Mechanical properties of soft interfaces.

Abstract

As the trend of miniaturization in devices and systems continues, it is important to understand their mechanical properties at the nanometer scale. In Micro-Electro-Mechanical Systems (MEMs) and implantable biomedical devices, interfacial forces (friction and adhesions) responsible for device failure are a major concern. Molecular films as thin as a monolayer are being actively explored to reduce adhesion and friction. However, many questions remain about the tribological properties of these systems. This thesis summarized the use of Interfacial Force Microscopy allows us to reliably create single asperity contacts and study the associated tribological properties on the nano and microscale. We have used this tool to study the mechanical properties of confinement of molecular films, including water, liquid-like-layer (on ice), alkyl monolayers, and phospholipid monolayers and bilayers. We find that the interfacial water created by premelting of ice or nanoconfinement between hydrophilic surfaces exhibit significant increase in viscosity. In the cases of alkyl or phospholipid thin films, mechanical properties, particularly friction, are strong functions of film structure and density. Results from these model systems are starting to form a foundation for our understanding of mechanical properties of soft interfaces at the nanometer scale.