Research On Optimization And Control Of Piezoelectric Ink-Jet Print Head

As a flexible,convenient and environmentally-friendly fabrication method,inkjet printing has become a popular technology in the materials,electronics and manufacturing industries.Piezoelectric inkjet print head is the key device that defines the printing accuracy and product quality of printed electronics.This study first analyzes droplet formation mechanisms in depth using simulation of bidirectional fluid-structure interaction.Numerical optimization of the structure of the piezoelectric inkjet print head and its driving voltage pulse is then conducted.Finally,experimental studies are carried out to obtain the optimal control parameters.The concrete research contents are as follows:(1)Simulation of droplet ejection of the tubular piezoelectric inkjet print head.An electromechanical coupling model of piezoelectric material along the radial polarization and a gas-liquid two-phase model of transient analysis are constructed for bidirectional fluid-structure coupling analysis of piezoelectric inkjet printing.The structural deformation and droplet ejection process of piezoelectric inkjet print head is analyzed,which helps to further reveal the mechanism of droplet ejection.The dynamic response of the radial displacement of the glass tube to the voltage excitation is obtained,and the viscous damping has been found to have a significant attenuation effect on the radial displacement of the glass tube.The effects of viscosity and surface tension of liquid materials on the droplet formation have also been studied and the countermeasures proposed.(2)Numerical optimization of the piezoelectric inkjet print head.In order to realize the miniaturization of the structural design and to explore the key factors affecting the printing performance,numerical investigation and parameter optimization of the structural model and pulse excitation voltage are carried out.Influences of the thickness of the glass tube and thickness of the piezoelectric tube on the actuation sensitivity are analyzed.The piezoelectric inkjet print head's nozzle length is optimized.Then,effects of different voltage waveforms on droplet ejection are compared.The voltage parameters of trapezoidal wave have been tuned to increase the droplet ejecting velocity.Finally,effects of different piezoelectric materials and piezoelectric tube layers on the driving performance of the print device are studied,and the corresponding optimization design methods proposed.(3)Experimental study of system integration and control of piezoelectric inkjet printing.Experimental modules of the piezoelectric inkjet printing experimental system are introduced.The methods for effectively improving the sharpness of the droplet ejection are explained.The formation process of the droplet is observed by an industrial camera,and the pressure interval of forming the droplet stably measured by a pressure sensor.In addition,the effects of voltage amplitude,inlet pressure and voltage frequency on droplet ejection control have been analyzed,and methods for improving efficiency of piezoelectric inkjet printing proposed.Finally,a new solution with viscosity and surface tension close to nano-silver solution is concocted.The optimal dwell time of pulse and inlet pressure for printing this solution have been determined,which will contribute to future experimental design and research.