI) in electromagnetic shielding. According to Zhu et al., modified graphene/cellulose nanofiber composites efficiently decrease near-field radiation interference by achieving shielding effectiveness up to 105 dB in particular frequency bands, as illustrated in Figure 8G^[105]. Figure 8H shows composite fiber for wireless smartphone charging. An electrospun spiderweb-like rGO/carbon composite nanofiber with -46.15 dB reflection loss in the microwave band and exceptional broadband absorption performance was created by Wang et al. [Figure 8I]^[107]. Structural design can control a material’s shielding mechanism. For example, GNF@tCu uses a triple impedance mismatch structure (“air-copper shell-graphene core”) to provide absorption-dominated shielding in the same frequency range, whereas GPFC materials show reflection-dominated shielding in the X-band with an effectiveness of 87.3 dB^[97]. Its lightweight and high-efficiency features are highlighted by its shielding performance, which shows 66% absorption loss and a shielding efficacy of 118.8 dB·cm³/g [Figure 8J and K]^[108]. Additionally, 67.86 dB shielding effectiveness is achieved by multilayer laminated fabrics with modest graphene loading, providing a feasible route for lightweight, structurally integrated electromagnetic protective textiles^[111].

Mechanical properties

Conditions for testing mechanical properties: All mechanical data for MXene-based fibers reported here were acquired at standard ambient temperatures (22-26 °C, 45%-55%), usually with a loading rate of 1-2 mm·min^-1 and a gauge length of 10 mm. The pertinent literature contains references to specific details. Specific testing criteria for composite fibers or fibers evaluated in non-ambient circumstances (such as after thermal treatment or in electrolyte solutions) are described in the original literature; this paper just offers a synopsis.

MXene’s distinct atomic-layer structure is the source of its intrinsic mechanical characteristics. Its basic unit, as depicted in Figure 9A, is made up of transition metal atoms (such as Ti, V, and Nb) joined to carbon/nitrogen atoms within the plane by strong covalent bonds, giving it remarkable in-plane strength and rigidity^[112]. Weaker van der Waals forces or hydrogen bonds cause interlayer bonding, which gives the material exceptional out-of-plane flexibility and deformability and produces a hierarchical structure that blends stiffness with flexibility. This gives monolayer MXenes remarkable mechanical characteristics^[117]. According to nanoindentation tests, monolayer Ti₃C₂T_x has an effective Young’s modulus of 0.33 ± 0.03 TPa, which is higher than rGO (0.25 ± 0.15 TPa) and GO (0.21 ± 0.02 TPa). For solution-processable two-dimensional materials, this value is among the highest that is currently known^[113] [Figure 9B].

Figure 9. (A) Structural schematic diagram of MXene. Reproduced with permission^[112], Copyright © 2021 The American Association for the Advancement of Science; (B) Comparison of effective Young’s moduli for several 2D materials: GO, rGO, MoS₂, h-BN, and graphene. Reproduced with permission^[113], Copyright © 2018 The American Association for the Advancement of Science; (C) Schematic illustrating the fabrication of core–shell ANF@M fiber by coaxial wet spinning, the evolution of the sheet orientation, and the cross-linking of MXene sheets with ammonium ions. Reproduced with permission^[114], Copyright © 2022 Springer Nature; (D) D-spacing and porosity of pure fiber when heated; (E) Orientation order of COC fibers at different draw-down ratios shown by WAXS patterns (inset). (D and E) are reprinted with permission from Ref.^[34], Copyright © 2023 John Wiley and Sons; (F) Cross-sectional SEM images of an anti-plane in deer antlers and PPM fibers; (G) Comparison of the tensile strength, toughness, and ductility of PPM fibers with porosities of 28.5%, 20.8%, 16.2%, and 11.8%. (F and G) are reprinted with permission from Ref.^[35], Copyright © 2025 Springer Nature; (H) The value of ΔR/R₀ changes with strain during the stretching process of MCSFs. The inserted SEM images are corresponding surface morphologies at different stages. Reproduced with permission^[58], Copyright © 2025 John Wiley and Sons; (I) In situ EELS spectra of the O K-edge of Mo₂TiC₂T_x; (J) Comparison of the post-anneal RT resistance (black circles) with the concentration of =O (red squares), given in units of x based on the chemical formula Mo₂TiC₂O_x. (I and J) are reprinted with permission from Ref.^[115], Copyright © 2019 Springer Nature; (K) SEM images of Ti₃C₂T_x MXene fiber. Reproduced with permission^[116], Copyright © 2020 Springer Nature; (L) specific areal capacitance of the BMX yarn electrodes from the GCD curves. Reproduced with permission^[31], Copyright © 2018 John Wiley and Sons; (M) CV curves of M7P3 fiber at different scan rates. Reproduced with permission^[32], Copyright © 2019 John Wiley and Sons. GO: Graphene oxide; rGO: reduced graphene oxide; h-BN: hexagonal boron nitride; ANF: aramid nanofiber; COC: cyclic olefin copolymer; WAXS: wide-angle X-ray scattering; SEM: scanning electron microscope; PPM: polypropylene microfiber; MCSFs: MXene induced conductive silk fibers; EELS: electron energy loss spectroscopy; RT: room temperature; BMX: biscrolled MXene/carbon nanotube yarn; GCD: galvanostatic charge-discharge; CV: cyclic voltammetry; GF: graphene fiber.

However, sheet orientation, packing density, interfacial interactions, and preparation methods have a major impact on the mechanical characteristics of MXene nanosheets when they are assembled into macroscopic fibers^[118]. The performance of pure MXene fibers usually falls short of the individual sheets’ theoretical values. For example, by controlling liquid crystal phase spinning in conjunction with ammonium ion-enhanced interlayer contacts, Eom et al. produced fibers with a tensile strength of roughly 63.9 MPa and a Young’s modulus of roughly 29.6 GPa^[116]. Zhou et al. used a synergistic approach of thermal stretching and interfacial crosslinking to further optimize the assembly process and create ultra-dense MXene fibers with a tensile strength of 585.5 MPa and toughness of 66.7 MJ·m^-3[119]. The overall mechanical properties of composite fiber systems are greatly improved by the addition of MXene. Liu et al. achieved a further increase to 502.9 MPa tensile strength and 48.1 MJ·m^-3 toughness for aramid nanofiber (ANF)@MXene core-shell fibers obtained via coaxial hydrospinning, as schematically shown in Figure 9C^[114]. Zhao et al. observed MXene/CNTs composite fibers achieving tensile strengths of 161 MPa at about 9 weight percent CNT loading^[120]. Additionally, the mechanical qualities of fiber substrates like cotton yarn are greatly improved by coating them with MXene. For example, cotton yarn coated with MXene showed an increase in tensile strength from 334 to 468 MPa^[121].

Advanced assembly techniques, multiscale interface engineering, and biomimetic structural design have all contributed to significant advancements in the mechanical properties of MXene-based fibers in recent years. He et al., for example, suggested a “dual-space-constrained spinning” approach^[122]. They accomplished highly ordered assembly of MXene and CNFs by imposing limitations at both the micro and nanoscale. The resultant fibers have an electrical conductivity of up to 1.27 × 10⁶ S·m^-1 and a tensile strength of 506.7 MPa. By using a dual method of “static filler densification + dynamic thermal stretching”, Zhou et al. greatly reduced the porosity and improved the layer orientation of MXene-CNT-polylactic acid (PLA) composite fibers [Figure 9D and E]^[34]. Tensile strength of 941.5 MPa, toughness of 147.9 MJ·m^-3, and superior electromagnetic characteristics were the outcomes. Gu et al. created a biomimetic model that included “strong covalent interfaces + slip-enabled physical interfaces + microporous structures”, drawing inspiration from the multi-level structure of antlers^[35]. MXene/PEDOT:PSS/polycyclohexane composite fiber was produced using this method. Figure 9F displays the cross-sectional SEM picture. It was the first to surpass the gigapascal strength threshold while retaining high conductivity and flexibility, achieving a tensile strength of 1,060.1 MPa, a fracture strain of 34.2%, and a toughness of 136.1 MJ·m^-3 at a porosity of 21% [Figure 9G]. Notably, Jia et al. used MXene/sodium alginate composite layers to replicate sericin, drawing inspiration from the core-sheath structure of real silk^[58]. MXene-induced conductive silk fibers were produced by securely bridging these layers onto degummed silk threads through hydrogen bonds and electrostatic interactions. Tensile strength of 1,037.9 MPa, toughness of 194.9 MJ·m^-3, electrical conductivity of 6,400 S·m^-1, and ultra-high strain sensitivity (GF = 2,269.3) are all impressive integrated features of this fiber [Figure 9H]. This work represents an efficient paradigm for concurrently enhancing mechanical, conductivity, and sensing qualities through biomimetic design and multiscale interface engineering, in addition to setting a new record for MXene-enhanced mechanical properties in natural fibers.

