How are liquid crystals used in wristwatches calculators portable computers and flat-screen televisions?

Liquid crystals are materials that possess both the flow properties of liquids and the ordered molecular structure of crystalline solids. Their use in devices like wristwatches, calculators, portable computers, and flat-screen televisions is based on their electro-optical properties.123

In these displays, liquid crystal molecules—typically of the nematic type—are sandwiched between two light-polarizing filters. When no electric field is applied, the molecules are arranged to twist the polarization of light, allowing it to pass through the filters and appear bright. When a small electric voltage is applied, the molecules realign along the field, effectively "untwisting" and preventing light from passing through, which makes that area appear dark.431

By applying this field to specific portions of a grid, individual pixels can be turned on or off to create numbers, letters, or detailed images. While simple devices use basic grids, complex displays like televisions often employ an "active matrix" of transistors to control these pixels rapidly. Because they are thin, lightweight, and consume very little power, they are ideal for portable electronics.43