Spontaneous Pattern Formation of Surface Nanodroplets from Competitive Growth.
Nanoscale droplets on a substrate are of great interest because of their relevance for droplet-based technologies for light manipulation, lab-on-chip devices, miniaturized reactors, encapsulation, and many others. In this work, we establish a basic principle for symmetrical arrangements of surface nanodroplets during their growth out of oversaturated solution established through solvent exchange, which takes place under simple and controlled flow conditions. In our model system, nanodroplets nucleate at the rim of spherical cap microstructures on a substrate, due to a pulse of oversaturation supplied by a solvent exchange process. We find that, while growing at the rim of the microcap, the nanodroplets self-organize into highly symmetric arrangements, with respect to position, size, and mutual distance. The angle between the neighboring droplets is 4 times the ratio between the base radii of the droplets and the spherical caps. We show and explain how the nanodroplets acquire the symmetrical spatial arrangement during their competitive growth and why and how the competition enhances the overall growth rate of the nucleated nanodroplets. This mechanism behind the nanodroplet self-organization promises a simple approach to control the location of droplets with a volume down to attoliters.
Soft Matter and Interfaces Group, School of Civil, Environmental and Chemical Engineering, RMIT University , Melbourne, VIC 3001, Australia.
Shuhua
S
Peng
Physics of Fluids Group, Department of Applied Physics and J. M. Burgers Centre for Fluid Dynamics, University of Twente , P.O. Box 217, 7500 AE Enschede, The Netherlands.|Max Planck Institute for Dynamics and Self-Organization , D-37077 Göttingen, Germany.
Detlef
D
Lohse
Soft Matter and Interfaces Group, School of Civil, Environmental and Chemical Engineering, RMIT University , Melbourne, VIC 3001, Australia.|Physics of Fluids Group, Department of Applied Physics and J. M. Burgers Centre for Fluid Dynamics, University of Twente , P.O. Box 217, 7500 AE Enschede, The Netherlands.
Xuehua
X
Zhang
diffusive interaction; self-organization; solvent exchange; surface nanodroplets