Microfabricated cantilever sensors were used to measure the surface stress induced by protein adsorption onto a gold surface. Two proteins, immoglobulin G (IgG) and albumin (BSA), were studied. The change of surface stress upon adsorption of IgG was found to be compressive, whereas that of BSA was tensile. This difference is elucidated in terms of protein deformation and packing. Most stress change occurs not on adsorption but over very long time scales, up to 12 h, as protein conformational changes occur. The ability to monitor slow protein changes (e.g., from protein denaturing) is a particular strength of the technique.

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Reversible, controllable optical nanocontraction and dilatation in a chalcogenide glass film was induced by polarized light, and a direct correlation of this optomechanical effect with the reversible optical-induced optical anisotropy (dichroism) also exhibited by the chalcogenide glass was observed. A microscopic model of the photoinduced, reversible structural phenomenon responsible for the optomechanical behavior is presented. The ability to induce an anisotropic optomechanical effect could form the basis of a number of applications, including polarized light-dependent optical nanoactuators, optomechanical diaphragm micropumps, and even motors driven by polarized light.

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