The Study Of Flexible Self-powered Sensors Based On Piezoelectric Materials

With the development of emerging portable/flexible sensors,monitoring human physiological signals is an effective way for disease diagnosis and health assessment.But the poor portability and flexibility of conventional healthcare sensing devices restrain the practical applications.For meeting the practical demand,researchers are focusing on developing portable and flexible sensors,which can attach to human body for detecting and distinguishing external mechanical stimulus.Multi-functions,flexible construction and embeddable power source are the key factors in flexible device application in human body.But,realizing these multi-functions through physical/chemical process of the device is a challenge.A flexible self-powering device for actively detecting body motion and degrading organic pollutants has been fabricated from PVDF/TiO2 nanofibers through high voltage electrospinning method.The sensor can be driven by external mechanical vibration,and actively output piezoelectric impulse.TiO2 nanostructures have been intensively investigated for polluted-water treatment due to their excellent characteristics of high photocatalytic efficiency,low cost,environmental friendliness,nontoxicity and high stability.However,in the process a large proportion of photo-generated electron-hole pairs recombine before the photocatalysis takes place,lowering down the photocatalytic efficiency.Based on coupling piezoelectric and photocatalytic properties of PVDF and TiO2,the photocatalytic efficiency could probably be enhanced.A flexible self-powered smelling device for real-time monitoring the environmental atmosphere(e.g.the mining environment)has been fabricated from piezo-gas-sensor matrix of ZnO-based composite nanowires(NWs)via soft photolithography technique.(1)A flexible self-powering device for actively detecting body motion has been fabricated from PVDF/TiO2 nanofibers.PVDF/TiO2 nanofibers are synthesized by high voltage electrospinning method.The device can be driven by external mechanical vibration,and actively output piezoelectric impulse.The outputting piezoelectric voltage can be significantly influenced by different applied deformation,acting as both the body-motion-detecting signal and the electricity power for driving the device.The device can detect various body motions,such as pressing,stretching,bending finger and clenching fist.(2)The flexible self-powered has distinct self-cleaning characteristic through piezo-photocatalytic coupling process.The photocatalytic activity of TiO2 and the piezoelectric effect of PVDF are coupled in a single physical/chemical process,which can efficiently degrade organic pollutants on the device.For example,methylene blue(MB)can be completely degraded within 40 min under UV/ultrasonic irradiation.The self-cleaning characteristic of the device basing on polarized PVDF/TiO2 nanofibers film can facilitate its practical application.The present results could provoke a possible new research direction for realizing self-powering multifunctional device.(3)A flexible self-powered smelling device for real-time monitoring the mining environment has been fabricated from piezo-gas-sensor matrix of ZnO-based composite nanowires(NWs)via soft photolithography technique.The device attached on human body can be driven by body motions and actively output piezoelectric signal.The outputting piezoelectric signal can be significantly influenced by surrounding gas atmosphere,acting as both the gas sensing signal and the electricity power for driving the device.The device includes four piezo-gas-sensor matrixs for cross-reactively detecting humidity,ethanol,hydrogen sulfide and methane and the device has can effectively differentiate humidity,ethanol,hydrogen sulfide and methane.The present results could provoke a possible new research direction for promoting the practical application of flexible self-powered smelling electronic-skin in specific occasion.