CAM colloquium - Friday, January 26
3:30 p.m.
655 Rhodes Hall

Speaker: Paul Steen, School of Chemical and Biomolecular Engineering, Cornell

Title: Dynamics and stability of coupled capillary-surfaces: adhesion inspired by Nature

Abstract: In a striking display from Nature, the palm beetle defends itself by adhering with extraordinary strength using liquid/gas surface tension, illustrating the power of parallel action and down-scaling to the micron size. Inspired by this example, we have set a technological goal to make a capillarity-based reversible super-adhesion device that works by manipulating arrays of droplets. This goal raises scientific challenges (in addition to fabrication challenges) owing to the nonlinearity inherent in systems of coupled liquid droplets and bridges. In this talk, we will describe some of the challenges already met and some that remain open. For example, the phenomenon of ‘volume-scavenging’ which has its basis in a stability theorem of Poincaré, is at the heart of two engineering issues important to the super-adhesion device — the multi-droplet adhesion pad and the droplet-droplet switch. Volume-scavenging is to be avoided for effective adhesion pad operation. In contrast, instability is used to advantage in the droplet-droplet switch which, like the light-switch, has on/off states. Toggling of the droplet-droplet switch is achieved by an electro-osmotic pump, whose invention has also been stimulated by the technological goal and which will be recounted.

Refreshments at 4:30 in 657 Rhodes Hall.