If you place two parallel conducting plates in a vacuum, a mysterious force will appear between them. This is known as the Casimir effect and its origin is rooted in quantum mechanics. It was predicted in the 1940s and has amazed scientists ever since with its apparent ability to get a force from the vacuum itself.
Researchers from Hong Kong University of Science and Technology and Princeton University have now unveiled a specially designed silicon chip to begin to harness this curious phenomenon. The chip is etched with micron-sized teeth, which experience a repelling force due to the Casimir effect. The breakthrough is reported in Nature Photonics.
"This is among the first experimental verifications of the Casimir effect on a silicon chip," co-author Professor Alejandro Rodriguez of Princeton said in a statement. "And it also allows you to make measurements of forces in very nontrivial structures like these that cause repulsion. It is a double-whammy."
The Casimir effect comes from the zero-point energy. Even when a system doesn’t have any field applied to it, its ground state (the least possible energy of the system) is not exactly zero. And this is what gives rise to the force. The vacuum is not as empty as we think it is.
The force can be repulsive or attractive depending on the set up of the system. The researchers investigated the repulsive side of things. If harnessed, this could help keep nanostructures apart, so they don’t stick to each other and break.
"Our paper shows that it is possible to control the Casimir force using structures of complex, tailor-made shapes," added co-author Ho Bun Chan, who led the Hong Kong team that built the silicon chip.
The chip has t-shaped teeth, which allowed them to harness this repulsion. The plates were placed 100 nanometers apart (about 1,000 times the size of a typical atom), and as they were pushed together, the Casimir effect pushed back.
"We tried to think about what kind of shapes Chan's group would have to fabricate to lead to a significant repulsive force, so we did some background studies and calculations to make sure they would see enough non-monotonicity as to be measurable," Rodriguez added.
The team is looking to explore different configurations that could create even larger repulsive forces.