Research Progress on Preparation and Application of Flexible Stress/Strain Sensors Based on Two-Dimensional Ti₃C₂ MXene

Ti₃C₂ MXene is a novel two-dimensional carbide with an accordion-like lamellar structure. The flakes of Ti₃C₂ MXene can slide or stack under tension or compression, which can change the number and length of internal conductive paths and directly affect the output electrical signals. Thus, Ti₃C₂ MXene can be used as sensing materials to measure the change of stress/strain. Combined with the elastic substrates, this material is used to make flexible sensors to monitor the motions and health signals of human-beings. This paper described the working principle of flexible stress/strain sensors made by Ti₃C₂ MXene composites. Recent methods to prepare the sensors were reviewed, i.e., electrospinning, filtration/coating, impregnation, screen printing, freeze drying, and freeze thawing. The key factors of the methods, i.e., flexible substrate, sensing parameters, sensor structure, detection limit, cycle times, sensing rage, responsive time and gauge factor, were represented. Some applications of the MXene-based sensors were discussed. Finally, the promising development of Ti₃C₂ MXene flexible sensors was outlooked and the problems to be solved were summarized.