Michigan Technological University
Department of Physics

is pleased to announce a colloquium

with

Colin Denniston

Dynamically Controlled Interfaces in Complex Fluids

In a simple fluid the boundary between the fluid and any solid surface is normally a static quantity defined by boundary conditions given at the beginning of the problem. Complex fluids, however, allow greater control of interfacial phenomena via the extra degrees of freedom associated with their internal structure and composition. This allows the boundary conditions to be manipulated both spatially and temporally. I illustrate this with two examples. In the first, I show how differential wetting of the components of a fluid mixture coupled to a concentration gradient can drive convective flows. I construct a quantitative model of this effect and demonstrate its use in the construction of an entropy driven nano-motor. In the second example I report on a novel method of dynamically controlling the boundary conditions at the surface of a nematic liquid crystal using a surface flexoelectric effect. By moving the surface directors one can manipulatedefects that lie near the surface. Understanding of this effect and how defects move in a liquid crystal can be used to create a bistable display that retains its state with no applied voltage.

Monday, January 27, 2003

4:00 p.m., Fisher 101

Refreshments will be served

MTU | Physics | Colloquium