Department of Mechanical Engineering

Faculty Candidate - Dr. Xiaopeng Qu

"Jumping droplets: from self cleaning to hotspot cooling"

Dr. Xiaopeng Qu

Research Scientist
Department of Mechanical Engineering and Materials Science
Duke University

Abstract

When condensate droplets merge together on a superhydrophobic surface, the newly formed droplets can spontaneously jump away from the surface. Powered by surface energy, this self-propelled phenomenon is independent of external forces. In this presentation, we will focus on two applications of these jumping droplets in biological self-cleaning and hotspot thermal management.

In the first application, the self-propelled jumping is used to autonomously remove contaminants from superhydrophobic surfaces. This new mechanism only requires the exposure to condensing water vapor which is ubiquitous in nature. The jumping condensate can remove both biological and inorganic contaminants that cannot be easily removed by gravity, vibration or wind. By eliminating the requirement for either impacting water drops or external forces, the jumping-condensate mechanism challenges the conventional wisdom of superhydrophobic self-cleaning (the “lotus effect”) with strong implications for engineering interfacial materials.

In the second application, the jumping condensate is used as an adaptive mechanism to return the working fluid toward the hotspots in a vapor chamber heat spreader. The direct return mechanism exploits the fact that the condensate droplets jump perpendicular to the superhydrophobic condenser. In a vapor chamber with parallel condenser and evaporator, the jumping droplets enable a hotspot cooling performance superior to solid heat spreaders. This new paradigm of hotspot cooling is particularly suited for managing mobile hotspots prevalent in microprocessors and power electronics.

Biography

Dr. Xiaopeng Qu is a Research Scientist in the Department of Mechanical Engineering and Materials Science at Duke University. After receiving his Ph.D. in Mechanical Engineering from Hong Kong University of Science and Technology in 2010, Dr. Qu worked as a postdoctoral researcher at the Max Planck Institute before joining Duke in 2012. Dr. Qu’s research interest is in microscale thermal and fluidic systems with applications ranging from thermal management to bioinspired materials.

Tuesday, May 20, 2014
1:30 PM
132 Fluor Daniel Building