Analysis of directional Mie scattering spectra through optical levitation

Abstract

Evaporation rates of droplets have been studied extensively due to their relevance in a variety of fields, such as atmospheric science, materials science, and biology. Optical levitation is a valuable tool for measuring evaporation rates due to their precise manipulation, non-invasive nature, and versatility in studying a wide range of droplet sizes and compositions. The current state-of-the-art technique for measuring the size of an evaporating droplet involves capturing far-field interference patterns on a screen using a camera, leading to imprecise and time-consuming measurements. In this thesis evaporation rates were measured using a recently discovered technique, directional Mie scattering spectra, which offers superior advantages compared to the existing methods. Experiments were conducted to compare the evaporation rates of water, ethanol, and a soap-water solution using both methods. It was found that directional Mie scattering spectra allowed for more precise measurements and enabled the characterization of the complete evaporation process. Specifically, a faster evaporation rate was observed for ethanol, while a slower evaporation rate was observed for the soap-water solution compared to water. The directional Mie scattering method, employed in this research, proves to be an effective tool for precise and comprehensive droplet analysis, offering new opportunities for further investigations in various scientific domains. Overall, this research provides novel insights into the evaporation rates of optically levitated droplets, highlighting the distinct behavior of different liquids and the significance of the directional Mie scattering method. The results enhance the understanding of evaporation processes and offer valuable opportunities for future interdisciplinary investigations.