Neat little experiment to showcase the extraordinary physical properties of a soap bubble
Step 1: What You Need
1. Diamagnetic suspension levitation rig. (height adjustable magnet, leveled in horizontal plane)
2. Pyrolytic graphite or bismuth. Pyrolytic graphite is the strongest diamagnetic substance known to man
3. Neodymium magnets, grade N52 works the best. I recommend ring or disc shaped magnets with a diameter of 8 mm - 15mm. If the magnet is too big it's hard to get it levitating, but if it's too small and it's hard to get the bubble to balance on the top.
3. Soap solution
4. A straw
5. Subzero temperatures. The warmest temperature where I was still able to freeze a bubble was -3 celcius. Do not attempt this on a windy day unless you have a good shelter from the wind
On the video, I made the magnets spinning with a 3,7 v battery and some copper wires, but that's just show offing. You can spin a levitating magnet with air stream - by blowing air through the straw. Also on the video I used a copper block underneath the pyrolytic graphite tile. Copper helps to stabilize the levitating magnet in one place eliminating sideways movement and therefore makes it little bit easier to keep it over the small graphite tile while making it spin. Copper is not necessary for the experiment.
Step 2: How to Proceed
Make the magnet levitate by adjusting the magnet above to the right distance. Blow through the straw to make the magnet spin. Dip the straw into the soap solution - blow a bubble and place it on the magnet. (Check how I do it on the video). Small 2 cm diameter bubble is good size. If the magnet is spinning very fast, a bigger bubble will have hard time staying on top because of centrifugal forces also a smaller bubble is more durable.
If you are just interested to freeze a bubble on a spinning magnet,
there is really no need to levitate the magnet. One ring magnet and a ball bearing + one magnet on top is enough to do the trick. Put the ball bearing into the hole of a ring magnet and BOOM you got yourself a magnetic spinning top. A magnet above at the right distance will keep the top upright and you can spin the magnetic top with air stream.