Jan 12, 2009
Nanowires lead to strong friction
Although strong adhesion of 1D nanostructures is well known, their friction behavior under loads has not been reported. A solid surface coated with a film of nanowires can have more than 10 times stronger friction than their macroscopic counterparts.
As one solid slides on another, there is friction. The magnitude of friction depends on, among other factors, the true contact area of the two solids. The true contact area usually is a small fraction of the nominal contact area due to surface roughness. When one solid is coated with a film of nanowires, which are flexible, the true contact area increases substantially.
In a recent paper in Nanotechnology, the authors reported the frictional behavior of SiC-SiO2 core-shell nanowires; the core being crystalline SiC and the shell being amorphous SiO2. The nanowires are coated on a solid surface, which is then slid on a reference solid. A variety of reference solids are used and they include glass, alumina, mica, and polytetrafluorethylene (PTFE). The use of nanowires film increases the friction coefficient by 5-12 times for these reference solid surfaces. In contrast to aligned 1D nanostructures, the nanowires film is immune from buckling under normal loads. As a result, the enhanced frictional force is further controllable through the change of normal loads.
The mechanism of enhancing friction is generic to all nanowires, and the enhanced friction can operate at various normal loads.
About the author
The work was performed at the Rensselaer Polytechnic Institute (RPI) and sponsored by the Department of Energy Office of Basic Energy Science (nanowires synthesis) and the National Science Foundation (mechanics). Hyun Woo Shim has recently completed his PhD and joined Intel at Portland, and Jaron Kuppers is a graduate student; both in the Interface Engineering Laboratory. Professor Hanchen Huang heads the Interface Engineering Laboratory, and is Professor of Mechanical and Nuclear Engineering at RPI (http://www.rpi.edu/~huangh); and in transition to School of Engineering Professor in Sustainable Energy at UConn (http://www.engr.uconn.edu/). Professor Huang’s research focuses on the design and synthesis of interfaces at the atomistic level, targeting applications in sustainable energy.