A high-performance flexible force sensitive conductive composite with programmed digital crack by femtosecond laser etching

Abstract

Stretchable strain sensors need to maintain high stability, high working range and high sensitivity for the long-term and cycle application. Herein, this work prepared a flexible force-sensitive conductive composite with digitally crack by a programmed femtosecond laser. Firstly, carbon nanotube (CNTs) layer were partially embed into the surface maleic anhydride-grafted styrene ethylene butylene styrene (SEBS-g-MAH) by hot pressing to obtain a layered conductive material (mCSM); then the mCSM was stretched to a strain of 100 % strain and a programmed femtosecond laser was used to etch the surface CNTs layer to prepare digital like cracks; finally, the pre-strain was relaxed and cracks in the composites were partially recovered. These partially recovered digital cracks favored the high conductivity and sensitivity. Thus, the fabricated composites had a high sensitivity (GF = 938.62 at 100 % strain) and wide working range (661.72 %). It also has excellent stability (500 stable cycles at 100 % strain) and works stably even under large strains. The crack structure (pre-strain, length, and density) played an important role in the sensing properties of the composite, the synergistic effect of these three is the basis for constructing a controllable crack and the key to providing its excellent sensing properties. These excellent sensing properties enable the sensors to monitor the full range of human motion, from small blinks to large joint movements, and to maintain good sensing performance over long periods of operation.