Molecular Dynamics Study of Bubble Nucleation on a Substrate with Nonuniform Wettability

In the present study, the molecular dynamics simulation method is adopted to study bubble nucleation on a platinum substrate with nonuniform wettability. The central region of the substrate has strong hydrophilicity and both sides have weak hydrophobicity. It is interesting that the bubble nucleation happens in the hydrophobic region when the substrate temperature is low, and the nucleation position moves to the hydrophilic region with the increase of the substrate temperature. The intrinsic regime for the change of nucleation position with the substrate temperature is fully illustrated based on the competition between the suffered potential restriction and the absorbed thermal energy of liquid atoms. When the liquid atoms on one region obtain enough thermal energy to break their potential barrier, they convert into a bubble nucleus. Both the potential barrier for liquid atoms clinging to the substrate surface and the solid-liquid heat transfer efficiency improve with the enhancement of substrate hydrophilicity. The potential barrier is decided only by the atomic distribution and interatomic interaction. However, the substrate temperature changes the absorbed thermal energy of the liquid atoms within a specific time, causing the movement of the nucleation position. Furthermore, a hydrophilic nanostructure is introduced to replace the central smooth hydrophilic region and promote lateral heat transfer to the liquid on the hydrophobic region, leading to the improvement of the bubble nucleation efficiency.