Levich Institute Seminar Announcement, 11/04/2008

Tuesday, 11/04/2008 2:00 PM Steinman Hall, Room #312 (Chemical Engineering Conference Room) Professor Paul Steen Cornell University School of Chemical and Biomolecular Engineering "The Palm Beetle, Adhesion Devices, Electroosmosis and Volume-Scavenging Amongst Coupled Droplets "

ABSTRACT

In a striking display from Nature, the palm beetle defends itself by adhering at extraordinary strengths to the palm leaf. Its survival depends on surface tension and its ability to manipulate a multitude of micron-sized liquid bridges. Inspired by this example, we seek to make a wet reversible super-adhesion device and, more generally, to manipulate systems of coupled droplets/bridges through actuation. In the first part of the talk, our discovery that actuation by electroosmotic pumping performs well against capillary pressures at small scales will be reviewed. The droplet-droplet switch, a two-component bi-stable system, illustrates. In the second part of the talk, the focus will be on volume-scavenging amongst many droplets in an array (scavenging needs be avoided in the adhesion-pad application). Coupled, communicating droplets naturally reconfigure owing to surface-area minimization. This coarsening behavior tends to concentrate volume as neighbors scavenge from one other until a single 'winner' emerges. The identity of the winner and the dynamics of coarsening depend on details of the coupling network. Our solution to this problem will be presented. In closing, there will be a summary of progress toward the device goal.

BRIEF ACADEMIC/EMPLOYMENT BACKGROUND:

Dr. Paul H. Steen has been at Cornell since 1982. He is a Professor in the School of Chemical and Biomolecular Engineering, with field affiliations in Applied Mathematics and Theoretical and Applied Mechanics. His research is in the area of dynamics and stability of fluid systems with interfaces. Current focus is on shape-changes of gas/liquid and liquid/liquid interfaces and stability issues arising in the continuous casting of thin sheets of metal. He is a fellow of the American Physical Society (1996) and has been active in APS/Division of Fluid Dynamics affairs as chair of the Fluid Dynamics Prize Committee, chair of the Acrivos Dissertation Award Committee and as a member of the Executive, Program, Publications and Frenkiel Award Committees. He has co-edited “A Gallery of Fluid Motion”, a DFD-APS project published by Cambridge University Press. He is an Associate Editor of the Journal of Fluid Mechanics. He has more than 60 journal publications and has edited several books. Prior to coming to Cornell, Steen received his PhD from The Johns Hopkins University in 1981 and held a post-doctoral position in Chemical Engineering at Stanford University, after having completed undergraduate degrees in Engineering and English Literature at Brown University. At Cornell, he has served as Director of Graduate Studies for Chemical Engineering. He has received an Alexander von Humboldt Fellowship and has been a Senior Guest Scientist at the Forschungszentrum Karlsruhe, Germany.

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