Electrical properties

The electrical conductivity of MXene fibers was predominantly determined using the four-probe method at room temperature (about 25 °C) and ambient humidity. The electrolyte type, concentration, and scan rate used for electrochemical measurements (capacitance, rate performance) are clearly described in the cited literature and summarized in the discussion sections. Unless otherwise noted, all capacitance values correspond to measurements made in aqueous electrolytes at room temperature (e.g., 1 M and 3 M H₂SO₄)^[9,123-126].

The key benefits of MXene, a new class of two-dimensional transition metal carbon/nitride compounds, come from its remarkable intrinsic conductivity and highly adjustable structural and surface chemical characteristics. With film conductivities of up to 6,000-8,000 S·cm^-1, the typical material Ti₃C₂T_x displays metalloid-like conductivity. Its high carrier mobility and metal-bond-dominated electrical structure are the causes of this characteristic. Many structural elements, such as surface functional group types, interlayer stacking states, lattice defect densities, and environmental stability, affect MXene’s conductivity. For example, conductivity can be increased by optimizing the electron distribution close to the Fermi level by introducing -O/-OH groups [Figure 9I and J] or selectively eliminating highly electronegative -F functional groups^[115]. Moreover, regulated transitions from metallic to semiconducting states are made possible by intercalating organic molecules or metal ions, which modulate the interlayer coupling strength. Charge transfer efficiency is further improved by high-temperature annealing, which successfully removes oxygen vacancies and lattice distortions. In general, good electrical conductivity is more likely to be achieved in MXene sheets with large dimensions, few defects, no surface end groups, and smaller interlayer spacing^[127].

The sheet size, orientation, pore structure, and preparation method are the main factors influencing the conductivity of MXene-based conductive fibers in fiber form. Sheet size has a major impact on the conductivity of pure MXene fibers. Using an NH₄⁺ ion solidification bath and additive-free wet spinning of large-sized Ti₃C₂T_x nanosheets, Eom et al. effectively produced pure MXene fibers with a conductivity of 7,713 S·cm^-1, as seen in Figure 9K^[116]. Even higher conductivities can be obtained by further improving internal layer ordering inside the fibers through optimal stretching orientation and solidification kinetics during spinning^[26]. Even though the conductivity of composite MXene fibers is often lower than that of pure MXene fibers, well-designed composite systems can nonetheless produce efficient conductive networks. For example, MXene/CNT composite fibers reach 1,715 S·cm^-1 at low CNT loading^[120], whereas MXene/PEDOT:PSS composite fibers show a conductivity of 1,489 S·cm^-1[32]. Additionally, coated MXene fibers exhibit exceptional performance. For example, a conductivity of 200 S·cm^-1 is obtained when 79 weight percent MXene loading is achieved on cotton yarn surfaces, demonstrating exceptional substrate flexibility and conductive functionalization capabilities^[121].

MXene-based fiber electrodes have excellent capacitive characteristics and quick ionic reaction in energy storage applications. In 1 M H₂SO₄ electrolyte, pure MXene fibers reach a volumetric capacitance of up to 1,265 F·cm^-3, which is comparable to the capacitance level of MXene films (≈ 1,500 F·cm^-3)^[21,33]. MXene-based composite fiber systems are also quite effective. As an illustration of the benefits of high active material loading, MXene/CNT-spun yarn shows a volumetric capacitance of 1,083 F·cm^-3 and a surface capacitance as high as 3,188 mF·cm^-2 in 3 M H₂SO₄ [Figure 9L]^[31]. According to research, electrolyte ion penetration and transport are facilitated by smaller MXene sheets with more edge defects and active sites, which results in better capacitive performance^[128]. Additionally, the electrochemical performance of the fibers is greatly influenced by their microstructure: fibers prepared with a chitosan coagulation bath have a higher density (≈ 3.6 g·cm^-3) and a volumetric capacitance that is roughly doubled in comparison to low-density fibers prepared with an acetic acid coagulation bath (≈ 1.7 g·cm^-3), suggesting that densely packed structures improve volumetric energy density^[21,23,24]. In terms of rate performance, MXene/PEDOT:PSS composite fibers showed good fast charge/discharge capability and structural stability, with a capacitance retention of 81.4% when the scan rate rose from 5 to 1,000 mV·s^-1 [Figure 9M]^[32].

Thermal properties

MXene’s optical characteristics are highly tunable, and the chemical makeup and spatial distribution of its surface end groups largely control its electronic structure and optical response^[129]. In addition to affecting the material’s bandgap structure and energy level arrangement, these functional groups also directly affect how light is absorbed, reflected, and transmitted across the ultraviolet to near-infrared spectrum. For example, because of strong surface polarization effects, MXene rich in -F and -OH functional groups usually shows low optical absorption coefficients in the visible area. On the other hand, MXene systems that have been altered with different end groups might show improved light-trapping effectiveness. The selective scattering mechanism of end groups toward high-energy photons is the main reason why adding surface functional groups can greatly increase material reflectivity in the ultraviolet (UV) spectrum. The interlayer structure of MXene has a significant impact on its optical characteristics in addition to surface chemical control. Light propagation paths between layers can be efficiently controlled by varying the interlayer gap using intercalants. The total transmittance and absorption properties of the material can be systematically controlled by increasing the interlayer distance, which improves multiple reflections and scattering. For MXene optical design, this structural tailoring in conjunction with surface chemical alteration offers a multifaceted optimization approach.

MXene’s excellent photothermal conversion capabilities are directly attributed to its exceptional and tunable optical characteristics. Through non-radiative relaxation processes, MXene effectively transforms light energy into heat after absorbing photons. This feature shows enormous potential for MXene-based fibers and fabrics in heat management applications for smart textiles, together with its intrinsic high electrical conductivity and processability. As seen in Figure 10A, the MXene/cellulose nonwoven created by Zhao et al. quickly warms to 100 °C at low voltages (3-6 V), allowing for regulated thermotherapy [Figure 10B] and antibacterial effects while retaining stability after thousands of flexures^[130]. Additionally, biomimetic structural design improves functional integration. For example, Wang et al. created MXene/ANF composite paper inspired by pearl layers, which combines high mechanical strength, effective electromagnetic shielding, and quick Joule heating response^[131]. As seen in Figure 10C, the temperature consistently increases to 146 °C at 4 V, which makes it appropriate for integrated electromagnetic shielding wearable systems and high-performance thermal management fabrics. Furthermore, self-healing functionality is made possible by the photothermal characteristics of MXene. In order to create a self-healing heater, Choi et al. coated polycaprolactone (PCL) fiber surfaces with MXene and AgNWs^[132]. As seen in Figure 10D, the material was heated to 61 °C by delivering a 1.6 V voltage upon injury, melting the PCL and enabling autonomous healing.

Figure 10. (A) Temperature profiles of M-fabric at different input voltages of 0, 1, 2, 3, 4, 5, and 6 V. Insets are the IR thermal images of the M-fabric at different input voltages; (B) Schematic illustration for the thermotherapy application of M-fabric when embedded in a neck-guarding pad. Digital photographs of different stances of head with M-fabric integrated neckpad and correspondingIR thermal images under an applied voltage of 3 V. (A and B) are reprinted with permission from Ref.^[130], Copyright © 2020 American Chemical Society; (C) Real data and linear fitting of saturation temperature vs. U2. Reproduced with permission^[131], Copyright © 2022 American Chemical Society; (D) Spontaneous healing characteristics of the fabricated SHH. The applied voltage was 1.5 V for healing. Digital images of SHH before cutting, after cutting, after 5 min of applying voltage, and during twisting of the healed sample. Optical microscope images of SHH (i) with cutting marks and (ii) after 5 min of applying voltage. Reproduced with permission^[132], Copyright © 2023 Springer Nature; (E) UV-Vis-NIR absorption spectra of nanofibers; (F) Time course plots of their temperatures under one-sun irradiation (1,000 W·m^-2); (G) The real-time temperature of the simulated skin was covered by if-Cloth, RC nanofibers and a white cotton cloth over 3 h under sunlight in Stockholm, Sweden. (E-G) are reprinted with permission from Ref.^[133], Copyright © 2023 Springer Nature; (H) The contact angle measurements for Ti₃C₂T_x (MXene) and for Ti₃C₂T_x-TBA. Reproduced with permission^[134], Copyright © 2021 American Chemical Society; (I) Oxidation times of 1-180 days. Reproduced with permission^[135], Copyright © 2025 Elsevier; (J) Schematic illustration of the energy textile prototype containing the aYSC device. Some examples showing that the energy textile prototype can power an LED. Reproduced with permission^[31], Copyright © 2018 John Wiley and Sons; (K) Schematic illustration of the large-scale production of MXene-coated yarns and 3D knitted energy storage devices. Reproduced with permission^[136], Copyright © 2020 Elsevier. IR: Infrared; SHH: spontaneously self-healing heater; UV: ultraviolet; NIR: near-infrared; RC: regenerated cellulose; TBA: tetrabutylammonium; aYSC: asymmetric yarn supercapacitor; LED: light-emitting diode; AgNWs: silver nanowires; BRU: biscrolled RuO₂/CNT yarn; BMX: biscrolled MXene/carbon nanotube yarn.

