Development of flexible and high sensitivity graphene foam based pressure sensors
Highlights
- Part 2 of the “Ultra-Thin Graphene Foam, Gii, Based Flexible Piezoresistive Pressure Sensors for Robotics”
- Pressure sensors are widely used devices in a variety of sectors from automotive, medical, industrial and consumer devices.
- Currently flexible pressure sensors are primarily based on capacitive, resistive and piezoelectric methods.
- Advanced materials such as Gii has been proposed as a promising material due to enhanced electric properties (fast device response, low recovery time and low power consumption), mechanical properties (high durability, conformability) providing compatibility with flexible substrates.
- NAs the sensors are still in the initial fabrication process more data needs to be collected and analyzed to fully understand the exciting implications these sensors can provide for a variety of industries.
Abstract
Pressure sensors are widely used devices in a variety of sectors from automotive, medical, industrial and consumer devices. These applications can range from ultrasensitive e-skin, touch screen displays, medical diagnostics and health monitoring [1]. To compete with current industrial sensors, a new easily fabricated, reproducible, and highly sensitive pressure sensor compatible with temperature sensitive substrates (plastic, fabrics, paper etc) is required.
Within this paper the fabrication process is described, as well as showing the use of PDMS as a protective layer. Characterization of the fabricated sensors showed a sensitivity of 0.0418 mV/kPa over a range from 1 to 50 kPa. Cyclic testing showed that the use of a protective PDMS coating increased the durability of the sensors, keeping the voltage produced steady with no visible drop after large numbers of presses.
Introduction
Currently flexible pressure sensors are primarily based on capacitive, resistive and piezoelectric methods.
Capacitive presents advantages such as the ability to operate with no power supply. However, drawbacks include non-linear output and sensitivity to the surrounding environment. Piezoelectric sensors are durable and self-powering while resistive pressure sensors provide advantages over the latter designs having simpler construction, robustness and long-term stability.
Advanced materials such as graphene have been proposed as a promising material due to enhanced electric properties (fast device response, low recovery time and low power consumption), mechanical properties (high durability, conformability) providing compatibility with flexible substrates. Graphene foam (GF), Gii, is a three-dimensional (3D) high surface area nanostructure exhibiting excellent potential for development of pressure sensors.
Currently graphene based resistive pressure sensors have shown high sensitivity at low pressures (<5kPa) enabling ultrasensitive detection [2]. It has also been shown that the use of graphene electrodes for capacitive pressure sensors provides a high sensitivity of 3.19kPa -1 [3].
In this work, we show the growth of GF by a catalyst free method onto a flexible substrate without the use of a transfer process (Integrated Graphene Ltd proprietary process), and a novel structure consisting of GF embedded in polydimethylsiloxane (PDMS) used as an active layer in resistive pressure sensors. GF were directly grown on polyimide substrates.