Soft Iontronic Capacitive Sensor for Beat-to-Beat Blood Pressure Measurements

Continuous beat-to-beat blood pressure (BP) monitoring provides hemodynamic information such as BP changes and waveforms over time, providing abundant information to more accurately diagnose a person's cardiovascular health compared to static cuff-based measurements. To overcome the shortcomings of current techniques, a highly sensitive (S = 108.52 kPa(-1) for 0-5 kPa range) soft capacitive sensor that can be worn like a Band-Aid is developed such that continuous beat-to-beat BP monitoring can be sustainably achieved after an initial calibration. The sensor leverages iontronic material with air gaps for the dielectric combined with highly wrinkled, stretchable electrodes; the resulting average sensitivity of this device is demonstrated to be higher than that of other comparable sensors in literature. For the hemodynamic capture, the operating frequency of 300 kHz is chosen to achieve higher temporal resolution in continuous BP monitoring. Further, the multi-island design in this work allows for rapid placement of the sensor without needing to accurately align with the underlying artery. Because of the improved sensitivity, the sensors can be adhered to the pulse points without an applanator. Finally, this sensor demonstrates sustained beat-to-beat blood pressure recordings that show excellent systolic, diastolic, and mean arterial pressure correlation with an FDA-cleared device, the Caretaker.