Thermal and infrared light self-repairing, high sensitivity, and large strain sensing range shape memory MXene/CNTs/EVA composites fiber strain sensor for human motion monitoring

Wearable electronic gadgets have always been in great demand for multifunctional flexible strain sensors. However, developing a flexible strain sensor with excellent characteristics such as high sensitivity, wide sensing range, and excellent durability continues to be a significant challenge. On the one hand, the two-performance metrics of high sensitivity and wide sensing range are mutually exclusive, because the former requires signifi-cant structural changes under small strains, whereas the latter necessitates the preservation of morphological integrity under large deformations. On the other hand, the usage of flexible strain sensors is invariably accompanied by the destruction of the conductive network, rendering the device unusable for an extended period of time. Here, based on the unique strain related microcrack structure of the Ti3C2Tx (MXene)/carbon nanotubes (CNTs) synergistic interaction and the shape memory property of ethylene vinyl acetate polymer (EVA), a MXene/CNTs/EVA fiber strain sensor was innovatively designed and prepared by swelling ultrasonic method. The results showed that the sensor combines a large strain sensing range (190%), high sensitivity (82.5), ultra -fast response speed (178.9 ms), and excellent durability and stability (> 10,000 cycles). What is even more exciting is that if the strain sensor is failure, it can be repaired by heating for 2 min or infrared irradiation for 5.4 s, and the mechanical and electrical properties of the repaired sensor can be restored to 92% and 94% of the original. In addition, this strain sensor can accurately monitor subtle and large movements of the human body (including elbow and finger bending, speaking, and mouth opening/closing), even if the damaged MXene/CNTs/ EVA fiber strain sensor has been repaired. The self-repairing MXene/CNTs/EVA composites fiber-based shape memory matrix has excellent potential as a wearable strain sensor.