Molecular dynamics modeling of water nanodroplet spreading on topographically patterned silicon dioxide and silicon nitride substrates

This article reports the investigation of the spreading behavior of a nanodroplet in a droplet-based scalable nanomanufacturing process using Molecular Dynamics (MD) modeling and simulation. The objective of the study is to understand the effect of substrate topology on the wetting behavior of nanodroplets at the molecular level. A water nanodroplet spreading on silicon dioxide (SiO2) and silicon nitride (Si3N4) substrates with different topologies was studied. A migration of the SiO2–water system from a hydrophilic to hydrophobic interaction was observed with an increase in the aspect ratio of the patterns. In contrast, for the Si3N4–water system the fluid–structural interaction shifted from a hydrophobic to hydrophilic behavior for patterns with corresponding higher aspect ratios. The MD models were validated using molecular kinetic theory. This research provides a foundation for extending the functional range of substrate and solvent combinations by manipulating the substrate topology. The results of this work are expected to serve in the effective control of the hydrophobic/hydrophilic nature of the substrates and therefore aid in the prediction of nanofeature deposition in droplet-based micro/nanomanufacturing processes.