Research On The Mechanism And Process Of Coaxial Focused Electrohydrodynamic Jet Printing For The Piezoelectric Nanostructure

Nanodevices possess the characteristics of high sensitivity,strong selectivity and low power consumption.There are great application prospects in the fields of electronic information,biomedical,environmental energy.The nanoscale structure is the basis of nanodevices and the key to achieving high performance of nanodevices.At present,the manufacturing process of nanoscale structures generally requires complicated process steps such as expensive focused ion beam,electron beam exposure,nanoimprinting,multi-layer etching,structure transfer,etc.,which have complicated process,low efficiency and high cost.It has hindered the wide application of nanodevices.Based on the theory of electrohydrodynamics and multiphysics,the mechanism of coaxial electrohydrodynamic jet constrained by electric field-fluid is studied,and a coaxial focusing electrohydrodynamic jet(CFEJ)nanoprinting method is developed.The detailed research work contains the following five parts:(1)The focused mechanism of the coaxial electrohydrodynamic jet is studied.The numerical simulation model of the forming process of the coaxial electrohydrodynamic cone-jet mode is established,and the formation mechanism of the nanoscale jet is detected.The relation between the scale ratio of the coaxial electrohydrodynamic jet diameter is established,and the coaxial focusd constraint mechanism is explored by analyzing the fourth-order symmetry equation of the electrohydrodynamic jet.Based on the three-phase flow and multiphysics combined action,the mathematical equations of the electric force superimposed fluid momentum are established.The generation and motion behavior of the charge in the solution under the action of the electric field are simulated and analyzed.The formation and evolution of the coaxial cone-jet mode are detected.The mechanism of the key process parameters on the coaxial jet is revealed,and the optimal parameter ranges for the formation of a stable coaxial electrohydrodynamic jet are obtained.(2)A CFEJ printing device was developed,and a coaxial electrohydrodynamic jet printing needle and key auxiliary devices were designed and manufactured.Based on the simulation research of the coaxial electrohydrodynamic jet printing needle,the shape and position parameters of the coaxial needle were obtained,and the coaxial focusd electrohydrodynamic jet printing needle device with adjustable position of the inner and outer needle was designed and manufactured to meet the coaxial electrohydrodynamic jet printing.A key auxiliary device for liquid electrode and temperature-adjustable substrate fixture was developed,which improved the stability of the coaxial electrohydrodynamic jet.and the controllability of the shape and size of the printed micro/nano structure.A coaxial focused electrohydrodynamic jet printing device control system was developed,which realized the coordinated control of each functional module of the device.(3)The CFEJ printing process was studied,and the influence of key process parameters on the jet and printing structure was determined.The AZ703 and the silicone oil was as the inner and outer liquid respectively to systematically study the variation law of the coaxial jet morphology with the printing parameters.The relation between the printing key parameters and the size and shape of the printed structure was studied.The size of the printed structure is inversely proportional to the voltage,the needle-substrate spacing,and the substrate speed,and is proportional to the flow rate of inner liquid.On this basis,the process parameters for the fabrication of nanoscale structure by using the CFEJ printing were optimized.(4)The high quality PZT piezoelectric nanowire structures were printed using PZT sol as a typical piezoelectric material.Based on the simulation and process research of CFEJ.PZT sol was used as the inner material,and PZT nano wire structures such as wire array,broken wire and beam were printed with a minimum feature size of 40 nm and a printing speed of 300 mm·s-1,which realizes efficient manufacturing of piezoelectric nano wire structures.After annealing,the PZT nanowires show a standard perovskite phase structure with a grain size of?5 nm,which is much smaller than that of bulk material(?10 ?m).The printed PZT nanobeams exhibit high performance such as high piezoelectricity,high electromechanical coupling performance and high flexibility.The piezoelectric constant d33,and Young's modulus E are 450 pm·V-1 and 21 GPa respectively,which provide the infrastructure for high-performance nanodevices.(5)The resonance performance of PZT nanobeams were studied based on the theory of piezoelectric vibration and nanobeam structure characteristics.The first-order characteristic frequency and main vibration mode of the longitudinal vibration of the nanobeam were obtained through theoretical analysis and modal simulation.Then,a longitudinal vibrating high-frequency harmonic oscillator was designed and fabricated using the printed by using the printed double fixed PZT nanobeam.Based on the principle of piezoelectric excitation-current pick-up,a nanobeam resonance test system was established and the resonance characteristics of PZT piezoelectric nanobeams were evaluated.The resonance frequency of the piezoelectric nanobeam was adjusted by the pre-tightening action of the gate DC bias voltage.