The rub with friction

March 02, 2015

Here's the rub with friction -- scientists don't really know how it works. Sure, humans have been harnessing the power of friction since rubbing two sticks together to build the first fire, but the physics of friction remains largely in the dark.

In a new paper in Nature Materials, Brandeis University professor Zvonomir Dogic and his lab explored friction at the microscopic level. They discovered that the force generating friction is much stronger than previously thought. The discovery is an important step toward understanding the physics of the cellular and molecular world and designing the next generation of microscopic and nanotechnologies.

The research was conducted as part of the Brandeis University Materials Research Science and Engineering Center.

Dogic and his team focused on the frictional forces of actin filaments, essential cellular building blocks responsible for many biological functions including muscle contraction, cell movement and cell division. All of these processes require filaments to move and slide against one another, generating friction. Scientists assumed that the frictional forces of these movements were minimal, acting more like weaker hydrodynamic friction -- like pulling an object through water -- than the larger solid friction -- pushing an object across a desk.

But Dogic and his team observed the opposite. They developed a new technique to measure friction, and when they dragged two actin filaments against each other, they observed frictional forces nearly 1,000 times greater than expected -- closer to solid friction than hydrodynamic friction.

This is due, in part, to interfilament interaction. Imagine filaments as two beaded strings, one on top of the other, pulled in opposite directions. As the strings move, the beads must go up and over their counterparts on the opposite string, generating even more friction. By observing this interfilament interaction, Dogic and his team were able to measure the frictional forces and tune them, altering the forces to include more or less friction.

"Before this research, we didn't have a good way of controlling or understanding friction," Dogic says. "We still have a lot more to understand but now, one of our oldest sciences is becoming less opaque."
The paper was coauthored by Brandeis scientists Andrew Ward, Fiodar Hilitski, Walter Schwenger and David Welch; A. W. C. Lau of Florida Atlantic University; Vincenzo Vitelli of the University of Leiden, and L. Mahadevan of Harvard University.

Brandeis University

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 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