Two-channel Epidermal RFID Sensor for the Analysis of Nasal Respiratory Flow

Abnormal breathing can be a symptom of an unhealthy status. Conventional diagnostic exams involve cum-bersome and intrusive instrumentation that are overall un-comfortable for the user. Ultra High Frequency (UHF) Radio Frequency IDentification (RFID) devices, instead, enable non-invasive wireless monitoring of respiration by means of epidermal antennas with embedded temperature sensors. Two sampling points in the same device could be useful to independently measure the respiratory flow of the two nostrils, which are known to work differently. At this purpose, this paper proposes a two-channel flexible epidermal sensor for the bilateral monitoring of nasal breathing based on temperature measurement. It compactly adheres on the prolabium, and comprises two coupled T-match asymmetric dipole antennas whose ICs are placed at the exit of the nostrils. The sensor can be read up to 60 cm. Experimental tests on some prototypes demonstrated that, thanks to negligible cross-sensitivity of the two ICs' temperature data, the breathing rate can be accurately estimated independently for the two nostrils.