Automated process for improved uniformity and versatility of layer-by-layer deposition

The recently developed practice of spraying polyelectrolyte solutions onto a substrate in order to construct thin films via the layer-by-layer technique has been further investigated and extended. Here we describe a fully automated system capable of depositing thin polymer films from atomized mists of solutions containing species of complementary functionality. Film growth is shown to be similar to that in conventional "dipped" LbL assembly, whereas the reported technology allows us to realize 25-fold decreases in process times. Furthermore, complete automation removes human interaction and the possibility of operator-induced nonuniformities. We extend the versatility of the spray LbL technology by depositing both weak and strong polyelectrolyte films, hydrogen-bonded films, and dendritic compounds and nanoparticles, broadening its range of future applications. Finally, the technology is used to uniformly coat an otherwise hydrophobic substrate from aqueous solutions. ESEM images indicate that the atomization process produces a conformal coating of individual nanofibers within the substrate, dramatically changing the hydrophilicity of the macroscopic surface. Such an automated system is easily converted to an array of nozzle banks and could find application in the rapid, uniform coating of large areas of textile materials.