Chang et al. used electrospinning to create MXene/cellulose smart textiles for photothermal synergistic applications^[133]. Figure 10E and F display their temperature-time curves and UV-Vis-near-infrared (NIR) absorption spectra under single-sun irradiation. These materials demonstrated dual functionality for solar-driven water treatment and personal thermal control, rising 5.6 °C more than cotton garments under outdoor sunlight [Figure 10G] while exhibiting effective water evaporation rates. Additionally, MXene’s strong near-infrared absorption creates opportunities for uses in biomedical and specialty textiles, including infrared stealth and photothermal therapy^[137-139].

Other performance

In addition to their remarkable conductivity, MXene materials’ distinct surface chemistry gives them superior solvent dispersibility and processing compatibility, providing a vital basis for their use in a variety of fiber production processes and intelligent textile integration. The surface of MXene produced by wet etching techniques has a large number of polar functional groups. Through surface chemical control, these groups not only facilitate the generation of stable colloidal dispersions in aqueous mediums but also permit excellent dispersion in a variety of organic solvents. Research shows that MXene exhibits low dispersibility in nonpolar solvents but forms uniform, persistent dispersions in extremely polar solvents including ethanol, dimethyl sulfoxide, and N-methylpyrrolidone directly verifying the polar nature of its surface end groups^[139]. Researchers have created several methods to control MXene dispersibility in order to fulfill the demands of high-concentration processing. Ionic intercalation was successfully used by Zhang et al. to modify surface hydrophobicity [Figure 10H], greatly increasing dispersion concentration in organic phases^[134]. As of right now, self-supporting MXene colloidal materials with solid contents as high as 19.4 weight percent have been effectively created. These materials include internal contained water, which allows them to preserve conductivity similar to that of freshly manufactured MXene while preserving good redispersibility. This invention offers a unique way to store, transport, and process the material on a large scale^[140].

However, one major issue limiting MXene’s practical use is its long-term stability under standard settings. Reduced conductivity and structural integrity result from oxidative deterioration, which is easily triggered by exposure to water and oxygen conditions. The material’s service life is prolonged and the oxidation process is effectively delayed by encapsulation with organic solvents to isolate moisture^[135]. Another successful tactic for improving stability is the creation of composite materials. For example, as Figure 10I^[135] illustrates, combining MXene with AgNWs to create an interlocking network structure not only greatly improves the tensile characteristics and interfacial bonding strength of the composite fibers but also significantly increases the system’s overall oxidation resistance.

MXene-based fibers show outstanding compatibility with textile manufacturing processes for end-use applications. Early research has demonstrated the viability of integrating MXene-based fibers onto textile substrates using conventional methods such as hand sewing [Figure 10J], knitting, or embroidery^[31,141]. This field has progressed to industrial-scale pilot production in recent years. Automated weaving of a variety of materials, such as MXene/polyurethane (PU) hydrospun fibers and MXene-coated cotton fibers, has been made possible using industrial-grade computerized circular knitting machines. Figure 10K displays schematic schematics of 3D-knitted energy storage devices, illustrating the capacity to create thick or porous fabric structures in accordance with design specifications^[121]. Precise design of intricate textile structures and useful patterns is made possible by this interoperability with scalable, automated textile manufacturing. It greatly speeds up the transition of MXene-based smart textiles from lab research to real-world applications by creating a strong industrial foundation for the development of high-performance, wearable textile electronics^[136].

Wet spinning

The most promising mainstream method for producing continuous, high-performance MXene-based conductive fibers on a big scale is wet-spinning. As shown in Figure 11A^[37,143], its fundamental idea is to assemble two-dimensional MXene nanosheets, which have exceptional intrinsic properties into one-dimensional macroscopic organized structures via a phase transition directed by hydrodynamics. To ensure effective structure transfer from the nanoscale to macroscopic fibers, this procedure must be implemented with systematic control over the rheological behavior of the spinning precursor, liquid crystal phase transitions, and solidification kinetics.

Figure 11. (A) Fabrication of MGP-T fiber via continuous wet spinning and thermal drawing, and the formation of MXene-based textiles. Reproduced with permission^[119], Copyright © 2022 Springer Nature; (B) Relationship between the MXene ink concentration (volumetric and mass) and the flake size (lateral size and aspect ratio) for isotropic to nematic phase transformation based on theoretical calculations. The stars represent the theoretical LC transition concentrations for L-Ti₃C₂ and S-Ti₃C₂ dispersions based on their average flake size (3.1 μm and 310 nm, respectively); (C) POM images of aqueous L-Ti₃C₂ and S-Ti₃C₂ inks at various concentrations demonstrating the nematic LC formation based on flake size and concentration; (D) Viscoelastic behavior of L-Ti₃C₂ at a concentration of 26.5 mg·mL^-1 (red solid symbols) and S-Ti₃C₂ at a concentration of 150 mg·mL^-1 (black hollow symbols); (E) Frequency dependency on G’/G” ratio for the L-Ti₃C₂ and S-Ti₃C₂ MXene inks; (F) Cross-sectional SEM images of LC MXene fibers using S-Ti₃C₂ flakes produced in an acetic acid bath. Schematic illustration of the fast coagulation mechanism when acetic acid was used as the coagulation bath (above). Cross-sectional SEM images of S-Ti₃C₂ fibers produced in the chitosan bath. Schematic illustration of the slow coagulation mechanism when chitosan was used as the coagulation bath (below). (B-F) are reprinted with permission from Ref.^[33], Copyright © 2020 American Chemical Society; (G) digital photograph of a ≈ 100-m-long MXene/PU fiber. Reproduced with permission^[142], Copyright © 2020 John Wiley and Sons; (H) Nitrogen adsorption-desorption isotherm of MAF with different dispersion concentrations. The inset is the corresponding specific surface area; (I) Cross-section and surface morphologies of the Ti₃C₂T_x MXene aerogel fibers. (H and I) are reprinted with permission from Ref.^[28], Copyright © 2021 John Wiley and Sons; (J) Cross section SEM images of overall fracture surface and MXene core; (K) Typical tensile stress-strain curves; (L) Proposed fracture process of ANF@M fibers. (J-I) are reprinted with permission from Ref.^[114], Copyright © 2022 Springer Nature. MGP-T: MXene-glutaraldehyde-polyvinyl alcohol fiber after thermal drawing; LC: liquid crystalline; POM: polarizing optical microscope; SEM: scanning electron microscope; PU: polyurethane; MAF: MXene aerogel fiber; ANF: aramid nanofiber; PVA: polyvinyl alcohol; MG: MXene-glutaraldehyde fiber; ET: electrothermal; EMI: electromagnetic interference.

The creation of MXene spinning solutions (or “inks”) with optimal rheological characteristics is the main requirement for attaining effective, continuous spinning. Excellent hydrophilicity is provided by the many -OH, -O, and other functional groups on the surface of MXene nanosheets, allowing for stable dispersion in polar solvents such water and N,N-dimethylformamide^[144]. MXene nanosheets go through a phase transition from isotropic to nematic liquid crystalline states when the dispersion concentration rises above a certain threshold. The Onsager rigid rod theory, which was first developed for rigid rod-like particles and then expanded to disc-shaped particles like MXene and GO, can quantitatively explain this behavior. According to the theory, the free energy of the system is dominated by the repulsive volume effect, which is the volume of space that a particle’s center is pushed from by the existence of another particle. The isotropic phase is preferred at low concentrations because the entropy gain from random orientation exceeds the entropy loss from repulsive volume. The repulsive volume per particle rises with concentration, increasing the entropy cost of random orientation. When a threshold concentration is exceeded, the system partially orients particles to increase entropy while simultaneously decreasing repulsive volume and increasing overall entropy. There is no need for interparticle attraction because this transition is solely entropy-driven.

