Carbon nanotubes dispersions in polymer matrix for strain sensing applications

We have performed studies on the correlation between mechanical deformations and electrical conductance on a new interesting hybrid material, a Single Wall Carbon Nanotubes (SWCNTs)/Poly(3,4-ethylenedioxythiophene) (PEDOT) composite. Two are the synthesis techniques utilized to prepare the composite material in form of few hundreds of nm thick films: a spin coating deposition starting from an aqueous dispersion of SWCNTs and PEDOT, and an electrochemical de*position starting from a dispersion of SWCNTs and EDOT monomer. The composite conductance changes induced by a modulated periodic elongation via a coherent technique have been monitored by measuring the voltage variations of a Wheatstone bridge connected with the films. The measurements were performed on SWCNTs/PEDOT composites layered on a rigid substrate. The piezoresistivity gauge factor (GF) of the various samples was evaluated by comparing their responses to mechanical deformations to those of a commercial strain gauge, sticked on a substrate of the same kind. We found no significant piezoresistive effect in the hybrid material films deposited by means of spin coating while the effect is remarkable for the composites prepared by means of the electrochemical technique. In this case the gauge factor is found to be up to 3-4 times higher than that of the commercial strain gauge.