We all know what happens to bubbles in water: They float to the top and disappear, eventually. In a bubbly foam bath, the bubbles are stabilized with surfactants and other ingredients. This extends their presence for some time.
Yet, they all soon disappear. However, when looking at smaller sized bubbles this is not quite the case. When the size of an air bubble in water is below a few microns, the influence of diffusion becomes meaningful. Now the random Brownian motion can overtake buoyancy: the bubbles no longer rise to the top in the case of Nano bubbles.
(You might also read about them as ultra-fine bubbles in the literature.) Environmental Engineering Science 35, 11(2018), pp. 1216-1227 by L.N. Meedoga, W.A. Hewage, and J.H. Batagoda under the title “
