Mathematical Modeling of Induced-Charge Electrokinetics

研究者及时开发了非线性“感应电荷”电动力学现象的新数学模型，其中电渗透流动或粒子运动是由作用于极化（金属或电介质）表面的感应双层电荷的电场驱动的。研究者和他的同事们花了五年的时间研究这种效应的统一理论，以及微流体和胶体的相关实验研究。尽管在预测新型流动方面取得了一些成功，但现有理论未能预测实验的一些关键特征，如高压下的流动逆转和高浓度下的流动抑制。该理论基于经典的泊松-能-普朗克方程，该方程仅对“小”电压（25 mV）严格有效，但实验通常涉及更大的电压（1 V），这会在表面附近凝聚反离子，违反稀释近似。研究者通过模拟由离子拥挤、溶剂的非线性介电常数和粘度以及法拉第反应引起的空间和相关效应，建立了这一体系的数学理论。通过实验验证了该理论，并将其应用于新型微流控器件的设计。这项工作与纳米技术和生物技术具有根本性的相关性。诱导电荷电渗透（ICEO）是最近发现的一种纳米级现象，在微流体和胶体中有许多应用。由于ICEO可以利用电池电压来操纵流体和颗粒，因此它可以成为革命性的新型便携式或植入式生物医学设备，例如微型药物输液泵和芯片上的诊断试剂。研究人员的数学工作旨在通过探索分子拥挤对高电荷表面附近电解质动力学的影响，提高我们对ICEO流动的理解，特别是在生物液体中。

Bazant0707641 The investigator develops timely new mathematical models fornonlinear "induced-charge" electrokinetic phenomena, whereelectro-osmotic flows or particle motions are driven by electricfields acting on induced double-layer charge at polarizable(metal or dielectric) surfaces. The investigator and hiscolleagues have worked for five years on a unified theory of sucheffects, as well as related experimental studies in microfluidicsand colloids. In spite of a number of successes in predictingnew types of flows, however, the existing theory fails to predictsome crucial features of the experiments, such as flow reversalat high voltage and flow suppression at high concentration. Thetheory is based on the classical Poisson-Nernst-Planck equations,which are strictly valid only for "small" voltages ( 25 mV), butexperiments typically involve much larger voltages ( 1 V), whichcondense counterions near the surface and violate the dilutesolution approximation. The investigator builds a mathematicaltheory for this regime by modeling steric and correlation effectsdue to ion crowding, nonlinear permittivity and viscosity of thesolvent, and Faradaic reactions. The theory is tested againstexperiments and applied to design new microfluidic devices. This work has fundamental relevance for nanotechnology andbiotechnology. Induced-charge electro-osmosis (ICEO) is arecently identified nano-scale phenomenon with many applicationsin microfluidics and colloids. Because ICEO can be exploited tomanipulate fluids and particles with battery voltages, it couldenable revolutionary new portable or implantable biomedicaldevices, such as tiny drug infusion pumps and diagnosticlabs-on-a-chip. The mathematical work of the investigator seeksto advance our understanding of ICEO flows, especially inbiological liquids, by exploring consequences of molecularcrowding on the dynamics of electrolytes near highly chargedsurfaces.