Low-Hysteresis Sericin-Based Composite Conductive Hydrogel as a Wearable Sensor for Joint Motion Monitoring in Rehabilitation Training

Abstract

In flexible sensing applications, the long-term reliability of hydrogels is challenged by sustained and cyclic mechanical deformations. Exposure to forces such as bending and stretching ultimately diminishes sensing fidelity and accelerates material fatigue, shortening the functional lifetime. To improve hydrogel durability and minimize hysteresis, this study develops a composite hydrogel composed of a copolymer matrix of 3-methacrylamidophenylboronic acid and acrylamide integrated with polydopamine-modified sericin and aluminum ions. Leveraging a synergy of three dynamic bonds (boronic ester, hydrogen, and metal coordination bonds), the hydrogel demonstrates outstanding self-healing, achieving 88% recovery in just 20 min. It also exhibits excellent mechanical characteristics, such as an elongation at break of 390% and a tensile strength of 31 kPa, along with a low hysteresis of 3.7% at 100% strain. Furthermore, the hydrogel exhibits stable electrical conductivity, high strain sensitivity, and low hysteresis. When used as a wearable sensor, it effectively provides real-time monitoring of human joint movements, maintaining a stable signal output even under prolonged and repeated deformation. These properties indicate significant potential for implementation in flexible sensing systems and rehabilitation training protocols.