When   Monday, April 20, 2009   Time   4:00 PM - 5:00 PM  
Where   Technological Instit M 416 2145 Sheridan Rd.   map it
Audience   - Faculty/Staff - Student - Public
Contact   Molly E Scanlon   +1 847 491 5586  
Group   McCormick-Colloquia Engineering Sciences and Applied Mathematics

Applied Math Colloquium

Title: Dynamics and Stability of Volume Scavenging Drop Arrays: Coarsening by Capillarity

Speaker: Professor Paul Steen, Cornell University

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 through its ability to manipulate an array of micron-sized liquid bridges.  Inspired by this example, we seek to make a wet reversible super-adhesion device and, more generally, to actively manipulate arrays of coupled droplets/bridges.  In the first part of the talk, our discovery that electroosmosis can pump effectively against capillary pressure at small scales will be reviewed.  To illustrate, the droplet-droplet switch, a two-component bi-stable system, is actively toggled using an eo pump.  In the second part of the talk, the focus will be on passive volume-scavenging amongst many droplets in an array.  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 dynamical systems problem will be presented.  In closing, there will be a summary of progress toward the adhesive-device goal.