Suppression of coffee-ring effect in random optical potentials

Thesis Type: Post Graduate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Arts and Sciences, Department of Physics, Turkey

Approval Date: 2017


Consultant: ALPAN BEK


Drying a liquid (e.g. water) drop containing uniformly dispersed microscopic particles results in the particles’ migration towards the edges of the drop; after the drop evaporates the suspended particles remain concentrated around the original drop edge. This so-called “coffee-ring” effect does not depend on the nature of the solvent or the solute; thus it is ubiquitous in nature and challenging to avoid. However, in many applications such as inkjet printing, coating and many other biological processes, there is need to suppress and control the coffee-ring effect due to the requirement of uniform deposition of the suspended particles. Such approaches include changing the shape of the particulate suspension, using acoustic waves, or adding hydrosoluble polymer during the evaporation. In this work, we investigate the evaporation of liquid droplets containing passive and active particles under random optical potentials. In particular, we experimentally show that while drops of a suspension of 3 µm diameter polystyrene particles show typical coffee-ring when no opticalpotentials are applied, they form uniform distribution, suppressing the coffee-ring formation when a random optical potential is present.