Electrokinetic Flow on Nanostructured Superhydrophilic and Superhydrophobic Surfaces

当电解质水溶液（如生理盐水）被具有净表面电荷的固体表面约束时，电动力流动是水动力和电动力效应耦合的结果。这种电流体动力学现象使许多工程应用成为可能，从水处理和基于膜的分离过程，到能量储存和用于药物输送和诊断的生物医学设备。传统的电动流动模型不能很好地解释在典型工程材料或先进纳米结构材料表面发现的纳米级物理或化学非均质性。该项目旨在更好地理解超亲水性（即强吸水性）或超疏水性（即强拒水性）纳米结构表面上的电动流动。所获得的知识将有助于开发可持续生产饮用水、食品和能源的关键技术，并设计更有效的纳米流体装置用于分析化学和生物医学。该项目将创建两项教育计划；“石溪大学流体动力学日”和“纳米级模拟在线学校”。该项目的研究和教育活动将重点关注STEM中代表性不足的少数民族的专业发展和参与，其中包括来自低收入家庭的本科生和研究生。本研究的目标将通过三个具体目标来实现：(1)制定一个紧凑的流体动力学描述，适用于超亲水性和超疏水性纳米结构表面上的电动力学流动，这将通过实验数据和分子动力学模拟来验证；(2)实验表征超亲水性和超疏水性纳米结构表面上的电动力学流动，确定不同pH和电解质浓度下稳态电渗透和压力驱动流速与纳米结构周期和高度的关系；(3)制造具有良好控制周期（30-130 nm）和高度（20-200 nm）的表面样品，以实现计划的实验研究。此外，在研究的纳米结构表面上形成的液-固/气界面的离子组成将通过x射线和红外光谱进行探测，以明确地确定电动流动实验中测量到的zeta电位的起源。提出的工作将为诸如不同疏水表面上电渗透流动和zeta电位增强的具体机制等开放性问题提供答案。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.