Role of wettability contrast on nanoscale condensation over hybrid wetting surface with gradient and patterned wetting configuration at various philic-phobic content

S Paul and D Chakraborty and SJ Esha and MN Hasan, SURFACES AND INTERFACES, 36, 102417 (2023).

DOI: 10.1016/j.surfin.2022.102417

This study aims to explore the effect of the relative philic-phobic strength on nanoscale condensation over hybrid wetting surfaces at various philic-phobic contents through molecular dynamics simulation. The molecular system under consideration essentially consists of argon atoms (liquid and vapor) bound by two platinum substrates. Following equilibration of the simulated system at 90 K, the temperature of the lower substrate is raised to induce evaporation of the adjacent liquid argon, which eventually condenses on the upper wall, maintained at equilibration temperature. Two different hybrid wetting configurations of the upper wall have been considered, namely: functional gradient wetting (FGW) and (b) patterned wetting. The relative strength as well as the content of philic-phobic segments for both hybrid wetting configurations have been altered to explore key metrics of nanoscale condensation process such as onset of nucleation cluster, coalescence and subsequent condensate growth mode, transient as well as time averaged condensation rate and heat transfer at the condensing wall. Results obtained in the present study indicate that combining strong hydrophilic segments with weak hydrophobic segments improves the performance of a hybrid wetting surface. Nonetheless, the difference between gradient wetting and patterned wetting distribution has been found to be small for higher philic content of the condensing wall. Also findings of the present atomistic study have been found consistent with classical theories in context to heterogeneous condensate nucleation, coalescence and subsequent growth.

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