Experimental investigations of the dynamics of centimeter-scale drops

Abstract

Historically the study of drop dynamics has been limited in length-scale due to the effects of bodyforces from gravity, as there is simply a limit to the size that an unsupported drop can be stably grown on Earth. These surface tension-contained systems, being uniquely free surface-dominated, can be utilized to pursue scientific investigations with applications to both the fields of fluid dynamics and biology. By introducing a technology capable of analyzing drop dynamics in a microgravity environment, novel scientific studies can be pursed which were not previously possible. This thesis follows, from an experimental standpoint, the development and initial works of one such technology: the Ring-Sheared Drop (RSD). The RSD is an inch diameter drop apparatus used for scientific investigations aboard the International Space Station (ISS). Pinned between two thin contact rings, the drop can be differentially rotated, allowing for the effect of shear to be isolated and studied in an interfacially dominated system. This doctoral work accomplishes this goal through a series of published (or soon to be) academic investigations. These studies serve to (I) develop a density-matched liquid analogue system to characterize the deformation of a differentially sheared drop, (II) quantify the influence of the outer bath in such density matched analogue systems and validate an asymptotic theory predicting drop shape, (III) quantify any influence of microorganisms on the stability of a growing liquid-gas drop in a microgravity environment, (IV) apply knowledge gained from the subsequent studies to begin the RSD’s mission aboard the ISS of studying the causes of neurodegenerative diseases by analyzing the kinetics of amyloid fibrils in shearing flow, and (V) develop a particletracking technique to enhance the scientific capabilities of the RSD beyond its original design.