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IFDL at WSUV investigates a variety of surface-tension dominated fluid phenomena including inkjet, droplet impact, wetting, coating. We use both theoretical modeling and experimental methods to understand various types of interfacial flows. IFDL is equipped with state-of-the-art equipment and simulation software to carry out research in microscopic flow area.

CFD Modeling of Microfluidic Flows

In this research area, we are investigating the complex interfacial fluid flows through high-speed imaging system and numerical simulation. The outcome of study can help understand the fundamental fluid physics involved in various microfluidic devices and improve the performace of these devices. A Cartesian grid based adaptive-mesh-refinement (AMR) CFD code based on open source code Gerris has been developed to simulate the free surface flows in inkjet devices.  If you would like to know more details, please contact us.

The comparison of droplet ejection from experimental images and simulation
The comparison of droplet ejection from experimental images and simulation

Droplet-Powder Interaction

Liquid droplet interaction with powder substrates is a ubiquitous phenomenon in nature and engineering applications. In recent years, various drop-on-demand inkjet technologies capable of precisely delivering pico-amounts of liquid have been adopted in a number of novel powder-based additive manufacturing processes. The interaction between micrometer-sized droplets and powder plays a significant role in the quality of products made by these 3D printing technologies. The task aims to gain fundamental knowledge of the influences of the interaction between micron-sized droplets and powders on the powder-based 3D printing process.

Figure: (a) Profiles of Droplet of DI water and 7.5 % isopropyl alcohol (drop diameter ~4 mm) on nylon powder substrate with porosity є = 0.28, 0.34and 0.4. (The equilibrium contact angle is affected by both surface tension and powder compaction). (b) droplet absorption by powders due to capillary force.

Figure: Numerical simulation of a 20-micron droplet impact on powders.

High Speed Imaging System for Microscopic Flows

In this project, we have developed a stroboscopic high speed imaging system that can be used to observe the droplet ejection of inkjet technology as well as fluid physics at micrometer scale. The stroboscopic high-speed photography relies on the repeatability of the fluid physical events. The key elements in the system will include a high resolution digital camera with a lens system capable of imaging a field of view of a few millimeters, connected to a PC for control and image storage, an inkjet printhead with drive electronics and data source, a very short duration (~20ns) flash light source with delivery optics, and delay generator to delay the flash relative to the initiation of the printing event and to measure that delay time accurately.

In-house high-speed imaging for inkjet process