72th Annual Meeting of the APS Division of Fluid Dynamics (November 23, 2019 — November 26, 2019)

V0081: Formation of Storm Eye and Mushroom Cloud Cascading in Nanoparticle-laden Evaporating Drops

Authors

• Jian Zhao, Department of Mechanical and Mechatronics Engineering, University of Waterloo
• Xianguo Li, Department of Mechanical and Mechatronics Engineering, University of Waterloo
• Zhong-sheng Liu, Energy, Mining and Environment Research Center, National Research Council Canada
• Zhao Pan, Department of Mechanical and Mechatronics Engineering, University of Waterloo

DOI: https://doi.org/10.1103/APS.DFD.2019.GFM.V0081

Drying the premixed solution of polymer, nanoparticles, and solvents with fast evaporation rates is commonly employed in a variety of industrial processes, particularly for electrochemical applications. We experimentally investigate the drying dynamics of a droplet, which is a mixture of ionomer, carbon-supported platinum nanoparticles, and isopropanol deposited on a clean glass slide at room condition. The droplets spread quickly on the glass surface after being placed by a needle. When the contact line of the droplet reaches its maximum diameter, the initially uniformly distributed nanoparticles start concentrating at the center of the droplet and form a ‘storm eye’ pattern. Simultaneously, small mushroom-cloud-like plumes onset at the edge of the droplet and shoot to the center. The small scale plumes grow and feed to large neighboring plumes, and bigger plumes form throughout the evaporation process. This inverse cascading behavior of plumes lasts until the droplet is dried, and a rich trace pattern of nanoparticles is left on the glass. The complex behavior of such a drying droplet is affected by the recipe of the mixture.