A Flexible Capacitive Sensor with Encapsulated Liquids as Dielectrics

Abstract

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.

Dielectrical liquid-based tactile sensing array with adjustable sensing ranges and sensitivity

“…The capacitive tactile sensor not only able to increase the sensitivity by sandwiching the material with high dielectric coefficient between the electrodes [4][5], but also the sensing range is able to adjust. Fang et al developed a capacitive CMOS-MEMS tactile sensor whose material can be changed during fabrication [6].…”

Decoupling Research of a Novel Three-Dimensional Force Flexible Tactile Sensor Based on an Improved BP Algorithm

“…The design principle for tactile sensors developed with different tactile-sensing mechanisms mainly concentrate on piezoelectricity [1,2], capacitance [3,4,5,6], optical fiber [7,8,9], single-walled carbon nanotube [10] technology, and so forth. For most of the tactile sensors, their sensing surface is divided into scattered areas without a continuous elastomer skin, and the sensing units are usually independent of each other.…”

Microflotronics: A Flexible, Transparent, Pressure‐Sensitive Microfluidic Film

“…Flexible substrates and materials have been increasingly utilized in these applications, because of the adaptability and conformability offered to the surfaces with different geometries and topologies. In prior literature, piezoelectric, resistive, capacitive and optical devices have been constructed and demonstrated, with mechanical sensing capacities on a variety of flexible substrates, including elastomeric nanocomposites and primarily deformable polymeric films (e.g., polyimide/PI, polyvinylidene fluoride/PVDF or poly(3,4‐ethylenedioxythiophene): poly(styrenesulfonate)/PEDOT:PSS) . However, the intrinsic properties of these materials impose severe limitations on their potential applications they can be utilized for.…”

“…Recently, microfluidics‐enabled sensing devices have shown promise in an array of unconventional applications, such as chemical and biological analyses, cellular manipulations, and electronic skin applications, by providing considerable sensitivity, favorable adaptability, and high flexibility, in which a minute amount of liquid substance responds to an external load by altering its physical properties or geometry . Microfluidic sensors can employ either detectable changes in optical properties of a miniature flow, or utilize the resistive or capacitive variations in a conductive fluid (e.g., liquid metals and ionic liquids).…”