Electrohydrodynamic printed nanoparticle-based resistive temperature sensor

Abstract

Temperature sensors based on the principle of a change of resistance are fabricated on polyethylene terephthalate (PET) substrates using a silver nanoparticles (AgNPs)-based ink using a bespoke drop-on-demand (DoD) electrohydrodynamic (EHD) printer. Two sensors consisting of either a single or double layer of silver were deposited using EHD printing and were found to exhibit an internal resistance of a few hundred ohms for the double-layer sensor compared to 1 kΩ for the single-layer sensor. The achieved pattern width was almost half the size of nozzle internal diameter (160 μm), and printed without treatment of substrate and nozzle. The sensors were characterized over a temperature range of 20 °C–110 °C. Both sensors showed a linear behavior with low hysteresis within the temperature ranges considered in this study and are found to recover the nominal resistance value with good reproducibility. The double-layer sensor showed high sensitivity with a temperature coefficient of resistance (TCR) of 3.4 × 10−3 , which is an order of magnitude larger than that observed for the single-layered sensor with a TCR of 8.41 × 10−4 . The sensors were also tested in a controlled humid environment and results are presented on the dependence of the internal resistance on the level of humidity. The proposed flexible printed sensors are promising for temperature monitoring systems and wearable technologies.