Toxic-Gas-Sensing Characteristics of Flexible Carbon-Nanotube-Network Thin-Film Devices Fabricated on Elastomer Substrates

Abstract

We report on the toxic-gas-sensing characteristics of density-controlled carbon-nanotube-network (NTN) thin-film devices prepared on flexible poly-dimethylsiloxane (PDMS) substrates. The devices were prepared by directly curing PDMS on selective vacuum-filtered NTN surfaces. The room-temperature NH3 gas-sensing characteristics showed that for a 9-mm-channel-length device, a 40-s exposure to 10-ppm NH3 resulted in a 17 % decrease in conductance. Comparing devices with uniform square resistances and differing channel lengths showed that while having the same surface reaction rate (4.17 x 10(-6) ppb(-1).s(-1)) to NH3, the longer NTN showed a higher sensor response. This was attributed to the increased semiconducting behavior of the longer NTN channels. We also found that the sensitivity may be improved further by reducing the nanotube density, which reduces the probability of forming metallic nanotube paths between the contacts.