Faradaic Micro-Fluidic Devices for Complex Fluids

摘要-0454956将研究一种在微流体装置中输送、计量、控制、分离和浓缩液体和生物颗粒的新电动手段。与现有的直流（DC）和交流（AC）电动技术不同，这种法拉第交流电动（FACE）机制通过瞬态法拉第电极反应产生微加工电极的大的准平衡极化，以驱动微通道中的流体和颗粒以超过1 cm/s的速度运动，代表了最强大的非机械微泵之一。由于采用高频（100 kHz）AC场，瞬态反应不会在微通道中产生气泡和离子污染物。它也不像DC场那样对DNA，蛋白质和生物颗粒造成损害。已经观察到各种新的单相和多相电动现象，具有不同的流动拓扑结构和不稳定性。流拓扑结构的丰富性归因于两个基本的法拉第极化机制，产生局部的压力汇和切向滑移速度。拟议的项目将对这种新的电动机制进行基本分析，并描述/量化其各种流动特性。这项基础研究将使我们能够优化基于这种新机制的微流体组件的设计，有时是通过利用新现象。这些研究包括一个匹配的渐近分析，以取代快速（US）反应和电容充电动力学与时间平均有效的静电和滑移边界条件的纳米尺寸的双层，从而简化了相关的多尺度数值研究。切向传导和电荷积累的几何奇点，这被认为是驱动一些异常流的分析，也将进行充分描绘复杂的时空电极极化动力学。由强流提供的高剪切速率引起许多生物颗粒分离和聚集现象，将详细研究这些现象以产生有效的颗粒-流体分离策略，用于荧光标签检测的生物颗粒和病毒。微加工交流电磁铁将产生横向洛伦兹力，以产生螺旋流以及电流涡流和线性FACE流。建议的基础工作将使我们能够富有成效地理解和利用这种新的FACE机制，以建立一个功能性的微流体技术与优化的电极几何形状和施加的电场。教育影响：建议的工作将为研究生提供异常丰富的教育经验。它将新物理现象的基础科学研究与工程设计项目相结合，以生产几乎可商业化的微流体设备。它涉及复杂的理论和数值分析，以及最先进的制造技术。在过去的四年里，我们的实验室已经在美国主要的研究型大学，两个领先的工业研究中心和两个本科生成员在顶级研究生课程的终身教职的5组成员。另外四个人将很快寻求终身职位。科学和技术影响：最近在用于病毒检测、细菌检测、化学色谱等的芯片级分析技术方面的基础科学研究已经并将继续推动医疗、环境和国家安全行业的重大技术进步。仍在开发中的一个主要组成部分是微流体：精确运输，混合和操纵流体的能力，更重要的是，芯片微通道内的微米和纳米级生物颗粒。电动力学是一种利用成熟的微制造技术来嵌入微电极以产生期望的微流体的方法。 该项目研究了一种新的电动机制，该机制首先由该小组揭示，有望比其他微流体组件更强大，可靠和灵敏。这项工作将为基于这种新机制的第一个功能性微流体组件奠定基础。

ABSTRACT - 0454956A new electro-kinetic means of transporting, metering, controlling, separating and concentrating liquid and bio-particles in a micro-fluidic device will be investigated. Unlike existing direct-current (DC) and alternating-current (AC) electro-kinetic techniques, this Faradaic AC Electro-kinetic (FACE) mechanism produces large quasi-equilibrium polarization of microfabricated electrodes via transient Faradaic electrode reactions to drive fluid and particle motions with speeds in excess of 1 cm/s in micro-channels, representingone of the most powerful nonmechanical micro-pump. Due to the high-frequency ( 100 kHz) AC field employed, the transient reactions do not produce bubbles and ionic contaminants in the micro-channels. It is also not as damaging to DNA, proteins and bio-particles as DC fields. A variety of new single-phase and multi-phase electro-kinetic phenomena, with qualitatively different flow topologies and instabilities, have been observed. The richness of the flow topologies is attributed to two fundamental Faradaic polarization mechanisms that generate a localized pressure sink and a tangential slip velocity. The proposed project will carry out a fundamental analysis of this new electro-kinetic mechanism and delineate/quantify its various flow properties. This fundamental study will allow us to optimize the design of micro-fluidic components based on this new mechanism, sometimes by harnessing the new phenomena. The studies include a matched asymptotic analysis to replace the fast (us) reaction and capacitive charging dynamics within the nm-sized double layer with time-averaged effective electrostatic and slip boundary conditions, thus simplifying the relevant multi-scale numerical studies. An analysis of tangential conduction and charge accumulation at geometric singularities, which are believed to drive some of the anomalous flows, will also be carried out to fully delineate the complex spatio-temporal electrode polarization dynamics. The high shear rate afforded by the strong flow causes many bio-particle segregation and aggregation phenomena, which will be studied in detail to produce effective particle-fluid separation strategies, bio-particle and virus for fluorescent tag detection. Microfabricated AC electro-magnets will produce transverse Lorentz forces to generate spiral flows as well as the current vortex and linear FACE flows. The proposed fundamental work will allow us to fruitfully understand and exploit this new FACE mechanism to build a functional micro-fluidic technology with optimized electrode geometries and applied electric fields.Educational Impact: The proposed work will provide graduate students with an unusually rich educational experience. It combines fundamental scientific studies of new physical phenomena with engineering design projects to produce nearly commercializable micro-fluidic devices. It involves sophisticated theoretical and numerical analyses, as well as state-of-the-art fabrication technology. In the last four years, our laboratory has placed 5 group members in tenure-track faculty positions at major U.S. research universities, two in leading industrial research centers and two undergraduate members at top graduate programs. Four others will be seeking tenure-track positions shortly. We expect the proposed project to make a comparable educational impact.Scientific and Technological Impact: Recent fundamental scientific research on chip-scale analytical techniques for viral assays, bacteria detection, chemical chromatography, etc. has and will continue to spur a major technological advance in the medical, environmental and national security industries. A major component that is still under development is micro-fluidics: the ability to precisely transport, mix and manipulate fluids and, more importantly, micro- and nanoscale bio-particles within the chip micro-channels. Electro-kinetics is one approach that utilizes mature micro-fabrication technology to imbed micro-electrodes to produce the desirable microfluidics. This project investigates a new electro-kinetic mechanism, first revealed by the group, that promises to be more powerful, reliable and sensitive than other micro-fluidic components. The proposed work will lay the fundamental groundwork for the first functional micro-fluidic components based on this new mechanism.