In this summary of some of my studies involving multilayer materials I will outline theory and experiment aimed at determining interface free energies and interface stresses. The first of these quantities, which is necessary to predict equilibrium geometries of polyphase materials at elevated temperatures, is obtained from analysis of elevated temperature creep experiments. The latter quantity, which leads to nonzero equilibrium elastic strains in small structures, is obtained from analysis of room temperature x-ray diffraction data.
The multilayer materials studied are composed of alternating layers of two different metals. The gross dimensions of the films (tens of m m thick and cms wide) belie the much finer features of the underlying layered structure (see the transmission electron microscope image of an aluminum/titanium multilayer fabricated in the Metallurgy Division and viewed in cross section). The layer thickness, which can be easily varied from m ms down to nms, permits interfacial quantities to be systematically amplified, thereby facilitating measurement of these interface quantities. In the process, the materials thus created begin to resemble a mixture of their constituents less and less and a completely new material, with potentially novel properties, more and more.
Beams of laser light can be used to mechanically manipulate matter from the level of atoms to biological cells. Here at NIST, I am applying such optical forces to study coherent waves of matter and adhesion in biological systems. In my talk, I will describe the physics behind the mechanical effects of light and its applications. In particular, I will explain how I am using optical forces to study adhesion of biomolecules.