Separation of Colloidal Particles by Diffusiophoresis

1702693：石头过滤是从溶液中去除颗粒的最常用方法。我们理所当然地认为，我们可以通过使用通常由多孔材料（如沙床）组成的过滤器，从水中去除各种颗粒物质，如污垢、细菌和病毒。过滤对于获得安全饮用水和其他适合工业加工的液体至关重要。然而，代替过滤的技术是利用“场”，如重力沉降，来去除颗粒和/或分离不同种类的颗粒。该项目研究了简单的化学梯度，甚至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大小分离。这种方法被称为扩散电泳，它适用于大范围的粒径，便携，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，当传统的过滤或沉淀方法可能效率极低甚至无效时，扩散电泳可能适用于使用环保盐的小颗粒的困难分离。本研究的目的是研究一大类颗粒的扩散电泳分离过程，例如不同大小、形状和表面电荷的刚性颗粒、液滴和囊泡，这些颗粒在受限构型下代表了广泛的生物、化学和工程材料和系统，例如多孔介质、结构表面和微器件。这里的“分离”是最广义的，例如，不同颗粒的分馏，颗粒从流体中分离，以及颗粒运输到特定目的地。扩散电泳是指由于渗透压的变化（化学电泳）和阳离子和阴离子扩散率差异产生的局部电场（电泳）而导致胶体颗粒的迁移。在这项工作的第一个方面，这些想法是在有限的几何和不同的粒子分离的特征。特别是，描述了时间依赖的扩散电泳策略，以实现长时间的粒子传输。在这项工作的第二个方面，扩散电泳是利用相间传质产生的，例如CO2气体的溶解。因此，描述了在无膜流动方法中去除颗粒的方法，并介绍了一种新的场流分馏策略。实验和建模将用于广泛的颗粒，所有类型的颗粒，刚性/软颗粒，细菌细胞，囊泡。该研究将有助于对密闭空间内扩散泳输运的基本认识，并改善宏观输运过程。

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.