Nanocomposite-Based Microstructured Piezoresistive Pressure Sensors for Low-Pressure Measurement Range.

Vasileios Mitrakos,Gerard Cummins,David Flynn,Fiona Denison,Marc Desmulliez,Lisa Macintyre,Philip Hands

doi:10.3390/mi9020043

Abstract

Piezoresistive pressure sensors capable of detecting ranges of low compressive stresses have been successfully fabricated and characterised. The 5.5 × 5 × 1.6 mm3 sensors consist of a planar aluminium top electrode and a microstructured bottom electrode containing a two-by-two array of truncated pyramids with a piezoresistive composite layer sandwiched in-between. The responses of two different piezocomposite materials, a Multiwalled Carbon Nanotube (MWCNT)-elastomer composite and a Quantum Tunneling Composite (QTC), have been characterised as a function of applied pressure and effective contact area. The MWCNT piezoresistive composite-based sensor was able to detect pressures as low as 200 kPa. The QTC-based sensor was capable of detecting pressures as low as 50 kPa depending on the contact area of the bottom electrode. Such sensors could find useful applications requiring the detection of small compressive loads such as those encountered in haptic sensing or robotics.

Highlights

In recent years an increasing variety of non-commercial contact pressure sensors based on flexible elastomeric materials have been reported
Total of five composite batches were produced for each filler-polymer during the evaporation step which may have led to the fracturing of the carbon nanotubes (CNT) and subsequent concentration displayed
The relative resistance of the Multiwalled Carbon Nanotube (MWCNT)-PDMS sensor was characterised as a function of the the evaporation step which may have led to the fracturing of the CNTs and subsequent shortening of compressive pressure load

Summary

Introduction

In recent years an increasing variety of non-commercial contact pressure sensors based on flexible elastomeric materials have been reported. Out of the aforementioned pressure sensors, those that rely on a piezoresistive force-sensitive response are the preferred choices for low-cost applications, due to the reduced complexity in the required readout electronics and manufacturing process. These piezoresistive materials can be compact since they generally consist of uniformly dispersed conductive particles within an elastomeric material. Piezoresistive sensors based on conductive elastomeric composites, such as carbon nanotubes (CNT)-Polydimethylosiloxane (PDMS) composites, usually exhibit their piezoresistive sensitivity to Micromachines 2018, 9, 43; doi:10.3390/mi9020043 www.mdpi.com/journal/micromachines

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