The Physics
An encyclopedia of scientific essays

Force on a Microelectromechanical System (MEMS)

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Bibliographic Entry Result
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Lang, George. The influence of the Casimir Force on MEMS and NEMS. Rutherford Appleton Laboratory.
Interaction Magnitude of the force(in nN)
Casimir 0.03 (sphere R=1mm; gap r=1mm)
Casimir 4 (Pair infinite parallel plates; gap r=1mm)
Electro-static (dependent on applied voltage or charging of the sample) 1-1000
Thermal 100
Surface tension 10
Electro-magnetic (motors) 0.01
Gravity 0.01
0.01โ€“1000 nN

Lang, George. The Casimir Force: Introduction. Rutherford Appleton Laboratory.

"For two parallel metallic plates of area of 1 cm squared separated by a large distance (on the atomic scale) of 1 micron, the value of the attractive force is approximately 10−7 N. [For more information look at Figure 1.]" 100 nN
Rebeiz, Gabriel M. RD MEMS: Theory, Design, and Technology. Wiley Interscience. Published by John Wiley & Sons, 2003. "The mechanical restoring force on a MEMS beam is given by Eq. (2.40) and is 30-120 micro-N" 30โ€“120 µN
Sio, Wannok. University of Kansas. MEMS [pdf]. 21 October 2002. "...the force that supports the water bug scales as the surface tension times the distance around the water bug's foot, and therefore the force on the bug's foot scales as S2. Change the size of a 2-m horse to a 2-mm water bug, the weight decreases by a factor of 10^-9, but the surface tension force only decreases by a factor of 10^-6, so surface tension force is the dominant in the smaller scale." 4.0 nN
Kim K, Liu X, Zhang Y, Cheng J, Wu XY, Sun Y. Mechanical characterization of polymeric microcapsules using a force-feedback MEMS microgripper. Conference of the Proceedings of the IEEE Engineering Medical Biology Society. (2008): 1845-8. "This paper reports a monolithic, force-feedback MEMS (Microelectromechanical systems) microgripper and its application to micro-scale compression testing of swollen hydrogel microcapsules during manipulation in an aqueous environment. The single-chip microgripper uses an electrothermal microactuator for grasping and integrates two capacitive force sensors, one for contact detection (force resolution: 38.5nN) and the other for gripping force measurements (force resolution: 19.9 nN)." 19.9โ€“38.5 nN

A microelectromechanical system (MEMS) is a combined system of mechanical elements assembled using microfabrication. These constituents include sensors, actuators and electronics on a silicon substrate. These devices are on the order of 20 micrometers to 1 millimeter in size. Due to their extremely small size, many classical physical theories won't work. MEMS technology allow for the ability to deposit thin layers of materials on a surface, apply a thin coat of patterned mask on films, and to etch precisely and selectively films on to a mask. MEMS technology allows previously complicated electromechanical systems to be less bulky and expensive.

MEMS can measure extremely small forces, such as electromagnetic, gravity and casimir, which act on microscopic objects. These forces range from 0.01 - 1000 nN. MEMS can be used to weigh a wide variety of objects. Recently, researchers were able to weigh a virus.

A mite less than 1 mm on a polysilicon MEMS gear-train
(Courtesy of Sandia National Laboratories,
SUMMiTTM Technologies,

MEMS have broadened the fields of engineering, communications, and biotechnology. These systems have enabled advancements in the Polymerase Chain Reaction (PCR). PCR is a technique that amplifies pieces of DNA and generates copies of a DNA sequence. MEMS technology increases the function for DNA amplification and identification. Also, improvements on biochips will allow for better detection of deleterious chemical and biological agents.

Just for fun, Cornell University researches have built the world's smallest guitar. This "nanoguitar" is about the size of a red blood cell. The nanoguitar suggests the possibility of manufacturing micro-mechanical devices. Though "strumming" this guitar will not produce beautiful music, this

Figure 1 (Courtesy of George Lang.)

Shirley Mei -- 2009