The aspect ratio of the particle has an inverse relationship with the critical concentration (φ_c) for this phase transition. The diameter-to-thickness ratio is the important aspect ratio for disc-shaped MXene sheets. Higher aspect ratios from larger sheet sizes translate into lower φ_c values. This suggests that lower mass concentrations can be used to reach the nematic phase [Figure 11B and C]. Nematic phase production is difficult in real-world applications because smaller sheets necessitate much higher concentrations to accomplish orderly packing, frequently approaching solubility limits. A logical foundation for choosing MXene flake size in fiber spinning is provided by this theoretical framework. Larger flakes in MXene dispersions are preferred because they can create a fully formed nematic phase at concentrations that are appropriate for experimentation. Achieving high-quality fiber spinning and subsequent orientation control requires this^[33,139].

The rheological conditions for spinning are supported by Onsager theory, which goes beyond phase behavior. A nematic dispersion that is appropriate for wet spinning needs to behave like a viscoelastic gel, which is defined by having a storage modulus (G’) that is higher than the loss modulus (G”) and being stable over a wide frequency range (G’/G” > 1, Figure 11D and E). The ordered structures created inside the rotating orifice are guaranteed to be maintained throughout solidification because to this mechanical integrity. As a result, Onsager theory not only clarifies why MXene layers spontaneously organize into a nematic phase, but it also shows how this phase transition may be used to create processable inks, which in turn converts ordered structures at the nanoscale into macroscopic fiber characteristics.

The key to wet spinning is to use chemical bath design and fluid shear forces in concert to “freeze” and further reinforce the ordered structures within the solution once a spinning solution with desirable liquid crystallinity and rheology has been obtained. The microstructure and characteristics of the fibers are determined by the solvent exchange kinetics, which are directly influenced by the composition of the coagulation bath. For example, Zhang et al. found that MXene nanosheets instantly solidified and formed a porous, open, loose network when pure acetic acid was used as the coagulation bath due to rapid solvent exchange. The resultant fibers had a conductivity of about 4,048 S·cm^-1, which was relatively low. The cross-sectional morphology of the fiber in Figure 11F illustrates how the slower exchange rate in a chitosan solution, on the other hand, allowed the nanosheets to completely rearrange and tightly pack before solidification, resulting in fibers with a more compact structure, smaller diameter, and significantly enhanced conductivity (approximately 7,748 S·cm^-1)^[33]. Multivalent cations (such as Mg²⁺, Ca²⁺, and NH₄⁺) can be added to the solidification bath to further improve the mechanical and electrical characteristics of the fibers. Through electrostatic cross-linking, these ions create strong interlayer connections and efficiently protect the negative charges on the MXene sheet surfaces, accelerating the creation of gel fibers while enhancing strength and conductivity. While complete fiber creation was impossible without ionic crosslinking, Li et al. showed that fibers spun from Mg²⁺-containing solutions attained tensile strengths up to 118 MPa and electrical conductivities of 7,200 S·cm^-1[145]. Another crucial stage in post-processing for fiber structure optimization is axial mechanical stretching. Internal cavities are eliminated and packing density and orientation are increased as a result of the tensile force pushing nanoplates farther along the fiber axis. Young’s modulus and electrical conductivity, for instance, are around 1.5 times higher in tensile-oriented MXene fibers than in non-stretched fibers^[26].

Through additional process condition optimization and creative structural design, researchers have diversified MXene fiber architectures and specifically improved their attributes based on the previously mentioned understanding of the spinning mechanism. Early research concentrated on increasing spinnability by combining MXene with hydrophilic nanomaterials (such as GO, CNTs) or polymers [such as regenerated cellulose (RC), PU] [Figure 10G]. Nevertheless, conductivity improvement was constrained by the use of insulating or low-conductivity matrices^[142]. Zhang et al. developed continuous wet spinning utilizing pure MXene liquid crystal dispersions, advancing the technology into high-purity, high-performance spinning, as their understanding of MXene’s nematic liquid crystal behavior deepened^[33]. Building on this basis, customized production of multifunctional fibers is made possible by carefully regulated spinning conditions. For example, Li et al. created MXene aerogel fibers with porosities greater than 96.5% using Ca²⁺-induced fast gelation in conjunction with supercritical CO₂ drying (N₂ adsorption-desorption isotherm shown in Figure 11H)^[28]. They are appropriate for applications like flexible sensing because they maintain the conducting network while displaying exceptional flexural elasticity and high specific surface area (fiber cross-section and surface morphology shown in Figure 11I). As seen in the cross-sectional SEM image in Figure 11J, Liu et al. created core-shell structured fibers with MXene as the conductive core and ANFs as the protective shell in order to address MXene’s vulnerability to oxidation and degradation^[114]. In addition to acting as a physical barrier, the ANF shell’s strong interfacial contacts with the MXene core improve the fiber’s mechanical strength and environmental stability [Figure 11K and L].

A unique set of key parameters that are essentially different from those of graphene are involved in the wet spinning of MXene fibers. There are two effects of sheet size: larger MXene sheets (e.g., lateral dimensions of 3.1 μm) encourage the formation of nematic liquid crystals at lower concentrations and result in higher conductivity (7,713 S·cm^-1); smaller sheets (310 nm) allow for finer diameter control but show more edge defects and less orientation^[33,128]. Continuous manufacturing of MXene/PU composite fibers longer than 100 meters has been accomplished, despite the fact that the spinning speed for pure MXene fibers is still underquantified^[143]. Weaving experiments on an industrial scale show speeds similar to graphene systems. It has been shown that stretch ratio and strain during stretching greatly improve performance: post-spinning stretching results in a 1.5-fold improvement in Young’s modulus and conductivity, which is explained by optimized interlayer orientation and decreased porosity^[26]. The solidification bath’s chemical characteristics are crucial for MXene: a chitosan bath inhibits ion exchange, resulting in dense stacking and raising conductivity to 7,748 S·cm^-1, whereas acetic acid causes quick solidification but creates a porosity network (4,048 S·cm^-1)^[33]. Interlayer bridging is further improved by multivalent cation crosslinking (Mg²⁺, Ca²⁺, and NH₄⁺), which raises conductivity to 7,200 S·cm^-1 and tensile strength to 118 MPa^[145]. Post-treatment parameters are very different from those for graphene: because of the substantial oxidation concerns, high-temperature annealing is rarely used. Rather, the preferred methods are room-temperature drying, supercritical CO₂ drying (appropriate for aerogel fibers with porosities > 96.5%^[28]), or protective encapsulation (such as ANF encapsulation^[58]). In contrast to graphene, environmental control - such as oxygen-free environments - is a crucial extra factor in preventing oxidative deterioration when spinning. The main obstacles in the production of modern MXene fiber are the interdependent interactions between these factors, especially the trade-offs between flake size, spinnability, and ultimate conductivity.

Other fabrication methods

While wet spinning shows great promise for producing high-performance continuous MXene fibers, other techniques including coating, electrospinning, and dual-winding provide a variety of efficient supplementary methods to satisfy the needs of different smart textile applications. These techniques take advantage of their special advantages in structural diversity, material composite shapes, and process simplicity.

Method of coating
Scalable integration is made possible by the simple, inexpensive coating process. Its fundamental idea is to quickly impart conductivity and certain functions by directly loading MXene dispersions onto pre-existing fiber, yarn, or fabric substrates via dip-coating, drop-casting, or spraying processes. Figure 12A depicts a schematic of the impregnation coating procedure. The creation of a strong interface binding between MXene nanosheets and the substrate material and the development of a stable MXene dispersion are essential for the effective application of this technique.

Figure 12. (A) Schematic of the dip coating process. Reproduced with permission^[146], Copyright © 2024 American Chemical Society; (B) Flake-size distribution of as-synthesized (L-Ti₃C₂) and probe sonicated (S-Ti₃C₂) MXene dispersions. First coating step (fiber coating) requires using S-Ti₃C₂ MXene flakes, which enables MXene penetration into the fiber level. Second coating step (yarn coating) uses L-Ti₃C₂ MXene flakes to cover the yarn surface to provide high conductivity. Reproduced with permission^[121], Copyright © 2019 John Wiley and Sons; (C) XPS N1s core level spectra of pristine nylon fibers and MXene-coated nylon fibers. Reproduced with permission^[136], Copyright © 2020 Elsevier; (D) Schematic illustration of electrospinning procedure for MPC textiles synthesis. Reproduced with permission^[147], Copyright © 2022 Springer Nature; (E) MXene/PVDF-HFP 2.5 wt% concentration SEM images. MXene/PVDF-HFP 3.5 wt% concentration film SEM image with droplets. Reproduced with permission^[148], Copyright © 2024 Elsevier; (F) four-point probe electrical conductivity measurements of MXene/nylon nanoyarns produced with different MXene concentrations and flake sizes. Reproduced with permission^[149], Copyright © 2020 John Wiley and Sons; (G) Piezoelectric charges of undoped fiber and MPC fiber on M5 site in response to an adult’s (75 kg) toe pressing; (H) Signals profiles for gait monitoring. (G and H) are reprinted with permission from Ref.^[147], Copyright © 2022 Springer Nature; (I) Schematic of the fabrication process for BMX yarns; (J) SEM images showing the surface and cross-section morphologies of the BMX yarn containing 97.4 wt% MXene; CV curves of a freestanding aYSC device measured at (K) different potential window at a scan rate of 10 mV·s^-1 and (L) at different scan rates at 1.5 V. (I-L) are reprinted with permission from Ref.^[31], Copyright © 2018 John Wiley and Sons. XPS: X-ray photoelectron spectroscopy; MPC: MXene-enabled piezoelectric composite; PVDF: polyvinylidene fluoride; HFP: hexafluoropropylene; SEM: scanning electron microscope; BMX: biscrolled MXene/carbon nanotube yarn; CV: cyclic voltammetry; aYSC: asymmetric yarn supercapacitor; PMN: lead magnesium niobate; PT: lead titanate; CNT: carbon nanotube.

