Characterizing Near-Wall Electrokinetics of Colloidal Particles

表征胶体颗粒的近壁电动学

• 批准号: 0828782
• 负责人: Minami Yoda
• 金额: $ 31.5万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-15 至 2012-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0828782&HistoricalAwards=false
• 关键词: Characterizing; Near; Wall; Electrokinetics; Colloidal

CBET-0828782YodaMicrofluidic "Labs on a Chip" (LOC) have revolutionized genomics and enzymatic assays by shrinking the contents of an entire analytical chemistry laboratory down to a few cm2. Shrinking from micro- to nanofluidics requires a fundamental understanding of interfacial transport since at these scales, the entire flow will be within 1 ìm of the wall-and surface (e.g. electrostatic) forces will become significant. Recently, a number of studies have suggested that the no-slip condition breaks down at submicron scales. Most of the experimental studies (e.g., microscale particle-image velocimetry or ìPIV) use techniques that determine the velocity of nanoparticle tracers, and assume that the tracer velocity is the fluid velocity. Yoda has recently shown that are ìPIV tracers excluded, most likely by electrostatic repulsion, from the first 100-150 nm next to the wall. Correcting their PIV data for this non-uniform tracer distribution gives no slip at the wall and velocity gradients in agreement with analytical predictions. Assuming, as is standard, uniformly distributed tracers gives false slip lengths 200 nm. To our knowledge, no other experimental studies have considered or quantified how near-wall particle distribution or electrostatic forces affect their data. We therefore propose a fundamental, mainly experimental, three-year investigation on the dynamics of colloidal particles suspended in a conducting solution near a planar wall subject to an external electric field for a variety of particle-solution-wall systems. This is a basic model of:- new nanoscale assembly techniques that exploit electrokinetic phenomena to preciselymanipulate and assemble nanoparticles suspended in a conducting liquid; and- PIV studies of the microscale electrokinetically driven flows used in a wide variety of LOC.The research objectives of this effort are to:I. Develop new colloidal tracers that access the flow region within 150 nm of the wall-including the wall EDL-and extend the measurement capabilities and accuracy of u/nPIV, the leading microscale velocimetry techniques.II. Understand which physical properties that affect the near-particle and wall charge distributions have the greatest impact on near-wall colloidal particle electrokinetics and why these properties have such an effect.The proposed research will build on an existing collaboration between the PIs, leveraging Yoda'snovel interfacial diagnostics and Olesik's novel nanoparticles and surface chemistry expertise.Intellectual merits: This work will advance knowledge and understanding of microfluidics by:- Developing particles, including new carbon nanoparticles, with well-controlled surface charge that can be used both as flow tracers and for electrokinetically driven nanoparticle assembly;- Improving the accuracy and near-wall capabilities of microscale velocimetry techniques - which could transform the debate on the breakdown of the no-slip condition; and- Determining how particle, wall and surface properties, by changing the near-particle and nearwall charge distributions, affect particle-wall interactions and dynamics.This research is potentially transformative because:- Robust, reliable and scalable methods for electrokinetically driven nanoscale assembly would transform nanoelectronics and bring the benefits of nanotechnology to the public;- Reliable and accurate interfacial velocimetry techniques will help develop new technologies based on surface forces for controlling and actuating flows at the sub-micron scale, and transform nanofluidic devices.Broader impacts: This work will support development of:- High-school level Web-based presentations on basic aspects of electrokinetically driven flow;- Hands-on demonstrations for 6th-12th grade students that show how micro and macroscale flows differ, for example, in terms of the different methods of propulsion (twisting vs. flapping) used by micro- and macro-organisms. Both PIs will continue to mentor students from underrepresented groups, and ensure that their outreach activities include schools with a high fraction of students from such groups

CBET-0828782 YodaMicrofluidic“芯片实验室”（Labs on a Chip，简称YDA）通过将整个分析化学实验室的内容物缩小到几平方厘米，彻底改变了基因组学和酶分析。从微流体到纳米流体的缩小需要对界面传输的基本理解，因为在这些尺度下，整个流动将在壁的1 μ m内，并且表面（例如静电）力将变得显著。 最近，一些研究表明，无滑移条件在亚微米尺度下失效。大多数实验研究（例如，微尺度粒子图像速度测量法（microscaleparticle-imagevelocimetry，简称PIV）使用确定纳米粒子示踪剂速度的技术，并假设示踪剂速度是流体速度。尤达最近表明，被排除的PIV示踪剂，最有可能是静电排斥，从第一个100-150纳米旁边的墙。校正PIV数据的这种不均匀的示踪剂分布给出了没有滑移的壁和速度梯度与分析预测一致。假设，作为标准，均匀分布的示踪剂给出200 nm的假滑移长度。据我们所知，没有其他实验研究考虑或量化近壁颗粒分布或静电力如何影响他们的数据。 因此，我们提出了一个基本的，主要是实验性的，为期三年的调查的动力学的胶体颗粒悬浮在导电溶液附近的平面壁受到外部电场的各种颗粒溶液壁系统。这是一个基本模型：-新的纳米组装技术，利用电动现象，精确地操纵和组装悬浮在导电液体中的纳米粒子;和- PIV研究的微尺度电动驱动的流动中使用的各种各样的微流体。开发新的胶体示踪剂，可进入壁面150 nm范围内的流动区域（包括壁面EDL），并扩展u/nPIV（领先的微尺度测速技术）的测量能力和精度。II.了解影响近粒子和壁电荷分布的物理性质对近壁胶体粒子电动力学的影响最大，以及为什么这些性质会产生这种影响。拟议的研究将建立在PI之间现有的合作基础上，利用Yoda的新型界面诊断和Olesik的新型纳米粒子和表面化学专业知识。智力优势：这项工作将通过以下方式促进对微流体的认识和理解：-开发具有良好控制的表面电荷的颗粒，包括新的碳纳米颗粒，其可用作流动示踪剂和电动驱动的纳米颗粒组装;- 提高微尺度速度测量技术的准确性和近壁能力-这可能会改变关于无故障的辩论，滑移条件;以及-通过改变近粒子和近壁电荷分布，确定粒子、壁和表面性质如何影响粒子-壁相互作用和动力学。这项研究具有潜在的变革性，因为：-用于电动驱动的纳米级组装的鲁棒、可靠和可扩展的方法将改变纳米电子学，并将纳米技术的好处带给公众;- 可靠和准确的界面测速技术将有助于开发基于表面力的新技术，用于控制和驱动水下流动，更广泛的影响：这项工作将支持以下方面的发展：-高中水平的电动驱动流的基本方面的网络演示;-为6 - 12年级的学生动手演示，显示微观和宏观尺度的流动如何不同，例如，在微观和宏观生物体使用的不同推进方法（扭转与拍打）方面。 这两所小学的校长会继续为来自代表性不足的学生提供辅导，并确保他们的外展活动包括这些学生比例较高的学校