Quantum Levitation - The Repulsive Casimir Force
Bardia Najjari Farizhendi
For long, it was believed that Casimir effect can only exist as an attractive interaction. Lately both analytical solutions to the more complex geometries and empirical researches have reported to have found instances of repulsive Casimir force, which seems to be the key to quantum levitation and micro/nano floating structures. Besides the technological importance, Casimir effects seem to be interconnecting a variety of unsolved questions such ranging from fundamental particle physics to dark matter and dark energy.
A Brief History of the Casimir Effect
The fact that an attractive force exists between two conducting metal plates was first predicted in 1948 by Hendrik Casimir of Philips Research Laboratories in the Netherlands. At the time, however, Casimir was studying the properties of "colloidal solutions". These are viscous materials, such as paint and mayonnaise, which contain micron-sized particles in a liquid matrix. The properties of such solutions are determined by van der Waals forces - long-range, attractive forces that exist between neutral atoms and molecules. One of Casimir's colleagues, Theo Overbeek, realized that the theory that was used at the time to explain van der Waals forces, which had been developed by Fritz London in 1932, did not properly explain the experimental measurements on colloids. Overbeek therefore asked Casimir to investigate the problem. Working with Dirk Polder, Casimir discovered that the interaction between two neutral molecules could be correctly described only if the fact that light travels at a finite speed was taken into account. Soon afterwards, Casimir noticed that this result could be interpreted in terms of vacuum fluctuations. He then asked himself what would happen if there were two mirrors - rather than two molecules facing each other in a vacuum. It was this work that led to his famous prediction of an...