The Research Of Ink-jet Printing Based On Electro-hydrodynamic(EHD)

Electro-hydrodynamic(EHD) technologies have been applied in numerous areas, such as EHD ink-jet, EHD pump, EHD enhanced heat transfer and EHD atomization etc. As a new type of printing technology, EHD ink-jet printing overcomes the limits of solution’s viscosities, nozzle sizes and driving pressures in the traditional ink-jet printing, and has advantages of good compatibilities with materials, high resolutions, well system stabilities and super control degrees. EHD ink-jet technology involves multiple physical quantities of electric, flow, material properties and environmental conditions surrounding, so the developments of control methods and technical mechanisms are currently the major points and difficulties in this research. During the process, cone-jets are formed in milliseconds and in the range of microns under high voltages, which make it difficult to study its development process using conventional experiments and technologies. In this dissertation, the research work focuses not only on the theory theoretical study, but also on the simulative and numerical analysis of EHD ink-jet printing.Firstly, put forward the basic principle of EHD printing, Taylor effect, meniscus status during the course and various jet-modes. The stability of cone-jet is also discussed using one dimensional E -Q modeling to summary the critical voltage and flow rate, which can solve most circumstances of specific flow pulsation, spray and cone-jet. Secondly, conduct four approximations for the governing equations of cone-jet formation: electro-quasistatic, electro-neutrality, zero diffusive current and incompressible flow. These approximate assumptions are the foundations for simulation analysis. Analyzing the forces acting on Taylor cone in the electric field, such results can be obtained: during the Taylor-cone section, tangential electric field force prevailingly maintains the stability of the Taylor cone; during the jet section, normal electric field force principally prompts the formation of the jet radius together with the surface tension. The potential field distribution obtained by simulation method explains the formation of cone-jet and the simulative cone-jet is very closest to the experimental results after normalization, which proves the validity of the four approximates. Finally, obtain the numerical profile of cone-jet by adjusting the physical model of condensation-heating of capillary liquid jet, and the influences of nozzle sizes, net heights, flow rates, mass fractions and surface tensions on the jet diameter are focused; then introduce the concept of surface tension in the droplet formation process on the collector, and the correlations of droplet diameters with the pulse voltage frequencies, the surface tensions and flow rates of the liquid are emphasized.