Soft lithography-mediated microscale patterning of silica on diverse substrates
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Nicholas Ferrell and Derek Hansforda) Department of Biomedical Engineering, The Ohio State University, Columbus, Ohio 43210
Rajesh Naik Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright Patterson Air Force Base, Ohio 45433 (Received 11 August 2008; accepted 8 December 2008)
We have developed a soft lithography-based process to create microscale patterns of silica on a diverse array of substrates. A sacrificial polymer layer was first patterned using a micromolding technique. A peptide was adsorbed on the substrate and the sacrificial layer was removed. The patterned peptide template then catalyzed the deposition of silica from a silicic acid solution. With this procedure, we have created both continuous and discontinuous silica patterns on metallic, ceramic, and polymer substrates.
I. 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 particularly 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 used 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 pursuit of these goals, we have developed a straightforward procedure for creating microscale patterns of silica on a diverse array of substrates. A soft lithographic technique is used to create a sacrificial layer on the desired substrate. Subsequently, a synthetic catalyst and silicic acid solution are applied to deposit silica in the chosen
a)
Address all correspondence to this author. e-mail: [email protected] This paper was selected as an Outstanding Symposium Paper for the 2007 MRS Spring Meeting, Symposium T Proceedings, Vol. 10008E. DOI: 10.1557/JMR.2009.0200
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J. Mater. Res., Vol. 24, No. 5, May 2009 Downloaded: 29 May 2014
pattern. With this procedure, we have created both continuous and discontinuous silica patterns on metallic, ceramic, and polymer substrates. Several previous studies have begun to unravel the array of genes, proteins, and mechanisms by which biosilicification, the in vivo synthesis of silica, is moderated. For example, proteins called silaffins5 and longchain polyamines (LCPAs)6 have been isolated from the frustule of the diatom Cylindrotheca fusiformis. Sponges synthesize silica with a different collection of macromolecules to control the deposition. Analysis of the organic filament occluded within the spicules
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