In 1948, Dutch physicist Hendrik Casimir – working with one of the fathers of quantum physics, Neils Bohr – developed an ingenious experiment to witness the invisible (at least, to us) wonders of quantum mechanics. Casimir placed two electrically neutral plates at a distance of one micrometer from each other in a vacuum. Without any force acting on them, you would expect the plates to remain perfectly still… but they didn’t. Instead, the plates came together through the invisible quantum fluctuations that permeate spacetime.
This experiment was an astonishing display of the invisible quantum world, and this phenomenon became known, rightly, as the Casimir effect. It took another 50 years before Yale physicist Steve Lamoreaux finally measured this incredibly small effect, but with the rise of nanotechnology during that same period, understanding the Casimir effect and how it would affect these incredibly small machines became vital. importance. Just as the design of satellites must take into account our understanding of relativity, nanotechnologies must be designed with the Casimir effect in mind.
Now, in the next step toward understanding this incredible phenomenon, scientists at the Chinese Academy of Sciences have found a method to “tune” this effect. Using a ferrofluid – a fluid that can be manipulated by magnetic fields – as an intermediate medium, the researchers used magnetic fields to create a reversible transition from Casimir attraction to repulsion. The results of the study were published at the end of May in the journal Nature Physics.
“The Casimir force induced by quantum fluctuations can be attractive or repulsive, depending on the dielectric permittivities [la capacidad de una sustancia para almacenar energía eléctrica en un campo eléctrico] and the magnetic permeabilities of the materials involved,” the article reads. “Our theoretical calculations predict that by varying the magnetic field, separation distance, and volume fraction of ferrofluid, the Casimir force can be tuned from attractive to repulsive. on a wide range of parameters in this system.”
As the article points out, it is difficult to alter the dielectric permittivities of a material, but the permeabilities of ferrofluids can be manipulated with magnetic fields. This is how the researchers designed an experiment that examined this type of manipulation between a gold sphere and a silicon dioxide substrate. As anticipated, the experiment allowed the researchers to precisely manipulate the Casimir attraction or repulsion of the two materials.
Achieving some kind of control over this incredibly small effect could have big implications for the creation of future nano- and microelectromechanical devices. Of course, there are other ideas surrounding the Casimir effect – also known as vacuum energy or zero-point energy – especially since it plays an important role in the study of Hawking radiation, based on black holes, which occupies a place featured prominently in debates about bubbles and warp engines. But for now, its enormous technological impact is mostly limited to the world of very small machines.
Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff from him at Gizmodo and Paste if you look hard enough.
