MICROSCOPIC PATTERNING OF ORIENTATED MESOSCOPIC SILICA THROUGH GUIDEDGROWTH

The supramolecular assembly of surfactant molecules at a solid-liquid interface can produce tubular structures with diameters of around 10 n m (refs 1-4), which can be used for the templated polymerization of me soporous silica thin films(3-5). The orientation of the tubules depend s primarily on the nature of the substrate-surfactant interaction. The se nanostructured films hold much promise for applications such as the ir use as orientated nanowires(6), sensor/actuator arrays(7-9) and opt oelectronic devices(10), But a method of patterning the tubules and or ientating them into designed arrangements is required for many of thes e possibilities to be realized. Here we describe a method that allows the direction of growth of these tubules to be guided by infiltrating a reaction fluid into the microcapillaries of a mould in contact with a substrate(11). An electric field applied tangentially to the surface within the capillaries induces electro-osmotic flow, and also enhance s the rates of silica polymerization around the tubules by localized J oule heating. After removal of the mould, patterned bundles of orienta ted nanotubules remain on the surface. This method permits the formati on of orientated mesoporous channels on a non-conducting substrate wit h an arbitrary microscopic pattern.