MEMS capacitor. Coloured scanning electron micrograph of a MEMS (microelectromechanical systems) reference capacitor. MEMS devices are constructed on a microscopic scale using technologies such as wet and dry etching and thin film deposition. Applications include sensors and optical displays. Materials used to construct MEMS devices include silicon and polymers such as plastics. A capacitor is a passive electrical component used to store energy electrostatically in an electric field. Magnification: x228, when printed 10 centimetres wide.