Nonequilibrated systems: Fluid flows and material synthesis

Abstract

The process of phase separation is ubiquitous in nature, occurring in wide range of materials, such as metallic alloys, polymer blends, and even in biological materials, such as cells. Better understanding of this nonequilibrium process, and the conditions leading to an equilibrium state, is critical for learning about mechanical properties of materials. Furthermore, exploiting nonequilibrated systems could lead to the generation of novel functional materials.Here, we study the nonequilibrium transient dynamics of an aqueous two-phase system, within microfluidic platforms. Aqueous poly-phase systems are a mixture of two or more different polymer or salt solutions, which phase separate and de-mix under certain conditions, resulting in two or more distinct polymer/salt-rich phases. Traditionally, in equilibrium, these systems are used as a separation platform. These poly-phase systems have been used for the separation and enrichment of particles, biomolecules, or cells, based on their affinity partitioning to each of the phases. Specifically, we explore how varying material properties of such nonequilibrated flow systems can give rise to secondary flows, and how we could exploit these fluid systems, while they are chemically out of equilibrium, as a template for structured materials. This thesis is comprised of three parts. In the first part, we explore buoyancy-driven flows within miscible fluids, which is a model system to study buoyancy-driven flow within nonequilibrated flow systems. In the second part, we study three-dimensional flow arising due to liquid-liquid phase separation within a two-phase flow system, coupled with preferential wettability. In the last part, we explore surface features arising from liquid-liquid phase separation within a co-axial flow system, for the generation of structured microfibers.