Self-Assembly of Ordered Colloidal Nanoparticle Films in Few-Micron Wide Laser-Desorbed Lines of Octadecylsiloxane Monolayers on Silicon Oxide Surfaces

We report about a maskless technique to deposit colloidal polystyrene particles in patterned stripes with a line width as narrow as 1.5 mm. Our approach is based on the digital patterning of a hydrophobic octadecylsiloxane self-assembled monolayer (SAM) on a silicon oxide surface by laser-assisted decomposition and desorption of its organic parts. For hydrophilic stripes of the micropatterned SAM area down to widths of approximately 1.5 mm, we observed ordered, mainly monolayered stripes of colloidal polystyrene nanoparticles using a modified vertical deposition technique, dipping the silicon substrate into a colloidal suspension at an angle of around 45° with respect to the surface normal of the liquid. The mechanism of this so-called ""slope self-assembly"" [Wu et al., Langmuir 2013, 29, 14017] and its limitations with respect to stacking can be explained in the framework of a meniscus moving along the steps of alternating surface energy with the decreasing width of the hydrophilic stripes during the deposition process [Fustin et al., Langmuir 2004, 20, 9114].