Separation of Colloidal Particles by Diffusiophoresis

1702693：石头过滤是从溶液中去除微粒的最常用方法。我们理所当然地认为，我们可以通过使用通常由多孔材料（如砂床）组成的过滤器来去除水中的各种颗粒物质，如污垢，细菌和病毒。过滤对于获得安全的饮用水和其他适合工业加工的液体至关重要。然而，代替过滤，存在使用“场”的技术，例如重力沉降，以去除颗粒和/或分离不同种类的颗粒。该项目研究了简单的化学梯度，即使是盐浓度的适度变化，如何在不使用过滤器或重力沉降的情况下运输颗粒并实现颗粒去除或按尺寸分离。这种方法被称为扩散电泳，它适用于广泛的颗粒尺寸，是便携式的，可以在现场或资源贫乏的环境中操作，并且可以根据各种应用的需要缩放到不同的尺寸。重要的是，当传统的过滤或沉降方法可能非常低效甚至无效时，扩散电泳可以用于使用环境友好的盐的小颗粒的困难分离。本研究的目的是研究扩散电泳驱动的大类颗粒的分离过程，例如，不同尺寸、形状和表面电荷的刚性颗粒，液滴和囊泡，在受限的配置中，其代表了广泛的生物、化学和工程材料和系统，例如多孔介质、结构化表面和微型器件。在此，“分离”被认为是其最广泛的意义，例如不同颗粒的分级、颗粒与流体的隔离以及颗粒到特定目的地的运输。扩散电泳是指由于渗透压变化（化学电泳）和由阳离子和阴离子的扩散率差异产生的局部电场（电泳）而引起的胶体颗粒的迁移。在这项工作的第一个方面，这些想法进行了探讨，在有限的几何形状和分离的不同颗粒的特点。特别是，时间依赖性的扩散电泳策略被描述为实现长时间的颗粒传输。在这项工作的第二个方面，使用相间质量传递，例如CO2气体的溶解，产生扩散电泳。因此，在无膜流动方法中用于去除颗粒的方法被描述，并且引入场流分级的新策略。实验和建模将针对各种颗粒，所有类型的颗粒，刚性/软颗粒，细菌细胞，囊泡进行开发。该研究将实现对受限空间中扩散电泳输运的基本理解，并改进宏观输运过程。

1702693: StoneFiltration is the most common method to remove particles from solution. We take it for granted that we can remove a wide range of particulate materials, such as dirt, bacteria, and viruses, from water by using filters that usually consist of porous materials, such as sand beds. Filtration is critical to obtaining safe drinking water and other liquids suitable for industrial processing. Nevertheless, instead of filtration there are technologies that use "fields", such as gravitational sedimentation, to remove particles and/or separate different kinds of particles. This project investigates how simple chemical gradients, even modest variations in salt concentration, can transport particles and achieve particle removal or separation by size without using filters or gravitational sedimentation. This approach is called diffusiophoresis, and it works for a wide range of particle sizes, is portable, can potentially be operated in field or resource-poor settings, and can be scaled to different sizes as may be required in a variety of applications. Importantly, diffusiophoresis may work for difficult separations of small particles using environmentally benign salts, when traditional filtration or sedimentation methods may be highly inefficient or even ineffective.The objective of the research is to investigate diffusiophoretic-driven separation processes for a large class of particles, e.g. rigid particles of different size, shape and surface charge, droplets, and vesicles, in confined configurations, which typify a wide range of biological, chemical, and engineering materials and systems, e.g. porous media, structured surfaces and microdevices. Here "separation" is considered in its broadest sense, e.g. fractionation of different particles, isolation of particles from the fluid, and transport of particles to specific destinations. Diffusiophoresis refers to the migration of colloidal particles owing to osmotic pressure variations (chemiphoresis) and local electric fields generated by differences in diffusivities of cations and anions (electrophoresis). In the first aspect of this work these ideas are explored in confined geometries and separation of different particles is characterized. In particular, time-dependent diffusiophoretic strategies are described to achieve particle transport over long times. In the second aspect of this work, diffusiophoresis is created using interphase mass transfer, e.g. dissolution of CO2 gas. Consequently, approaches for removing particles in a membrane-less flow approach are described, and a new strategy for field flow fractionation is introduced. Experiments and modeling will be developed for a wide range of particles, particles of all types, rigid/soft particles, bacterial cells, vesicles. The research will achieve fundamental understanding of diffusiophoretic transport in confined spaces and improve macroscopic transport processes.