Micro-machining increases battery life in portable devices

A way of increasing battery life in devices such as laptop computers, personal TVs and camcorders has been developed at the University of Michigan and the National Taiwan University. Researchers have developed a film which increases the display brightness by 100 percent or more when placed over a screen, hence saving energy.

Using a new technology, similar to that used by Intel Inc. in the fabrication of the Pentium III chip, Liwei Lin and his colleagues have significantly improved conventional processes to make brightness enhancement films. These films serve to improve the brightness of liquid crystal displays, and consist of microstructures (structures the size of a fraction of a millimetre) built on top of transparent plastic films.

They conserve energy by redirecting and redistributing light so that its direction is concentrated, and have been used in consumer electronics devices since the early 1980s. Conventional methods of making the films use mechanical technologies, which make it difficult to achieve microstructures with very smooth surfaces. As a result light rays can be reflected and refracted unpredictably, causing the energy losses.

The new technique produces micropyramids by combining micro-machining and plastic moulding technologies, making it easy and inexpensive to mass-produce the new films. The advantage of micro-machining is its ability to build fine mould inserts, making micropyramids with very smooth surfaces.

The pyramid structures are designed to prevent energy losses by allowing the majority of light rays from a restricted range of directions to pass through, thereby concentrating the output. Because of the increased smoothness of the surfaces of the pyramids the brightness is enhanced without additional power, and energy loss is minimal. In this way an increase in brightness of 100 percent or more can be achieved without any extra input energy being required.