Fabrication of Wearable Hydrogel Sensors With Simple Ionic-Digital Conversion and Inherent Water Retention

A growing interest in the application of artificial skin sensors in the fields of wearable biomedical devices, human-machine interface, and robotics has been noticed in recent years. However, the fabrication of wearable, transparent, cost-effective, and biocompatible wearable sensors with a simple circuit is very challenging. In the present work, a multi-functional wearable hydrogel sensor with a simple and low-cost ionic-digital converter was fabricated to perform gesture recognition and pressure measurements. Biocompatible, transparent, and flexible ionic hydrogel with inherent water retention was used as control panels to recognize gestures or pressures applied by the fingers. The impedance values of these hydrogel panels were studied at different working frequencies, and their water retention capacities with different components were also investigated. By using the LC resonance-based capacitive sensing circuit method with an optimized working frequency, the as-fabricated hydrogel sensor successfully recorded the capacitance between hydrogel panel and fingers after 7 days of exposure to air. Experimental results demonstrated that different gestures, finger movements, and touch pressures were successfully recognized by measuring capacitance values.