Organic temperature sensors based on conductive polymers patterned by a selective-wetting method

Organic temperature sensors are constructed using the temperature dependence of the electrical conductivity of conductive polymers, in which sensor patterns are defined by inkjet printing on selective-wetting surfaces. A poly(3,4-ethylenedioxythiophene) (PEDOT)-based conductive polymer dissolved in a non-aqueous solution was employed as a robust material against humid conditions. The selective-wetting patterns were fabricated using a liquid-repellent fluoropolymer layer and subsequent irradiation of vacuum ultraviolet (VUV) light through a shadow-mask pattern to obtain lyophilic areas. The PEDOT-based conductive polymer was printed by inkjet onto these selective-wetting surfaces, which resulted in the formation of patterns of resistors consisting of the conductive polymer. The patterned resistors exhibited a temperature coefficient of resistance (TCR) of −0.75%/°C at 23 °C, and small variation of resistance coefficient of 4.1%, which is comparable to the variations of metal resistors as references fabricated by photolithography. Organic temperature sensors consisting of the polymer resistors and metal reference resistors were demonstrated to function at -10–80 °C under ambient conditions.