Research On The Preparation Technology Of Flexible Pressure Sensor Based On EHD Electrospray

EHD printing is a new micro-nano 3D printing technology emerging in recent years.Due to its high printing accuracy,simple equipment operation,wide material sources and low cost,it has attracted wide attention,and has a wide application prospect in flexible electronics,biomedical and wearable devices and other fields.At present,the flexible pressure sensor has the problems of low sensitivity and poor stability.In order to solve the above problems,a piezoresistive flexible pressure sensor with three-layer structure of packaging layer,functional layer and electrode layer was successfully prepared.The electrode layer was prepared by EHD printing technology,and nano silver conductive ink was used as the printing material to spray printing directly on the flexible substrate.The main contents of this dissertation are as follows:(1)Combining with the basic theory of electrohydrodynamics,the different modes of fluid injection and cone jet mode are systematically analyzed theoretically.Then,finite element simulation software(COMSOL Multiphysics)was used to simulate the electric field distribution under the electrostatic field and the conical jet.(2)A high-resolution three-dimensional experimental platform for EHD printing is built.The motion accuracy of the experimental platform is 0.05mm,and the effective stroke of X,Y and Z axes is 30cm,30cm and 20cm respectively.Taking the glass slide as the receiving substrate,the spray printing process of EHD was observed through experiments,and the shape change of cone jet and the line width change of printing wire under different voltage and pressure were studied,which verified the correctness of theoretical analysis and numerical simulation.The cone of conical jet will"shorten"with the increase of voltage and"elongate"with the increase of air pressure;over voltage will lead to multiple jets,and over pressure will make the liquid tend to jet vertically.For PET receives the base board,the experiment studied the spray print voltage spray,spray printing pressure and printing velocity influence on print graphics and rule,finally it is concluded that a set of optimum process parameters for ac pulse amplitude of voltage 1300V,500Hz frequency and duty ratio50%,8mm Hg pressure,spray printing speed of 24 mm/s.Under these parameters,the line width of nano silver wire is 100?m,which has high precision and good quality.(3)A three-layer piezoresistive flexible pressure sensor is designed and prepared.The packaging layer is PDMS film and the functional layer is MWCNTs/PDMS composite.The preparation of electrode layer is made by using the EHD printing technology of silver nano ink on PET film to prepare the interdigital electrode.Finally,the flexible pressure sensor was obtained and it exhibited sensing area of2?2cm²,high sensitivity(GF=3.26 kPa^-1),fast response time(55ms)and recovery time(72ms),and high stability(>1000 strech and release cycles).