Diatom-Enabled Scalable Nanomanufacturing for Photonic Devices

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As a major group of microalgae, diatoms have long been the inspiration and source material in many research fields. The intricate morphology of the abundant nanostructured silicon dioxide exoskeletons (also known as frustules) have led to numerous studies. To date, diatom frustules have been used in fluorescence immunoassays because their nanopores provide large surface areas for the bonding of bio-molecules. They have also been used as anode materials in dye sensitized solar cells because of their excellent light scattering property. The numerous nanostructures on diatom frustules are markedly uniform, however, they are seldom used in the scalable manufacturing of nanopatterns. This award advances the knowledge of how to utilize diatom frustule nanostructures on a large scale, by developing a better understanding of the interaction between diatom frustules and their surrounding gas/liquid/solid environments. This understanding is harnessed to produce large-area, uniform diatom frustule assemblies, followed by the replication of their nanostructures in two- and three-dimensions. Specifically, the photonic properties of these assemblies and their replicas are investigated and tailored towards specific photonic applications. The project provides a series of outreach modules tailored towards educating young researchers, including women and underrepresented minorities, and for fostering their passion in nanoscience and nanomanufacturing technologies.Diatoms are unicellular photosynthetic microalgae which are ubiquitous in aquatic environments and remarkably diverse, with the estimated number of living species on the order of tens of thousands. As a potentially low-cost biomaterial, diatom frustules contain dense arrays of highly uniform nanopores, the diameters of which are as small as 40-60 nm. To fully utilize these remarkable nanostructures, diatom-enabled scalable nanomanufacturing approaches are explored in this work. Typical diatom frustule morphologies (e.g. Coscinodiscus sp. and Pinnularia sp.) are used to investigate different strategies in developing large-area frustule monolayers. This project addresses the fundamental and technological issues of the interactions between frustule and liquid-air and liquid-solid interfaces, and harnessing these interactions to achieve uniformly oriented compact frustule monolayers for subsequent nanopatterning. By analyzing computational and experimental results of such interactions, this research seeks to optimize diatom monolayer assembly formation through optimizing the frustule surface treatment and fluid flow conditions. Following the frustule assemblies, nanopattern transfer techniques are studied towards the 2D and 3D replication of frustule nanostructures through surface micromachining and micro-molding techniques. In addition, the light scattering properties of the frustule assemblies and their replicas are investigated. The replicated nanopatterns mirroring the hierarchical nanopores of the frustules are specifically tailored towards photonic applications, such as IR absorbers and photonic crystal filters.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.