Brandeis Magazine

Here’s the rub with friction — scientists don’t really know how it works.

Although humans have been harnessing its power since rubbing two sticks together to build the first fire, the physics of friction remain largely in the dark.

Now, Brandeis research is showing that frictional force on the microscopic level is much stronger than previously thought. Associate professor of physics Zvonimir Dogic and his lab studied actin filaments, essential cellular building blocks responsible for many biological functions, including muscle contraction, and cell movement and division. All these processes require filaments to move and slide against one another, generating friction.

The frictional forces of such movements were thought to be minimal, similar to the hydrodynamic friction created by pulling an object through water. But when Dogic’s team dragged two actin filaments against each other, they observed frictional forces nearly 1,000 times greater than expected — closer to the solid friction created by, say, pushing an object across a desk. They were also able to “tune” the forces to add or subtract friction.

Learning more about the strength of frictional forces is an important step toward understanding the physics of the cellular and molecular world, and will help innovators design the next generation of microscopic- and nano-level technologies.

“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.”