PZT Nanowires/graphene Film Flexible Heterogeneous Integration And Its Piezoresistive Properties

In recent years,with the rapid development of electronic information technology,sensor technology is moving towards the process of flexibility,multi-function,miniaturization,high performance,integration and passivity.The existing sensor preparation materials,structures and principles need to be innovated and upgraded.Force sensitive active material is an important research direction of new sensor materials.At present,force sensitive active materials mainly include metal materials,inorganic semiconductor materials and carbon based materials.Graphene has become one of the most popular materials for flexible pressure sensor because of its unique two-dimensional honeycomb structure,which has excellent electrical and mechanical properties.However,the graphene film pressure devices fabricated by chemical vapor deposition（CVD）are insufficient in terms of flexibility and sensitivity.Therefore,it is still a great challenge to study the graphene film-based pressure sensors which has both flexibility and high sensitivity and good application prospects.Graphene films exhibit excellent piezoresistive properties under strain and can withstand up to 25%of elastic strain,accompanied by changes in conductivity and electronic band structure.In this paper,two-dimensional graphene and one-dimensional Lead Zirconate Titanate（PZT）nanowires are integrated into flexible heterogeneous materials,which are used as active materials to construct a flexible pressure sensor with enhanced sensitivity.The mechanism,preparation,piezoresistive properties and application of the device are studied in depth.The polarized charge produced by piezoelectric nanowires under mechanical stress can be used as an ionization impurity to increase the scattering carrier of graphene,thus changing the conductivity of graphene.In addition,the piezoelectric properties of self-made PZT nanowires were studied by Piezoelectric Force Microscope（PFM）.The measured piezoelectric constant is relatively high（88 pm/V）,so the high piezoelectric characteristics of PZT nanowires are more conducive to the increase of graphene scattering carriers.In this paper,the piezoresistive performance of the sensor is studied by using the self built test platform.The results show that the device has an enhanced sensitivity of 2.95×10^-2kPa^-1,which is higher than the sensitivity of most graphene film-based pressure sensors.Then,the piezoresistive performance of the device under bending strain was also measured.It is found that the piezoresistive performance under bending strain is better than that under stress.Finally,through the practical application experiments such as finger bending test and handwriting letter test,the application potential of the device in wearable and handwriting authentication technology is proved.