Efficient Analytical Model of Conductivity of CNT/Polymer Composites for Wireless Gas Sensors

This paper presents an analytical model of conductivity and sensitivity of passive wireless sensors for biohazard gas detection with lower computational cost and reasonable accuracy. Based on the effect of electron tunneling among the carbon nanotubes embedded in a polymer matrix, an analytical model for conductivity of the composite is presented. This model provides significantly lower computational cost as compared to the numerical resistive network models. By incorporation of electron tunneling effects, this model also provides closer approximation to experimental results in comparison to the models based on the percolation theory, which are highly relevant for filler/polymer composite applications designed around the percolation threshold. Using this conductivity model, the conductivity and sensitivity of the composite films are estimated in the presence of an organic gas. The change in the film resistance due to the absorption of the gas is investigated for different filler and gas concentrations. From the phase of the reflected radio frequency signal, the applications of the sensor for passive wireless gas sensing is estimated in a lossless transmission system terminated with a composite film as the load. This paper is useful for design and development of biohazard gas sensors for real-time remote monitoring.