Engineered deposition of coatings from nano- and micro-particles: A brief review of convective assembly at high volume fraction

In this paper, we review the state of the art of a simple, easily controlled convective assembly technique for rapid deposition of structured micro- and nano-particle coatings. The advantages afforded by this method arc improved process efficiency and reduced material consumption relative to standard dipcoating techniques. Structured coatings larger than a few square centimeters are deposited in minutes from aqueous suspension volumes of approximately 10-20 mu l. The governing mechanism of particle deposition is convective assembly at high volume fractions. Our research with monodisperse polystyrene latex showed that a volumetric flux balance incorporating the evaporating solvent and assembling particle fluxes can accurately relate the deposition process parameters to the coating structure and properties. Operational 'phase' diagrams were constructed that demonstrate good correspondence between coating thickness and structure to the operational parameters of the coatings process predicted on the basis of the material balance model. These 'phase' diagrams may be instrumental in turning the colloidal deposition into a usable and scaleable technology. This deposition, technique can be applied to a variety of colloidal systems, including the fabrication of conductive and antireflective coatings, surface-enhancing Raman scattering (SERS) substrates, and lithographic masks. (c) 2007 Elsevier B.V. All rights reserved.