MyoDEA: A Self-Sensing Dielectric Elastomer Actuator for Real-Time Muscle Stiffness Monitoring

Abstract

Monitoring muscle stiffness in real-time during dynamic muscle activity is critical for rehabilitation, athletic training, and human-robot interaction. Existing technologies often require bulky hardware and complex multi-component systems, limiting reliable stiffness measurement in daily activities. In this work, we introduce MyoDEA, a centimeter-scale and 770 mg device based on a novel self-sensing dielectric elastomer actuator (DEA) for time-varying muscle stiffness detection. This DEA generates a 2.5 times higher blocked force than previously reported power-dense DEAs at operating frequencies below 10 Hz, while maintaining comparable bandwidth and energy output at resonance. A new self-sensing method is also developed to enable integrated actuation and sensing within a single DEA. The MyoDEA achieves continuous muscle stiffness tracking at 10 Hz over a range of 30, k Pa to 140 kPa. Human-subject experiments with MyoDEA worn on the forearm over the flexor digitorum superficialis (FDS) muscle belly demonstrate reliable continuous stiffness tracking during isometric gripping across 0%-80% maximum voluntary contraction (%MVC).