Microelectromechanical systems, or MEMS, are microscopic machines—devices only fractions of an inch in size, which can perform useful functions.

MEMS are an outgrowth of the technology used to create the integrated chip (IC). Integrated chips are small electrical circuits on tiny pieces of silicon. Their size and speed has revolutionized the design of electronic circuitry, which has spawned the electronic and computer revolutions. To understand MEMS it is necessary to understand the way in which ICs are constructed.

Electrical circuits—pathways of a metallic conductor—are usually carved into a piece of silicon by a technique called photolithography. A circuit design is first laid out, usually using computer-assisted design (CAD) software. This pattern is then duplicated on a "mask," a stencil-like pattern of chromium on a glass plate. The piece of silicon is painted with a "photoresist"--a polymer sensitive to ultraviolet...