Human Breathing Monitoring by Graphene Oxide Based Sensors

Non-invasive monitoring of human health is of a high importance for early detection of illnesses and improving life quality. Breath monitoring is important for detection of severe diseases such as lung cancer or sleep apnea. In this work, we introduce a breath sensor based on a graphene oxide film deposited on silver interdigitated electrode and a flexible substrate. The graphene oxide film was then thermally annealed to partially reduce the graphene oxide. The measurements of sensor impedance carried out at different humidity levels show a high decrease by several orders of magnitudes by increasing the relative humidity. Sensitivity to humid air results from the high hydrophilicity of the graphene oxide due to its oxygen functional groups. The change of transport mechanism from Nyquist plot shows the change of the sensor impedance from the capacitive behavior to a semicircle of parallel resistance and capacitance. The sensors show an ultrahigh sensitivity to humidity at high humidity values, a very low response time of less than one second and an excellent repeatability of the measurements. For tracking human breathing, the reaction on natural breathing was acquired by a digital oscilloscope together with an IoT mobile application to visualize the results in real time and store them for further processing. The sensor performance shows that it is suitable as a noninvasive and flexible breath-monitoring sensor system. The proposed sensor can be a step to flexible and cheap wearable sensors for detection of human breath and hazardous breath airborne such as COVID-19.