MXene has a negative charge in aqueous solutions due to the abundance of oxygen-containing functional groups on its surface, such as -O and -OH. Tight adherence is thus made possible by MXene’s easy formation of high electrostatic attraction and hydrogen bonding interactions with positively charged substrates or those rich in polar functional groups (e.g., -OH, -COOH, -NH₂). For example, MXene creates a three-dimensional electrical network by penetrating into the interstitial spaces within yarns [Figure 12B] and uniformly coating the surface of individual fibers on both synthetic and natural fibers, such as nylon and cotton^[121]. Additionally, as seen in Figure 12C, X-ray photoelectron spectroscopy (XPS) investigation suggests that -OH groups on the MXene surface may establish Ti-N covalent connections with amide groups in nylon fibers, greatly increasing interfacial bonding strength and durability^[136]. On hydrophobic substrates with low surface energy and few active sites, like polyester or silver-plated nylon, MXene, however, shows poor adherence. Therefore, in order to improve interface compatibility with MXene, surface modification is usually necessary. (1) Polymeric binders like PEDOT:PSS, which function as “bridges” to simultaneously adhere MXene and the substrate, improve coating uniformity and bond strength; (2) Chemical coupling, such as modification with silane coupling agents to graft active groups onto the substrate surface, enabling electrostatic bonding with negatively charged MXene; and (3) Physical activation, such as oxygen plasma treatment, which introduces oxygen-containing polar groups onto the substrate surface to improve hydrophilicity.

Process compatibility and functional design flexibility are two clear benefits of the coating approach. Simple cyclic coating cycles can provide precise control over MXene loading. For example, Bi et al. created a high-speed continuous dip-coating method that orients MXene sheets on nylon fiber surfaces using shear forces^[146]. This technique shows the coating method’s potential for high-performance fiber mass manufacturing by enabling wide-range MXene loading control with a single coating pass and obtaining linear resistivity as low as ~10 Ω·cm^-1. To combine several uses, more intricate multilayer composite coating patterns have been created. In order to create multifunctional hybrid aerogel fibers with effective electromagnetic shielding, compressible resilience, and adjustable shielding mechanisms, Jia et al. progressively constructed PEDOT:PSS and MXene “dual coatings” on an ANF scaffold^[150]. Moreover, multifunctional integration like photothermal response and superhydrophobicity is made possible by the sequential deposition of adhesive, conductive, and functional layers on fibers with irregular cross-sections, indicating the coating method’s great potential for building application-specific smart fiber systems^[59].

Despite these benefits, the resulting conductive layers’ abrasion resistance and long-term service stability are still difficult to achieve, especially in situations where coatings may peel or break due to frequent bending, stretching, or washing. Optimizing coating procedures and implementing suitable encapsulating protection can result in significantly increased durability.

Electrospinning
Using high-voltage electric fields, electrospinning is a flexible method for creating continuous polymer fibers with sizes ranging from nanometers to micrometers. MXene/polymer composite nanofiber membranes or yarns can be made in a single step by dispersing MXene nanosheets in polymer solutions such polyvinyl alcohol (PVA), poly (ethylene oxide), polyacrylonitrile (PAN), or chitosan. MXene layers are usually encased or embedded in ultrafine fibers during this process, creating three-dimensional fiber networks with high specific surface area. Ion adsorption and surface Faraday reactions are made easier by this shape, suggesting possible uses in flexible electrodes and sensing. Figure 12D^[151] shows a schematic of the procedure. However, traditional electrospinning confronts two key obstacles when manufacturing fibers with high MXene content. On one hand, MXene’s high conductivity causes rapid charge dissipation in the spinning jet, leading to process instability or even short circuits. However, MXene has a tendency to aggregate in the polymer matrix, especially at high concentrations, which makes uniform dispersion challenging. This limits electrochemical accessibility and overall conductivity by producing non-uniform fiber shape and bead-like features [Figure 12E]^[148].

Researchers have created a number of cutting-edge methods to get around these restrictions. By substituting a solidification bath for the traditional collector, Levitt et al.’s “one-step bath electrospinning” technique^[149] stabilizes the jet process of highly conductive spinning solutions [Figure 12F]. Creating core-shell structures is another tactic. In order to reduce reliance on intrinsic fiber conductivity while retaining flexibility, Shao et al. built a core-shell architecture using conductive yarn as the core and MXene composite fibers as the shell^[152]. Post-treatment of composite fibers is another important way to improve performance. Recently, Su et al. introduced MXene into piezoelectric polymer devices^[147]. They greatly increased fiber piezoelectric responsiveness by promoting crystalline phase transitions and improving polarization through interactions between MXene surface functional groups and polymer chains. Applications such as human motion monitoring demonstrate the potential of this method [Figure 12G and H]. In the meantime, Chang et al. successfully created composite fiber fabrics that combined mechanical stability and high photothermal conversion efficiency by encasing MXene within a RC matrix^[133]. These materials are appropriate for solar-powered water evaporation and personal heat management due to their just 0.1 mm thickness. This study provides new insights for creating multifunctional smart fabrics by demonstrating how encapsulation structures efficiently protect MXene from environmental deterioration, improving its light absorption capability and cycling stability in humid circumstances.

The double-winding approach
The double-winding method utilizes pre-fabricated stretchable CNT films as a scaffold and conductive pathway to assemble nanomaterials like MXene, which are difficult to directly spin into macroscopically continuous yarns^[31,153]. Figure 12I depicts the process flow diagram, which consists of two essential steps. First, using techniques like drop casting or impregnation, MXene dispersions are evenly deposited onto stretched CNT films. Subsequently, the loaded films undergo mechanical twisting, causing them to spiral-contract and consolidate into yarns. During this process, MXene nanosheets are effectively captured and encapsulated within the helical internal voids or “corridors” formed by the CNT network^[153]. Cross-sectional and longitudinal SEM photos in Figure 12J show that successful confinement of MXene layers within the yarn’s helical structure is confirmed by scanning electron microscopy examination. In order to build high-performance fiber-based electrochemical devices, this architecture creates a special open microenvironment. The CNT network offers continuous electronic conduction pathways and crucial mechanical support, and the numerous interlayer voids enable quick electrolyte permeation and effective ion transport^[31].

The capacity to obtain exceptionally high active material loading (up to 95-98 wt%), which allows the electrochemical performance of the composite yarn to approach that of pure MXene materials, is the method’s greatest benefit. Research shows that the resulting MXene/CNT composite yarn has exceptional energy storing properties. For example, the double-wound yarn supercapacitor described by Wang et al. fared better in specific capacitance, energy density, and power density than the majority of modern fiber-based devices^[31]. Further research by Yu et al. showed that this technique successfully combines the highly conductive network of CNTs with the pseudocapacitive characteristics of MXene to produce fiber electrodes with exceptional performance [Figure 12K and L]^[153]. Double-wound yarns have a wide range of potential applications in fuel cell electrodes, artificial muscles, and energy storage devices due to their distinctive structure and high loading capacity^[154].

However, there are intrinsic obstacles to this technology’s further development. First, its effectiveness is largely dependent on expensive, high-quality CNT scaffold materials (such as oriented arrays or films). Additionally, the size of the prefabricated CNT bodies limits the continuous length of the final yarn, which prevents large-scale, inexpensive manufacture. Second, more thorough and methodical research and assessment is needed to determine the biocompatibility and long-term biosafety of CNT materials for wearable textile applications in direct skin contact^[155]. Therefore, even though the double-winding method is indispensable for producing ultra-high nanomaterial loading and creating specialized fiber structures, its future development is still dependent on advances in low-cost CNT preparation methods, process integration and optimization, and additional clarification of biosafety issues.

