Up and down with MEMS

Physicists at Lucent Technologies’ Bell Labs have made a microscopic seesaw that moves in response to a little-known but strong and pervasive force predicted by quantum mechanics.

Physicists at Lucent Technologies’ Bell Labs have made a microscopic seesaw that moves in response to a little-known but strong and pervasive force predicted by quantum mechanics, the widely-accepted scientific theory that describes the behaviour of atoms and other microscopic particles.

This experiment is said to show that esoteric physical effects are important in designing nanoscale machines and also suggests that such effects might be used to make extremely sensitive sensors in the future.

According to quantum mechanics, empty space has a little energy associated with it, a picture that is different from the classical understanding of a vacuum as completely empty space without any energy. In the quantum description, a vacuum is teeming with virtual photons that produce constantly oscillating electromagnetic fields.

In 1948, Dutch physicist Hendrik Casimir predicted that this zero-point energy would produce an attractive force between uncharged parallel metallic plates that are very close together. The ‘Casimir force’ was first measured precisely by physicists in 1997.

Bell Labs physicists recently realised that the Casimir force could be used to tilt microscopic microelectromechanical systems (MEMS) seesaws.

They built the seesaw using a tiny metallised plate that was balanced on a hinge and kept parallel to the surface of a silicon chip.

When a gold plated sphere suspended on a wire was brought close to the seesaw – an experimental set-up similar to the two parallel plates – the seesaw was attracted toward the sphere in agreement with Casimir’s prediction.

Their results show that quantum mechanical effects play a significant role in MEMS systems when the separation between components is in the nanometer range.

‘This experiment has opened up an entirely new sensitivity range for MEMS devices,’ said David Bishop, director of Bell Labs’ micromechanics research.

‘In addition to making powerful optical switches with MEMS technology, we use MEMS techniques to do heady scientific work that may lead to wonderful devices,’ concluded Bishop.

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