Flexible Multi-Layer Sensor for the Wireless Implementation of Dual-Heat-Flux Monitoring of Body Temperature

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 natural body cavities. Dual-heat-flux thermometry offers an indirect method to estimate deep body temperature from the surface of the skin with four sampling points on the same device, that however is currently wired, bulky and rigid. Therefore, its comfort and applicability are limited. Ultra High Frequency (UHF) Radio Frequency IDentification (RFID) devices, instead, can enable non-invasive wireless monitoring of temperature over the skin by means of epidermal antennas with embedded temperature sensors. By combining RFID technology with dual-heat-flux method, this paper presents a preliminary design of a dual-heat-flux epidermal RFID thermometer. It is flexible and more compact, and can be read wirelessly by an hand-held reader.