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.

This article demonstrates that the micro-topography of the surface with respect to the pattern size and pitch influences cell adhesion and proliferation. Extensive research has shown the dependence of cell proliferation on substrate chemistry, but the influence of substrate topography on cell attachment has only recently been appreciated. To evaluate the effect of substrate physical properties (i.e., periodic microstructures) on cell attachment and morphology, we compared the response of several cell types (fibroblasts, HeLa, and primary hepatocytes) cultured on various polydimethylsiloxane (PDMS) patterns. PDMS has been used as an artificial construct to mimic biological structures. Although PDMS is widely used in biomedical applications, membrane technology, and microlithography, it is difficult to maintain cells on PDMS for long periods, and the polymer has proved to be a relatively inefficient substrate for cell adhesion. To improve adhesion, we built polyelectrolyte multilayers (PEMs) on PDMS surfaces to increase surface wettability, thereby improving attachment and spreading of the cells. Micrographs demonstrate the cellular response to physical parameters, such as pattern size and pitch, and suggest that surface topography, in part, regulates cell adhesion and proliferation. Therefore, varying the surface topography may provide a method to influence cell attachment and proliferation for tissueengineering applications.