Unveiling Viscoelastic Response of Capacitive-type Pressure Sensor by Controlling Cross-Linking Density and Surface Structure of Elastomer

Abstract

Research on pressure sensors using elastic materials is actively underway to develop next-generation devices for applications in healthcare monitoring, haptic sensors, and electronic skin. Capacitive-type pressure sensors have several advantages among various types of pressure sensors because they can be manufactured in a small size, and their sensitivity is superior to other types of pressure sensors. Capacitive-type pressure sensors consist of two electrodes and an intermediate active layer, typically made up of elastomer such as polydimethylsiloxane (PDMS). Because a change in thickness of the elastomer upon applied pressure is a key operating mechanism, viscoelastic properties of elastomer should be considered when optimizing sensor performance. In this study, we examined viscoelastic properties of PDMS by controlling its cross-linking density. Effects of cross-linking density on performances of pressure sensors were also analyzed. Dynamic mechanical analysis and swelling method were employed to measure an accurate cross-linking density which significantly affected sensitivity, hysteresis, and recovery rate of pressure sensors. Performances of pressure sensors were also studied according to surface patterns (i.e., dome, square) of PDMS and surface treatment (i.e., UV/ozone, perfluordecyltrichlorosilane). Pressure sensing characteristics were optimized by incorporating dome structure and appropriate surface treatment on PDMS. Results of this study demonstrate that viscoelastic response of elastomer is vital for optimizing properties of capacitive-type pressure sensors.

Natural bamboo leaves as dielectric layers for flexible capacitive pressure sensors with adjustable sensitivity and a broad detection range

“…Sensitivity (S) of the capacitive sensor relies on the slope of the capacitance change versus the applied pressure curve, expressed by the equation: S ¼ d(DC/C 0 )/dP (where C and C 0 refer to the capacitance at the loading and initial states, DC is the variation of capacitance (C À C 0 ), P represents the applied pressure). 41,42 The comparison of the three pressure sensors' relative capacitance changes was provided in Fig. 3a.…”

A water‐soluble micropatterned MoS2 quantum dots/polyvinyl alcohol film as a transient contact (pressure) and non‐contact (humidity) as touch and proximity sensor

“…Similarly, for dome and square shape pressure sensor sensitivity was 1.44 × 10 −3 and 2.45 × 10 –1. 36 Elastomers with elastic or sponge‐like structures have been considered to be especially useful for wearable applications and one‐step, cost effective, and rapid fabrication of large‐area porous elastomers remains a challenge. Parameswaran et al developed cost effective single, step method pressure sensor using 3D porous PDMS and ITO‐PET as electrodes.…”

Fabrication of conductive and superhydrophobic poly(lactic acid) nonwoven fabric for human motion detection

“…With the rapid development of emerging industries such as touchable displays, 1 electronic skins, 2 intelligent robotics, 3 and wearable devices, 4 sensors as the most important components have been paid enormous attention. According to the difference of function, pressure sensors can be divided into piezoresistive pressure sensor, 5,6 capacitive pressure sensor, 7 and piezoelectric pressure sensor 8 . As one of the important representatives, piezoresistive pressure sensor is promising in wearable devices because of their high sensitivity, fast response, cost‐effective process, and simplified signal collection 9 .…”