Simple Moisture Sensing Element Using Carbon Nanotube Composite Paper

We propose a unique moisture sensing element (including humidity sensor) using carbon nanotube (CNT) composite paper. The CNT composite paper is a composite material consisting of CNTs and cellulose paper, which can be easily produced using a method based on the Japanese washi papermaking process. Since this composite paper contains CNTs, it is a conductive paper. In addition, the cellulose fibers that make up the paper are known to show a volume change of up to 35% with humidity. The proposed moisture sensing element uses this volume change and the electrical resistance derived from the CNT network contained in the composite paper. Through various experiments, it was confirmed that the electrical resistance of the CNT composite paper changes in response to moisture of various sizes, such as water droplets and vapors (humidity). It was concluded that these changes were the result of the volume change of paper fibers due to moisture, which greatly affected the structure of the CNT network contained within the composite paper. The results of this study will be useful for the practical application of simple and flexible paper-based moisture sensing elements in the near future.