Diatom nanopore membrane devices for molecular transport and biomembrane studies

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Intellectual Merit: Nanopore membranes have become indispensible tools for filtration. However, these membranes have several drawbacks. To accomplish molecular separation, the nanopores have to be of the same size as the molecules. If mechanical stability is to be maintained, such small nanopores will be very long, significantly slowing down molecular transport. Nanopores patterned using electron or ion beam lithography in silicon dioxide or silicon nitride membranes have the benefit of having a well-controlled size and can be controlled in thickness, however they are costly to manufacture. Biomineralized structures, such as silica diatom shells, offer an alternative approach towards nanopore membranes. Some species exhibit a narrow size distribution of nanopores on the order of 40 nm while they can grow up to 200 µm in diameter. Diatom shells have a hierarchical pore structure, stabilizing the nanopore membrane with two sets of larger pores. Since they consist of silica, they are optically transparent and can be functionalized using silane chemistry. In the proposed project the possibility of using the silica diatom shells as nanomembranes in microdevices will be explored. Using chemical pre-patterning of silicon dioxide surfaces the diatom shells will be aligned to pre-defined structures on a wafer scale, allowing to combine bottom-up and top-down device architectures. By chemically functionalizing the silica nanopore surface, for example using Atomic Layer Deposition, the molecular transport properties through the nanopores can be tailored, allowing molecular separation studies. Furthermore, the pores themselves can act as support structures for so-called nano-Bilayer Lipid Membranes, which show an increase in lifetime by a factor of 30 on top-down silicon nitride nanopores.Broader Impact:The research will have a tremendous impact in the field of nanofluidic devices, eventually replacing the track-etched nanopore membranes that are currently used for filtration. Since the pore sizes are small and the pore length is short without compromising the mechanical stability, faster diffusion of molecules is expected. The expected lifetime improvement of nano-Bilayer Lipid Membranes will have a transformational impact on the field ion channel reconstitution. The interdisciplinary program targets to recruit and retain highly talented students as well as underrepresented and minority students. Graduate students will be educated to become future engineers by preparing them for the challenges that lie ahead by involving them in the proposed research activities. Undergraduate students will be engaged via the Undergraduate Research Initiative scholarship program that has been established at ASU. In collaboration with the Down-to-Earth Science (DES), an NSF-funded GK-12 track II project at Arizona State University, the proposed project will offer a novel educational opportunity for faculty and graduate students to share their research results with the K-12 community, providing a new thrust through the integration of cutting edge research in nanotechnology into the secondary school curriculum. The research component will be linked with an assessment plan, enabling feedback on the effectiveness of the educational impact, enabling an improvement of the initial teaching concepts.