Continuous Convective Assembling of Fine Particles into Two-Dimensional Arrays on Solid Surfaces

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by Lidiya Mishchenko


Antony S. Dimitrov and Kuniaki Nagayama, Langmuir 1996, 12, 1303-1311


Convective assembly, colloid, disjoining pressure, force balance, hyrdostatic pressure, dynamic equilibrium


"Forming regular textures of an arbitrary size on smooth solid surfaces is the challenge of future technology to produce new types of optical gratings, optical filters, antireflective surface coatings, selective solar absorbers, data storage, and microelectronics. Here we present a novel approach to form such sophisticated textures: controlling the growth of particle arrays on smooth and wettable solid surfaces. The obtained centimeter-size polycrystalline monolayer films consist of closely packed fine particles. Coloring of the monolayer which arises from the light diffraction, interference, and scattering exclusively inherent in textured films shows the size of the differently oriented crystal domains building the film. The results show that the higher the particle monodispersity, the lower the particle volume fraction, and the higher the environmental humidity, the larger the size of the forming domains."

Soft Matter Example

The theory in this paper serves as a seminal work for understanding convective colloidal assembly. The basic principle is that if a wetting vertical substrate is withdrawn from a solution of colloidal crystals at a particular rate (to be calculated), one may be able to deposit a monolayer of colloids on the substrate.

No later paper seems to contradict the basic principle behind this assembly. There have been papers, however, that go into more detail about the fluid flow responsible for the convective formation of colloidal crystals and how this flow results in fcc packing. Also, some papers did not use the withdrawal method employed here to create monolayers, but instead left the substrate in the suspension, and created multilayer colloidal crystals (through pure evaporative assembly).

"Figure 1. Sketch of the particle and water fluxes in the vicinity of monolayer particle arrays growing on a substrate plate that is being withdrawn from a suspension. The inset shows the menisci shape between neighboring particles."