Investigation of the Zeta Potential of Electrically Polarized Inrterfaces

美国国家科学基金会-化学与传输系统分部-颗粒与多相过程项目（1415）提案编号：0730391主要研究者：Sides， Paul隶属：卡内基梅隆大学提案题目：电极化界面Zeta电位的研究本研究的领域是电化学定向的电极上胶体粒子的自组装。关于实验观察到的电极附近胶体粒子依赖电解质运动背后的机制的假设将被测试。实验观察到，在交流极化过程中，相位角与两个粒子的聚集或分离之间存在相关性。期望的角度是90度。观察到的角度在氢氧化钾溶液中小于90度，在碳酸氢盐溶液中大于90度。颗粒在KOH中分离，在KOH中聚集。相对于90度的相位角与颗粒是否聚集或分离之间的相关性已经在几种电解质和电极的组合中得到验证。这种依赖于解的相关性的原因尚不清楚。假设是，所需的额外力来自一种称为“法拉第耦合电渗透”（FCEO）的流动机制，这种机制是由电极双层中的横向电场分量与电荷相互作用驱动的。FCEO打破了电场与粒子电荷之间“基于粒子的电渗透”（PBEO）相互作用所产生的强作用力的对称性。FCEO改变了粒子的行为，使粒子高度和电场不呈现预期的_/2相关系。这项研究将提高对在表面上形成有序粒子层的重要力的认识。潜在的应用领域是传感器和光学技术。这一建议的思想要点是假设电场与粒子和电极的双层相互作用引起的电渗透流不仅是理解极化电极附近单个粒子行为的关键，也是理解多粒子系统聚集/分离行为的关键。证明这一假设将完成对粒子远程组装的理解。问题是丰富的科学和工程；它涉及到胶体、电化学和流体力学现象的结合。提出的研究包括新颖的实验和多物理场电流体力学计算机模拟。建议的调查是完成这一最微妙影响之谜所必需的顶点研究。更广泛的影响本研究的现象是胶体科学和技术的根本兴趣。新的显示技术利用电场与包裹在液体中的粒子的相互作用。给定电荷的细胞可以通过电流体动力学流动来操纵，甚至可以进行分类。电渗透流在这个问题的细节之外的技术中很重要，特别是在液体的微流体输送中。获得的新观点也将支持已经插入胶体科学课程的实验室实验的发展。这项研究将成为卡内基梅隆大学研究生和本科生培训的一部分，他们将成为科学和工程界的生产性代理人。

National Science Foundation - Division of Chemical &Transport Systems Particulate & Multiphase Processes Program (1415)Proposal Number: 0730391 Principal Investigators: Sides, Paul Affiliation: Carnegie Mellon University Proposal Title: Investigation of the Zeta Potential of Electrically PolarizedInrterfaces The field of this research is electrochemically directed self-assembly of colloidal particles on electrodes. A hypothesis about the mechanism behind an experimentally observed electrolyte-dependent motion of colloidal particles near an electrode will be tested. The experimental observation is that a correlation between a phase angle and the aggregation or separation of two particles during ac polarization exists. The expected angle is 90o. The observed angles are less than 90o for KOH and greater than 90o for bicarbonate solution. The particles separate in KOH and aggregate in KOH. This correlation between the phase angle relative to 90o and whether the particles aggregate or separate has been verified for several combinations of electrolyte and electrode. The reason for this solution dependent correlation remains unknown. The hypothesis is that the required extra force arises from a flow mechanism called "faradaically coupled electroosmosis" (FCEO) driven by interaction of lateral electric field components with charge in the electrode's double layer. FCEO breaks the symmetry of the strong force arising from the "particle based electroosmosis" (PBEO) interaction between the electric field and particles' charge. FCEO modifies the particle behavior such that the particle height and electric field do not exhibit the expected _/2 phase relationship. The research will improve knowledge of forces important in the formation of ordered layers of particles on surfaces. The potential application areas are sensors and optical technology. Intellectual Merit The intellectual thrust of this proposal is the hypothesis that electroosmotic flow due to interaction between electric fields and the double layers of the particle and electrode is the key to understanding not only the behavior of a single particle near a polarized electrode but also to understanding the aggregative/separative behavior of multi-particle systems. Proving this hypothesis would complete the understanding of remote assembly of particles. The problem is rich in science and engineering; it involves the combination of colloidal, electrochemical, and hydrodynamic phenomena. The proposed investigation includes novel experimentation and multiphysical electrohydrodynamic computer simulations. The propose investigation is the capstone study necessary to complete the puzzle of this most subtle effect. Broader Impact The phenomena of this study are of fundamental interest to colloid science and technology. New display technologies employ the interaction of electric fields with particles encapsulated with liquids. Cells, given their charge, can be manipulated by electrohydrodynamic flows and even sorted. Electroosmotic flow is important in technologies beyond the details of this problem, particularly in microfluidic transport of liquids. The new perspectives gained will also support the development of laboratory experiments already inserted into the colloid science curriculum. The research will be a part of the training of a graduate student and undergraduates at Carnegie Mellon, who will become productive agents in the scientific and engineering community.