Flexible Capacitive Pressure Sensor Based on PDMS Substrate and Ga-In Liquid Metal

A novel flexible pressure sensor, based on polydimethylsiloxane (PDMS) and eutectic gallium-indium (EGaIn) liquid metal, was developed for detecting various applied pressures. The sensor was fabricated with PDMS polymer-based electrode channels that are filled with EGaIn liquid metal. The liquid metal-based electrodes were designed to form four capacitors (C1, C2, C3, and C4). Conventional printed circuit board technology was used to manufacture the master mold to form the PDMS-based electrode channels. Corona discharge treatment was employed to bond the PDMS layers at room temperature, under atmospheric pressure. The capability of the fabricated pressure sensor was demonstrated by investigating the capacitive-based response of the device for varying applied pressures. Average capacitance changes ranging from 2.3% to 12.0%, 2.6% to 11.8%, 2.5% to 12.2%, and 2.7% to 13.1% when compared with the based capacitance of 14.1, 15.1, 13.8, and 13.3 pF were obtained for C1, C2, C3, and C4, respectively, for applied pressures ranging from 0.25 to 1.10 MPa. A linear relationship was obtained for the average capacitance change with a sensitivity of 0.11%/MPa and a correlation coefficient of 0.9975. The results obtained thus demonstrate the feasibility of employing liquid metal-based electrodes for the fabrication of flexible pressure sensing devices.