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"One of the researchers' most recent discoveries using the new tool was a way to arrange tiny objects so that the ordinarily attractive Casimir forces become repulsive," said the university. "If engineers can design MEMS so that the Casimir forces actually prevent their moving parts from sticking together, rather than causing them to stick, it could cut down on the failure rate of existing MEMS."

According to the university, the forces come from particles that wink in and out of reality in confined spaces.

"When objects get very close together, there's little room for particles to flash into existence between them. Consequently, there are fewer transient particles in between the objects to offset the forces exerted by the transient particles around them, and the difference in pressure ends up pushing the objects toward each other," said MIT

A formula for calculating such forces exist, "but in the vast majority of cases that formula remains impossibly hard to solve", said MIT.

However, a clutch of MIT scientists have found an analogy that allows arbitrary Casimir problems to be solved.

"The researchers' insight is that the effects of Casimir forces on objects 100nm apart can be precisely modelled using objects 100,000 times as big, 100,000 times as far apart, immersed in a fluid that conducts electricity," explained the university. "Instead of calculating the forces exerted by tiny particles flashing into existence around the tiny objects, the researchers calculate the strength of an electromagnetic field at various points around the larger ones."

In their paper 'Theoretical ingredients of a Casimir analog computer', in the Proceedings of the National Academy of Sciences, they prove that these computations are mathematically equivalent.

For objects with odd shapes, calculating electromagnetic-field strength in a conducting fluid is complicated, but achievable.

"Analytically, it's almost impossible to do exact calculations of the Casimir force unless you have some very special geometries," said Los Alamos Casimir specialist Diego Dalvit. With the MIT technique, however, "in principle, you can tackle any geometry. And this is useful. Very useful."

Using the tool, the MIT and Harvard researchers together designed shapes, for example the one pictured, that will repel rather than stick.

SOURCE

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