Graphene-assisted wetting transition on grooved surfaces: A molecular dynamics study

Abstract

The various high aspect ratio micro/nano structures that are duplicated by the widely applicable micro/nanomolding process would require excellent wettability of the structured mold for full filling of the liquid-like materials into microcavities. Herein, by employing molecular dynamics (MD) simulations, the influence of a monolayer graphene (MLG) on the wetting behaviors of grooved copper is thoroughly investigated, indicating that MLG is an effective approach in modulating the wettability of the structured copper surfaces. Moreover, the extracted outcomes signify that the coating with MLG reduces remarkably the required activation energy for the infiltration of water molecules into the copper groove, thereby triggering the wetting transition from the Cassie-Baxter (CB) to the Wenzel (WZ) state. In addition, by varying the coating locations and dimension of the MLG, it is unveiled that the sidewall coating of MLG plays a crucial role in reducing the free energy barrier needed to surmount the transition state. Interestingly, as the coating height of sidewall MLG increases, the energy barrier is reduced, and the grooved surface becomes more attractive to water molecular, attaining a stable WZ state by employing a height beyond the critical value of MLG coating of 12.4 Å in our model. Our work provides useful insights into the tunable wettability of the grooved surfaces by nanocoating engineering, suggesting that MLG can be an effective coating solution in the fabrication of novel micro/nanostructures with high aspect ratios.