Improved Sensitivity of Flexible Conductive Composites Throughout the Working Strain Range Based on Bioinspired Strain Redistribution

Elastomer conductive composites (ECCs) are wonderful candidates for stretchable strain sensors. However, the sensitivity of ECC-based flexible strain sensors is limited in low-strain range, the main working range for human movements, due to the insignificant geometric change of the sample shape and weak tunneling effect of the conductive network. Herein, bioinspired heterogeneous thermoplastic polyurethane (TPU)/carbon black (CB) composites (TCs) are assembled by hot pressing two TCs with different Young’s moduli in series. The modulus of the TCs is controlled by the CB content, Young’s modulus of TPU, and plasticizer content. Experimental results and finite element analysis (FEA) confirm that the low Young’s modulus component undergoes higher strain compared with the high Young’s modulus component, resulting in a more serious change of the conductive network and higher gauge factor (GF) values. Compared with homogeneous TCs, the GF of heterogeneous TCs was improved by a factor of 20.7 and 9.6 in the low-strain (0–6%) and high-strain range, respectively. The relationship between modulus variety and GF is quantitatively described, and the GF values depend on the Young’s modulus of the individual components. Constructing a heterogeneous structure with different Young’s moduli is a valuable and facile way to increase the sensitivity of ECC-based flexible strain sensors.