RUI: Electrohydrodynamic Flow in Microchannels

具有显著电导率梯度的电驱动流对于各种片上分析至关重要，例如场放大样品堆叠，等电聚焦和电泳分析，其中各种样品和缓冲流的电导率未知或控制不良。在一些应用中，如低雷诺数微通道混合，不稳定性是可取的，而在其他应用中，如场放大样品堆叠（FASS），不稳定性是不可取的。在这项资助下进行的工作将建立在对规则流道中基本不稳定机制的理解之上，并将重点放在开发新的计算工具上，以评估更复杂和现实几何形状的电动流动。主要研究方向有三个：(1)进行高保真的、直接的数值模拟（DNS），以探索传输的统计。这些DNS将作为更易于处理和计算效率更高的模型的基线比较，(2)使用商业有限元软件扩展当前的数值方法，以包括除简单通道流动以外的几何形状，以及(3)通过交流电场、表面修饰或通道几何形状来优化和控制混合速率。这些组合机制有望成为低雷诺数混合的快速、被动机制。这项研究计划将在富兰克林·w·奥林工程学院实施，这是一所新的本科学院，其中44%的学生是女性。这项资助的一个重要的更广泛的影响是这些学生直接参与开展研究目标。本科生将参与修改现有的计算模型，开发大型计算数据集的分析和可视化工具，并使用商业有限元软件帮助将这项研究扩展到新的应用领域。该项目还将为本科生提供体验研究的机会，并增强他们对研究生学习的兴趣。

Electrically driven flows with significant conductivity gradients are critical to a variety of on-chip assays such as field amplified sample stacking, isoelectric focusing, and electrophoretic assays where conductivities of various sample and buffer streams are either unknown or poorly controlled. In some applications, such as low Reynolds number microchannel mixing, the instability is desirable and in other applications, such as field amplified sample stacking (FASS) the instability is undesirable. The work performed under this grant will build upon the understanding of the basic instability mechanisms in regular flow channels and focus on developing new computational tools for evaluating electrokinetic flows in more complex and realistic geometries. The three main research thrusts are: (1) Performing high fidelity, direct numerical simulations (DNS) of electrokinetic flows in order to explore the statistics of the transport. These DNS will serve as a baseline comparison for more tractable and computationally efficient models, (2) Extending current numerical methods to include geometries other than simple channel flows using commercial finite element software, and (3) Optimization and control of mixing rates through AC electric fields, surface modification, or channel geometry. These combined mechanisms hold promise as a rapid, passive mechanism for low Reynolds number mixing. This research program will be implemented at the Franklin W. Olin College of Engineering, a new undergraduate college, in which 44% of the students are female. A significant broader impact of this grant is direct involvement of these students in carrying out the research objectives. Undergraduate students will be involved in modifying the existing computational models, developing analysis and visualization tools for large sets of computational data, and helping to expand this research to new application areas using commercial finite element software. The project will also afford undergraduates the opportunity to experience research, and to enhance their interest in graduate study.