Carbon Nanotube‐Based Piezoresistive Sensors Fabricated by Microwave Irradiation

Abstract

Herein, piezoresistive nanocomposite sensors that consist of polydimethylsiloxane (PDMS) elastomer and multiwalled carbon nanotubes (CNTs) are fabricated via the microwave irradiation method. The effects of microwave curing on the materials' electrical, mechanical, and piezoresistive behaviors are investigated by comparing properties with those obtained from the thermal‐cured nanocomposites. Microstructures, porosities, and qualities of CNT dispersion of the manufactured nanocomposites are studied using a scanning electron microscope (SEM). Electrical resistivities of the nanocomposites with various CNT loadings are found to be significantly reduced for microwave‐cured nanocomposites due to the potential improvement of CNT dispersion and enhancement of CNT alignment in comparison with the thermal‐cured nanocomposites. Cyclic compressive tests are performed to determine compressive modulus and piezoresistive properties of the developed nanocomposite sensors. Microwave‐cured sensors demonstrate improved compressibility and similar average gauge factors at strains between 3% and 20% in comparison with the thermal‐cured sensors. The piezoresistive behavior of the microwave‐cured sensors with the lowest CNT concentration is characterized, showing little dependency on strain rate, small drift during an 800‐cycle durability test, and viscoelastic creep response that matches the response seen during an application. The sensors are demonstrated as wearable sensors by detecting human motions including sitting and standing, swaying, and grabbing an object.