Development of an improved wearable device for core body temperature monitoring based on the dual heat flux principle

Objective: In this paper, a miniaturized wearable core body temperature (CBT) monitoring system based on the dual heat flux (DHF) principle was developed. Approach: By interspersing calcium carbonate powder in PolyDimethylsiloxane (PDMS), a reformative heat transfer medium was produced to reduce the thermal equilibrium time. Besides, a least mean square (LMS) algorithm based active noise cancellation (ANC) method was adopted to diminish the impact of ambient temperature fluctuations. Theoretical analyses, finite element simulation, experiments on a hot plate and human volunteers were performed. Main results: The results showed that the proposed system had the advantages of small size, reduced initial time (~23.5 min), and good immunity to fluctuations of the air temperature. For the range of 37–41 °C on the hot plate, the error compared with a Fluke high accuracy thermometer was 0.08 ± 0.20 °C. In the human experiments, the measured temperature in the rest trial (34 subjects) had a difference of 0.13 ± 0.22 °C compared with sublingual temperature, while a significant increase of 1.36 ± 0.44 °C from rest to jogging was found in the exercise trial (30 subjects). Significance: This system has the potential for reliable continuous CBT measurement in rest and can reflect CBT variations during exercise.