Printable Graphene-Polyurethane Sensor on Nylon Cuff for Wearable Blood-Pressure Monitoring

Objective: To design a wearable pressure sensor on conventional BP cuff/cuffless fabric that accurately measures blood-pressure and respiration rate continuously. Design and method: A printable stretchable graphene-polyurethane sensor is employed to sense the artery movement. It works on the principle of piezoresistance where the electrical resistance of the sensor changes with mechanical strain. This signal can be amplified and converted to digital using analog to digital convertor. Therefore, the signal produced from the movement of the artery and hence the heart can be acquired in real-time. This data can be used to measure the heart rate, respiration rate and blood-pressure. This printable sensor could replace the silicon piezoresistive sensor used in conventional digital BP monitors. The wearable sensor could also be calibrated easily with standard BP measurement methods. Further, cuffless monitoring could be performed by correlating the strain in wearable fabric with pressure exerted on artery. Results: The performance of the graphene-polyurethane sensor was compared to commercial silicon piezoresistor based sensors used in conventional digital monitors. The sensitivity of graphene-polyurethane sensor was compared to silicon sensor. Further the pulse ripple amplitude with change in pressure typical of oscillometric method were observed and recorded. Since the graphene-polyurethane sensor is in direct contact with arteries, this improves the dynamic sensing ability. Further, the printable stretchable sensor design is more compact electronic and power design. Conclusions: Wearable cuffless blood pressure monitors using graphene-polyurethane sensors that can be printed on fabric were designed and tested alongside conventional digital blood pressure monitors. The sensitivity of the graphene-polyurethane sensors to arterial pulse was more than twice that of the commercial silicon based piezoresistors.