Melikhan Tanyeri
University of Chicago, USA
Title: Observation of droplet dissolution in aqueous media using a hydrodynamic trap
Biography
Biography: Melikhan Tanyeri
Abstract
We present a novel flow-based method to study the dissolution of individual microdroplets in aqueous solutions. For most two-phase systems, liquid-liquid miscibility is characterized by a small and often negligible quantity, thereby leading to the assumption that many emulsion systems are immiscible. Similarly, during emulsion generation, vast quantities of aqueous microdroplets are produced in host oil-based solutions and are considered stable for long periods of time. A careful study of oil-water miscibility at the micro scale will provide valuable insight into these systems. In this work, we report a new method enabling quantitative analysis of dissolution of an individual microdroplet in the immiscible medium. We observed that micro droplets, normally immiscible in host medium, dissolve substantially under planar extensional flow conditions. Furthermore, we developed a model accurately capturing the dissolution dynamics of individual droplets in the immiscible medium. We observed dissolution of individual oil micro droplets in aqueous solutions under planar extensional flow. Specifically, we confined single microdroplets at the stagnation point of a planar extensional flow generated at the junction of two perpendicular microchannels. We quantitatively analyzed micro droplet dissolution by acquiring consecutive images of a hydrodynamically-trapped microdroplet, and by measuring the change in average droplet diameter as a function of time. We demonstrated that dissolution of the oil phase in host aqueous solution could be substantial under laminar flow. In the absence of flow, the size of the oil microdroplets does not significantly change over a long period of time, as expected. We developed a model to explain flow-enhanced dissolution of micro droplets under planar extensional flow. This study demonstrates flow-induced dissolution of immiscible fluid-fluid systems at the micro scale and shows that the dynamics of dissolution can be predicted accurately by a numerical model. This novel method will enable fast and precise measurement of solubility and diffusion coefficients for immiscible two-phase (liquid-liquid and gas-liquid) fluid systems with potential applications towards food, cosmetic and pharmaceutical industries.