Rubber-based piezoresistive sensing: a new approach based on hydrodynamic flow of material deformation describing nonlinear signals in stretchable sensors

Abstract

The nonlinearity of piezoresistive response is critical in developing strain sensors, various self-monitoring applications and wearable electronics based on filled rubbers. This parameter could change dramatically when scaling up from small-size prototypes to full-scale production. The present work focuses on the nonlinear signals in stretchable rubber-based sensors, their origin and dependence on size of samples. Thus, a set of rectangular, piezoresistive samples differing in width was prepared from natural rubber reinforced with carbon black filler. Their electric resistance was tested under planar strain/recovery conditions at 25 and 50% strain amplitudes. It was found that piezoresistance and the related nonlinear phenomena significantly depended on the size of the samples. For the first time, hydrodynamic flow of deformed material was used to explain the nonlinearities of the piezoresistive signal. The trajectory, velocity, and magnitude of this flow were accounted for by a newly developed empirical equation describing the evolution of local resistivity under the strain/recovery process.