Reduction of Parasitic Capacitance of A PDMS Capacitive Force Sensor.

Tatsuho Nagatomo,Norihisa Miki

doi:10.3390/mi9110570

Abstract

Polymer-based flexible micro electro mechanical systems (MEMS) tactile sensors have been widely studied for a variety of applications, such as medical and robot fields. The small size and flexibility are of great advantage in terms of accurate measurement and safety. Polydimethylsiloxane (PDMS) is often used as the flexible structural material. However, the sensors are likely subject to large parasitic capacitance noise. The smaller dielectric constant leads to smaller influences of parasitic capacitance and a larger signal-to-noise ratio. In this study, the sensor underwent ultraviolet (UV) exposure, which changes Si–CH3 bonds in PDMS to Si–O, makes PDMS nanoporous, and leads to a low dielectric constant. In addition, we achieved further reduction of the dielectric constant of PDMS by washing it with an ethanol–toluene buffer solution after UV exposure. This simple but effective method can be readily applicable to improve the signal-to-noise ratio of PDMS-based flexible capacitive sensors. In this study, we propose reduction techniques for the dielectric constant of PDMS and applications for flexible capacitive force sensors.

Highlights

Polymer-based flexible micro electro mechanical systems (MEMS) tactile sensors have been widely studied for a variety of applications, such as medical and robotics fields [1,2,3,4,5,6,7,8,9,10,11]
We characterized the combination of these two techniques, techniques, i.e., UV-treatment and chemical washing, for the first time and i.e., UV-treatment and chemical washing, for the first time and demonstrated demonstrated reduction of the parasitic capacitance of polydimethyl siloxane (PDMS)-based sensors to enhance the signal-toreduction of the parasitic capacitance of PDMS-based sensors to enhance the signal-to-noise ratio noise ratio (SNR) using the flexible sensors we developed in our prior work [11]
We experimentally investigated how long the low dielectric constant of PDMS membrane was maintained after treatment

Summary

Introduction

Polymer-based flexible micro electro mechanical systems (MEMS) tactile sensors have been widely studied for a variety of applications, such as medical and robotics fields [1,2,3,4,5,6,7,8,9,10,11]. The small size and flexibility are of great advantage in terms of accurate measurement and safety. This trend is further accelerated by the electrodes that are robust against deformation. Graphene is a promising candidate and the sensors with graphene electrodes were reported along with their fabrication technologies [7,8]. Liquid metal is another candidate, which can form the electrodes by being filled up inside microchannels [9,10,11]. We reported flexible MEMS sensors made of polydimethyl siloxane (PDMS) structural layers and three-dimensional liquid metal electrodes to detect both normal and shear force [10,11]

Methods

Discussion

Conclusion