Design and Experimentation of a Batteryless On-Skin RFID Graphene-Oxide Sensor for the Monitoring and Discrimination of Breath Anomalies

Real-time and comfortable monitoring of the human breathing could allow identifying anomalies in the rhythm and waveform to be correlated with several pathologic disorders of respiratory and cardiovascular systems. A wireless sensor based on a flexible Kapton substrate, suitable to be stuck over the face skin like a plaster and provided with a graphene-oxide (GO) electrode, is here proposed for application to the monitoring of the moisture emitted during inhalations and exhalations. The GO-based electrode increases its dc resistance when exposed to humidity with a sensitivity of 60 Ω/RH. The device is compatible with the radiofrequency identification (RFID) standard in the UHF band. When used in battery-less mode, it can be read up to 60 cm. The RFID sensor has been successfully experimented in a measurement campaign involving 10 volunteers asked to reproduce a set of predefined normal and pathological breaths. The resulting resistance traces permit to well clusterize the breath patterns with respect to the respiration rate (extracted by a fast Fourier transform) and to the average peak variation of the sensor's resistance with an accuracy close to 90%.