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Patterned multilayer films composed of poly(allylamine hydrochloride) (PAH) and poly(sodium 4-styrenesulfonate) (PSS) were prepared using dip and spin self-assembly (SA) methods. A silicon substrate was patterned with a photoresist thin film using conventional photolithography, and PAH/PSS multilayers were then deposited onto the substrate surface using dip or spin SA. For spin SA, the photoresist on the substrate was retained, despite the high centrifugal forces involved in depositing the polyelectrolytes (PEs). The patterned multilayer films were formed by immersing the PE-coated substrates in acetone for 10 min. The effect of ionic strength on the pattern quality in dip and spin multilayer patterns (line-edge definition and surface roughness of the patterned region) was investigated by increasing the salt concentration in the PE solution (range 0-1 M). In dip multilayer patterns, the presence of salt increased the film surface roughness and pattern thickness without any deformation of pattern shape. The spin multilayer patterns formed without salt induced a height profile of about 130 nm at the pattern edge, whereas the patterns formed with high salt content (1 M) were extensively washed off the substrates. Well-defined pattern shapes of spin SA multilayers were obtained at an ionic strength of 0.4 M NaCl. Multilayer patterns prepared using spin SA and lift-off methods at the same ionic strength had a surface roughness of about 2 nm, and those prepared using the dip SA and lift-off method had a surface roughness of about 5 nm. The same process was used to prepare well-defined patterns of organic/metallic multilayer films consisting of PE and gold nanoparticles. The spin SA process yielded patterned multilayer films with various lengths and shapes.

We have designed the controlled release platforms based on polyelectrolyte (PE) blend multilayer films to investigate the release mode and kinetics at the nanoscale level. The model blend multilayer films are composed of positively charged layers with weak polyelectrolytes (PEs) (linear poly(ethylenimine), LPEI) and negatively charged blend layers with mixtures of strong (poly(sodium 4-styrenesulfonic acid), PSS) and weak (poly-(methacrylic acid), PMAA) PEs. The blend multilayer films ([LPEI/PSS:PMAA] n ) with well-defined internal structure were prepared by the spin-assisted layer-by-layer (LbL) deposition method. Release properties of the multilayer films were systematically studied as a function of blend ratio by neutron reflectivity (NR), ellipsometer, AFM, FT-IR spectroscopy, and quartz crystal microbalance with dissipation (QCM-D). Since PSS strong PEs serve as robust skeletons within the multilayer films independent of external pH variation, the burst disruption of pure weak PE multilayer films was dramatically suppressed, and the release kinetics could be accurately controlled by simply changing the PSS content within the blend films. These release properties of blend multilayer films form the basis for designing the controlled release of target active materials from surfaces.

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We have significantly enhanced the power conversion efficiency of dye-sensitized solar cells based on TiO2 nanotube membranes by increasing the inner surface area of the channels.