Nanomanipulation and characterization of structural proteins.

A methodology is presented for simultaneous mechanical testing and atomic force microscopy imaging of single collagen fibrils under load. This method holds the promise for determining single-fibril modulus and strength in various experimental preparations. Examples of this utility include characterization of deformation and failure modes of naturally occurring and engineered structural proteins. Additional promise of this technique is robotic surgery at the submicron scale for repairing neuronal tracts and capillaries with structural proteins. A series of algorithms for tying knots at the nanoscale in single fibrils is also presented.

Scanning tunneling microscopy studies of temperature-dependent etching of diamond (100) by atomic hydrogen.

We present a technique for obtaining atomic resolution ultrahigh vacuum scanning tunneling microscopy images of diamond (100) films, and use this technique to study the temperature dependence of the etching of epitaxial diamond (100) films by atomic hydrogen. We find that etching by atomic hydrogen is highly temperature dependent, resulting in a rough and pitted surface at T approximately 200 and 500 degrees C, respectively. At T approximately 1000 degrees C etching results in a smooth surface and is highly anisotropic, occurring predominantly in the direction of dimer rows. This observation supports recent theoretical models that propose anisotropic etching as the mechanism for the growth of smooth diamond (100) films.