Micropatterning of functional dye films on wettability-patterned surfaces using soft liquid-phase adsorption

We discuss a “soft” liquid-phase adsorption (SLPA) technique to control formation of organic dye films on wettability-patterned templates by using methanol/hexane emulsions. Wettability-patterned templates were fabricated by the formation of self-assembled monolayers of silane-coupling agents on glass plates followed by UV-ozone treatment through a metal mask. Rhodamine B and thymol blue films were formed selectively on the hydrophilic regions of the wettability-patterned templates. The thickness of the rhodamine B films increased with a decrease in immersion temperature and with an increase in immersion angle of the wettability-patterned templates in the emulsions. The thickness of the thymol blue films was significantly larger than that of the films fabricated by conventional film-forming techniques such as spin-coating and dip-coating. The thymol blue films served as pH-responsive devices under exposure to HCl and NH3 gasses. The SLPA technique allows for the fabrication of organic thin films on wettability-patterned templates with little material consumption and a few film-forming processes, contributing to application to the fabrication of organic photonics and electronics devices with reduction of environmental burdens.