Touch-mode capacitive pressure sensor with graphene-polymer heterostructure membrane

Abstract

We describe the fabrication and characterisation of a touch-mode capacitive pressure sensor (TMCPS) with a robust design that comprises a graphene-polymer heterostructure film, laminated onto the silicon dioxide surface of a silicon wafer, incorporating a SU-8 spacer grid structure. The spacer grid structure allows the flexible graphene-polymer film to be partially suspended above the substrate, such that a pressure on the membrane results in a reproducible deflection, even after exposing the membrane to pressures over 10 times the operating range. Sensors show reproducible pressure transduction in water submersion at varying depths under static and dynamic loading. The measured capacitance change in response to pressure is in good agreement with an analytical model of clamped plates in touch mode. The device shows a pressure sensitivity of 27.1 0.5 fF Pa−1 over a pressure range of 0.5 kPa–8.5 kPa. In addition, we demonstrate the operation of this device as a force-touch sensor in air.

Recent Progress on Flexible Capacitive Pressure Sensors: From Design and Materials to Applications

“…[ 61,77,78 ] A heterostructure diaphragm (graphene and polymer composite materials) based TMCPS array has been fabricated on thin silicon substrate, however, any other material could be utilized in place of silicon, as the researchers proposed for future work. [ 79,80 ] Commercially available household materials, like Al‐coated polyimide (PI) foil and double‐sided tape, are utilized for designing flexible TMCPS. [ 81 ] The sensor is fabricated [Figure 3f] by cutting two circular pieces from Al‐coated PI sheet and then using three layers of double‐sided tape along the edges to paste the pieces together.…”

Surface Texture Detection With a New Sub-mm Resolution Flexible Tactile Capacitive Sensor Array for Multimodal Artificial Finger

“…When pressure is applied over that limit, the upper membrane deforms and the capacitance increases until the top membrane is totally collapsed. Indeed, based on the studies reported in [19]- [21], the behavior of the membrane can be simplified in two main distinct operating modes: the normal mode (region 1), when the membrane is freely suspended on the cavity and characterized by a linear and high sensitive response; the touch mode (region 2), at a pressure over a transition point (incipient touch), the membrane goes in direct contact with the base of the cavity until it totally collapses.…”

Sensitive capacitive pressure sensors based on graphene membrane arrays

“…There are different ways to readout the deflection of the membrane and thereby quantify the pressure difference. In capacitive graphene pressure sensors, the deflection is readout by measuring the capacitance between the graphene membrane and a reference electrode [9][10][11][12] . As the pressure-induced deflection increases the mechanical stress and tension in the membrane, it can be measured using the piezoresistive effect [13][14][15] and can be probed via the mechanical resonance frequency 2,3,16 .…”