A bistable LCD screen that retains its image without power. Cholesteric LCDs use nematic liquid crystal molecules in a layered, spiral formation (chiral nematic), and power is only required to change the image. An advantage of most cholesteric screens over the common nematic LCD is that they can be viewed in bright sunlight. They can also be made on flexible plastic rather than glass. See liquid crystal and LCD.
Write, Retain and Erase
Boogie Boards use cholesteric LCDs to retain the user's notes written with an accompanying stylus. Pressing a button erases the board by switching the screen from its reflective planar state to its transmissive focal-conic state. (Image courtesy of Kent Displays Inc., www.myboogieboard.com)
A Cholesteric Readout
This authentication token circuit board uses a cholesteric readout to display the current password. (Image courtesy of Linear Dimensions Semiconductor, www.lineardimensions.com)