Numerical Investigation of Microporous Insulation for Power Reduction in Zero-Heat-Flux Thermometry

Zero-heat-flux (ZHF) thermometry is a clinically validated method for non-invasive core body temperature monitoring, yet its broad adoption in wearable applications is constrained by the high power consumption of the heater element. In this study, we numerically investigate the role of microporous insulation in minimizing energy demand while preserving measurement accuracy. A three-dimensional finite element model of a ZHF probe was implemented in COMSOL Multiphysics 5.4, consisting of a resistive heater, a microporous insulation shell, and a skin-equivalent substrate regulated by proportional-integral-derivative (PID) control. A Taguchi L9 orthogonal array was utilized to systematically investigate the effects of porosity (0-90%), insulation thickness (2-4 mm), and the convective heat transfer coefficient (5-15 W/m²·K) on the thermal performance of the ZHF thermometry system. Two performance metrics-heater energy consumption and settling time-were analyzed using analysis of variance (ANOVA). The results indicated that porosity accounted for more than 95% of the variance in heater power and over 80% of the variance in settling time. The configuration with φ = 90% and t = 3 mm demonstrated a balanced trade-off between energy efficiency and transient response for low-power ZHF thermometry. These findings provide design insights for energy-efficient wearable temperature sensors.