Soft, Stretchable, and Conductive Hydrogel Based on Liquid Metal for Accurately Facial Expression Monitoring

Soft electronics have emerged as a prominent research domain, with diverse applications from medical monitoring to soft robotics. Liquid metal (LM) has emerged as a promising material for soft electronics due to its high electrical conductivity (3.4 x 10(6) S m(-1)) and fluidity at room temperature. However, the dispersion of LM nanoparticles and the performance of LM composites in soft electronics applications have not been extensively explored. In this study, a novel approach for the direct dispersion of LM nanoparticles in biocompatible hyaluronic acid (HA) to create multifunctional LM/HA hydrogels is presented. The LM/HA hydrogel displays remarkable electromechanical properties, including high stretchability (2,700%) and conductivity (116 S m(-1)), as well as excellent sensitivity (GF = 4.8) as a sensing material. Specifically, a facial expression monitoring system is developed utilizing the LM/HA hydrogel as the sensing material, along with a microcontroller, signal-processing circuits, and a Bluetooth transceiver. The LM/HA hydrogel adheres closely to the skin surface to ensure the accuracy of facial expression monitoring. In summary, this study not only advances the understanding of the properties of LM but also expands the potential application scenarios of multifunctional LM hydrogels in soft robotics and implantable sensors.