Self-Assembly of Nanoparticles from Evaporating Drops and Liquid Films: Science, Engineering and Applications

你有没有想过，在固体基底上蒸发含有纳米颗粒的液体，可以获得各种各样的自组装存款结构。存款的形状各不相同，从环周围的咖啡滴，六角形细胞和分形图案。一个由哥伦比亚大学科学家组成的跨学科小组将结合实验、理论和数值技术，研究相关的迷人的多尺度物理学。该团队拥有以下技能：多相流（Attinger，PI），胶体（Somasundaran），模式识别（Chang）和开源计算流体动力学（Spiegelman）。纳米粒子的复杂自组装将通过使用第一物理原理来解释所产生的自组装图案（我们称之为自上而下的方法），并通过识别图案中的特征来研究，这些特征是特定基本定律或传输规则的标志（自下而上的方法）。智力优点：实验将涉及在各种基底上的复杂流体微滴的点样，荧光显微镜和激光轮廓术来扫描三维沉积物。第一个智力上的优点将是描述与相图的自组装的纳米粒子在液体蒸发过程中的固体基板上。在这种情况下使用的相图是新颖的，并允许一个简单的，但强大的竞争运输现象，如在润湿线，马兰戈尼再循环，静电和货车范德华力，浮力和介电电泳的大小比较。相图将提供多相过程之间的复杂相互作用的洞察和概述，受液滴或膜的几何形状的影响：流体力学，传热，传质，胶体相互作用。 其次，一个可用的专有2D轴对称数值代码与移动网格能够非常准确地跟踪自由表面将扩展到3D（见钱德拉合作信）。 这将允许模拟更广泛的边界条件，允许考虑薄膜和复杂的几何形状。 从第一原理解释蒸发液滴和液膜中纳米颗粒的自组装是一种具有挑战性的方法，考虑到多种传输现象和时间/长度尺度。因此，我们也将开发一个自下而上的方法，基于模式识别的自组装功能。更广泛的影响：拟议的研究将提供创新的解决方案，在固体基底上图案化纳米颗粒，应用于有机电子和生物传感器的生物分子图案化。 将研究将打印分辨率提高两个数量级（见Sonoplot字母）和图案化均匀颗粒层的方法。该提案中开发的模式识别算法将与法医专家MacDonell合作进行测试，以识别生物分子（见Zenhausern信）并提高血迹模式分析的准确性（见合作信）。此外，该提案中开发的3D代码将作为开源代码免费分发，允许每一位感兴趣的科学家研究涉及液滴和薄膜传输现象的问题，如液滴冲击，液滴蒸发，薄膜干燥。资金将支持一名研究生。

Have you ever wondered at the variety of self assembled deposit structures that can be obtained by evaporating liquids containing nanoparticles on top of a solid substrate. Deposit shapes vary from rings around a coffee drop, to hexagonal cells and fractal patterns. An interdisciplinary team of Columbia University scientists will study the related fascinating multiscale physics, using a combination of experimental, theoretical and numerical techniques. The team has the following skills: multiphase flow (Attinger, PI), colloids (Somasundaran), pattern recognition (Chang) and open-source computational fluid dynamics (Spiegelman). The complex self-assembly of nanoparticles will be studied by using first physical principles to explain the resulting selfassembled patterns (what we call a top-down approach), and by identifying features in the patterns that are signs of specific basic laws or transport rules (bottom-up approach).Intellectual Merit:Experiments will involve the spotting of microdrops of complex fluids on various substrates, fluorescence microscopy and laser profilometry to scan the three dimensional deposits. The first intellectual merit will be to describe with a phase diagram the self-assembly of nanoparticles during liquid evaporation on a solid substrate. The use of a phase diagram in that context is novel and allows a simple but powerful comparison of the magnitude of competing transport phenomena, such as evaporation at the wetting line, Marangoni recirculation, electrostatic and van der Waals forces, buoyancy, and dielectrophoresis. The phase diagram will provide an insight and an overview of the complex interplay between multiphase processes, influenced by the geometry of the liquid drop or film: fluid mechanics, heat transfer, mass transfer, colloidal interactions. Second, an available proprietary 2D-axisymmetric numerical code with a moving mesh able to very accurately track the free surface will be extended to 3D (see Chandra collaboration letter). This will allow the simulation of a wider ranges of boundary conditions, permitting the consideration of thin films and complex geometries. Explaining the self-assembly of nanoparticles from evaporating drops and liquid films from first principles is a challenging approach, given the multiple transport phenomena and time/length scales. Therefore, we will also develop a bottom-up approach based on pattern recognition of selfassembled features. We will test the hypothesis that the patterns tell us the about the physics that created them.Broader Impact:The proposed research will deliver innovative solutions to pattern nanoparticles on solid substrates, with applications in organic electronics and patterning of biomolecules for biosensors. Methods to increase printing resolution by two orders of magnitude (see Sonoplot letter), and to pattern uniform layers of particles will be investigated. The pattern recognition algorithms developed in this proposal will be tested to identify biomolecules (see Zenhausern letter) and enhance the accuracy of bloodstain pattern analysis, in collaboration with forensics expert MacDonell (see collaboration letter). Also, the 3D code developed in this proposal will be distributed freely as an open-source code, allowing every interested scientist to study problems involving drop and film transport phenomena such as drop impact, drop evaporation, film drying. Funding will support one graduate student.