A carbon nanotube based NTC thermistor using additive print manufacturing processes

A fully printed carbon nanotube (CNT) based negative temperature coefficient (NTC) thermistor was developed for temperature sensing applications. The multi-layer NTC thermistor was fabricated using additive print manufacturing processes on a flexible polyethylene terephthalate (PET) substrate. Two silver (Ag) electrodes were printed using screen printing process. CNT based active layer was deposited by means of gravure printing. Organic and silver encapsulation layers were deposited using screen printing. The capability of the fabricated thermistor was investigated by measuring its response towards temperatures varying from −40 °C to 100 °C, in steps of 10 °C. As the temperature was increased from −40 °C to 100 °C, the resistive response of the thermistor decreased exponentially with an overall percentage change of 53% with the temperature coefficient of resistance (TCR) of −0.4%/°C. The stability of the printed thermistor towards relative humidity (RH) varying from 20% RH to 70% RH, in steps of 10% RH at two constant temperatures of 30 °C and 50 °C, was also studied. A maximum change of 0.34% and 0.1% was observed at 30 °C and 50 °C, respectively when compared to its base resistance at 20% RH. In addition, a response time of ≈300 ms and a recovery time of 4 s were measured for the printed thermistor with an accuracy of ± 0.5 °C.