Self-powered smart pressure sensors by stimuli-responsive ion transport within layered hydrogels

Self-powered ionic sensors represent an emerging class of device capable of detecting and converting external stimuli, such as pressure and temperature, into electrical outputs without the need for an external power source. However, they often suffer from relatively low sensitivity, and their detection capability is typically limited to the magnitude of external stimulus. In this study, we present a smart pressure sensor consisting of nanowire electrodes and three-component ionic hydrogels with distinct stiffnesses and ion selectivities. Our hydrogel device effectively converts external pressure into a convective flow of cations, which are efficiently captured by the nanowire electrodes, yielding remarkable electrical outputs. In addition, upon local compression, the hydrogel device induces a convective flow that guides cations to the nearest electrode with minimal frictional force. This creates local inhomogeneous ionic distributions around the electrodes, enabling the detection of the local position and directional movements of the applied pressure without the need for additional electrical circuits. By enabling the simultaneous detection of pressure magnitude, local position, and movement, our device is capable of encoding intricate movements into distinct electrical outputs, thereby presenting a novel avenue for the development of advanced self-powered sensors with enhanced capabilities.