Coupling Electrokinetics and Rheology: Novel Flows, Interactions and Particle Motions

耦合动电学和流变学：新颖的流动、相互作用和粒子运动

• 批准号: 1066853
• 负责人: Aditya Khair
• 金额: $ 34万
• 依托单位: Carnegie-Mellon University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-04-01 至 2015-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1066853&HistoricalAwards=false
• 关键词: Coupling; Electrokinetics; Rheology; Novel; Flows

Award 1066853PI: KhairMost fluids are non-Newtonian. Complex, non-Newtonian, fluids, comprising of micro-scale entities such as colloids, polymers, cells, or vesicles in a viscous medium, are ubiquitous. Blood, inks, foodstuffs, paints, and personal-care products are just a few examples. While the deformation dynamics, or rheology, of complex fluids under hydrodynamic flows has been well studied, comparatively nothing is known about electrokinetic phenomena (e.g. electro-osmosis and electrophoresis) of complex fluids under applied electric fields. This is surprising, given that electric fields are routinely used to transport, control, and manipulate complex fluids in micro- and nano-fluidic technologies. This project identifies and quantifies electrokinetic effects in complex fluids, including novel flows, interactions, and particle motions, thereby forming the foundation of a new field: electrokinetics in non-Newtonian media. The results of the research will be transformative to current microfluidic technologies that utilize electrokinetic flows and complex fluids, e.g. micro-capillary electrophoresis and lab-on-a-chip separations, and further offer the basis for designing new, previously un-envisioned technologies.Intellectual Merit Systematic, complementary experiments and modeling of electrokinetic phenomena in complex fluids, focusing on non-linear electro-osmotic flows; novel electrophoretic particle motions and interactions; and field-directed colloidal assembly are being examined. A key experimental step is the formulation of "non-Newtonian electrolytes" with controllable rheological properties, including viscoelasticity, shear-thinning, and normal stress coefficients. The electro-osmotic flow of non-Newtonian fluids in microfluidic channels is expected to possess non-linear and temporally complex dependencies on applied electric fields. Importantly, the comparison of experimentally measured electro-osmotic flows against computed flow profiles requires care in choosing an appropriate rheological description of the fluid. Modeling work on electrophoresis suggests several novel, experimentally accessible consequences of non-Newtonian rheology, including an explicit dependence of electrophoretic velocity on particle size and shape, and rheology-mediated electrophoretic interactions between colloids. Crucially, all of these effects are absent in Newtonian fluids, illustrating the dramatic influence of complex fluid rheology on electrokinetic phenomena. The knowledge gained from these investigations aids in elucidating the role of viscoelasticity on the single particle dynamics and collective behavior of colloids assembled above electrodes by AC fields. Broader ImpactThis work will furnish an unprecedented understanding of electrically driven flows in complex fluids, offering broad impacts to micro/nano-fluidic technologies that utilize electric fields to transport micro-structured materials. A specific case is capillary electrophoresis for separation of macro- and bio-molecules: Here, the results obtained to-date suggests that the rheology of the continuous phase may provide a route to novel gel-free capillary electrophoresis protocols, due to the explicit dependence of electrophoretic velocity on particle shape and size in a non-Newtonian fluid. The work on particle dynamics above electrodes in AC fields yields new paradigms for directed assembly of colloidal microstructures in viscoelastic fluids. In education, graduate students and undergraduate researchers are receiving cutting-edge experimental and theoretical training in microfluidics, electrokinetics, and complex fluids. A new graduate/upper-undergraduate level course on Micro- and Nano-Scale Fluid Physics will be developed to showcase central themes and results of our research. The visually dramatic nature of non-Newtonian fluid flow is ideally suited to form the scientific core of outreach activities. To this end, a connection to the wider Pittsburgh community is achieved by designing educational modules for K-12th students, made age- and content-appropriate via consultation with dedicated outreach programs at CMU.

奖项1066853 PI：Khair大多数流体都是非牛顿流体。复杂的非牛顿流体，包括微观尺度的实体，如胶体，聚合物，细胞，或在粘性介质中的囊泡，是无处不在的。血液、墨水、食品、油漆和个人护理产品只是其中的几个例子。虽然复杂流体在流体动力学流动下的变形动力学或流变学已经得到了很好的研究，但相对而言，对复杂流体在施加电场下的电动现象（例如电渗和电泳）知之甚少。这是令人惊讶的，因为电场通常用于在微流体和纳米流体技术中传输、控制和操纵复杂流体。该项目识别和量化复杂流体中的电动效应，包括新颖的流动，相互作用和粒子运动，从而形成一个新领域的基础：非牛顿介质中的电动力学。该研究成果将对目前利用电动流和复杂流体的微流体技术（例如微毛细管电泳和芯片实验室分离）产生变革性影响，并进一步为设计新的、以前未设想过的技术提供基础。智力优势复杂流体中电动现象的系统性、互补性实验和建模，重点是非线性电渗流;新的电泳粒子运动和相互作用;和场定向胶体组装正在检查。一个关键的实验步骤是制定“非牛顿电解质”的流变性能可控，包括粘弹性，剪切稀化，和正常的应力系数。微流控通道中非牛顿流体的电渗流具有非线性和时间复杂的电场依赖性。重要的是，实验测量的电渗流对计算的流量剖面的比较需要小心选择一个适当的流变描述的流体。电泳建模工作提出了几个新的，实验上可访问的非牛顿流变学的后果，包括明确的依赖于颗粒大小和形状的电泳速度，和流变介导的胶体之间的电泳相互作用。至关重要的是，所有这些效应都不存在于牛顿流体中，说明了复杂流体流变学对电动现象的巨大影响。从这些调查中获得的知识有助于阐明粘弹性对单粒子动力学和集体行为的胶体组装在电极上的AC场的作用。更广泛的影响这项工作将提供一个前所未有的理解电驱动的复杂流体的流动，提供广泛的影响微/纳米流体技术，利用电场传输微结构材料。一个具体的情况是用于分离大分子和生物分子的毛细管电泳：在这里，迄今为止获得的结果表明，连续相的流变学可以提供一种新的无凝胶毛细管电泳协议的途径，由于在非牛顿流体中电泳速度对颗粒形状和尺寸的明确依赖性。在交流电场中电极上方的粒子动力学研究为粘弹性流体中胶体微结构的定向组装提供了新的范例。在教育方面，研究生和本科生研究人员正在接受微流体，电动力学和复杂流体方面的尖端实验和理论培训。将开发一个新的研究生/高本科水平的微纳米尺度流体物理课程，以展示我们的研究的中心主题和成果。非牛顿流体流动的视觉戏剧性性质非常适合形成推广活动的科学核心。为此，通过为K-12学生设计教育模块，与更广泛的匹兹堡社区建立联系，通过与CMU的专门外联计划进行协商，使年龄和内容适合。