Title: Physics and Applications of Nanoscale Fluid Flows
Description: Nanofluidics is an emerging field with many science and engineering applications. The physics of material transport through nanochannels are of interest in filtration, sensing, device miniaturization, and biomimetics. To address such ambitions with nanofluidic tools will require advancements in our understanding and control over nanofluidic systems. This work contributes to electrokinetic phenomena, characterization techniques, and applications in nanofluidics. Ion transport data through nanopipettes are used to validate a finite element model for nonlinear electrokinetic flows. With the model, we conclude that asymmetric surfaces induce fluid vortices and provide insight into supporting mathematical techniques. We then establish nanobubble-plugged nanopipettes as promising ionic devices due to the electrokinetic effects of three-phase interfaces. Using cryogenic transmission electron microscopy, ion current measurements, and extensive physical modeling, we conclude that nanobubble plugs are metastable, slow-growing, and induce strong current rectification and enhancement.

All these insights let us study microbial surfaces using electrokinetic phenomena detected by a scanned nanopipette. Over immobilized Pseudomonas aerugonsa cells and Δphz-type biofilms, we detect topographic and surface charge properties due to voltage-dependent signals through a scanned nanopipette probe. Our efforts establish a fast hopping probe scanning ion conductance microscopy technique for long-range surface charge detection. Finally, we use an integrated carbon nanotube channel to demonstrate how solid-state charge can drive electrokinetic flows through Coulomb drag coupling.