We present a case study about inkjet printing as a tool for molecular patterning of silicon oxide surfaces with hydrophobic functionality, mediated by n-octadecyltrichlorosilane (OTS) molecules. In contrast to state-of-the-art techniques such as micro contact printing or chemical immersion with subsequent lithography processes, piezo drop-on-demand inkjet printing does not depend on physical masters, which allows an effective direct-write patterning of rigid or flexible substrates and enables short run-lengths of the individual pattern. In this paper, we used mesithylene-based OTS inks, jetted them in droplets of 10 pL on a silicon oxide surface, evaluated the water contact angle of the patterned areas and fitted the results with Cassie's law. For inks of 2.0 mM OTS concentration, we found that effective area coverages of 38% can be obtained. Our results hence show that contact times of the order of hundred milliseconds are sufficient to form a pattern of regions with OTS molecules adsorbed to the surface, representing at least a fragmented, inhomogeneous self-assembled OTS monolayer (OTS-SAM).

We report about a maskless technique to deposit colloidal polystyrene particles in patterned stripes with a line width as narrow as 1.5 μm. 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 μm, 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]

We evaluated the wet‐chemical formation of octa‐decyltrichlorosilane (OTS) self‐assembled monolayers on silicon substrates with a silicon oxide layer. Our investigations were focussed on the influence of the reaction time on the surface energy. The surface energy was thereby calculated by measuring the static contact angle of two probe liquids on the surface. We found that only high reaction times of several hundred minutes yield a high quality monolayer with a minimal surface energy. A clear increase of the dispersive part of the surface energy for short reaction times is found. This can be explained by a high ratio of gauche‐conformation within the alkyl chains accompanied by a rather slow rearrangement of the chains inside the monolayer to form a densely packed all‐trans conformation. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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