Transparent, Breathable Temperature and Humidity Sensor using Ion Gel and Polymer Thin Films

Abstract

In this study, a transparent and highly breathable thin-film temperature and humidity sensor was developed as a concept proof for multimodal patchable devices using ion gels. The sensor can detect temperature and humidity selectively by using two types of ionic liquids for sensing layers. Ionic liquids were compatibilized with polymers to form a semi-solid state, called ion gels. Polydimethylsiloxane (PDMS) thin film was used for substrates. Carbon nanotube (CNT) transparent electrodes were fabricated onto PDMS substrate by spray coating method. Ion gel sensing layers were also spray-coated onto CNT electrodes. The fabricated sensor exhibited more than 80 % visible light transmittance and 3.9 times higher water vapor transmission than skin evaporation. LCR meter was used for measuring the impedance of temperature and humidity sensors. As a result, selective detection of temperature and humidity was achieved by using two types of ion gels with different hydrophilicity. These results suggest the easy fabrication of multimodal patchable devices by using various types of ionic liquids.