Miniaturization has allowed a growing number of electronic functions to be packed into pocket-sized designs and, in the case of microelectromechanical-systems (MEMS) devices, even mechanical functions can be included in those designs. MEMS devices are perhaps best known as miniature switches, although they are also gaining popularity when used as frequency sources, such as oscillators. They can be packaged in similarly small enclosures as purely electronic devices, but how do MEMS devices differ from similar-sized electronic circuits, such as monolithic-microwave integrated circuits (MMICs)?
The most essential difference between MEMS and MMICs is that MEMS are designed to function with moving parts, as electromechanical devices, while MMICs are meant to operate fully electronically. Because of the mechanical capabilities, MEMS devices are capable of producing high-frequency resonances (serving as resonators and oscillators), as well as the reverse function of detecting vibration (as in audio microphones).