Comment on “Size dependence of bubble wetting on surfaces: breakdown of contact angle match between small sized bubbles and droplets” by H. Zhang and X. Zhang, Nanoscale, 2019, 11, 2823

Abstract

The main result of the commented article is based on the use of an erroneous technique in the derivation of the equation for the contact angles of surface bubbles. A correct derivation gives the same Young equation as for sessile droplets, and therefore supplementary contact angles for bubbles and droplets. This cannot explain the presented results of simulations of nanosized droplets and bubbles where there are also several questions. We suggest a possible source for the difference in the contact angle size dependence for droplets and bubbles as related to the line tension and adsorptions at the interfaces.