3D-printed highly stable flexible strain sensor based on silver-coated-glass fiber-filled conductive silicon rubber

Flexible sensors have been tremendously attractive in wearable electronics, soft robots and human-machine interaction devices. In this work, conductive silicon rubber (CSR) filled with silver-coated-glass fiber (AGF) and carbon fiber (CF) was embedded into polydimethylsiloxane (PDMS) matrix to fabricate a flexible strain sensor (FSS) in a 3D-printing (3DP) process. It was found that the addition of CF and plasticizer synergistically formed a support-structure which guaranteed the CSR to be extruded out easily in the 3DP process. The printed FSS demonstrated its highly stable properties with a gauge factor (GF) of 8–10 at different strain rate, the coincident resistance recovery process in cyclic load of different strain, as well as the stable durability with monotonous peak in 600 strain-release cycles. Furthermore, it was able to distinguish a superimposed load at frequencies of 1/12 Hz and 1/36 Hz with aids of Fast Fourier Transformation (FFT) analysis. Migrating evolution of AGFs in a stretched CSR was observed to further explore and paraphrase the mechanism of resistance response and the high GF of the FSS. The printed FSS was capable to monitor the movement of various joints and further distinguish a superimposed human motion, showing its potentially practical application in soft robots and wearable electronics.