Study on the characteristics of thermo-electrodes of various deposition parameters for the flexible temperature sensor

In the paper, the flexible temperature sensor based on polyimide is designed and fabricated by magnetron sputtering technology. The impact of vacuum degree, sputtering power, and argon flow rate on the roughness and deposition rate of two thermo-electrodes [indium tin oxide (ITO)/indium oxide (In2O3)] is investigated with orthogonal experiment. The thermoelectric properties of the sensor are greatly improved by low temperature heat treatment. The sensitivity of the ITO film and In2O3 film increases by 2.61 times and 2.89 times, respectively, after 1 h low-temperature heat treatment. According to the comprehensive evaluation, an innovative step annealing process is proposed to optimize the heat treatment of the prepared thermo-electrodes. The fabricated flexible thin film thermocouples exhibit great operating characteristics in the low temperature measurement range. When the hot end's temperature reaches 181.5 °C, the thermoelectric force can reach 7.84 mV and the average Seebeck coefficient can reach 50.55 μV/°C. The repeatability and hysteresis error of the sensor is ±0.88% and 1.90%, respectively. The sensor in this work shows great application potential for in situ real-time temperature measurement in robotic dexterous hands, electronic skin, and foldable devices.