Skip to Content
Uncategorized

Repulsive Force Could Eliminate Nanofriction

A force that causes nanoscale objects to repel each other has engineers dreaming of quantum levitation.

When two objects are so close together that the distance between them is about the same size as quantum fluctuations called virtual particles, they’re pulled together. This effect, caused by the Casimir force, is not something that humankind has had to worry about until recently. But as researchers develop nanomechanical devices for communications and computation, so-called “stiction” has emerged as a potential stumbling block that might, for example, limit the density of memory chips. But there’s a flip side to the Casimir force that might enable, rather than hinder, nano devices. Hendrik Casimir, who described his eponymous force in 1948, and Evgeny Lifshitz, who expanded his work, predicted that at slightly larger distances, this force should turn repulsive. Now researchers at Harvard University and the National Institutes of Health have seen this repulsive force in the lab for the first time.

In this illustration of the Casimir force, a tiny gold sphere and plate experience “stiction” (right). But with the right combination of materials, as at left, where a gold sphere is paired with a silica plate, the Casimir force reverses, becoming repulsive. Future nanoscale devices might take advantage of this effect. Credit: U. Christensen

The researchers reversed the Casimir force through their choice of materials. Whether the force is attractive or repulsive, it turns out, depends on the relative dielectric permittivities of the two surfaces and of the medium that lies between them. (Dielectric permittivity is a material property that describes how a material interacts with electrical fields.) When the researchers brought together a gold-coated sphere about 40 micrometers in diameter and a silica plate, both submerged in the liquid bromobenzene, they measured a repulsive Casimir force. The gold sphere was attached to an atomic force microscope, which was used to detect this repulsion. These results are described in the journal Nature.

These results suggest that it should be possible to create stictionless, friction-free nanomechanical devices based on what the researchers call quantum levitation. It’s not yet clear what applications will be found for quantum levitation, but according to a press release from Harvard, the researchers have filed a U.S. patent covering nano devices based on the phenomenon. Think friction-free ball bearings and ultrasensitive chemical detectors.

The Harvard researchers were led by Federico Capasso, a physicist who developed the first quantum-cascade laser at Bell Labs in the mid-1990s. He has also been featured in our 10 Emerging Technologies section in 2007 for his work on optical antennas.

Deep Dive

Uncategorized

Uber Autonomous Vehicles parked in a lot
Uber Autonomous Vehicles parked in a lot

It will soon be easy for self-driving cars to hide in plain sight. We shouldn’t let them.

If they ever hit our roads for real, other drivers need to know exactly what they are.

stock art of market data
stock art of market data

Maximize business value with data-driven strategies

Every organization is now collecting data, but few are truly data driven. Here are five ways data can transform your business.

Cryptocurrency fuels new business opportunities

As adoption of digital assets accelerates, companies are investing in innovative products and services.

Yann LeCun
Yann LeCun

Yann LeCun has a bold new vision for the future of AI

One of the godfathers of deep learning pulls together old ideas to sketch out a fresh path for AI, but raises as many questions as he answers.

Stay connected

Illustration by Rose WongIllustration by Rose Wong

Get the latest updates from
MIT Technology Review

Discover special offers, top stories, upcoming events, and more.

Thank you for submitting your email!

Explore more newsletters

It looks like something went wrong.

We’re having trouble saving your preferences. Try refreshing this page and updating them one more time. If you continue to get this message, reach out to us at customer-service@technologyreview.com with a list of newsletters you’d like to receive.