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Abstract Bubbles will rest at the surface of a liquid bath until their spherical cap drains sufficiently to spontaneously rupture. For large film caps, the memory of initial conditions is believed to be erased due to a visco-gravitational flow, whose velocity increases from the top of the bubble to its base. Consequently, the film thickness has been calculated to be relatively uniform as it thins, regardless of whether the drainage is regulated by shear or elongation. Here, we demonstrate that for large bare bubbles, the film thickness is highly nonuniform throughout drainage, spanning orders of magnitude from top to base. We link the film thickness profile to a universal non-monotonic drainage flow that depends on the bubble thinning rate. These results highlight an unexpected coupling between drainage velocity and bubble thickness profiles and provide critical insight needed to understand the retraction and breakup dynamics of these bubbles upon rupture. 

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. 

At the appropriate length scales, capillary forces exerted by a liquid in contact with a compliant solid can cause the solid's deformation. Capillary forces are also able to align particles with discrete wettabilities – or Janus particles – at liquid interfaces. Their amphiphilic properties enable Janus particles to orient themselves at liquid interfaces such that both of their surfaces are facing their preferred fluid. However, it is unclear how to spontaneously obtain varying degrees of rotational alignment. Here we extend ideas of elasto-capillarity to modulate rotational alignment by connecting amphiphilic Janus cylinders in an antisymmetric configuration. As the Janus cylinders rotate they cause a twisting deformation of rod. We develop both a mathematical model and a physical macroscale setup to relate the angle of twist to the elastic and interfacial properties, which can be used to tune the extent of alignment of Janus particles at air–water interfaces. We additionally extend our analysis to calculate the twist profile on a compliant element with a distributed capillary torque.