Porous structure induced crack redistribution in surface conductive layer for high-performance fiber-based flexible strain and pressure sensors

Constructing crack structure has been proven as an effective method to prepare highly sensitive strain/pressure sensors. However, the crack-structured strain/pressure sensors usually show limited sensing range because of the rapid destruction of conductive networks. Herein, a porous poly(styrene-b-ethylene-b-butylene-b-styrene) (SEBS)-based fiber with surface carbon nanotube (CNT) conductive layer is prepared by melt extrusion foaming and ultrasonic treatment. Cracks generate in the conductive layer under stretching due to the modulus mismatch. It is found that the introduction of porous structure leads to the redistribution of surface cracks. The conductive layer around pores cracks first under small strain due to the stress concentration effect, and the conductive layer away from pores then cracks under large strain, which prevents the rapid destruction of the conductive networks. Consequently, the porous conductive fiber-based strain sensors exhibit both high sensitivity (gauge factor of 27.2 at the strain of 350%) and wide sensing range (0%-350%). Furthermore, a high-performance flexible pressure sensor is fabricated by perpendicularly stacking two porous SEBS@CNTs fibers, which can be applied in wearable human motion monitoring and information transmission. Our study inspires a new idea and proposes a simple strategy for fabricating high-performance crack-structured flexible strain/pressure sensors with high sensitivity over a wide sensing range.