Piezoresistive anisotropy in conductive silicon rubber/multi-walled carbon nanotube/nickel particle composites via alignment of nickel particles

Abstract

Conventional piezoresistive sensors of flexible conductive polymer composites (FCPC) are mostly isotropic because of the weak controllable fabrication strategies. In this study, a facile strategy was introduced to fabricate the polydimethylsiloxane (PDMS)/multi-walled carbon nanotubes (CNT)/aligned nickel particles (Ni) composites under a low magnetic field. The PDMS pre-polymer firstly mixed with CNT and Ni particles with ultrasonic and solvent assistant, and then cured under a magnetic field with a magnetic flux density of 75 mT to form the composites. Because of the alignment of Ni particles, the PDMS/CNT/align-Ni composites exhibited obviously electrical, mechanical and piezoresistive anisotropy. Specifically, the compression modulus of the composites with 0.23 vol% CNTs and 3.93 vol% Ni particles was ∼4.93 and ∼3.66 MPa at the direction parallel to (X direction) and vertical to the alignment direction of Ni particles (Y direction), respectively. The anisotropic index of the electrical conductivity could reach 2.6 × 105 in the PDMS/CNT/aligned-Ni composites containing 0.23 vol% CNT and 3.37 vol% Ni particles. Furthermore, the PDMS/CNT/aligned-Ni composites showed a negative piezoresistive effect at X direction and a positive piezoresistive effect at Y direction.