Underwater spiders inspire bubble study that could help industry trap waste gas

Some spiders can live underwater by trapping a layer of air around their body, which they use to breathe. The authors were inspired to study how creatures, such as the diving bell spider (Argyroneta Aquatica) trap air, and have described how those study results could be crucial in controlling bubble movement in industrial flow situations.

The team coated a fiber thread with a commercial water-repellent spray and immersed the fiber in water. They watched how bubbles clung to the thread and were guided along it if the thread was at an angle to the horizontal. Although superficially similar to a well-known situation of water droplets on a thread in air, the team found the forces were quite different for the bubble in liquid case, said team member Hélène de Maleprade.

“Air is easy to move, but water is not. The friction always happens in the water. It’s harder to move the water around the bubble rather than to move the bubble itself,” she said.

The team’s analysis found that the friction forces on the bubble came from the skin of water around the bubble, in contrast to the water droplet in air case, in which much of the friction comes from the points at either end of the droplet-thread contact region.

The team varied the viscosity of the liquid through which the bubbles were travelling and confirmed the frictional forces increased as expected.

The team propose that a network of fibers could be useful for trapping and guiding away bubbles in liquid flow-based industries, a mechanism that could be crucial, for example, where a problematic accumulation of toxic or inflammable gases could occur.

Source: “Tightrope bubbles,” by Hélène De Maleprade, Matthias Pautard, Christophe Clanet, and David Quéré, Applied Physics Letters (2019). The article can be accessed at https://doi.org/10.1063/1.5102148 .