Materials World Network: Electric Field Induced Microfluidic Manipulation

该NSF材料世界网络奖支持德国哥廷根的马克斯普朗克动力学和自组织研究所（MPI）与堪萨斯州曼哈顿的堪萨斯州立大学之间的国际合作研究。这两个小组将合作研究微流体在拓扑结构微通道中的静态和动态。微流体，即在封闭通道中或在基板表面上对微升或纳升的液体或液体溶液的受控操纵，随着芯片上化学工厂、快速可变焦距光学液体透镜和高可见度视频速度电子纸的产生而获得越来越多的技术重要性。这种液体操纵通常通过使用电场来控制，特别是通过电润湿效应来控制，电润湿效应控制液滴在表面上的接触角。目前，还没有很好地理解电场效应、润湿层、表面滑移、基底的表面形貌和液体形态不稳定性的相互作用如何结合联合收割机来控制形貌结构化通道中液体的时间动力学。在堪萨斯将研究润湿层和平面表面上的表面滑移的影响以及它们如何通过电场和/或液体剪切的存在而改变。均匀的润湿层预测进行电流体动力学的不稳定性（并打破成nanodroads）足够大的电场，其中液体剪切的附加效果发挥未知的作用。均匀的润湿层，表面纳米液滴或电场诱导的表面排序预计会影响在固/液界面处发现的滑移行为。Goettingen的MPI小组将研究电润湿过程中表面形貌的相互作用，以及这种形貌如何影响沿微流体通道传播的时间依赖性液体细丝，以及这些通道内从液体细丝到液滴的液体形态不稳定性。这两个小组之间将有频繁的人员交流，因为润湿层和滑移的存在（在堪萨斯研究）将在控制微流体通道中的扩散和形态破裂的时间依赖性方面发挥重要作用（在哥廷根研究）。这些交流将加强和促进两个集团之间的教育、文化和国际合作。该研究将为更好地理解拓扑结构微流体器件中液体的静态和动态电操纵提供基础。这些信息预计将在微流体装置设计的许多不同领域中具有重要的实际用途。该项目由德国国家科学基金会（DFG）资助。

This NSF Materials World Network award supports international collaborative research between the Max Planck Institute (MPI) for Dynamics and Self-organization in Goettingen, Germany and Kansas State University in Manhattan, KS. The two groups will collaborate in studying the statics and dynamics of microfluidics in topographically structured microchannels. Microfluidics, the controlled manipulation of microliters or nanoliters of liquid or liquid solution in closed channels or on a substrate surface is gaining increasing technological importance with the creation of chemical factories on a chip, fast variable focal length optical liquid lenses and high visibility video speed electronic paper. This liquid manipulation is frequently controlled via the use of electric fields and in particular via the electrowetting effect, which controls the contact angle of droplets on surfaces. Currently it is not well understood how the interplay of electric field effects, wetting layers, surface slip, surface topography of the substrate and liquid morphological instabilities combine to govern the time dynamics of liquids in topographically structured channels. The influence of wetting layers and surface slip on planar surfaces and how they are changed by the presence of an electric field and/or liquid shear will be studied in Kansas. Uniform wetting layers are predicted to undergo an electrohydrodynamic instability (and break up into nanodroplets) for sufficiently large electric fields where the additional effects of liquid shear play an unknown role. Uniform wetting layers, surface nanodroplets or electric field induced surface ordering is expected to influence the slip behavior found at solid/liquid interfaces. The MPI group in Goettingen will study the interplay of surface topography during electrowetting and how this topography influences the time dependent liquid filament spreading down microfluidic channels, as well as, liquid morphological instabilities from liquid filaments to liquid droplets within these channels. There will be frequent exchanges of personnel between the two groups because the presence of wetting layers and slip (studied in Kansas) will play a major role in governing the time dependence of both the spreading and morphological break up in microfluidic channels (studied in Goettingen). These exchanges will strengthen and enhance the educational, cultural and international cooperation between the two groups. The proposed research will provide the fundamental foundations for a better understanding of the static and dynamic electrical manipulation of liquids in topographically structured microfluidic devices. This information is expected to be of significant practical use for many different fields in microfluidic device design. The counterpart project is funded by the German National Science Foundation (DFG).