Conformation Regulation of Ti ₃ C ₂ T _<i>x</i> MXene via Interfacial Energy for Tunable Strain-Sensing Behaviors

The processing of two-dimensional transition-metal carbides or nitrides (MXenes) has boosted their applications in numerous technological fields, ranging from energy storage to electromagnetic shielding and flexible sensing devices. The microstructure design of MXene films is key to the mechano-responsive performance. Here, we propose a simple and efficient method to modulate the microstructure of the MXene film via different solvents. MXene films with microstructures ranging from flat stacking, warping, and crumpling to folding tubes and cages are obtained through tuning the Hansen solubility parameters of the solvents, giving rise to distinctive strain-sensing behaviors. The MXene devices obtained from nonpolar solvents demonstrate an anomalous negative resistance–strain response, which was illustrated by a compression-crack synergetic sensing mechanism. Such strain sensors can generate distinct waveforms across varying amplitudes in response to the same movement rather than merely exhibiting amplitude differences. This enhances the specificity of strain recognition, offering the potential for precise motion identification and standardized movement training.