Pressure Sensor for Wrist Pulse Monitoring

Pressure Sensor for Wrist Pulse Monitoring

High performance biodegradable electronic devices are becoming popular due to their enormous applications as biomedical implants or short term communication devices. They are biocompatible and eco-friendly. For example, wearable or implantable biodegradable pressure sensors are very useful for cardiovascular or blood flow monitoring.
But unfortunately, very few previous researches have focused on developing biodegradable pressure sensors. Here we propose a composite of Polylactic-co-glycolic acid (PLGA) and Polycaprolactone (PCL) for biodegradable piezo-capacitive pressure sensor fabrication for low-pressure measurement in tactile ranges of (0 < P < 5 kPa). An electrospun PLGA-PCL composite membrane has been used as elastomeric dielectric sandwiched between two biodegradable iron-zinc (Fe-Zn) bilayer electrodes, deposited on degradable Polyvinyl alcohol (PVA) substrate using electron beam deposition, and encapsulated in PLGA thin films for device fabrication. PLGA-PCL nanofibrous dielectric membrane is highly compressible and porous having tunable mechanical as well as dielectric properties and has been reported first-ever for biodegradable pressure sensor application.
The sensitivity of the sensor was found to be 0.863 ± 0.025 kPa−1 in the low-pressure region (0 < P ≤ 1.86 kPa) which is quite high as compared to previous literature on biodegradable sensors so far while it adapted to a value of 0.062 ± 0.005 kPa−1 for the high-pressure region (1.86 kPa < P ≤ 4.6 kPa). The lowest detected value was 1.24 Pa (at 10mgf).
The sensor showed a good average response and recovery times of 251 ms and 170 ms respectively. In vitro degradation studies of the sensor were performed in PBS solution and sensor lost 60% of its initial weight during first two weeks of degradation and continued to degrade even after that. After one week of incubation, the sensor showed a 19.5% decrease in low-pressure measurement range while there was no significant difference in the upper detection range. It has been used to measure the arterial pulse wave on the wrist and a 4 × 4 pressure sensor array was made to demonstrate its use in mapping different pressure points.

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