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Page 24 of 57 Zheng et al. Soft Sci. 2026, 6, 32

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 and a gauge length of 10 mm. The pertinent literature contains references to specific details.
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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 Ti C T has an effective Young’s modulus of 0.33 ± 0.03 TPa,
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2 x
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 [Figure 9B].
[113]
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 . Zhou et al. used a synergistic approach of thermal stretching and
[116]
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 toughness for aramid nanofiber (ANF)@MXene core-shell
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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 . Additionally, the mechanical qualities of fiber substrates like cotton yarn are greatly improved by
[120]
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 × 10 S·m and a tensile strength of 506.7 MPa.
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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] . Tensile strength of 941.5 MPa, toughness of 147.9 MJ·m , and superior
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[34]
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 . MXene/PEDOT:PSS/polycyclohexane composite fiber was
[35]
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 at a porosity of 21% [Figure 9G].
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