Drying Out Microbe-Filled Droplets

Ocean sprays, coughs, and sneezes are just a few of the ways that droplets full of bacteria and salt can get aloft on a breeze. How do these bacteria stay viable even as their droplet evaporates? That’s the question behind this video’s research.

When a bacteria-laden droplet or a salt-laden droplet dries, the evaporating droplet’s contact area shrinks, leaving behind only a concentrated lump of bacteria or salt. But when droplets contain both salt and bacteria, the drying droplet’s contact line gets pinned, leaving a larger area stain. The bacteria’s presence seems to promote crystallization of the salt, which–in turn–traps water in isolated spaces, perhaps helping the bacteria stay viable longer. (Video and image credit: R. Ran et al.)

Animation of three droplets drying out. When all three components–water, salt, and bacteria–are in a droplet, the drying process looks very different. #2026gosm #aerosols #biology #contactLine #droplets #evaporation #flowVisualization #fluidDynamics #physics #pinning #science #sessileDrop

A Drop of Algae

Spheres of a Volvox colonial algae glow green inside a droplet in this award-winning microphotograph by Jan Rosenboom. Pinned on an inclined surface, the droplet is frozen in a balance between gravity and surface tension that keeps its shape–and its contact angles–asymmetric. Droplets will also take on a shape similar to this when air is blowing past them. (Image credit: J. Rosenboom; via Ars Technica)

#biology #contactLine #droplets #fluidDynamics #fluidsAsArt #science #sessileDrop