UV-ozone patterning of micro-nano fibrillated cellulose (MNFC) with alkylsilane self-assembled monolayers

We report on a facile photolithography-based procedure for surface energy patterning of novel micro-nano fibrillated cellulose (MNFC) films and demonstrate spatial control of protein adsorption. The kinetics of oxidative degradation of chemisorbed hydrophobic alkylsilane monolayers on MNFC upon exposure to UV/ozone and the effect on the adsorption of bovine serum albumin (BSA) as a function of pH were studied using surface sensitive techniques. Wetting properties, surface morphology and surface chemical composition of the MNFC films were investigated by using water contact angle goniometry, atomic force microscopy and X-ray photoelectron spectroscopy, respectively. Optical microscopy was used to give a spatial-specific visualization of adsorbed dye-tagged BSA. UV/ozone exposure turned the initially hydrophobic alkylsilane covered MNFC substrate into a hydrophilic surface. As a result, significant changes in local wetting characteristics were observed leading to a quantitative change in BSA adsorption. Moreover, by using a UV mask, it was possible to create a hydrophobic-hydrophilic pattern on the MNFC film, and thus spatially-resolved adsorption of protein patterns were achieved. These results extend the understanding and further the applicability of MNFC films towards microfluidic-based (bio)diagnostics.