Synopsis: Fine Tuning Friction

Frictional forces between surfaces coated with charged polymers can be adjusted with external electric fields.
Synopsis figure
C. Drummond, Phys. Rev. Lett. (2012)

Without lubrication, most machinery, from wagon wheels to turbocharged car engines, would shudder to a halt. The reason is friction, a highly complex phenomenon that generates heat and damage on surfaces in contact. While conventional friction-reduction methods involve passive control by adequate lubricant choice, Carlos Drummond of the CNRS Centre de Recherche Paul Pascal, France, reports in Physical Review Letters that there are sophisticated ways to actively adjust frictional forces with electric fields.

Drummond started from the knowledge that external electric fields can modify the conformation of electrically charged molecules. By using molecules that spontaneously get adsorbed at surfaces, he deposited coatings of charged polymers called polyelectrolytes on smooth mica planes. These molecules form “polymer brushes” because they attach to the surface and stick out like bristles on a toothbrush. When two of these mica surfaces are put together, the frictional force between them depends on how the polymer brushes interpenetrate. The author applied an electric field by means of electrodes attached to the backsides of the mica and showed that this altered the polymer conformations, resulting in a dramatic change in friction.

Because the electric response is rapid, and electrical signals are straightforward to generate, Drummond envisions that the effect may be useful for many applications, ranging from wear reduction in artificial prostheses to real-time control of tactile sensations. One could imagine human-computer interfaces by which tactile friction conveys information to the vision impaired. – David Voss


Features

More Features »

Subject Areas

Chemical PhysicsMaterials Science

Previous Synopsis

Next Synopsis

Astrophysics

New Shape to Nuclear Pasta

Read More »

Related Articles

Synopsis: Protons in the Fast Lane
Energy Research

Synopsis: Protons in the Fast Lane

A proposed graphene-based material could offer speedy transport of protons without the need for water. Read More »

Synopsis: A Crystal Ball for 2D Materials
Materials Science

Synopsis: A Crystal Ball for 2D Materials

Researchers predict new two-dimensional materials whose structures differ from their three-dimensional counterparts. Read More »

Viewpoint: Electron Pulses Made Faster Than Atomic Motions
Atomic and Molecular Physics

Viewpoint: Electron Pulses Made Faster Than Atomic Motions

Electron pulses have shattered the 10-femtosecond barrier at which essentially all atomic motion is frozen in materials. Read More »

More Articles