Hydrogel Soft Valve With Shape-Memory Actuators for Advanced Cuff Gripping and Fluid Control

Valves play a critical role in regulating flow, preventing backflow, and controlling pressure in hydro-pneumatic systems. However, most existing valves are based on rigid metallic components, which significantly restrict their applicability in biomedical fields and safe human–machine interactions. In this study, we introduce an innovative soft valve mechanism that integrates shape-memory alloy (SMA) wire with a circular hydrogel matrix, tailored for applications in cuff gripping and fluid flow control. Our hydrogel-encapsulated shape-memory annular (HESA) valve demonstrates the ability to transition between relaxed and contracted states within a rapid 8 s timeframe, exerting a force of approximately 15 mN and achieving up to 20% flow control efficiency. Although hydrogels can dehydrate and degrade over multiple actuation cycles, the HESA can be easily rehydrated to restore its initial performance and maintain significant stretchability. We demonstrate enhanced fluid control performance through the use of serially arranged HESA valves that offer a scalable solution for complex fluid management systems. In addition, we developed a real-time monitoring approach for hydrogel-based soft actuators using resistance changes (⁠$ΔR/R0$⁠) measured via an LCR meter, enabling precise performance tracking and timely rehydration to maintain functionality over extended actuation cycles. This innovative approach ensures sustained functionality and efficiency, underscoring the potential of the HESA valve for a variety of biomedical applications, including precise drug delivery systems, minimally invasive surgical tools, and advanced prosthetics.