Lightweight Probe Cover for Wearable Thermal Device Designed Through Topology Optimization

Core body temperature (CBT) is a useful indicator of physiological changes. Wearable CBT sensors have been developed, including those based on the heat flux method, which is noninvasive but sensitive to environmental changes. An improved method that uses a high-thermal-conductivity material to cover the probe has been recently developed. However, the probe cover increases the sensor weight. Here, we develop a lightweight probe cover that maintains high measurement accuracy. The cover shape was designed using topology optimization. The total probe weight is 15 g, which is significantly lower than that reported in our previous study and is comparable to the weight of a commercial wearable sensor (12 g). Numerical simulation demonstrates that a sensor with the proposed cover can achieve a high accuracy of $0.009~^{\circ }$ C, exceeding the tolerance error of $0.1~^{\circ }$ C of an electronic thermometer. A human experiment shows that the wearable CBT sensor can measure temperature with an accuracy ( $0.027~\pm ~0.016~^{\circ }$ C) higher than the tolerance error of an electronic thermometer, although not as high as the designed accuracy. The results demonstrate that the sensor has potential for practical applications.