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MEMS Actuators

Reliable actuators are critical components in most MEMS devices. Well-known for developments in electrostatic comb-drive actuation [1], Sandia also uses thermal actuators [2] extensively. This page provides a look at some of the common actuators used in MEMS at Sandia.

Thermal Actuators

V-Shaped Thermal Actuators

The v-shaped thermal actuator shown in the figure below is commonly referred to as a "chevron", or "bent-beam" thermal actuator. It is used in applications requiring high force and reliability. These actuators are based on the constrained thermal expansion of the angled beams (a result of Joule heating when a current is passed through the legs of the actuator), resulting in motion of the center shuttle in the direction shown by the arrow in the figure.

Thermal Actuator
V-shaped thermal actuator for on-chip inplane high-force linear-motion actuation.

Thermal Ratcheting Actuator

The Thermal Ratcheting Actuator (ThRA), is a V-shaped actuator attached to a ratcheting hub that provides a drive capable of high-force 360+ degree rotational motion.

Thermal Ratcheting Actuator
[3] Thermal ratcheting actuator.

Electrostatic Actuators

Torsional Ratcheting Actuator (TRA)

The Torsional Ratcheting Actuator is used when high-torque rotational motion is needed. Ratcheting allows full unidirectional 360+ degree motion.

Thermal Ratcheting Actuator
Torsional Ratcheting Actuator.

Parallel Plate Actuation

Electrostatic parallel-plate actuation is used extensively in RF MEMS, oscillators, resonators, mirrors, switches, and other applications requiring only small displacements. These actuators can be designed using simple equations.

Comb Drives

The electrostatic "comb-drive" is a common MEMS actuator, used in gyroscopes, microengines, resonators, and many other MEMS applications. The force output is generally less than 50 uN, but the linear and highly predictive behavior (very good predictions can be made using simple equations) make it a popular MEMS actuator. Comb drives have been used in microengines by combining the actuator with a rotary transmission [2].

Thermal Ratcheting Actuator
[4] SEM of a typical comb-drive resonator.


[1] Baker, M.S., Plass, R.A., Headley, T.J. and Walraven, J.A., "Final Report: Compliant Thermo-Mechanical MEMS Actuators LDRD #52553," Sandia Report SAND2004-6635, printed December 2004. Download SAND Report (.pdf)

[2] E. J. Garcia and J. J. Sniegowski, "Surface Micromachined Microengine," Sensors and Actuators A, Vol. 48 (1995) 203-214.

[3] Baker, Michael S. "Design and Reliability of a MEMS Thermal Rotary Actuator," TEXMEMS IX, Texas Tech University, Lubbock TX, September 17, 2007.

[4] Tanner, D.M., Owen, A.C., Jr., and Rodriguez, F., 2003, "Resonant Frequency Method for Monitoring MEMS Fabrication," Proceedings of SPIE - The International Society for Optical Engineering, Vol. 4980, pp. 220-228.

More Literature on MEMS Actuators ...

J.H. Comtois, V.M. Bright, M.W. Phipps, "Thermal microactuators for surface-micromachining processes", Proc. SPIE 2642 (1995) 10–21.

L. Que, J.-S. Park, Y.B. Gianchandani, "Bent-beam electro-thermal actuators for high force applications", Proceedings of the IEEE Micro Electro Mechanical Systems, 1999, pp. 31–36.

R. Cragun, L.L. Howell, "Linear thermomechanical microactuators", Proceedings of the IMECE, ASME International Mechanical Engineering Congress & Exposition, November, 1999, pp. 181–188.

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