Anisotropic spinodal dewetting as a route to self-assembly of patterned surfaces

The ability to pattern surfaces on a microscopic length scale is of importance for technological applications such as the fabrication of microelectronic circuits and digital storage media. Devices fabricated entirely from polymers are now available, opening up the possibility of adapting polymer processing technologies to fabricate cheap, large-area devices using non-lithographic techniques--for example, by exploiting dewetting and phase separation in thin films. But the final pattern adopted by the polymer film using such approaches requires a template printed onto the substrate by optical lithography, microcontact printing or vapour deposition. Here we describe a simple process for patterning surfaces that does not require a template. Our method involves the spinodal dewetting of a polymer surface by a thin polymer film, in which a liquid film breaks up owing to the amplification of thermal fluctuations in film thickness induced by dispersion forces. A preferred orientation is imposed on the dewetting process simply by rubbing the substrate, and this gives rise to patterns of remarkably well-aligned polymer lines. The width of these lines is well-defined, and is controlled by the magnitude of the dispersion forces at the interface, which in turn can be varied by varying the thickness of the polymer substrate. We expect that further work will make it possible to optimize the degree of order in the final morphology.

Neutron Reflectivity Study of the Adsorption of beta-Lactoglobulin at a Hydrophilic Solid/Liquid Interface.

Adsorption of a globular protein on a hydrophilic solid/liquid interface was investigated. Neutron reflectivity was used to determine structural information on an adsorbed beta-lactoglobulin layer at a hydrophilic silicon surface. The thickness of the protein film was found to be compatible with the diameter of the native protein, indicating that possible conformational changes of the protein during adsorption are not gross enough to alter the shape of the protein. The amount adsorbed is consistent with that derived by our ellipsometry measurements, obtained in similar experiments. Evidence for significant H-D exchange in the adsorbed protein was found. Copyright 1999 Academic Press.