Authors: E.P. Furlani
Affilation: Eastman Kodak Company, United States
Pages: 444 - 447
Keywords: ink jet, ink jet printing, jet instability, slender jet analysis, jet breakup, jet modulation
Liquid microjets are inherently unstable and can be modulated in a controlled fashion to create steady streams of picoliter-sized droplets at frequency rates in the hundreds of kilohertz. Such modulation has been achieved using CMOS/MEMS technology, which enables low-cost high-throughput droplet generators for applications that range from printed electronics to high-speed inkjet printing. The design of microfluidic printing devices requires rigorous and time-consuming CFD analysis. In this presentation we discuss a method for performing rapid parametric analysis of droplet generation that is useful for the design of such devices. We present a model for predicting the nonlinear deformation and breakup of modulated slender microjets. We adopt a one-dimensional slender-jet approximation and model the behavior of the jet using a system of coupled thermal/fluidic PDEs. We use the method of lines to reduce the PDEs to a system of ODEs, and solve for the free-surface, velocity, and temperature along the jet. We present parametric studies of jet breakup as a function of modulation amplitude and wavelength, and discuss how these parameters influence the time-to-breakup, the size of filaments, and the structure of the free surface at pinch-off. We also present a fabricated CMOS/MEMS inkjet printhead and describe its underlying device physics.