Bolometric Effect Enhanced Ultrafast Graphene Based Do-It-Yourself Wearable Respiration Sensor for Personal Healthcare Monitoring

The report demonstrates the Near Infrared (NIR) illuminated enhanced breath sensor utilizing direct writing of solvent free graphene pencil on biodegradable cellulose paper to monitor different respiration patterns and rate for non-invasive personal healthcare monitoring. Various breath patterns such as deep, slow and fast breathing were tested and interestingly the fabricated sensor was able to distinguish the pattern based on the frequency and the amplitude of current peaks obtained. Also, the fabricated sensor was able to identify the hydration level of the individual where in 25-35 % decrement in the sensor current value was observed when the measurements were performed after consuming water. To enhance the desorption process of water molecules, breath sensing was performed under NIR illumination where the photo response was bolometric in nature which results in the faster desorption process due to the heat generated. The fall time observed under NIR illumination was 1.32sec and without NIR illumination was 2.01 sec suggesting a 34% improvement in the performance of the fabricated sensor. The change in the current under human breath exhalation is due to the electron transfer process and swelling of the graphene sheets. Detailed conduction mechanism of graphene under NIR illumination is presented suggesting the combination of both bolometric nature and direct photoconductivity with the former predominantly affecting the conductivity. The successful demonstration of such low-cost, do it yourself wearable enhanced respiration sensor is a major step ahead in the non-invasive personal healthcare monitoring and hold potential for commercialization.