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The periodic stripe structure is a spectacular consequence of
the confined nature of the film. It is a result of the competition
between elastic inner forces and surface anchoring forces. The
surface anchoring forces want to align the liquid crystals parallel
to the bottom surface and perpendicular to the top surface of
the film. The elastic forces work against the resulting "vertical"
distortions of the director field. When the film is sufficiently
thin, the lowest energy state is surprisingly achived by "horizontal"
director deformations in the plane of the film. The current picture
shows a 1-dimensional periodic pattern; 2-dimensional periodic
patterns can also be observed (click on link below for next picture).
Both periodic phases have similar energies such that they can
coexist, as shown in the picture http://www.lci.kent.edu/deflat2.html.
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