Evaporation of Binary-Mixture Liquid Droplets: The Formation of Picoliter Pancakelike Shapes

Small multicomponent droplets are of increasing importance in a plethora technological applications ranging from the fabrication self-assembled hierarchical patterns to design autonomous fluidic systems. While often far away equilibrium, involving complex and even chaotic flow fields, it is commonly assumed that these systems with small drops surface tension keeps shapes spherical. Here, studying picoliter volatile binary-mixture isopropanol 2-butanol, we show dominance forces at scales can play dual role: Minute variations along interface create Marangoni flows strong enough significantly deform drop, forming micron-thick pancakelike otherwise typical large puddles. We identify conditions under which flattened form explain why, universally, they relax back spherical-cap shape toward end drop lifetime. further formation suppresses “coffee-ring” effect leads uniform deposition suspended particles. The quantitative agreement between theory experiment provides predictive capability modulate tiny implications range technologies miniature optical lenses coating, printing, pattern deposition.Received 17 February 2021Accepted 7 June 2021DOI:https://doi.org/10.1103/PhysRevLett.127.024501© 2021 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBinary fluidsContact line dynamicsDrops & bubblesEvaporationLiquid-gas phase transitionMarangoni convectionSurface effectsThin fluid filmsWettingCondensed Matter, Materials Applied PhysicsPolymers Soft MatterFluid Dynamics