A zinc-ion battery-type self-powered strain sensing system by using a high-performance ionic hydrogel

Flexible strain sensors based on conductive hydrogels have profound implications for wearable electronics and health-monitoring systems. However, such sensors still need to integrate with energy providing devices to drive their functions. Herein, we develop a soaking-free polyacrylamide/carboxymethyl cellulose/tannic acid (PAAM/CMC/TA) hydrogel containing 2 M ZnSO4 + 0.1 M MnSO4 electrolyte for a novel zinc-ion battery-type self-powered strain sensing system. The synthesized hydrogel possesses desirable stretchability (tensile strain/stress of 622%/132 kPa), self-healing and self-adhesive properties, as well as good ionic conductivity (0.76 ± 0.04 S m-1). A mechanically durable Zn-MnO2 battery is developed using the PAAM/CMC/TA hydrogel and it can deliver a high specific capacity (223.0 mA h g-1) and maintain stable energy outputs under severe mechanical deformations. The electrochemical behavior of the battery can recover even after several self-healing cycles. Due to the excellent strain and pressure sensing properties of the PAAM/CMC/TA hydrogel, the battery combined with a fixed resistor served as a self-powered wearable sensing device, which could translate different human movements into distinguishable electrical signals without an external power supply. Our work provides guidance for the development of next-generation self-powered sensors.