Self-powered ionic sensors overcoming the limitation of ionic conductors as wearable sensing devices

Abstract

Ionic hydrogel-based sensors (I-sensors) enable a wide range of wearable applications. However, limited by the signal carriers (i.e., ions) of ionic hydrogels, the I-sensors cannot work stably under commonly used portable direct current (DC) power sources for wearable devices owing to inevitable variation of their chemical compositions. Here, we present a new strategy for designing high-performance self-powered ionic hydrogel-based sensors (SPI-sensors) for wearable applications by simply replacing the metal electrodes of I-sensors with the battery electrodes. The strategy can not only maintain a stable ion concentration within I-sensors due to the insertion/extraction of ions on two battery electrodes during the signal transmission but also endow the sensors with self-powering capacity. The as-prepared SPI-sensors show ultrahigh stability, ultrawide sensing range (~2000%), and high sensitivity, and can recognize an ultrasmall strain of 0.01%, which is superior to the existing I-sensors. This study first demonstrates the feasibility of accurately detecting the full-range human motions based on the internal resistance change of well-designed batteries, paving a new way for practical application of I-sensors.