A methodical comparison of MXene and graphene fibre preparation techniques

Although there are several fabrication methods for both graphene and MXene fibers, there are notable variations in each method’s scalability, cost, fiber characteristics, and applicability for a certain application. Wet spinning, coating, electrospinning, dry/dry jet spinning, and dual-winding/template-assisted chemical vapour deposition are the five most representative preparation techniques. Table 3 provides a thorough side-by-side comparison of these techniques along important practical dimensions.

Biosensing and healthcare monitoring

A crucial material basis for building flexible sensing platforms that can continuously and in real time monitor environmental and human physiological signals is provided by the integration of MXene-based conductive fibers into textiles. Physical, chemical, and biological signals are captured via its sensing method, which is based on reversible changes in conductive pathways within the fiber network in response to external stimuli (such as strain, pressure, or molecule adsorption).

MXene fibers use their high conductivity and strain sensitivity in physiological and motion signal monitoring to monitor a variety of activities, including joint movements and breathing. For example, Cheng and Wu used wet spinning to create Kevlar/MXene composite fibers that were incorporated into smart masks for high-sensitivity respiratory monitoring^[143]. Seyedin et al. used MXene/PU core-sheath fibers made by coaxial wet spinning to detect large-range movements such as limb joints^[143]. These fibers’ exceptional flexibility and endurance allowed for joint motion monitoring when they were woven into textile sleeves. Additionally, Zhang et al. showed exceptional flexibility in composite nanofiber membranes made by electrospinning MXene nanosheets inside a polyvinylidene fluoride (PVDF) polymer matrix^[158]. Figure 13 A-C illustrates how these membranes can be put together to create devices that track different human movement positions. Microstructural design greatly improves the functional dimensions and performance metrics of MXene fiber sensors in terms of tactile and pressure sensing. For example, Pu et al. used layer-by-layer (LbL) self-assembly directly onto commercial PU monofilaments to create fibrous strain sensors^[159]. In order to create a multilayer sensing structure [AgNW/waterborne polyurethane (WPU)-MXene]₃, the fiber was alternatively dip-coated in AgNW/WPU dispersions and Ti₃C₂T_x MXene inks over the course of three cycles. Robust interfacial adhesion and uniform coating were guaranteed by the strong hydrogen bonding interactions among MXene, AgNWs, and WPU. The AgNW/WPU network’s slip-dominated deformation properties, which guarantee conductive path integrity under high strains, and the MXene layers’ crack-propagation-dominated behavior, which produces quick resistance changes, work in concert in this design. This sensor’s large operating range (0%-100%) and ultra-high strain coefficient (GF value exceeding 1.6 × 10⁷ at 85%-100% strain) make it the perfect option for accurate motion recording^[159]. Through logical microstructural engineering, carbon-based materials have also shown remarkable sensing capabilities in parallel with MXene-based strain sensors. For example, Zhou et al. described a hierarchical carbon strain sensor that, by creating a crack-propagation-controlled conductive network, simultaneously achieves great sensitivity (range factor > 800) and an ultra-wide operational range (> 300%)^[160]. This work provides important insights for the ongoing optimization of fiber-based wearable electronics by illuminating how structural design concepts, similar to those used in MXene fiber sensors, can overcome the long-standing trade-off between sensitivity and stretchability. Moreover, by combining two different sensing systems into a single fabric system, Ma et al. created integrated “dual-sensing” smart textiles^[60]. They utilized traditional core-sheath yarn technology for tension sensing, which involves twisting conductive rGO/CNT-coated PAN fibers around a PU core filament to create helical core-sheath yarns. Under tension, the contact resistance between the twisted conductive fibres monotonically decreases, generating a negative pressure-resistance effect. Two layers of MXene-coated conductive fabric are positioned between a three-dimensional spacer fabric filled with Ecoflex^TM elastomer to form the capacitive sensor that makes up the pressure-sensing component. The sensor has compressibility and quick recovery because to this three-dimensional spacer construction. Through array weaving, both sensors are seamlessly incorporated into knitted clothing that is extremely stretchy. As shown in Figure 13D-F^[60], the system concurrently detects and distinguishes tensile strain (up to 90%) and pressure (up to 110 kPa) without mutual interference by independently monitoring resistive changes in the core-sheath yarn and capacitive fluctuations in the pressure sensor.

Figure 13. (A) Schematic of piezoelectric electronic devices mounted on the finger, wrist, arm and sole of feet for real-time sensing and energy harvesting; (B) Current output signals after rectification under 1.5 Hz and 64 kPa pressure. Inset: amplified diagram of current signals before and after rectification; (C) Dynamic output voltage for different hand area bends. (A-C) are reprinted with permission from Ref.^[156], Copyright © 2023 Springer Nature; (D) (top) Schematic of the seamless E-textile with inset pictures of the stretching, bending, and twisting capabilities. (bottom) Schematics for dual tactile (pressure) and tension (stretch) sensing for a taekwondo suit. Pink insets represent the pressure sensing for a knee upon striking and blue insets represent the stretch sensing for the textile on the back of the taekwondo suit when the athlete stretches forward; (E) Stress-strain curves of core-sheath yarns obtained using a tensile testing machine under an elongation speed of 500 mm·min^-1 with an initial length of 5 cm; (F) Relative capacitance response and sensitivity of the pressure sensor. (D-F) are reprinted with permission from Ref.^[60], Copyright © 2021 Elsevier; (G) Schematic diagram of the acoustoelectric device and different frame hole sizes along with the sound test setup. Reproduced with permission^[157], Copyright © 2025 American Chemical Society; (H) Schematic illustration of pseudo-streaming behavior occurred at wet/dry interface and the mechanism of current generation; (I) Real-time Voc and HEG surface temperature under 1 standard sun radiation; Infrared image of HEG under 1 standard sun radiation; (J) Schematic diagram of devices for flexible wearable electronics; Schematic diagram and picture of HEGs driven an electronic watch. (H-J) are reprinted with permission from Ref.^[158], Copyright © 2025 Elsevier. HEG: Hydroelectric generator; PLA: polylactic acid.

MXene’s huge specific surface area and abundance of surface functional groups provide it sensitive resistance responses and a significant adsorption capacity for gas molecules and biomarkers in the areas of chemical and biomolecular sensing. Lee et al. created MXene/rGO hybrid fibers for ambient gas monitoring that showed excellent signal stability after 2,000 bending cycles and a far better response sensitivity to ammonia (NH₃) at room temperature than single-component fiber sensors^[37]. MXene sensors built on flexible natural rubber substrates provide a viable method for non-invasive breath analysis by detecting volatile organic compounds like ethanol^[161]. Additionally, MXene has been investigated for use in biomedical sensing, including the integration of electrospun fibers for glucose monitoring^[162]. Nevertheless, the majority of these biosensors are still in the lab’s proof-of-concept phase. Before practical implementation is possible, important issues like selectivity, long-term stability, signal drift, and biocompatibility in complicated wearable contexts must be methodically resolved.

Adaptable energy harvesting and storage

Because of their high intrinsic conductivity and abundance of electrochemical active sites, MXene-based conductive fibers emerge as an ideal material platform for building fiber-based energy storage and harvesting systems, meeting the pressing need for flexible, lightweight, and integrable power units in wearable electronics. High volumetric capacitance and metallic-like conductivity are characteristics of MXene materials, such as Ti₃C₂T_x^[21]. Through techniques like wet spinning, these characteristics can be successfully transmitted to macroscopic fibers. For example, Zhang et al. generated pure Ti₃C₂T_x MXene fibers with a volumetric capacitance of about 1,265 F·cm^-3 and a conductivity as high as 7,750 S·cm^-1, exceeding several fibers made from other two-dimensional materials (e.g., rGO) in capacitive performance^[33].

However, pure MXene fibers frequently have restricted mechanical characteristics. Researchers have created two primary approaches to attain performance balance in order to overcome this: coatings and composites. Guo et al. pioneered the preparation of MXene/CNT composite fibres via hydrospinning, employing liquid-crystalline CNTs as a scaffold to embed MXene nanosheets and prevent their re-stacking^[163]. This hybrid fiber functions as a porous substrate with excellent conductivity. A core-shell structured MnO₂@MXene/CNT fiber system was then created by electrochemically depositing a MnO₂ shell onto the surface of the pre-fabricated MXene/CNT fibers under carefully regulated conditions (1.3 V, 20 min). In this hierarchical structure, the MnO₂ shell contributes strong pseudocapacitance through quick Faradaic reactions, while the conductive MXene/CNT core layer offers effective electron transport and mechanical support. A volumetric capacitance of up to 371.1 F·cm^-3 is achieved by this synergistic combination, which is a 46.6% improvement over virgin MXene/CNT fibers. After 10,000 charge-discharge cycles, symmetrical fiber-shaped supercapacitors made of these fibers maintain 86.3% of their original capacitance^[163]. Coating techniques show more promise for scalability. Commercial fibers like cotton yarn can be coated with MXene dispersions to produce functional yarns with conductivities of about 440 S·cm^-1. In solid-state electrolytes, fabrics made from these yarns can have surface capacitances of up to 760 mF·cm^-1[121]. These yarns have been successfully incorporated into fabric supercapacitor prototypes that can power sensor systems through automated knitting platforms^[136]. Moreover, quasi-solid-state magnesium-ion supercapacitors built using gel electrolytes and Mg²⁺-crosslinked Ti₃C₂T_x fibers provide information for creating new, secure wearable energy storage devices^[145].

