Design of CNT Polymer Composite Based Strain Sensor to Study the Effect of Humidity and Electrical Conductivity

Abstract

The high electrical conductivity of carbon nanotubes(CNTs) has motivated their incorporation into polymers for several purposes, including electrical conductivity enhancement and sensing. Some studies have suggested that thin films of CNT/polymer composites canbeused for humidity sensing. This study focuses on the influence of humidity on the electrical conductivity of CNT modifie depoxy composite. The degree of sensitivity to the humidity of the developed composite is compared to other sensing capabilities (strain and temperature). It was found that a change in humidity from 5% relative humidity (RH) to 95% RH can cause an 80% reduction in conductivity. This significant reduction must be considered if a CNT-based strain sensor is to be developed. A gauge factor of 3.7 was obtained for CNT-epoxy strain sensor suggesting ~4% change in conductivity as a result of 1% strain. This suggests that a modest change in humidity can completely compromise the accuracy of CNT-based strain sensors.