Controlled silica deposition on soft-lithography fabricated poly-L-lysine templates
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1008-T05-28
Controlled silica deposition on soft-lithography fabricated poly-L-lysine templates Randall Butler1, Nicholas Ferrell1, Rajesh R. Naik2, and Derek J. Hansford1 1 The Ohio State University, Columbus, OH, 43210 2 Air Force Research Laboratory, AFRL/MLPJ 3005 Hobson Way, Bldg 651, Wright Patterson AFB, OH, 45433-7702 ABSTRACT We describe the combination of soft-lithographic patterning and biomolecule-induced deposition to create microscale patterns of silica on a diverse array of substrates. A soft lithographic technique was used to create a sacrificial layer of the polymer poly(n-propyl methacrylate) (PPMA) on the desired substrate. Subsequently, poly-L-lysine was deposited on the substrate, after which removal of the PPMA yielded a pattern of PLL on the substrate. Exposure of the PLL template to a silicic acid solution resulted in silica deposition in the pattern spatially and geometrically controlled by the PLL. With this procedure, we have created both continuous and discontinuous silica patterns on metallic, ceramic, and polymer substrates. While morphology of the deposited silica varied between substrates, the ability to pattern silica through this templated growth was demonstrated on all investigated substrates. EDS, optical micrography, and SEM analysis verified the controlled deposition of silica on the PLL template patterns. This PLL template-mediated induction of silica formation may facilitate the incorporation of silica in new microdevices and serve as a prototype process for controlled deposition with other biomolecule-material systems. INTRODUCTION A wide variety of organisms synthesize inorganic materials in intricate forms via organic macromolecules that serve as templates to control deposition, a process known as biomineralization. A common example of such inorganic materials is silica, which is deposited in various structures by diatoms, radiolarians, sponges, and plants [1]. Diatoms, in particular, have been the focus of much research because they produce amorphous silica cell walls called frustules with nanoscale detail at ambient temperature and pressure and near neutral pH [2,3]. These abilities are in contrast to industrial silica production methods, which are often energyintensive and require extreme reaction conditions [2]. It is hoped, therefore, that the molecular mechanisms employed by diatoms will allow the inexpensive production of new silicon-based materials with features at a smaller scale than is achievable with current technology [2-4]. In the process of elucidating the mechanism for the deposition of silica onto naturally occurring proteins, a number of synthetic compounds have been shown to likewise catalyze the precipitation of silica. . The cationic polymers polyallylamine hydrochloride [5,6] and poly-Llysine (PLL) [7] lead to the precipitation of amorphous silica spheres when mixed with a silicic acid solution under ambient conditions; mixtures of the two polymers produce novel morphologies [7]. While photolithography has enabled the fabrication of many microdevices,
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