title: Fingering inside the coffee ring.
abstract: Colloidal droplets including micro- and nanoparticles generally leave a ringlike stain, called the "coffee ring," after evaporation. We show that fingering emerges during evaporation inside the coffee ring, resulting from a bidispersed colloidal mixture of micro- and nanoparticles. Microscopic observations suggest that finger formation is driven by competition between the coffee-ring and Marangoni effects, especially when the inward Marangoni flow is overwhelmed by the outward coffee-ring flow. This finding could help to understand the variety of the final deposition patterns of colloidal droplets.
authors: X-ray Imaging Center, Department of Materials Science and Engineering, Pohang University of Science and Technology, San 31, Hyoja-dong, Pohang 790-784, Korea. bmweon@hotmail.com
authors: Byung Mook
authors: BM
authors: Weon
authors: Jung Ho
authors: JH
authors: Je
mesh_terms: D000465:Algorithms; D003102:Colloids / Q000737:chemistry*; D003198:Computer Simulation; D008956:Models, Chemical; D012212:Rheology / Q000379:methods*
chemical_list: D003102:Colloids