Evaluation of thickness‐dependent temperature coefficient in a thin film thermocouple and its in vivo test using a porcine model

A micromachined thin film thermocouple (TFTC), that is, a contact-type temperature sensor, was fabricated to diagnose the physiological state. The TFTC involved two metal films (copper and constantan) with considerably different Seebeck coefficients. Six types of TFTCs with different film thickness values were fabricated and experimentally characterized to determine the thickness-dependent temperature coefficient attesting to a high sensitivity of the sensors. The performance of each TFTC was evaluated by measuring the induced thermal electric motive force and temperature in the temporal and spatial domains by using a data acquisition board and an infrared camera, respectively. Moreover, an in vivo experiment of the proposed TFTC with the highest temperature coefficient (38.9 µV/°C) was conducted by measuring the body temperature difference of an anesthetized porcine model during its euthanasia process to evaluate the device performance.