Water vapor condensation on substrates with nanoscale hydrophilic spots: A molecular dynamics study

Theoretical and Three-Dimensional Molecular Dynamics Study of Droplet Wettability and Mobility on Lubricant-Infused Porous Surfaces

“…The water-hexane interfacial tension can be adjusted by varying the energy parameter ε wo . In addition, the inter-particle interaction between water and copper or between hexane and copper is defined using the standard 12–6 L–J potential: ,, U i j = 4 ε i j [ ( σ i j r i j ) 12 − ( σ i j r i j ) 6 ] …”

“…Hence, hexane with a relatively simple molecular structure, which was used in the previous works, , is selected as the lubricant/oil fluid (o). The coarse-grained model in the MD simulation has been widely utilized to reduce the computational cost and extend the time and length scales compared to the all-atom model. ,,,, Hence, the coarse-grained models for water and hexane molecules developed by Chiu et al are employed in this work. The mapping scheme for atomistic coordinates of molecules into corresponding coarse-grained bead positions and the force field between coarse-grained beads have been designed and confirmed comprehensively.…”

“…The released surface energy during coalescence allows droplets to jump off the surface. Thanks to the greatly reduced departure size as low as 1 μm, , superhydrophobic surfaces promise remarkable enhancement in condensation heat transfer. − , However, this outstanding non-wetting functionality easily becomes invalid due to the low mechanical stability of micro/nanostructures and the possible liquid impalement resulting from external forces, pressure, or erosion. Furthermore, at a high saturation or large surface subcooling, the occurrence of uncontrolled nucleation within structures gives rise to flooding condensation with great heat transfer deterioration. , …”

Uniform and Persistent Jumping Detachment of Condensed Nanodroplets

“…The spots with a diameter of D are positioned at the centers of lattices. Superhydrophilic patterns have been widely used to realize droplet manipulation ,, and lowering the energy barrier and subcooling for nucleation. ,− As illustrated in Figure b, the superhydrophilic spots act as nucleation seeds inside each lattice to trigger a uniform condensation. Consequently, as droplets grow large enough, they coalesce with droplets in neighboring lattices and jump off, aided by off-plane flow directed by the lattice walls, leaving the vacant lattices for a new round of nucleation.…”

“…Besides experimental efforts, molecular dynamics (MD) simulation serves as a powerful tool to investigate nanodroplets. Previous related works mainly focus on the jumping of two coalesced droplets ,, or the wetting behavior of condensate. − Insights into the jumping detachment of numerous condensed nanodroplets are still lacking.…”