Abstract: Achieving condensate microdrop self-removal(CMDSR) function on polymer surfaces is very significant. However, this is difficult because of very low thermal conductivity of polymer, and so the reports on polymer surfaces with CMDSR function are very sparse. Based on preliminary analyses, two kinds of anodic aluminum oxide(AAO) templates with different geometric parameters of tapered nanopores were chosen as the mold templates in injection-compression molding(ICM) in this work. It was demonstrated that the tapered nanostructure on the AAO templates was more accurately replicated onto the polypropylene(PP) surfaces via the ICM. The closely and more orderly aligned tapered nanopillars, which are similar to those on cicada wing, were formed on the PP replica surfaces. For the PP replica surface with the nanopillars exhibiting obviously smaller values of both wetting-state energy ratio(0.46) and tip diameter/center interspace ratio(0.26), the condensate microdrops remained bright and spherical on the surface. Interestingly, when adjacent microdrops grew large enough to coalesce, frequent out-of-plane jumping occurred and the merged microdrops could depart from the replica surface without any external forces, thus constantly renewing the surface. That is, the PP replica surface exhibited an obvious CMDSR function, which maintained significantly lower coverage of the condensate microdrops and smaller values of their sizes(<40 μm) on the surface. It should be noted that this function was created on the replica surfaces without any low surface energy chemistry modification. The results demonstrate that it is feasible to rapidly and massively fabricate superhydrophobic polymer surfaces with CMDSR function.

Key words: Bionic nanostructured surface, Condensate microdrop dynamic behavior, Self-removal, Super-hydrophobicity, Injection-compression molding, Polypropylene