Today we take another look at the oddities of non-newtonian fluids or shear thickening fluid.
Materials
Cornstarch mixed with water.
A speaker.
ToneGen (free tone generation software)
Saran wrap.
Procedure
Cover the speaker with the saran wrap and then pour the cornstarch and water into the speaker, turn on tone gen and set for 120hz.
Result
The vibrations caused by the speaker create some odd behavior in the STF.
Observations
This stuff is so neat. The more I play with it the neater it is. Non-newtonian fluids do the oddest things when hit with specific frequencies. The blob with the connecting strand is especially neat. It appears solid as it is bouncing around the speaker but once it takes flight it resumes it normal fluidity. I played with this stuff for a few hours the day I filmed this and this was the most singular example of it doing strange things. I will eventually film this at regular speed so everyone can see what it looks like to the observers, I do believe that this stuff is even stranger to watch in real time.
The other day I was browsing the net and ran across a page that had eight videos of shear thickening fluids. STFs are also known as non-newtonian fluids. It is a fluid that does not behave like your typical fluid. A standard fluid is always the same viscosity, a STF changes its viscosity in response to pressure. In this case we are looking at cornstarch and water, with a bit of food coloring.
Materials
A few cups of corn starch.
Enough water so the corn starch is nice and thick but still behaves like a fluid when sloshed around.
*Warning – It will not behave like a fluid when you are stirring it. It will break and freeze up, that is normal, stir slower.
A sub-woofer with amplifier.
A source of specific frequency noise generation. In this case I used ToneGen.
Procedure
Place something flat and relatively thin over the speaker. I used the top of a tupperware bowl. Pour some of the STF on the lid. Turn on the speaker and set the frequency generator to 200hz.
Result
This stuff is just about as creepy and cool as it gets. Initially you will watch the vibrations and not much will happen. Eventually however (or when you poke it) it will start to grow and dance of its own accord. It is rather creepy to witness at normal speed. Later this week I will get a few clips at normal speeds so you can see what it is like. As it is however this gives us a good chance to study the dynamics of the situation. Of course, knowing how STFs work the exhibited behavior makes perfect sense. The vibrations cause the fluid to become more solid, however the pauses between the vibrations allows the material to soften a bit, but the next wave pushes more material up and makes it solid again. This is repeated so often that you get these odd growths.
Additional tests
I plan on testing this with several frequencies and arrangements in an attempt to see just how creepy we can make this.
If you have not had a chance to play with this I highly recommend you do so. It is truly fascinating and is a wonderful exercise for adults and children alike. My daughter was absolutely fascinated by what she was seeing. Even with a spoon or your hands this stuff is hours of fun.
