- The Casimir effect is a quantum phenomenon in which two materials, when placed close together, can be attracted or repelled by quantum fluctuations.
- A new study from researchers at the Chinese Academy of Sciences reports that they’ve successfully manipulated this effect by reversing the transition of attractive to repulsive using a ferrofluid as intermediate medium.
- The ability to control the Casimir effect in this way could be a big breakthrough for engineering nanotechnology, which is often designed with the Casimir effect in mind.
In 1948, Dutch physicist Hendrik Casimir—who worked 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 within one micrometer of each other in a vacuum. Without any forces acting upon them, you might expect the plates to remain perfectly still… but they didn’t. Instead, the plates were pulled together via the invisible quantum fluctuations that permeate spacetime.
This experiment was a stunning display of the invisible quantum world, and this phenomenon became known, quite rightly, as the Casimir effect. It’d be another 50 years before the 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 impact these incredibly small machines became vitally important. Sort of how the designs of satellites need to take our understanding of relativity into account, so too must nanotechnologies be designed with the Casimir effect in mind.
Now, in the next step toward understanding this incredible phenomenon, scientists from the Chinese Academy of Sciences have found a method of “tuning” this effect. Using a ferrofluid—a fluid that can be manipulated using 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 in late May in the journal Nature Physics.
“The quantum fluctuation-induced Casimir force can be either attractive or repulsive, depending on the dielectric permittivities [the ability of a substance to store electrical energy in an electric field] and magnetic permeabilities of the materials involved,” the paper reads. “Our theoretical calculations predict that, by varying the magnetic field, separation distance and ferrofluid volume fraction, the Casimir force can be tuned from attractive to repulsive over a wide range of parameters in this system.”
As the paper notes, it’s challenging to alter the dielectric permittivities of a material, but you can manipulate the permeabilities of ferrofluids with magnetic fields. This is how the researchers designed an experiment examining this kind of manipulation between a gold sphere and a silicon dioxide substrate. As predicted, the experiment allowed the researchers to accurately manipulate the Casimir attraction or repulsion of the two materials.
Gaining some kind of control over this incredibly small effect could have big implications for the creation of future nano- and micro-electromechanical devices. Of course, there are other ideas surrounding the Casimir effect—also known as vacuum energy or zero-point energy—especially as it plays a role in studying the black hole-based Hawking radiation that features prominently in discussions about warp bubbles and warp drives. But for now, its very large technological impact mostly pertains 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 at Gizmodo and Paste if you look hard enough.