Electrowetting Effects and Nanoscale Transport

With support from the Chemical Measurement and Imaging Program in the Division of Chemistry, Professor Paul Bohn and his group at the University of Notre Dame are studying the design, behavior, and possible applications of new artificial materials inspired by Nature, particularly architectures consisting of layered films where each layer has a different pore structure. The work is motivated by applications ranging from molecular separations to catalysis. For example, these materials can selectively remove unwanted components in applications such as beverage clarification, clearance of pathogens from blood, and in controlled release of drugs and highly selective sensors for disease-specific biomarkers. These experiments will establish the know-how to control the wetting characteristics of the liquid on the wall, thereby making it possible to use advanced fluid control concepts in technological applications, such as separations in complex fluids. The work is also coupled with the development of new multi-university programs that cut across disciplinary lines and address specific NSF goals, including the development of a diverse, globally competitive STEM (science, technology, engineering and mathematics) workforce, increased partnerships between academia and industry, and increased economic competitiveness. The project addresses transport in nanoscale confined volumes, which highlights a core set of scientific phenomena - wetting/dewetting, hydrophobicity, stochastic fluctuations in fluid flow, electrokinetics, etc. - that exhibit fundamentally distinct behavior on the nanoscale. The research is organized around two overarching objectives: developing single molecule-based electrokinetic and spectro-electrochemical probes of transport in one-dimensional (1D) nanostructures; and applying these tools to explore the interaction between electrically-modulated wetting phenomena and nanoconfined flows. The first objective will be addressed by fabricating structures to access transport in the ultralow Peclét number regime; developing correlative and frequency-domain measurements to characterize fluid transport and fluid-wall interactions; and implementing these measurement strategies to study electrokinetic flows in confined 1D nanocylinder and nanochannel flow formats. The second objective will be pursued by developing nanoconfined architectures that support electrowetting phenomena; and applying electrowetting principles to control nanoconfined flow in both model systems and in hierarchically-organized, multi-lamellar structures with depth-varying porosity. These experiments will establish the conditions necessary to control the wetting characteristics of the solvent-wall system. Studies will be implemented in a well-defined water-organic solvent interface that can support quantitative electrochemical and spectroscopic experiments capable of reporting on the state of the aqueous-organic interfaces as a function of applied potential. These studies are directed at establishing the design rules, structural motifs, and operating principles needed to achieve a high level of control over molecular transport in nano-confined volumes. 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.