Low-Impedance and Degradable Soft Dual-Mode Hydrogel Sensor for Real-Time Strain and Bioelectric Signal Acquisition

Wearable bioelectronic systems demand materials that strike a balance between mechanical softness, reliable electrical performance, and biocompatibility. Yet, many conventional gels fall short in practice often showing high interfacial impedance, limited stretchability, and poor degradability, making them less suitable for emerging applications in flexible healthcare technologies. Here we report a degradable, low-impedance Hydrogel developed through a simple aqueous synthesis using waterborne polyurethane (WPU), poly(vinyl alcohol) (PVA), and sodium tetraborate (STD). The gel forms a hybrid cross-linked network based on dynamic borate ester bonds and hydrogen bonding, which imparts both good conductivity and mechanical adaptability. Functionally, the material operates as both a soft strain sensor and a bioelectrical interface. It can detect joint motion with high sensitivity and simultaneously record clean electrophysiological signals such as electromyography (EMG), electroencephalography (EEG), and electrocardiography (ECG). When benchmarked against commercial Ag/AgCl electrodes, the gel exhibits noticeably lower skin–electrode impedance and enhanced signal clarity. The ability to acquire both strain and EMG signals through a single, integrated interface opens up the possibility of motion artifact reduction and genuine multimodal sensing, without adding complexity to the system. With its softness, conductivity, and environmental degradability, this gel presents a versatile and promising platform for future wearable healthcare devices, neuromuscular diagnostics, and human–machine interaction systems.