Hydrogel Transducer for Wearable Devices: Energy Supply, Electrostatic Protection, and Circuit Modeling

Abstract

The application of flexible materials in wearable devices holds great potential. In this paper, a multifunctional integrated hydrogel transducer is developed. It realizes power generation based on the potential difference between copper and aluminum electrodes and the humidity difference of the hydrogel, while it has both humidity sensing and overvoltage protection functions. The device uses NaCl-containing polyacrylamide hydrogel as the conductive medium. Utilizing the potential difference between the copper and aluminum electrodes, it generates an open-circuit voltage of 0.4 - 0.6 V and drives the directional migration of ions to generate a short-circuit current of 20 - 40 µA. Experiments show that the short-circuit current increases significantly with ambient humidity, enabling it to sensitively detect changes in air humidity. When used as a load, it exhibits diode characteristics when the voltage is higher than 1.6 V or lower than -0.8 V, effectively limiting the amplitude to protect against static impact. By modeling the equivalent circuit containing the diode, the working mechanism of the device in the energy supply and circuit protection modes is revealed. Compared with the traditional hydrogel transducer, this device realizes the integration of power generation, humidity sensing and limiting protection for the first time. This significantly improves the self-powering and anti-static shock ability of wearable devices in complex environments, providing a new strategy for self-powering and circuit protection of wearable devices.