Microelectromechanical systems (MEMS) refer to devices that have characteristic length of less than
1mm but more than 1 micron, that combine electrical and mechanical components, and that are fabricated
using integrated circuit batch-processing technologies. Current manufacturing techniques for MEMS
include surface silicon micromachining; bulk silicon micromachining; lithography, electrodeposition,
and plastic molding; and electrodischarge machining. The multidisciplinary field has witnessed explosive
growth during the last decade and the technology is progressing at a rate that far exceeds that of our
understanding of the physics involved. Electrostatic, magnetic, electromagnetic, pneumatic and thermal
actuators, motors, valves, gears, cantilevers, diaphragms, and tweezers of less than 100 micron size have
been fabricated. These have been used as sensors for pressure, temperature, mass flow, velocity, sound and
chemical composition, as actuators for linear and angular motions, and as simple components for complex
systems such as robots, lab-on-a-chip, micro heat engines and micro heat pumps. The lab-on-a-chip
in particular is promising to automate biology and chemistry to the same extent the integrated circuit has
allowed large-scale automation of computation. Global funding for micro- and nanotechnology research
and development quintupled from $432 million in 1997 to $2.2 billion in 2002. In 2004, the U.S.National
Nanotechnology Initiative had a budget of close to $1 billion, and the worldwide investment in nanotechnology
exceeded $3.5 billion. In 10 to 15 years, it is estimated that micro- and nanotechnology markets
will represent $340 billion per year in materials, $300 billion per year in electronics, and $180 billion per
year in pharmaceuticals.