Tungsten-Oxide/Liquid Electrical-Double-Layer Capacitive Sensors and EIS Characterization for Liquid Pressure Monitoring.

This study proposes a novel electrical-double-layer (EDL) capacitive sensor by using tungsten oxide in direct contact with the liquid for accurately monitoring the liquid pressure, with self-powered potential. Experimental results show a negative correlation between the output potential of the sensor and the liquid pressure. The sensor is also calibrated over the range of −3.0 to −2.4 kPa with a sensitivity of 0.18949 V/kPa and a resolution of 28.98 Pa in tap water. The capacitance of the EDL and transfer resistance on the tungsten oxide/liquid interface at different liquid pressures are measured by using electrochemical impedance spectroscopy (EIS). Evidence that an increase in liquid pressure leads to a decrease in the thickness of EDL and a decrease in the output potential of tungsten oxide. The difference in ion concentration hinders the amount and rate of ion exchange between the EDL and the liquid, causing small and slow changes in potential. In conclusion, the liquid pressure sensors have application advantages of low cost, simple construction, and low power consumption. Furthermore, the research contributes to the growth and understanding of the liquid-solid electricity generation.