Experimental Research On Drop-on-demand Electrohydrodynamic Jet Printing Of Micron Flexible Structures

In recent years,Electrohydrodynamic Jet Printing(EJP)technology has been increasingly widespread in the fields of flexible displays,biomedical micro devices,MEMS sensors and flexible electronic packaging.The use of EJP technology can break through the limitations of extrusion-based printing and inkjet printing on the inner diameter of the nozzle and the resolution of the forming structure,but the stability of jet and the consistency of printing need to be further improved.The high-insulation polymer substrates commonly used in flexible electronic devices are easy to accumulate residual charges during the process of electrojet printing and generate electrostatic repulsion on the subsequent jets,which affects the stability and controllability of printing.In this paper,the electrojet flow behavior on the flexible substrate under different needles and printing parameters was simulated,and the needle structure and parameter range of fine jet formation were obtained,which enhanced the stability and performance of electrojet printing on the flexible substrate.Then,the influence of high-viscosity materials printing on flexible substrate was studied,the EJP process of micron flexible structure was formed,and the influence of process parameters on the size and morphology of the formed structure was determined.A variety of micro flexible structures and patterns were printed on demand.The research content mainly includes the following three parts:Firstly,an EJP platform was built and the fluid supply method was optimized to improve the stability of high viscosity ink flow in the printing process.An EJP head device with low-temperature auxiliary was developed,to improve the control of width and thickness of the flexible structure prepared by EJP process.A control system of EJP was developed to realize the coordinated control of each functional module of the device.Secondly,a simulation model of electrojet formation was established.The influence of the needle,voltage and pressure on formation of jet on flexible substrate was simulated and analyzed to obtaine the needle structure and parameter range for stable jet formation,which weakened the residual charge accumulation effect on flexible insulating substrate surface and enhanced the stability and controllability of jet formation on flexible substrate.Finally,the EJP process on flexible substrate was studied to determine the influence of process parameters such as voltage waveform,pressure,printing speed,printing height,pulse high voltage and pulse frequency on the characteristics of the printing structure.The EJP process of micron flexible structure was studied to determine the influence of voltage,pressure,printing speed and printing height on the formation of high-viscosity flexible structure.Dot and line array structures and patterns were printed on PET substrate when a variety of polymers were used as the printing materials.Polyline,meandering and overhanging flexible structures with high viscosity were printed when the high-viscosity polymers and conductive silver paste were used as the printing materials.The potential of electrohydrodynamic jet printing in the high quality and high efficiency on-demand fabrication of micron flexible structures was demonstrated.