Nonequilibrium Materials Synthesis: Understanding and Controlling the Formation of Hierarchically Structured Microtubes

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TECHNICAL SUMMARYThis project focuses on inorganic, tubular materials formed during spatially controlled reaction processes. These hollow tubes have inner radii 1-100 µm and result from the precipitation of amorphous silica and metal hydroxides. The overall phenomenon is not well understood and its potential as a model case for system-level materials science widely unexplored. Under this grant, supported by the Solid State and Materials Chemistry program of the Division of Materials Research, the PI will develop a pressure-controlled reactor system to produce millimeter-long microtubes with radii of down to 1 µm. In addition, the size and shape of these microtubes will be controlled using variable electric fields and pressure changes. Another central goal is to nano-engineer the physico-chemical characteristics of the tube wall by binding, trapping and adsorbing a variety of molecules and particles. Moreover, the group will integrate tubes into microfluidic devices where they will add functionalities such as enhanced separation regions, chemical sensors, and catalytic processing stations. These experimental projects will be complemented by modeling efforts that aim to develop a reaction-transport model capable of capturing key aspects of the large-scale growth dynamics based on the precipitation kinetics, diffusion, and advection processes. An important part of the broader impact of this project is to communicate its key ideas and results to non-experts. The project will pursue this goal through a multi-faceted video outreach program. In addition, it will advance the education of undergraduate, graduate and postdoctoral students at the Florida State University.NON-TECHNICAL SUMMARYModern technologies produce materials and devices in ways that differ fundamentally from the strategies employed by biological systems. These differences are the likely explanation as to why materials with hierarchical architectures and self-healing features tend to elute conventional engineering approaches but are abundant in biology. A key question in this context is how chemical reactions can cause the formation of complex structures that are thousands to millions times larger than the individual molecules. The project will tackle this big question by studying inorganic reactions that are known to produce hollow tubes. The diameter and length of these rigid structures is comparable to human hair but can also be significantly thinner. The tube walls typically consist of amorphous silica (porous glass) and metal hydroxides or oxides, which create interesting catalytic and optical properties. If successful, this research will (i) result in quantitative models of nano-to-macro growth processes, (ii) provide reactor systems that can shape the tubes during growth, (iii) demonstrate chemical modifications of the wall material that introduce chemical sensing and/or processing capabilities, (iv) explore applications towards uses in microfluidic and lab-on-a-chip technologies. The project also aims to communicate its scientific ideas and results to non-experts. The intriguing life-like appearance and overall visual appeal of the basic phenomenon will greatly assist in this effort. Specific plans include targeted video outreach through FSU's Global Educational Outreach Program, Podcasts, and popular websites such as YouTube. In addition, the project will advance the education of several undergraduate, graduate and postdoctoral students. The PI will also continue his commitment to involve underrepresented groups and participate in programs that aim to increase their leadership roles in research and academia.