MXene fibers are used in energy harvesting to transform scattered environmental energy sources, including mechanical, light, and thermal energy, into electrical power. Mokhtari et al. created a nanogenerator by combining PVDF-trifluoroethylene (TrFE) electrospun fibers with MXene flakes, utilizing the triboelectric effect^[157]. As shown in Figure 13G, this device produces an output power density of 19 mW·cm^-3 by converting low-frequency acoustic vibrations (< 200 Hz) into electricity. Simultaneously, MXene’s highly effective broadband light absorption and localized surface plasmon resonance effect provide remarkable photothermal conversion capabilities, allowing coated fabrics to show antibacterial qualities and quick heating under sunshine. More significantly, MXene fibers are also very effective materials for joule heating. MXene-fiber textiles can serve as sustainable heat sources in addition to active thermal management thanks to their dual photothermal and electrothermal conversion capabilities. They can generate electricity from gathered solar energy or heat from human waste when combined with flexible thermoelectric generators, opening the door for self-powered smart textile systems. Based on cellulose nanocrystal-MXene composite cotton fabric, Yang et al. created a flexible hydroelectric generator, according to preliminary research^[158]. Continuous power generation under moisture exposure is made possible by its current generating method, as seen in Figure 13H. The photothermal impact of the MXene further improves output performance under illumination [Figure 13I], showing promise for using human or environmental perspiration as a source of energy for wearable technology [Figure 13J].

Thermal management

With their very effective and adjustable electrothermal, photothermal, and infrared radiation capabilities, MXene-based fibers offer a vital material basis for creating adaptive thermal management smart textiles that can react dynamically to human and environmental demands. Joule heating, photothermal conversion, and infrared radiation regulation, which correspond to active heating, passive solar heating, and radiative thermal management modes, respectively. They are the three main components of their thermal management methods.

When it comes to Joule heating, MXene’s low transverse thermal conductivity and strong in-plane electrical conductivity allow for effective and consistent electrothermal conversion even at low applied voltages^[164]. For example, MXene/PVA composite fibers made by hydrospinning and thermal stretching show great promise as wearable flexible heating materials because they provide fine steady-state temperature control within 90-130 °C by voltage modulation and accomplish rapid heating (>10 °C/s) at 3-5 V^[119]. Building MXene conductive networks on traditional textile substrates is a more workable approach. For example, at safe voltages of 6-12 V, MXene put onto cotton, polyester, or silk surfaces by spraying or impregnation techniques produces notable and consistent heating effects^[164,165]. Surface temperatures can reach 80-150 °C while maintaining the fabric’s elasticity, breathability, and wear comfort, as seen in Figure 14A^[165,166]. These active heating materials have promising uses in outdoor sports, arctic activities, and customized precision heating.

Figure 14. (A) Joule heating performances of silicone-coated M-textile. Reproduced with permission^[166], Copyright © 2018 John Wiley and Sons; (B) Temperature increase profiles of the RMFs under 0.33, 0.50, and 1.0 W of NIR light. Reproduced with permission^[167], Copyright © 2021 Springer Nature; (C) The room-temperature IR emissivity spectra of MXene coatings at a range of 1-25 μm. Dash lines show the comparison of solid solution MXenes. The shadows show the two atmospheric windows. Reproduced with permission^[168], Copyright © 2023 Elsevier; (D) Schematic illustrating the interaction of IR light with MXenes, and heat transfer mechanisms coupled to structure parameters in MXenes. Reproduced with permission^[169], Copyright © 2025 American Chemical Society; (E) IR images of skin covered by commercial textile and MXene-functionalized textile. Reproduced with permission^[170], Copyright © 2022 The American Association for the Advancement of Science; (F) Thermal emissivity and sunlight reflectivity of the pristine TPU and TPU/SiO₂ nanofiber mat. The yellow area denotes the spectra of solar irradiance and the blue area denotes the atmospheric window; (G) Schematic diagram illustrating the passive cooling effect and photograph showing the testing setup. (F and G) are reprinted with permission from Ref.^[171], Copyright © 2023 Elsevier; (H) Plots of EMI SE vs. different mesh grids and thicknesses of the 17-1.1-50 M textile; (I) Changes in resistance and EMI shielding performance after 5,000 cycles of bending; (J) Schematic for EMI shielding mechanism of C-PM e-textiles. (H-J) are reprinted with permission from Ref.^[114], Copyright © 2022 Springer Nature. RMFs: MXene nanobelt fibers; NIR: near-infrared; IR: infrared; TPU: thermoplastic polyurethane; EMI: electromagnetic interference; SE: shielding effectiveness; C-PM: crosslinked PVA/MXene; UV: ultraviolet; AM: air mass.

MXene (specifically Ti₃C₂T_x) shows broad-spectrum high absorption throughout the solar spectrum in photothermal conversion, notably in the near-infrared region. The effectiveness of photothermal conversion is further improved by its surface plasmon resonance effect. When exposed to simulated sunlight, MXene-coated fabrics can quickly heat up to nearly 50 °C. This characteristic gives textiles important photothermal antibacterial qualities in addition to enabling passive personal heating. For example, after 20 min of simulated sunlight exposure, MXene-loaded cotton garments showed over 95% suppression of Escherichia coli^[167] (Figure 14B shows the temperature rise trend under near-infrared light). Zuo et al. developed a multi-mode thermal management fiber system that can store and release thermal energy by further integrating MXene conductive/photothermal networks with phase-change materials (such as polyethylene glycol, PEG) to improve thermal management intelligence^[172]. This technology allows for better prolonged thermal comfort management by buffering microclimate temperature changes in the human body through material phase transitions during external temperature variations.

In terms of controlling infrared radiation, MXene type (e.g., Ti₃C₂T_x vs. Nb₂CT_x), stoichiometry, and microstructure can be changed to actively design MXene’s emissivity in the mid-infrared atmospheric window band [Figure 14C and D]^[169]. The emissivity of MXene can be adjusted between around 0.06 and 0.59^[168]. Low emissivity fabrics (such as Ti₃C₂T_x coatings as low as 0.06) efficiently reduce the loss of human thermal radiation, improving warmth in cold climates and facilitating infrared stealth [Figure 14E]. On the other hand, higher emissivity MXene fabrics facilitate the dissipation of human thermal radiation, which makes them appropriate for radiative cooling under hot conditions [Figure 14F and G]^[170,171].

Even though MXene-based fibers have several benefits for adaptive heat management, much of the present research is still in the lab. Three main issues need to be systematically resolved for practical application: the material’s resilience to repeated use and washing, its technical viability for large-scale integration with current textile manufacturing processes, and the upcoming difficulty of combining sensing and feedback control to create adaptive closed-loop systems. To further enhance their practical application, future research must seek synergistic innovation at the material, structural, and system levels.

EMI shielding and intelligent interactions

Smart textiles are facing more serious EMI problems due to the high integration of electronic devices and the extensive use of wireless communication technologies. Concurrently, maintaining consistent communication between their internal functional modules has emerged as a crucial obstacle. Because of their high conductivity, light weight, flexibility, and superior processability, MXene-based conductive fibers present a viable approach for building flexible EMI shielding fabrics and highly dependable interconnect circuits.

The main causes of MXene’s effective EMI shielding are multiple internal reflections, absorption losses brought on by its multilayer flake structure, and electromagnetic wave reflection brought on by its high conductivity. In addition to maintaining MXene’s inherent qualities, turning it into one-dimensional fiber shapes gives the material exceptional textile processing versatility. For example, Liu et al. created RC@MXene/GO core-shell fibers by coaxial wet spinning, where the robust MXene/GO shell greatly increased the mechanical robustness of the fiber^[114]. Mesh density can be used to effectively change the shielding efficiency (SE) of such fibers when they are woven into mesh structures. The SE value rises from roughly 8.4-19.0 to 26.5-32.9 dB when the mesh pitch is reduced from 3 to 1 mm. SE levels greater than 100 dB are made possible by additional multilayer stacking. EMI SE curves for various mesh thicknesses are shown in Figure 14H. Researchers created a method for direct functionalization on commercial fabric surfaces in order to enable scale production. Dense conductive coatings are created on fiber surfaces by repeatedly dipping cotton, linen, and other textiles into MXene dispersions. According to studies, the fabric exhibits exceptional environmental stability and longevity, achieving a SE value of roughly 80 dB after several immersion cycles and maintaining roughly 90% of its performance even after two years of storage^[173].

