Cellular Polypropylene Piezoelectret Devices For Human Energy Harvesting And Self-Powered Sensing

By virture of the advantages of smart management and portabilityetc, wearable electronics are being more and more popular, having extensive applications in health monitor and intelligent communication, etc. The power source of wearable electronics is an problem that may bring inconvenience, as batteries need to be charged frequently. In order to convert the abundant mechanical energy generated by human body into electricity, we develop flexible electro-mechanical energy transducers based on cellular polypropylene(PP) piezoelectret, and demonstrate the applications as self-powered sensors. The main contents and results of this thesis are listed below:1. Cellular PP is fabricated via hot expanding meyhod and the best expanding condition is explored. After 6 weeks, the d33 piezoelectric coefficient of the Cellular PP still keeps at about 200 pC/N.2. Flexible piezoelectret generator is fabricated based on cellular PP and the detailed power generating processes are studied. Specifically, the thickness variations of the air layers inside the cellular PP will change the surface charges densities in the two electrodes, resulting alternating currents.The maximum peak output power density of the flexible piezoelectret generator can reach 52.8 mW/m2. The generator can act as a self-powered health sensor to detect the cough and artery pulse, indicating its potential applications in personal health monitor.3. Paper-based flexible piezoelectret generator is fabricated by adhering carbon conductive paper on both sides of the cellular PP, which shows better output performance than common flexible piezoelectret generator. Paper-based flexible piezoelectret generator can be used as non-contacted sound detector, distinguishing sounds with different frequencies accurately. Moreover the sound detector can detect the sound generated by human, indicating its potential applications in mobile health and personal identification.