MADISON To understand friction on a very small scale, a team of University of Wisconsin-Madison engineers had to think big.
Friction is a force that affects any application where moving parts come into contact; the more surface contact there is, the stronger the force. At the nanoscale mere billionths of a meter friction can wreak havoc on tiny devices made from only a small number of atoms or molecules. With their high surface-to-volume ratio, nanomaterials are especially susceptible to the forces of friction.
But researchers have trouble describing friction at such small scales because existing theories are not consistent with how nanomaterials actually behave. Through computer simulations, the group demonstrated that friction at the atomic level behaves similarly to friction generated between large objects. Five hundred years after Leonardo da Vinci discovered the basic friction laws for large objects, the UW-Madison team has shown that similar laws apply at the nanoscale.
The team, which was led by Izabela Szlufarska, an assistant professor of materials science and engineering, and included materials science and engineering graduate student Yifei Mo and mechanical engineering assistant professor Kevin Turner, published its findings in the Feb. 26 issue of the journal Nature.
Current nanoscale friction theories are based on the idea that nanoscale surfaces are smooth, but, in reality, the surfaces resemble a mountain range, where each peak corresponds to an atom or a molecule.
The UW-Madison team performed computer simulations that looked at nanoscale materials as a collection of atoms, monitoring their positions and interactions throughout the entire sliding process. "For the first time, we modeled friction at length scales very similar to experiments, while maintaining atomic resolution and realistic interactions between atoms," say Szlufarska.
The team discovered simple laws of nanoscal
|Contact: Izabela Szlufarska|
University of Wisconsin-Madison