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Magic Bubble Wands

In this activity students learn about minimal surface structures by trying to blow bubbles in many shapes.

If you play with bubbles and soap films, you’ll notice they come in predictable shapes. When floating around in the air, a bubble will become a sphere; and when in a flat bubble wand, a soap film is always flat, no matter the shape of the wand.

Bubble shapes are simple and predictable because deforming a bubble takes energy. Bubbles tend to spring back to the shape that is stretched as little as possible. That shape is called the minimal surface. That is why a free-floating bubble is a sphere—a sphere has the least surface area for a given volume of air. Another way to think about this is that a bubble is stretched most evenly as a sphere (as compared to an egg shape, or a cube). 

Objectives

  • Make a bubble and understand its structure.

Materials

Key Questions

  • What shape of bubble do you think will come out of each shape of bubble wand?
  • Why are bubbles always spherical?
  • What has more surface area (what would take more soap film to create) a cube or a sphere?
  • What are minimal surface structures?Is there any way to make a different shaped bubble?

What To Do

Activity

  1. ​Create a few 2-D bubble wands by twisting a pipe cleaner into a shape other than a circle (e.g. square, triangle, heart, star, butterfly etc.)
  2. Experiment with the different wand shapes to create bubbles. Do the bubbles match the shape of the pipe cleaner wand? What is happening? Why do you think the wands all create the same bubble shape?

Extensions

  • Try making square and other shaped bubbles in the activity.
  • Examine commercially made wands, hypothesize and test reasoning for design.

Other Resources

Exploratorium | Bubbles