Polydopamine-Based Multifunctional Hydrogel for Flexible Supercapacitor and Pressure Sensor Applications

Flexible energy storage devices and sensors are two key factors for wearable electronics. Designing a multifunctional component that combines a sensor and high-performing energy storage is exciting but remains a great challenge. Here, a multifunctional hydrogel with mechanical properties has been prepared by introducing polydopamine (PDA) into a chemically crosslinked network of poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG). A film electrode containing PDA is grown in situ on the hydrogel, and the resultant device can be employed as a supercapacitor and pressure sensor simultaneously. The supercapacitor exhibits an areal specific capacitance of 210.2 mF cm–2 at a current density of 0.2 mA cm–2. As a flexible sensor, the device has a broad pressure range and good sensitivity (0.57 kPa–1) with a pressure range of 0–5 kPa. The device can stably detect human motion from a gentle wrist pulse to tight clutching, providing a solution for integrating energy storage devices with functional sensors in wearable electronic applications.