Pressure-conductive rubber sensor based on liquid-metal-PDMS composite

We present a pressure-conductive rubber sensor using a liquid-metal-polydimethylsiloxane (PDMS) composite suitable for incorporation onto surfaces with a complex curvature such as the human body. The composite is synthesized by physical mixing of Galinstan and PDMS based on magnetic stirring. This composite is conductive only when a mechanical pressure exceeding the threshold value or strain is applied; the pristine state of the composite is not conductive. The threshold value can be controlled by adjusting the mixing ratio of liquid metal and PDMS. This material is mechanically robust, allowing it to operate reliably under various elastic deformations such as pressing, stretching, and bending without structural failure and performance degradation. Moreover, a fabricated sensor array can detect the distribution of the applied pressure in plane. As a feasibility study, we demonstrate a pressure-conductive rubber sensor for detecting finger movements and bio-signals such as blood pressure and respiration rate. Our results reveal that our rubber sensor is practical as a wearable sensor because of its mechanical robustness and electrical reliability.