The Study Of A Multi-function Device Based On Piezo-photoelectric Coupling Effect Of ZnO

The emerging portable/wearable electronics accompanying with the human body day in and day out have attracted worldwide research attentions for their potential applications in health-monitoring or bionic organs.The flexible sensing electronics,such as various electronic-skins(e-skins),can attach to human body(on or under the skin),establish the body-electric interface,and mimic the human sensory tissue.The emerging e-skins can be designed to mimic comprehensive properties of human perception via flexible device techniques.Thus,a vision e-skin for image recognition is one of the hot research topics for the applications in bionic organs and robots.In our previous work,a novel smelling e-skin for mimicking the olfactory epithelium has been reported.The vision is another important traditional recognition method of human perception.The artificial flexible vision e-skin may have great applications in the bionic retina and robots,e.g.making blinds re-see the blue sky.The traditional idea of building the artificial vision device is constructing an integration system from photodetector,signal processor,data analyzer and battery.Currently,the most commonly utilized approach is to power them by energy storage units such as batteries or capacitors.However,there are two major shortcomings.One is the limited lifetime,so that they cannot self-sustainably drive the electronics.The other is the difficulty of practical application,which could cause some problems if not dealing with its size properly.Thus,there is an urgent demand to design a new self-sustainable flexible vision e-skin that can rapidly recognize visual image and actively output bionic electric vision signal without external bulky battery.In this thesis,a new self-powered flexible vision e-skin has been realized from pixel-addressable matrix of piezophototronic ZnO nanowire(NW)arrays.The working mechanism is based on the optoelectronic/piezoelectric coupling effect(piezophototronic effect)of ZnO.Meanwhile,the piezophototronic effect applied in photocatalysis improvement method can availably enhance the efficiency of degradation of organic pollutants.The details are as follows:(1)Fabrication of a self-powered flexible vision e-skin:Firstly,the ZnO nano wire arrays were vertically aligned on a Ti substrate by a simple seed-assisted hydrothermal method.ZnO nanowire arrays were carefully smeared onto the Kapton substrate,and the nanowires were horizontally aligned on the substrate with uniform direction.The cross-finger electrodes are made by photolithography,resist development,etching and deposition of Ti.(2)UV detection:High UV detection performance of the new self-powered flexible vision e-skin had been fabricated based on excellent optoelectronic/piezoelectric coupling effect of ZnO.The e-skin can actively output an electrical impulse through the piezoelectric effect of the ZnO nanowire arrays,and the output piezoelectric voltage is significantly influenced by the intensity of UV light.And the piezoelectric voltages of the e-skin were decreased with increasing UV intensity.(3)Image recognition:The e-skin device has a 6×6 pixel-addressable matrix structure,and can map multi-point UV-stimuli through a multichannel data acquisition method,realizing image recognition.The piezophotodetecting performance of each pixel under patterned UV illumination is measured independently.For example,the“turn right”mask covering the UV light,forming the corresponding illumination pattern.The pixels have different response with different UV illumination,which forms a contrastmap and can be used to recognize the trafic indicator.(4)Photocatalysis:Semiconducting photocatalyst using unexhausted/renewable solar energy to degrade organic pollutants in wastewater has been considered as a promising green technique for environmental remediation.Piezoelectric field of ZnO nanostructures under applied deformation can effectively separate photo-induced electron-hole pairs(piezophototronic effect),reducing the carrier recombination.Under ultrasonic stimulation and solar illumination,Ag/ZnO nanotetrapods can completely degrade methyl orange within 25 min.The high piezo/solar-photocatalytic efficiency of Ag/ZnO nanotetrapods can be ascribed to the coupling of surface plasmon resonance and piezophototronic effect in the solar photocatalytic process.