A General Approach to Patterning Micron-Scale Particles
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A General Approach to Patterning Micron-Scale Particles Nathanael Sieb and Byron D. Gates Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, V5A1S6, Canada ABSTRACT Multiple techniques have been developed to assemble micro- or nanostructured materials into well-defined patterns. These techniques are, however, often dependent on the size, shape, composition and/or surface chemistry of the structures being patterned. We have developed a general approach to pattern materials with a wide range of physical and chemical characteristics. We are able to assemble these materials into isolated or interconnected patterns covering areas up to ~1 mm2. INTRODUCTION We have demonstrated the ability to transfer insoluble particles from a liquid-liquid interface onto a solid substrate in a controlled manner. Using our technique, we have produced micron-resolution patterns in less than 60 minutes from start to finish. One of our goals is to rapidly assemble a variety of materials into patterns with micron-scale (or smaller) features covering large areas. Recently, a number of studies have been pursued to understand and control the self-assembly of particles at either liquid-air or liquid-liquid interfaces [1-7]. Pioneering work has also been done to assemble spherical particles into regular structures on substrates using template-assisted self-assembly [8,9]. Another method being pursued to achieve regular patterns of self-assembled particles utilizes microcontact printing to transfer close-packed layers of particles onto a solid support [10-12]. Our technique combines elements of these methods into a universal method to fabricate patterns of particles on various surfaces irrespective of particle stability. For example, we use a poly(dimethylsiloxane) (or PDMS) stamp to transfer polystyrene (PS) particles from a liquid-liquid interface onto a silicon substrate; particles are trapped in the grooves of the stamp and transfer from the ridges of the stamp onto the silicon. Our approach provides the ability to create well-defined patterns from a broad range of materials. EXPERIMENTAL Materials We fabricated PDMS stamps using polymer precursors purchased from Dow Corning (Midland, MI; Sylgard 184). From Alfa Aesar (Ward Hill, MA) we purchased 1H,1H,2H,2Hperfluorodecyltrichlorosilane, which can covalently link to the surface of oxidized PDMS. One of the liquids for our liquid-liquid interface was perfluoro(methyldecalin) (PFMD), tech. grade, obtained from Oakwood Products (West Columbia, SC). Another liquid for the interface was light paraffin oil (Saybolt viscosity of ~130 SUS at 100 °F) purchased from EMD Chemicals (Gibbstown, NJ). Carboxylic acid functionalized PS microspheres (10.1% solids in water) with a diameter of 1.04 µm were obtained from Bangs Laboratories (Fishers, IN). To screen the
carboxylic acid groups on the surface of the PS particles, we bought a solution of tetraethylammonium hydroxide (TEAH) (20% in water) from Sigma Aldrich (Oakville, ON). The solutions of PS particles were
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