26 May 2010
Research uses 'void' to remove friction in MEMS devices
Researchers at Massachusetts Institute of Technology (MIT) hope to overcome the forces of friction endured by accelerometers, gyroscopes and other MEMs chips. The scientists are harnessing a power called the Casimir force that only manifests at the nanoscale to sidestep friction by causing parts to naturally repel, rather than attract, each other.
MEMS chips like accelerometers and gyros have tiny moving parts inside that perform similar functions as their full size counterparts, but in a form factor that can be mass-produced on semiconductor fabrication lines at a fraction of the cost. As mechanical parts are shrunk to the micro or even nanometer scale, the effects of friction become disproportionately large. Most difficult is starting a MEMS from a dead stop, since it must overcome 'stiction', which measures the force that must be overcome to get a MEMS part moving.
MIT researchers have studied how MEMS parts could be architected so that they repel each other at startup, instead of attract. Then friction and 'stiction', could be easily overcome, making MEMS parts draw less power and be more reliable and longer lived. MITs claim to have demonstrated how naturally repelling architectures can be crafted, by harnessing a force that only manifests at the nanoscale: the Casimir force - a free source of energy that nixes friction in tiny mechanical devices.
The researchers have designed a prototype consisting of an ellipsoid plunger that gets inserted into a complementary hole in a flat plate. The shapes of the hole and the plunger ensure that the Casimir force is balanced until the plunger is moved, at which point the Casimir force causes the parts to repel, thus overcoming the forces of stiction.
The MIT researchers also showed how well known calculations that predict the strength of an electromagnetic field between two objects can be used to calculate the amount and direction of the Casimir force as it applies to nanoscale moving parts. According to MIT, once empowered, MEMS designers should be able to employ the Casimir force to counter friction in all sorts of new MEMS chips.
Funding was provided by the Army Research Office, the MIT Ferry Fund and the Department of Energy (DoE).
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