If the surface tension varies along an interface between two fluids, an imbalance of forces causes the Marangoni effect to occur. Surface tension depends on temperature and concentration of the surface, so changes or fluctuations in these two properties can cause a flow. This can occur when evaporation induces a flow inside of a droplet. In the case shown in the video, a soap film is stabilizing the surface tension of the bubble, which allows it to self-heal after the water drop passes through.

I enjoyed this particular example because of its sheer simplicity and captivating qualities, however, there is quite a bit of science and physics of what is going on within the soap-bubble and with surface tension. In this way the video is deceptive yet eye-catching. Surrounding the base of the bubble, ripples extend outward, exhibiting the appearance of buoyancy and is another great example of fluid flow dynamics and its associated properties.

This clip was shot by Gaven Mitchell, a student of Scientific Photography at RMT University, and Vision Research’s own Phil Taylor, an Application Engineer in Singapore.