Prof. Chang-Jin Kim
Department of Mechanical and Aerospace Engineering, UC Los Angeles
BSAC PhD 1991
November 25, 2014 | 12:30 to 01:30 | 540 Cory Hall
Host: Ming Wu
Unlike in regular scale, where tubing is needed to manipulate liquids, sub-millimeter scale liquids can be handled as discrete objects using the liquid-air interface as virtual walls. This unusual option is a result of surface tension dominating other mechanical forces in microscale. Early devices implementing this method include satellite-free inkjet printing; droplet-based micro RF switch; and complete miniature fuel-cell system with no moving part. These early successes led to two platform technologies based on surface tension. The first is the mechanism of electrowetting-on-dielectric (EWOD), which can manipulate droplets simply with voltages. As the number of manipulative functions grew (e.g., creating and moving droplets, mixing and separating droplets, separating particles in a droplet), the field of EWOD-based digital microfluidics has been established. Two application examples will be presented: on-chip sample preparation for MALDI-MS and on-chip synthesis of radiotracers for PET scan. The second platform technology is superhydrophobic (SHPo) surfaces on which water flows with less friction. We have obtained an unequivocal drag reduction as much as 75% in turbulent-boundary-layer flows, which represent water vehicles traveling in open sea. Furthermore, we have developed surfaces that remain SHPo indefinitely under water, removing both of the main bottlenecks. This is an example of surface-tension engineering, which is based on microscale physics, being applied to large-scale systems.
www.mae.ucla.edu/people/faculty/chang-jin-kim
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