Tribology is the science and technology of interacting surfaces in relative motion and includes studies of friction, adhesion, lubrication, and wear. Understanding interrelated tribological phenomena is critical for most mechanical devices, as demonstrated by applications in the automotive, aerospace, and manufacturing industries. Today, these issues are the focus of significant studies in emerging technologies involving micro- and nanoscale mechanical components and present new technical challenges for tribologists. The goal of this project is to develop measurement techniques and instrumentation that enable us to isolate different mechanisms that govern friction at the nanoscale.
Friction and wear are major causes of mechanical failures and dissipative energy losses. These shortfalls account for a significant portion of the annual gross domestic product in the United States, amounting to approximately $800 billion in 2010. It is estimated that tens of billions of U.S. dollars could be saved by the proper use of lubricants. In response to this need, both solid and liquid lubricants have been developed to minimize frictional energy losses, reduce equipment maintenance, and extend device lifetimes. Today, these issues are the focus of significant studies in emerging technologies involving micro- and nanoscale mechanical components and present new technical challenges for tribologists working at the nanoscale.
In comparison with macroscopic devices, the separations between objects in a micro- or nanoscale system are much smaller and can be less amenable to stable lubrication. In addition, with liquid lubricants, the viscosity of the fluid impedes motion of micro- and nanoscale parts, and surface tension can cause these parts to warp and adhere. Hence, while macroscale lubrication schemes can rely on the formation of a solid or liquid interface where a lubricant slides against itself, this approach is precluded at the micro- and nanoscale. Tribological principles applicable to micro- and nanoscale devices (i.e., nanotribology) must therefore focus primarily on surface interactions at the original interface. A detailed understanding of this difference is key to controlling friction at the nanoscale.
We are developing techniques to perform fundamental measurements of atomic- and nanoscale forces on scientifically and technologically relevant materials and systems, including engineered nanostructures and electronically active surfaces. Methods to determine the contributions to these forces from individual material properties, including electrical conductivity, thermal conductivity, structure, and composition will fuel investigations into novel methods for controlling tip-sample forces and dissipation during both the assembly and operation of micro- and nanoscale devices. The project involves the incorporation of Raman spectroscopy with high-speed, high-resolution atomic force microscopy and in situ measurements of the thermal properties of materials.