Improved Capacitive Pressure Sensors Based on Liquid Alloy and Silicone Elastomer

This letter reports sensitivity-improved capacitive pressure sensors fabricated using liquid alloy and highly compliant silicon elastomer. Multilayer elastomer layers prepared by replica moulding were stacked and bonded to form three isolated disk-shaped cavities whose diameters are 3 or 5 mm. Top and bottom cavities (both are 200-μm tall) were filled with eutectic gallium-indium to realize compliant parallel electrodes. The cavity in the middle (1-mm tall) was left empty to make it compressed with applied pressure. The overall diameter and height of fabricated pressure sensors are 6 or 7.5 mm and 4 or 6 mm, respectively. After fabricated liquid alloy capacitive pressure sensors were connected with external inductors to construct LC resonant circuits, their resonance frequencies were characterized with applied pressures ranging from 0 to 10 kPa. We found that liquid-alloy capacitive pressure sensors exhibit improved sensitivities over identically sized sensors with solid electrodes.