Electrokinetic Flow on Nanostructured Superhydrophilic and Superhydrophobic Surfaces

Suny At Stony Brook, Stony Brook NY

Investigators

Abstract

Electrokinetic flows result from the coupling of hydrodynamic and electrodynamic effects when aqueous electrolyte solutions (e.g., saline) are confined by solid surfaces with net surface charge. This electro-hydrodynamic phenomenon enables numerous engineering applications that range from water treatment and membrane-based separation processes, to energy storage and biomedical devices for drug delivery and diagnostics. Conventional models for electrokinetic flows do not properly account for nanoscale physical or chemical heterogeneities found on the surface of typical engineering materials or on advanced nanostructured materials. This project aims to develop a better fundamental understanding of electrokinetic flows on nanostructured surfaces that are superhydrophilic (i.e., strongly water-attracting) or superhydrophobic (i.e., strongly water-repelling). The knowledge gained will help in the development of key technologies for sustainable production of drinking water, food, and energy, and the design of more effective nanofluidic devices for analytical chemistry and biomedicine. Two educational initiatives will be created with this project; the “Fluid Dynamics Day at Stony Brook University” and “The Nanoscale Simulation Online School”. Research and educational activities in this project will have strong focus on the professional development and participation of underrepresented minorities in STEM, which include undergraduate and graduate students from low-income households. The objectives of this research will be pursued through three specific aims: (1) formulation of a compact hydrodynamic description valid for electrokinetic flows on superhydrophilic and superhydrophobic nanostructured surfaces, which will be validated against experimental data and molecular dynamics simulations; (2) experimental characterization of electrokinetic flows on superhydrophilic and superhydrophobic nanostructured surfaces, to determine steady-state electroosmotic and pressure-driven flow rates as a function of the nanostructure period and height for different pH and electrolyte concentration; and (3) fabrication of surface samples having well-controlled periods (30-130 nm) and heights (20-200 nm) to enable the planned experimental study. In addition, the ionic composition of the liquid-solid/vapor interfaces formed on the studied nanostructured surfaces will be probed by x-ray and IR spectroscopy to unambiguously establish the origin of the zeta potentials measured in the electrokinetic flow experiments. The proposed work will provide answers to open questions such as the specific mechanisms for electroosmotic flow and zeta potential enhancement on different hydrophobic surfaces. 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.