Flexible and Wireless Multipoint Epidermal Temperature Sensor

Measurement of body temperature is the most frequent medical screening performed in both hospital and domestic environments. Dual-heat-flux (DHF) thermometry provides an indirect method to estimate deep body temperature, which is unpractical and uncomfortable to be measured, from the easily accessible surface of the skin, by exploiting four temperature sampling points on the same device. This paper combines, for the first time, the DHF method with the flexible epidermal Ultra High Frequency (UHF) Radio-Frequency IDentification (RFID) technology to replace bulky and wired state-of-the-art DHF devices. Four RFID integrated circuits (ICs) with embedded temperature sensors are used in place of the wired temperature probes so that they will be in charge of both sensing and wireless transmission of the data by means of four small antennas also embedded in the device. By integrating the antennas within elastomeric substrates, a highly conformable plaster-like device is achieved. It is flexible and soft and can be read from a distance of more than 15 cm regardless of the curvature of the body region where it is placed, and also in the case of moderate displacement (±5 cm) with respect to the external interrogator.