Optical detection of changes in glass surface properties induced during wet photolithography

Recently Yee et al. (Adv. Mater. 2004, \textbf{16}: 1184-1189) demonstrated a wet UV-photolithographic method for patterning phospholipid bilayers into two-dimensional arrays of voids and patches on hydrophilic glass surfaces. In this method, the glass surface is chemically etched to remove organic contaminants and expose hydrophilic groups before a bilayer is formed on top of it, using the method of small unilamellar phospholipid vesicle fusion. The bilayer is subsequently illuminated with short-wavelength UV light through a photomask, creating voids in the irradiated regions. We studied the effects of the chemical etching and subsequent UV irradiation on the surfaces of commercially available microscope glass slides using an oblique-incidence optical reflectivity difference (OI-RD) microscope. We found that the UV irradiation after chemical etching further changes the properties of the surface, even in the absence of a lipid bilayer. As a result, irradiating the chemically etched surface before the UV-photolithography step prevents further UV-induced changes in surface properties. We found that the lipid bilayer formed on such an UV-irradiated surface retains its fluidic properties.