Flexible and high-sensitive capacitive sensors are demanded to detect pressure distribution and/or tactile information on a curved surface, hence, wide varieties of polymer-based flexible MEMS sensors have been developed. High-sensitivity may be achieved by increasing the capacitance of the sensor using solid dielectric material while it deteriorates the flexibility. Using air as the dielectric, to maintain the flexibility, sacrifices the sensor sensitivity. In this paper, we demonstrate flexible and highly sensitive capacitive sensor arrays that encapsulate highly dielectric liquids as the dielectric. Deionized water and glycerin, which have relative dielectric constants of approximately 80 and 47, respectively, could increase the capacitance of the sensor when used as the dielectric while maintaining flexibility of the sensor with electrodes patterned on flexible polymer substrates. A reservoir of liquids between the electrodes was designed to have a leak path, which allows the sensor to deform despite of the incompressibility of the encapsulated liquids. The proposed sensor was microfabricated and demonstrated successfully to have a five times greater sensitivity than sensors that use air as the dielectric.
jp "'KeioUniversity Flexible and highly-sensitive capacitive sensors that are capable of deteeting pressure distribution on curved surfaces are on demand these days, Using solid dielectric material could deteriorate the sensors flexibilitM while using air as the dielecnic might compromise the sensors sensitivity, EM) propose a distributed capacitive sensor encapsulated in liquid that has high permittivity constant, namelM DI water and glycerin, as the dielectric. Tliis design can increase the sens{tivity while maintaining the flexibility of the sensors. The proposed sensor was micro-fabricated and proven te maintain its flexibility while being deforrned. The sensitivity enhancement of the device is te be demonstrated by comparing some charaeteristies ef the devices; between that with and without liquid encapsulated.The experiment results shewed that the devices with liquids encapsulated were more sensitive when higher pressure is applied, and arrrplification rat{os of the devices with DI water and glycerin increased ± 7 and ± 3.5 times respectively, as compared te the device without the liquid encapsulated.
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