minimal surface

Soap bubbles

Surface tension – The property of the surface of a liquid that allows it to resist an external force, due to the cohesive nature of its molecules.

Why bubbles are round: The surface tension of water provides the necessary wall tension for the formation of bubbles with water. The tendency to minimize that wall tension pulls the bubbles into spherical shapes.

Surface Tension and Droplets: Surface tension is responsible for the shape of liquid droplets. Although easily deformed, droplets of water tend to be pulled into a spherical shape by the cohesive forces of the surface layer.

Engineering ideas

  • surface, surface tension, property, cohesion, molecules

Do It
Challenges for you to work on…

  • Floating paper clip made of steel with copper plating. The high surface tension helps the paper clip – with much higher density – float on the water.

Learn more…

  • Minimal surfaces – no matter how wildly twisting a curve is, as long as it is simple, it will “relax” to a circle and then disappear. The surface tension of an interface, like a soap bubble, is proportional to its curvature; for example, the dynamics of ink in an ink jet plotter is affected by its surface tension. Other applications include the evolution of boundaries between fluids and removing noise from an image.
  • Fluid Mechanics demonstrations