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Post Aligned Bistable Nematic Device
The operation of a novel post aligned bistable nematic (PABN) display
under development at HP-labs has been successfully modelled using
our program. The device consists of LC material sandwiched between
two surfaces. The top surface is smooth, while the bottom surface
is covered in a regular array of microscopic 3-D posts[1]. It has
been possible to simulate the operation of the whole device by considering
a single post with periodic boundaries.
Two distinct stable states exist: the tilted and planar states.
We have identified that these two states are separated by an energy
“barrier” associated with a pair of topological defects
located at opposing corners of the posts.
 
Planar State |
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Tilted State |
In order to switch between the two states, and traverse
the barrier, energy must be provided by an external electric field.
This is achieved by a pair of electrodes on the top and bottom surfaces
of the device. The device can be switched between the two states
by applying short pulses of opposing polarities to the electrodes.
The surface of the posts is treated in a way that
restricts the director to remain tangential to the LC-solid surface
interface at all times. In order to switch between the two stable
states where the tilt angles are opposite along the corners, the
director field must pass through a high-energy state involving topological
defects.
[1]. Kitson S. Geisow A. “Bistable Alignment of Nematic Liquid
Crystals Around Microscopic Posts”, Mol. Cryst. Liq. Cryst.,
vol. 412, pp. 153-161, 2004.
This page last modified
2 June, 2006
by e.willman
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