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

The ability to pattern surfaces on a microscopic length scale is of importa nce for technological applications such as the fabrication of microelectron ic circuits and digital storage media. Devices fabricated entirely from pol ymers are now available, opening up the possibility of adapting polymer pro cessing technologies to fabricate cheap, large-area devices using non-litho graphic techniques(1,2)-for example, by exploiting dewetting(3) and phase s eparation(4-6) in thin films. But the final pattern adopted by the polymer film using such approaches requires a template printed onto the substrate b y optical lithography, microcontact printing(4,5) or vapour deposition(3). Here we describe a simple process for patterning surfaces that does not req uire a template. Our method involves the spinodal dewetting of a polymer su rface by a thin polymer film, in which a liquid film breaks up owing to the amplification of thermal fluctuations in film thickness induced by dispers ion forces(7-14). A preferred orientation is imposed on the dewetting proce ss simply by rubbing the substrate, and this gives rise to patterns of rema rkably well-aligned polymer lines. The width of these lines is well-defined , and is controlled by the magnitude of the dispersion forces at the interf ace, which in turn can be varied by varying the thickness of the polymer su bstrate. We expect that further work will make it possible to optimize the degree of order in the final morphology.