For example, vertical levitation of interdigitated fingers up to 0.5 m m has been demonstrated under applied voltage of 20 V for an 18-finger device. The majority of capacitive devices use electrodes that dissipate charges quickly. Some, however, are made of dielectric materials that develop permanent ordering of molecular dipoles or retain charges . A class of charged material, called electrets , is made of organic polymers such as Teflon or poly (methylmethacrylate) ( PMMA ). The electrets can be charged through global or local electron injection , to a surface density of or greater.
Capacitance is an object's ability to store an electric charge . Reasonably, this object is referred to as a capacitor . A capacitor that stores this charge in an electric field between two conductive plates is known as a parallel plate capacitor. The non-conductive material that is between these two plates is known as a dielectric . Dielectrics change the amount of charge a capacitor can hold and , in practice, what the particular capacitor would be used for (e.g. high frequency circuits, high voltage circuits, etc). The equation for the capacitance of a parallel plate capacitor is: C = ( εA ) / d where ε is the permittivity of free space or dielectric, A is the surface area of overlap between the plates, and d is the distance between the plates. What Is Capacitance?
A representative application using the parallel-plate electrostatic actuation principle is the DMD chip made by Texas Instruments Inc. A DMD chip consists of a large array of micromirrors, or binary light switches. Each mirror is made of a reflective plate capable of rotating about a torsional support hinge. Two electrodes are embedded below the reflective plate, each covering one half of the plate area on each side of the torsional hinge. Two sets of parallel capacitors are thus formed, between each of the underlying electrodes and the mirror surface above. By applying voltages to either bottom electrode, the mirror device would tilt under electrostatic attractive force, by ± 7.5 degrees, to deflect incoming light.
The DLP4710 digital micromirror device (DMD) is a digitally controlled micro-opto-electromechanical system (MOEMS) spatial light modulator (SLM). When coupled to an appropriate optical system, the DMD displays a very crisp and high quality image or video . The device is a component of the chipset comprising the Digital Light Processing, DLP4710 DMD, controller and PMIC/LED drivers. The compact physical size of the DLP4710 coupled with the controller and the PMIC/LED driver provides a complete system solution that enables small form factor, low power, and high resolution HD displays. • 0.47-Inch (11.93-mm) Diagonal Micromirror Array 1920 × 1080 Array of Aluminum Micrometer-Sized Mirrors, in an Orthogonal Layout • Micron Micromirror Pitch: 5.4 • Micromirror Tilt (Relative to Flat Surface): ±17° • Bottom Illumination for Optimal Efficiency and Optical Engine Size • Polarization Independent Aluminum Micromirror Surface