CAREER: Exploring Fast Mass Transport in Carbon Nanofluidics

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CBET - 1653767PI: Duan, ChuanhuaRecent experiments indicate that flow through channels that have nanometer dimensions and smooth carbon surfaces is significantly enhanced compared with flow through channels that have similar or larger dimensions but other types of surfaces. However, the mechanism of flow enhancement in these nanochannels is not fully understood, in part because prior experiments produced highly variable results. This award will support a series of experiments to help reconcile ambiguities in prior experiments and, more importantly, to help uncover the underlying mechanisms of flow enhancement at nanoscale dimensions. Unlike most prior experiments that used flow through arrays of nanochannels in a thin membrane, this project will measure flow of water and ions through individual nanofluidic conduits. A new method of nanochannel design and fabrication, coupled with capillary flow, will be used to directly measure the hydraulic resistance, ionic conductance and mobility, as well as water and ion flow enhancement in single, well-defined carbon nanotubes and graphene nanochannels. Correlations between flow enhancement and material properties, supported by computational modeling, will elucidate key factors that make flow through carbon nanofluidic conduits unique. The results will be useful in designing and fabricating carbon nanofluidic devices and structures for a variety of applications, including water desalination, batteries and fuel cells, lab-on-a-chip, as well as in interpreting certain flows in geology, biology and physiology. The award includes support for educational activities for students at all academic levels. Cartoon animations and hands-on lab kits that illustrate the unique physics of flow at the nanoscale will be developed for use by K-12 students. The project will provide opportunities for undergraduates, especially those from underrepresented groups, to participate in the research. Since research using membranes consisting of multi-conduit carbon nanotubes or graphene nanochannels introduces ambiguities due to conduit-size polydispersity, this award will study water and ion transport in single carbon nanotubes and graphene nanochannels with well-defined sizes, surface properties and barrier materials. The experiments will test the hypothesis that fast mass transport of water and ions in these channels results from unique surface-water and surface-ion interactions, which strongly depend on the substrate or barrier material as well as on the confinement and surface properties of these carbon nanofluidic conduits. Experimental measurements will be compared with molecular dynamics simulations that consider explicitly effects of substrate/barrier material, surface charge, and ion-water interactions. The carbon nanofluidic devices fabricated in this project will also provide investigators a platform to study selective ion and gas transport, which could not only improve understanding of carbon nanofluidics, but also expand its practical applications to chemical and biological separations processes.