Getting Rid of Friction by Nanoengineering

Illustration: Christine Daniloff/MIT and Alexei Bylinkskii

 Rub your palms together and you feel warm, that's friction at work. Though friction is a boon when it lets us walk on the ground without slipping, it is a bane as well when it dissipates energy in machines. Now, a new technique enables zero friction between two surfaces by controlling the alignment and spacing between atoms.
Researchers at MIT have come up with an experimental technique to simulate the friction between two surfaces by controlling parameters such as spacing between atoms at the surface of contact. This can lead to very low and even total disappearance of friction, aptly termed as Superlubricity.

MIT's Lester Wolfe Professor of Physics, Vladan Vuletic, thinks that the ability to control and manipulate friction between surfaces is especially useful in the realm of nanomachines where friction forces impose greater wear and tear as compared to their bigger counterparts.

“There’s a big effort to understand friction and control it, because it’s one of the limiting factors for nanomachines, but there has been relatively little progress in actually controlling friction at any scale,” Vuletic says. “What is new in our system is, for the first time on the atomic scale, we can see this transition from friction to superlubricity.”

Manipulating Friction

Not Aligned: Minimum Friction   Image:Wikipedia

The team simulated friction by generating an optical lattice by crossing two laser beams in opposite direction to get sinusoidal waveform (blue in the illustration) where the peaks and troughs are respective maximum and minimum intensities of the electric field. The red spheres are ions made by charging ytterbium atoms emanating from a small heated oven, using light to ionize them. After ionization they are trapped on a metal surface by applying voltages to the surface. The ions positive charge helps repulsion among themselves and this charge can be used to create the relative spacing so that the optical lattice and the ions are incommensurate, i.e., they do not align perfectly. The springs in the illustration symbolize "Coulomb force"

Aligned : Maximum Friction    Image: Wikipedia

“What we can do is adjust at will the distance between the atoms to either be matched to the optical lattice for maximum friction, or mismatched for no friction,” Vuletic says.

The team believes that their breakthrough could not only revolutionize the mechanics of nanomachines, but also could help in molecular biology where biomolecular motors, proteins and other biological processes can be controlled with friction, or its lack thereof.

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