#Rain; #Biodiversity; #SmallOrganisms; #Leaves
New York, Jul 18 (Canadian-Media): The effect of rain was studied by Kim et al. published in Proc. Natl. Acad. Sci. U.S.A. 117, 13901 (2020) and found that high-speed water drops do not simply bounce off of these nanostructured surfaces.
These raindrops falling at terminal velocity are seen as giant ballistic objects when viewed by a butterfly or felt by a leaf.
So how do smaller organisms survive a rainy day? Many biological surfaces have nanoscale texture and show superhydrophobicity. On impact, each drop spreads, shock-like waves form, and the drop shatters. As the liquid spreads across the “rough” surface, the shock waves nucleate holes in the upper liquid film, the holes coalesce, the liquid rebounds, and contact time is reduced by 70 percent.
This is also a perfect mechanism to send waterborne fungal spores flying. Thus, superhydrophobicity means that an organism out in the rain gets neither wet nor cold and can carry on flying unperturbed, as birds and butterflies do.
Microbumps on insect and leaf surfaces generate tiny shock waves that shatter raindrops and make them rebound, thus reducing wetting.
Image credit: Kim et al., Proc. Natl. Acad. Sci. U.S.A. 117, 13901 (2020)