Electrostatic actuators

There are two types of optical communication systems passive reflective systems and active-steered laser systems [War 01, War 05], A passive reflective system, such as a comer-cube retroreflector (CCR), consists of three mutually orthogonal mirrors that form the comer of a cube. Light entering the cube bounces off the mirrors and is reflected back to the sender. By electrostatically actuating the bottom mirror, the orthogonalty can be disturbed and the reflection is no longer returned to the sender. 

Fig. 9. Principal design of the electrostatically actuated membrane pump [from ref. 27]...

Voiculescu, L, Zaghloul, M.E., McGill, R.A., Houser, E.J., Fedder, G.K. (2005). Electrostatically actuated resonant microcantilever beam in CMOS technology for the detection of chemical weapons. IEEE Sens. J. 5 641-7. 

O. Frangais and I. Dufour, Enhancement of elementary displaced volume with electrostatically actuated diaphragms application to electrostatic micropmnps,... 

R. R. A. Syms, B. M. Hardcastle, and R. A. Lawes, Bulk micromachined silicon comb-drive electrostatic actuators with diode isolation, Sensors Actuators A 63, 61, 1997. 

Goll C, Bacher W, Bustgens B, Maas D, Ruprecht R, Schomburg WK. An electrostatically actuated polymer microvalve equipped with a movable membrane electrode. J Micromech Microeng 1997 7 224-6. 

A more advanced process that can include capacitive sensors, electrostatic actuators, and piezoresistive sensors on the same chip is also made possible by bulk micromachining. 

The role of the electrodes in electrostatic actuators is of critical importance for the actuation performances. The ideal electrode materials should process both high electrical conductivity and mechanical stretchability in compliance with the large deformation of the laminated dielectric elastomer during actuation. In addition, the electrodes should also provide a uniform and stable charge distribution on both of the surfaces. 

Recently, a large number of stretchable electrode materials for electrostatic actuation have been explored. The thin metal films are pioneered as the earliest candidates due to their high electrical conductivity, but they greatly suffered from the disadvantage of small strain less than 1%. Alternatively, the metallic nanoparticles including titanium, gold, and palladium were coated on the elastomer surfaces through metal ion implantation method. 

Bullen D, Liu C (2006) Electrostatically actuated dip pen nanolithography probe arrays. Sensor Actuat A-Phys 125(2) 504-511... 

Instead of an array of fixed-sized FP optical filters, a tunable scheme would be an alternative. A conventional tunable filter comprises, usually, an air-gap cavity and one movable mirror using, for example, electrostatic actuation. Comparing both schemes, the array of fixed-sized FP optical filters has the following disadvantages ... 

Fig. 2 Schematic illustration of the principal types of membrane actuations in micropump, (a) Thin-film piezoelectric actuation, (b) stack piezoelectric actuator, (c) parallel plate electrodes for electrostatic actuation, (d) thermopneumatic actuation using thermal expansion of a secondary working fluid...

Microactuators, Fig. 1 Diagrams of (a) in-plane electrostatic comb-drive actuator and actuation force and (b) out-ofplane parallel plate electrostatic actuator... 

Hah D, Toshiyoshi H, Wu MC (2002) Design of electrostatic actuators for MOEMS applications, design, test, integration and packaging of MEMS/ MOEMS. Proc SPIE 4755 200-207... 

Xie J, Shih J, Lin Q, Yang B, Tai YC (2004) Surface miciomachined electrostatically actuated micro prai-staltic pump. Lab Chip 4 495-500... 

The schematic of synthetic jet is shown in Fig. 2. It consists of a cavity open to the flow through a sUt or orifice. The bottom waU of the cavity is driven by a moving surface, which can be either a piston or a vibrating membrane. The vibration of the membrane can be achieved using electrostatic actuation, piezo-ceramic material, and differential thermal expansion of the electrode material with silicon layer underneath. When the membrane or piston moves inward of the cavity, the fluid is pushed out of the cavity, and when the membrane or piston moves back, the fluid is sucked into the cavity. The namre of flow through the slit opening depends on (a) the... 

The most common macroscopic actuators are motors. Electromagnetic motors do not operate efficiently at the microscale, but alternative actuation mechanisms become favorable. In conventional MEMS, other types of actuators have been used to generate movement, such as electrostatic actuators, thermal actuators, piezoelectric crystals, SMAs, and magnetic actuators. 

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