Our recent paper (1) demonstrates that the major pathway to produce submicron drops from bursting submillimeter bubbles depends crucially on the gas density, and justifies how the flapping mechanism of the bubbles' cap as they burst might be responsible for it. Ganan-Calvo's (2) comment raises concerns about this paper. His arguments are incorrect. First, Ganan-Calvo (2) argues that ref. 1 does not rule out jet drop formation from a cascade of daughter bubbles. On the contrary, ref. 1 has precisely addressed this issue. Bird et al. (3) report that the average daughter bubble size is roughly 0.08 times the parent bubble size. If the bubbles with cap radii of curvature R = 73,137,199, 870, and 1,080 μm do produce daughter bubbles, based on the relation determined by Berny et al. (4), the theoretical dried sizes of jet drops from these daughter bubbles would be 24, 52, 83, 532, and 700 nm. However, the size distributions in ref. 1's figure 2 peak at 35, 50, 76, 66, and 71 nm, respectively. Ganan-Calvo argues that the first three values are similar between these two pairs. However, the differences between the last two values (532 nm vs. 66 nm, 700 nm vs. 71 nm) are very substantial and cannot be explained by jetting from a cascade of daughter bubbles. Moreover, there is no reason to believe that the daughter bubble mechanism would only work for bubbles with R = 73, 137, and 199 μm, and not for bubbles with R = 870 and 1,080 μm. The truth is that the droplets are formed by another mechanism, which involves the gaseous atmosphere, as ref. 1's observations demonstrate.
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