Flexible Self-Powered Electret Pressure Sensor For Physiological Monitoring

Flexible medical electronics,which have advantages of miniaturization,portability,low cost and no interference of life,are playing significant role in the field of Internet of Medical Things?IoMT?or intelligent healthcare.Flexible sensors capable of monitoring physical,chemical and biological signals,which can act as a key medium for communicating internal physiological condition and outside world,could imply vital health status or parameters and play essential role in flexible medical electronics.Among them,pressure sensors are widely reported,as it could tell important information about artery,heart,breath system,etc through perceiving common mechanical physiological signals in bio-interface.Traditional flexible pressure sensors such as resistive and capacitive pressure sensors rely on power supply,which will inevitably cause inconvenience of life.Flexible self-powered electret pressure sensors have advantages of high output,low cost and lightweight,showing great potential in human physiological signal monitoring.However,few researches,especially on the high performance human interface related flexible pressure sensor,have been conducted.In this thesis,we focus on exploring highly flexible electret pressure sensor with capabilities of high sensitivity,wide pressure range,and high linearity for human physiological monitoring.Main results are listed below:1.Based on the parallel-plate capacitor model,the charge distribution,electric potential and electric field of self-powered electret pressure sensors were theoretically studied for investigating parameters influencing the output of the self-powered pressure sensors.Further studying the relationship between the deformation of air gap and the electrical output of the self-powered pressure sensor,we revealed parameters influencing the sensitivity of self-powered pressure sensors and proposed a hollow microstructured pressure sensitive electret nanogenerator by vapor assisted template method.The pressure sensor had high sensitivity of 18.98 V·kPa^-1,fast response time?about 57 ms?and good stability?>10000?.We demonstrated that the sensor could be successfully used for monitoring the heartbeat,breath,body movement and other physiological signal during sleep without skin contact.2.Through the theoretical study of factors affecting the pressure range of self-powered sensors,a hierarchical flexible self-powered pressure sensor was fabricated for multifunctional cardiovascular monitoring.The pressure sensor not only possessed high pressure-sensitivity(7.989·kPa^-1)but also had wide working pressure range of 0.1⁶0 kPa.Moreover,good cycle stability?>8000?,and fast response time?40 ms?were also achieved.Because of the high performance,the hierarchical self-powered pressure sensor was successfully used for monitoring human pulse wave and cardiovascular condition including arterial stiffness and heart condition.3.A high-performance cellular polypropylene self-powered pressure sensor with high linear sensitivity and wide linear range was prepared and explored.The self-powered pressure sensor has a wide linear pressure-sensing range of 0⁵0 kPa and high sensitivity of0.09 V·kPa^-1,which is far beyond that of many reported pressure sensors.Based on the theoretical study,factors influencing the output and the sensing performance were demonstrated.A strategy for improving the sensitivity was proposed by tuning the orientation of space charges and multiplying method.Finally,the high-performance cellular self-powered pressure sensor was successfully utililzed for monitoring physiological signals such as respiration,heartbeat and body movement during sleep,exhibiting excellent stability in use.