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.