Nematic liquid crystals in thin geometries
Presenter
December 8, 2009
Keywords:
- Non-Newtonian fluids
MSC:
- 76A05
Abstract
Keywords: Nematic Liquid Crystal, non-Newtonian, lubrication theory, asymptotics, electric field effects, interfacial instability,
free boundary problem, LCD
Abstract: Nematic liquid crystals are materials intermediate between the liquid and
solid states. They are typically composed of long, rod-like molecules,
which have a tendency to align with their neighbors, imparting a short-range
(but no long-range) orientational order - although nematics flow, like
conventional liquids, they also retain some elastic character. This gives rise
to complex behavior that does not arise in Newtonian liquids. Moreover, their
response to an applied electric field gives
nematics wide application in the electronic display industry.
We consider mathematical models for three different problems.
Two are classical fluid-dynamical setups: a small droplet spreading
on a flat substrate; and a two-dimensional "liquid bridge" (or liquid sheet)
under tension. These are free boundary problems, and the thin geometry in
each case enables the use of "lubrication" analysis to systematically derive
reduced mathematical models governing the free surface evolution. The
spreading drop analysis leads to variants of the classical 4th order "thin
film" equation, which can exhibit instability in certain regimes. The "liquid
bridge" problem leads to new versions of the so-called Trouton model
for Newtonian viscous sheets.
The third problem arises in
the display industry, and is concerned with manufacturing a "bistable"
display device, that can exhibit two optically-distinct configurations in the
absence of an electric field. Such a device has the potential for considerably
reducing the power demands of a display, with accompanying benefits for
battery lifetime and device portability.