Extensive research in recent years by various investigators has brought out the complexities involved in the study of nanoscale friction behaviour. Contrary to classical friction laws postulated by Amontons and Coulomb centuries ago, nanoscale friction force is strongly dependent on normal load and sliding velocity as well as environmental factors. The strong sliding velocity dependence is of critical interest in, for example, the design of high speed microelectromechanical (MEMS) devices and components such as micromotors, microgear drives and microgas turbines.
We conducted nanotribological investigations at sliding velocities that encompass regimes of scientific as well as engineering interest. Various materials, coatings and lubricants that are considered potential solutions for nanotechnology applications were evaluated. Theoretical formulations have been developed to design a comprehensive analytical model that explains the non-linear nature of nanoscale friction. The model takes into consideration the contributions of atomic scale stick-slip, adhesion at the contacting interface, and high impact velocity related deformations at the contacting asperities. It relays the complex dependence of operating parameters, material properties and the surface structure (or roughness).
Finding slippery surfaces for nanodevices with moving parts is a subtle business. However, using this new model and our current understanding of the interdependence of mechanical and tribological properties we can identify tribologically ideal materials with low adhesion and friction for nanotechnology applications (see Figure 1).
