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1066853PI：Khairmast Fluids是非牛顿的。复合物，非牛顿，流体，包括粘性培养基中胶体，聚合物，细胞或囊泡等微尺度实体的液体，无处不在。血液，墨水，食品，油漆和个人护理产品只是几个例子。虽然已经对流体动力流下的复杂流体的变形动力学或流变学进行了充分的研究，但相对较为含有的电场下复杂流体的电动现象（例如电渗透和电泳）的尚无。鉴于电场通常用于在微流体技​​术中运输，控制和操纵复杂的流体，这是令人惊讶的。该项目识别并量化了复杂流体中的电动效应，包括新的流动，相互作用和粒子运动，从而形成了一个新领域的基础：非牛顿介质中的电动动力学。该研究的结果将转化为利用电动流和复杂流体的当前微流体技术，例如微毛细血管电泳和实验室芯片分离，并进一步提供了设计新的，以前无效的技术的基础。Intellectual绩效系统性系统性，互补实验和复杂流体中电动现象的建模 - 渗透流；新型的电泳粒子运动和相互作用；正在检查和场定向的胶体组件。一个关键的实验步骤是具有具有可控性的流变特性的“非牛顿电解质”的制定，包括粘弹性，剪切和正常应力系数。微流体通道中非牛顿流体的电渗透流有望具有非线性和时间复杂的依赖性对所施加的电场的依赖性。重要的是，实验测量的电渗流流与计算的流量曲线的比较需要在选择适当的流体描述时要注意。关于电泳的建模工作表明，非牛顿流变学的几种新颖，实验可及的后果，包括电泳速度对粒度和形状的明确依赖，以及胶体之间的流变学介导的电泳相互作用。至关重要的是，牛顿流体中所有这些影响都没有，这说明了复杂的流体流变对电动现象的巨大影响。从这些研究中获得的知识有助于阐明粘弹性在AC场上由电极上方组装的胶体的单个粒子动力学和集体行为的作用。更广泛的影响，这将为复杂的流体中的电动流提供前所未有的理解，从而为微/纳米流体技术提供了广泛的影响，该技术利用电场运输微型结构材料。一个具体情况是用于分离宏观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，由于显式依赖性，连续相的流变可能为新型无凝胶毛细血管电泳方案提供了途径非牛顿流体中粒子形状和大小的电泳速度的。 AC场中电极上方的粒子动力学的工作为粘弹性流体中胶体微结构的定向组装提供了新的范式。在教育方面，研究生和本科研究人员正在接受微流体，电动学和复杂流体的尖端实验和理论培训。将开发新的有关微型和纳米级流体物理学的新研究生/高年级课程，以展示我们的研究中心主题和结果。非牛顿流体流动的视觉性质非常适合构成外展活动的科学核心。为此，通过针对K-12学生设计教育模块，通过与CMU专门的外展计划进行咨询来实现与更广泛的匹兹堡社区的联系。