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The influence of the CASIMIR Force on MEMS and NEMS
Miniature mechanical/electromechanical systems are becoming increasingly useful
in many applications. With the decrease in device dimensions additional forces on
Microelectromechanical Systems (MEMS) and Nanoelectromechanical Systems (NEMS)
have to be considered that are normally neglected in macro-systems.
The Casimir Effect is the cause of one such force. For example one of the principal
causes of malfunctioning in MEMS is stiction, namely, the collapse of movable elements
into nearby surfaces, resulting in their permanent adhesion. This can occur during
fabrication, especially due to capillary forces, or during
operation. The Casimir effect is potentially an important underlying mechanism
causing this phenomenon. The problem is technologically important, because
it adversely affects the production yield on batch fabricated devices, and
also plagues many devices in operation.
A comparison of the strength of various forces in MEMS/NEMS structures
for an object size of 1 micron are listed in the table.
At these dimensions the applied electrostatic force required to operate a MEMS/NEMS may
be an order of magnitude larger than the Casimir force. In structures less than
1 micron thermal stress and surface tension are also important and these forces
can be 100 to 1000 times larger than the Casimir force for a 1 mm gap.
Gravity and electromagnetic forces can be neglected in this case.
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Interaction
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Magnitude of the force(in nN)
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| Casimir |
0.03 (sphere R=1mm; gap r=1mm) |
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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 |
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