Flexible and Wireless Multi-Sensor Thermometer based on Dual-Heat-Flux Model

A change in body temperature can be a symptom of an unhealthy status, or can reflect physical activity and medicine intake. Temperature measurements over the skin are practical and non-invasive, but a reliable evaluation of core temperature requires invasive measurements in body cavities. Dual-heat-flux (DHF) thermometry offers an indirect method to estimate deep body temperature from the surface of the skin with four sampling points on the same device. DHF thermometers are currently wired, bulky, and rigid, but they can be made flexible and wireless by means of Ultra High Frequency (UHF) Radio Frequency IDentification (RFID) Integrated Circuits (ICs) having embedded temperature sensors. This paper presents the thermal design and preliminary temperature measurements of a multi-channel epidermal thermometer that combines RFID technology with the DHF method. The estimation of deep body temperature from wireless measurements on the surface of the skin seems feasible, with an error of about $0.5^{\mathrm{o}}C$, still improvable.