Flexible four-point conjugate thin film thermocouples with high reliability and sensitivity.

Thin film thermocouples (TFTCs) are designed by finite element analysis and fabricated on the flexible substrate (polyimide) based on radio frequency magnetron sputtering technology, which can be used to measure the temperature of the curved surface. Various novel structures of TFTCs with several multi-junctions are designed to improve the stability and the reliability of measurement. The characteristics of its thermoelectric output are simulated by software. As the temperature range varies between 10 °C and 200 °C, the electromotive force behavior experiments show that the average Seebeck coefficient of the TFTCs can reach 25.8 µV/°C, the resolution of sensor is less than 0.1 °C, and the temperature drift is only 1.3%, 1.2%, 1.0% at 84 °C, 110 °C, and 142 °C, respectively. The maximum drift rate of TFTCs is 0.234 °C/min at 142 °C. The flexible TFTC temperature sensor shows great advantages in sensitivity, stability, reliability resolution, and measuring range.