MXene-functionalized fibers operate as extremely dependable, flexible, elastic conductors that link functional modules including sensing, power supply, and display in smart textile system integration [Figure 14I]. Researchers created fibers with specific features to guarantee stable conductivity under extreme deformation. For example, MXene/AgNWs conductive layers were coated onto electrospun TPU nanofiber membranes by Zhang et al., who then precisely twisted the membranes into helical yarns^[174]. By utilizing interlayer interlocking effects between the conductive network and elastic nanofiber network, this structure allows the yarn to sustain high conductivity (1.12 × 10⁵ S·m^-1) even at 300% tensile strain. Additionally, multifunctional smart textile systems can be built to achieve synergistic operation of sensing, power supply, and shielding functions by combining MXene composite fibers (such as Kevlar/MXene fibers) with multimodal sensing and energy storage capabilities through knitting or sewing processes^[143]. Figure 14J shows the shielding method for EMI.

In conclusion, because of their exceptional mechanical flexibility, customizable surface chemistry, and high conductivity, MXene-based conductive fibers have become a key component for building next-generation multifunctional smart textiles. MXene fibers have advanced beyond simple conductivity to incorporate sensing, power delivery, thermal management, and electromagnetic shielding systems through scalable fabrication techniques like hydrospinning, coating, and electrospinning in conjunction with complex structural designs like multilayers, core-shell configurations, and spirals. This illustrates how widely they can be used in smart textiles. The fibers’ electrochemical performance, sensing sensitivity, heating efficiency, and electromagnetic shielding efficacy have all been significantly improved, clearly exhibiting their useful potential in wearable electronics. However, a number of crucial issues must be methodically resolved in order to move from laboratory prototypes to scalable, commercial products: long-term stability under challenging usage conditions (such as oxidation resistance and wash durability), process consistency and controllability in large-scale continuous production, performance optimization during multifunctional integration, and compatibility with current textile manufacturing processes. In order to further explore novel application models in cutting-edge situations like biomedical interfaces and human-machine interaction integration, future research should concentrate on integrated co-design spanning materials, structures, devices, and systems. This will propel the ongoing development of MXene-based smart textiles toward increased wearability, dependability, and usefulness.

Textile processing adaptability

Even though graphene and MXene-based fibers have made great strides in their inherent mechanical, electrical, and electrochemical qualities, their successful incorporation into commercial smart textiles ultimately depends on a feature that is less talked about but just as important: textile processing adaptability. This includes the fiber’s ability to maintain its functional qualities while withstanding mechanical, thermal, and chemical stressors that are encountered during standard textile manufacturing processes, including knitting, weaving, braiding, washing, and finishing. We suggest a multifaceted assessment framework built on four pillars: (i) spinnability and weavability; (ii) flexibility and bendability; (iii) mechanical robustness under cyclic deformation; and (iv) post-treatment compatibility, in order to close the gap between laboratory-scale fiber innovation and industrial-scale textile manufacturing. With a focus on the existing state and upcoming difficulties for graphene and MXene fibers, Table 4 provides a summary of this approach by mapping evaluation metrics to relevant empirical situations from the literature review.

Interfacial bonding and charge/stress transfer mechanisms

The essential area for charge carrier exchange and mechanical stress is the interface between graphene (or GO) and MXene. Depending on the type of interfacial bonding, synergistic mechanisms can be identified. The lowest interfacial temperature resistance and the strongest stress transfer capabilities are provided by covalent bonding. For example, conjugated covalent bridging structures are created at the margins of GO by the amidation reaction between amine-functionalized polymers and carboxyl groups, which simultaneously improves electrical conductivity and tensile strength^[63]. Similarly, carbonization-treated polydopamine-coated MXene/GO composites produce nitrogen-doped carbon bridge structures that significantly improve material mechanical integrity and rate performance^[177]. Multivalent cations (Ca²⁺, Mg²⁺, NH₄⁺) are used in ionic crosslinking as “ionic bridges” between surface negative functional groups (-COO^-, -O^-) on GO or MXene. This technique adds reversible sacrificial bonds to increase toughness in addition to densifying fibers by removing interlayer vacancies^[38,145,178]. In hydrated GO/MXene complexes, hydrogen bonding is common. Constrained water molecules create ordered hydrogen-bond networks between neighboring nanosheets, preserving parallel orientation throughout gelation and drying, according to Yang et al.^[36]. This important discovery helps to reduce internal flaws. π-π interactions take center stage when conjugated polymers (like PEDOT:PSS) or CNTs are added. The otherwise limited out-of-plane charge transfer in vertically aligned two-dimensional sheets is enhanced by these interactions, which create continuous electronic channels at heterogeneous interfaces^[176,177].

Nanoscale organization: pore volume, stacking, and orientation

The anisotropic properties of the fiber are determined at the nanoscale by the arrangement of individual nanosheets. Three basic structural patterns have been identified: in-plane conductivity and modulus are maximized by parallel alignment along the fiber axis. Shear-induced orientation during wet spinning, which is frequently aided by liquid crystal spinning slurries, is how this structure is accomplished^[15]. This design is further optimized by large-small flake hybridization, in which smaller GO flakes fill interstitial spaces to increase density and decrease electron scattering, while bigger flakes form a continuous directed framework^[15,50]. Aligned transversely to the fiber axis, perpendicular orientation creates open nanoconductive routes that facilitate quick ion transport, which is essential for high-rate electrochemical energy storage. Guan et al. showed that plug flow preserves this metastable structure by removing destructive shear pressures, but expansive flow in microchannels creates tensile stress and flips nanosheets into vertical alignment^[176]. Three-dimensional electrical pathways are created by overcoming the interlayer conductivity restrictions of two-dimensional materials by inserting CNTs as bridges between layers [Figure 15C]. Functional spatial separation is achieved by heterogeneous layered and core-shell structures: highly conductive cores (like MXene/CNT) guarantee effective electron transport along the fiber axis, while functional or protective shells (like GO, ANF, and PU) offer environmental barriers, mechanical reinforcement, or extra pseudocapacitive effects^[122,175]. Enhanced SAXS orientation factors^[175] confirm that the shell layer’s spatial confinement effect also encourages core ordering during coaxial spinning.

Microscale morphology: dimensional properties, surface texture, and porosity

Surface engineering and hierarchical pore design are two further ways to modify fiber characteristics at the microscale level. As ionic conduits, ordered nanopores (usually 10-50 nm in size) created between vertically aligned layers improve rate capability and lower diffusion resistance^[176-178]. By modifying the solidification kinetics and the rheological characteristics of the spinning slurry, such microporous structures can be created, according to small-angle X-ray scattering study^[176]. Roughened or pleated surfaces improve interfacial adhesion with gel electrolytes and expand the effective area for electrochemical processes. Rapid solidification or post-processing enlargement are frequently used to produce this effect^[53]. One-dimensional/two-dimensional heterostructure networks are created by weaving CNTs or conductive polymers across MXene/graphene layers. This creates continuous conductive frameworks that drastically lower interlayer contact resistance. Conductivities surpassing 10⁵ S·m^-1 have been successfully attained using this method while preserving mechanical flexibility^[178,177].

Integration of design concepts at different scales: from the molecular to the macroscopic

When these concepts are merged hierarchically across various scales, hybrid fiber engineering’s full potential becomes apparent. Hybrid fibers are able to overcome the performance constraints of separate components thanks to this cross-scale synergistic design. For example, CNT-VA-GMF^[176] combine: (i) π-π interactions between CNTs and nanosheets at the molecular scale; (ii) ionic transport via nanoscale vertical channels; (iii) electrolyte permeation via microscale porous structures; and (iv) the macroscale weavability needed for textile supercapacitors. Function-driven multiscale design is also demonstrated by M₄₂PG₃₈ fibers^[177], which fuse: (i) ionic crosslinking between PEDOT:PSS and GO/MXene; (ii) stretch-induced vertical orientation; (iii) nanoscale interlayer voids; and (iv) surface-grafted nano-AgI for low-temperature operation.

In conclusion, this area has progressed from empirical blending to multi-level structural engineering that is rationalized. In order to understand intricate structure-property connections across scales, future efforts will involve utilizing computational modeling and in situ characterization techniques for predictive design of interfacial chemistry and hierarchical structures.