Nano-bearings on the test bench

October 03, 2014

About 3500 years ago, man invented the wheel to make life easier. Then, thanks to Leonardo Da Vinci's genius, the wheel was made smaller to obtain ball bearings. And today? "Today we are trying to get even smaller: scientists are thinking about nano-bearings", comments Andrea Vanossi, of the CNR - Democritos and the International School for Advanced Studies (SISSA) of Trieste, among the authors of a study that has just been published in Nanoscale. "In the future we'll have many nano-machines capable of carrying out the most diverse tasks, for example transporting medicines inside the human body. In order to save energy, many of these vehicles will have to able to move efficiently, using as little energy as possible, and "nano"-sized ball bearings may help achieve this goal".

"Scientists thought they could use C60, a hollow carbon nanosphere, measuring one nanometre in diameter", explains Erio Tosatti, SISSA professor and another author of the study", but there's a problem: the experimental results are at complete variance with each other". C60 has a temperature (260° Kelvin) at which the molecules suddenly become free to rotate, which hopefully has a role in friction. The two most important experiments carried out to date, however, have yielded conflicting results: above this temperature, when the material was made to slide over a substrate, in one case there was no significant decrease in friction, whereas in the other the decrease was dramatic, a good 100%. "What's going on? If we assume that the measurements are correct and the experiments performed correctly (and we have no reason to believe otherwise) how do we explain this difference?", wonders Vanossi. "For this reason, we decided to verify".

The team (a collaboration between SISSA, the International Centre for Theoretical Physics "Abdus Salam" ICTP of Trieste, the Italian National Research Council CNR, and the Swiss Federal Laboratories for Materials Science and Technology) conducted a theoretical, simulation-based study.

"We simulated the tiny tip of an electron microscope bearing a C60 flake, which was dragged over a surface also made of C60", explains Vanossi. "We discovered that when the flake was attached in such a way that it couldn't rotate the friction did not decrease, even if we raised the temperature to above 260° K. It's as if the bearings making up the flake interlocked with the substrate, with no nano-bearing effect. However, when the flake was free to rotate there was a dramatic drop in friction and the flake could slide over the surface far more smoothly". But here the drop in friction is not due to the ball bearing effect, but to the change in contact geometry.

The two states therefore reproduce the results of the two experiments. "Our data faithfully reflect the empirical observations", concludes Tosatti. "This of course does not bode well for the future use of fullerite to reduce friction at the nanoscale, in that the nanobearing function is not confirmed, but it does finally shed light on the physics of this problem".
-end-


International School of Advanced Studies (SISSA)

Related Physics Articles from Brightsurf:

Helium, a little atom for big physics
Helium is the simplest multi-body atom. Its energy levels can be calculated with extremely high precision only relying on a few fundamental physical constants and the quantum electrodynamics (QED) theory.

Hyperbolic metamaterials exhibit 2T physics
According to Igor Smolyaninov of the University of Maryland, ''One of the more unusual applications of metamaterials was a theoretical proposal to construct a physical system that would exhibit two-time physics behavior on small scales.''

Challenges and opportunities for women in physics
Women in the United States hold fewer than 25% of bachelor's degrees, 20% of doctoral degrees and 19% of faculty positions in physics.

Indeterminist physics for an open world
Classical physics is characterized by the equations describing the world.

Leptons help in tracking new physics
Electrons with 'colleagues' -- other leptons - are one of many products of collisions observed in the LHCb experiment at the Large Hadron Collider.

Has physics ever been deterministic?
Researchers from the Austrian Academy of Sciences, the University of Vienna and the University of Geneva, have proposed a new interpretation of classical physics without real numbers.

Twisted physics
A new study in the journal Nature shows that superconductivity in bilayer graphene can be turned on or off with a small voltage change, increasing its usefulness for electronic devices.

Physics vs. asthma
A research team from the MIPT Center for Molecular Mechanisms of Aging and Age-Related Diseases has collaborated with colleagues from the U.S., Canada, France, and Germany to determine the spatial structure of the CysLT1 receptor.

2D topological physics from shaking a 1D wire
Published in Physical Review X, this new study propose a realistic scheme to observe a 'cold-atomic quantum Hall effect.'

Helping physics teachers who don't know physics
A shortage of high school physics teachers has led to teachers with little-to-no training taking over physics classrooms, reports show.

Read More: Physics News and Physics Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.