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CPM Seminar
Nancy Burnham
Swiss Federal Institute of Technology When a nanometer-sized point is brought close to or put in contact with a sample, e.g. by means of the tip of an atomic force microscope, the point-sample interaction is surprisingly complex. As one might expect,there is repulsion when the two bodies touch, but also attractive forces exist and play a significant role in the overall behavior. If one of the materials is plastic, quantized force and conduction occurs in `atomic wires' formed by ductile extension upon point-sample separation. Subharmonics and chaos, due to the nonlinear nature of the interaction, can be observed when the sample is dynamically excited at frequencies above the system's resonance. The pointed tip can also be used to probe the properties of modern materials, whose mechanical response can vary laterally on the submicron scale. Examples include phase transitions in polymer blends, the dependence of the elastic modulus on the structure of carbon nanotubes, and anisotropy and asymmetry in the friction of lipid monolayers.
Monday, November 16th 1998, 15:30 |