LAUSR

Slower-motion bubble collapse The collapse of viscous bubbles is of practical interest to geophysics, glass manufacturing, and food processing. Previous studies have suggested that gravity or small punctures may play a role in the wrinkling and collapse of viscous bubbles. By studying bubbles with a range of viscosity and by tilting them both sideways and upside down, Oratis et al. conclude that gravity is not a factor. Instead, surface tension and dynamic stress of the compressed liquid seem to be the main driving mechanisms for the behavior of the bubbles and the wrinkling instability. Science, this issue p. 685 Rather than gravity, surface tension and dynamic stress drive viscous liquid bubble wrinkling and collapse. Viscous bubbles are prevalent in both natural and industrial settings. Their rupture and collapse may be accompanied by features typically associated with elastic sheets, including the development of radial wrinkles. Previous investigators concluded that the film weight is responsible for both the film collapse and wrinkling instability. Conversely, we show here experimentally that gravity plays a negligible role: The same collapse and wrinkling arise independently of the bubble’s orientation. We found that surface tension drives the collapse and initiates a dynamic buckling instability. Because the film weight is irrelevant, our results suggest that wrinkling may likewise accompany the breakup of relatively small-scale, curved viscous and viscoelastic films, including those in the respiratory tract responsible for aerosol production from exhalation events.