Use of finite element analysis to optimize probe design for double sensor method-based thermometer

Body temperature is an essential vital sign for assessing physiological functions. The double sensor method-based thermometer is a promising technology that may be applicable to body temperature monitoring in daily life. It continuously estimates deep tissue temperature from the intact skin surface. Despite its considerable potential for monitoring body temperature, its key design features have not been investigated. In this study, we considered four design factors: the cover material, insulator material, insulator radius, and insulator height. We also evaluated their effects on the performance of the double sensor thermometer in terms of accuracy, initial waiting time, and the ability to track changes in body temperature. The probe material and size influenced the accuracy and initial waiting time. Finite element analysis revealed that four thermometers of different sizes composed of an aluminum cover and foam insulator provided high accuracy (<0.1 °C) under various ambient temperatures and blood perfusion rates: R=20 mm, H=5 mm; R=15 mm, H=10 mm; R=20 mm, H=10 mm; and R=15 mm, H=15 mm. The initial waiting time was approximately 10 min with almost the same traceability of temperature change. Our findings may provide thermometer manufacturers with new insights into probe design and help them fabricate thermometers optimized for specific applications.