Flexible capacitive sensor encapsulating liquids as dielectric with a largely deformable polymer membrane

Abstract

Flexible and highly-sensitive capacitive sensors that are capable of detecting pressure distribution on curved surfaces are now in demand. Using solid dielectric material could limit the sensors flexibility, while using air as the dielectric might compromise the sensors sensitivity. Proposed is a distributed capacitive sensor that contains highly dielectric liquid, which increases the sensor sensitivity while maintaining their flexibility. Since the liquid used in this work is incompressible, an escape reservoir is used that allows the liquid between the electrodes to flow into the reservoir when external pressure is applied and the gap between the electrode decreases. In prior work, the escape reservoir was designed to be alongside the sensing area, which resulted in a large footprint. A sensor has been designed that contains encapsulated highly dielectric liquid and allows the liquid to escape beneath the sensing area. The footprint was successfully reduced by 75%. The encapsulated liquid enhanced the maximum measurable pressure from 100 kPa to 800 kPa. The amplification ratios of the sensitivity with DI water and glycerine increased 7 and 3.5 times respectively, as compared to the device without the liquid encapsulated.