Non-Newtonian fluids are fun... until they aren't.
One time a group of college students I hung out with got a bulk order of silly putty. This was fun to play with. Until someone had the idea of dropping it from about 6 feet up onto the floor. It shattered. Picking up slivers of silly putty from the carpeted floor was not fun.
Elsefluid ... a different category (shear thinning - https://en.wikipedia.org/wiki/Shear_thinning ) has it so that if you drop something through it, it takes {some time}. If you immediately drop another thing through it at the same spot, it takes {some less time}. One of the chemistry professors wanted to do some experiments with this type of fluid and had his grad students develop a proof of concept. There are some challenges with this - it can't be a thin cylinder of the fluid you drop it through since the distance to the walls is a variable in the speed too. It also needed to be a tall enough cylinder with enough viscosity that you could time it with a stopwatch (initially). One such fluid that has this property is ketchup. They bought 10 gallons of ketchup from the local grocery store (that's all that was on the shelf ... seriously, you need about 7x 20 oz bottles to make one gallon), poured it into a large cylinder... realized that they needed a clear bottom to see it, made a new cylinder with a plexiglass bottom, and did the experiment. They dropped steel ballbearings from height into the the ketchup and timed the duration it took to drop one and the same spot that another had just traveled through vs a new spot. It worked and so they then worked on synthesizing 40 liters of a particular polymer that had that property (another significant effort - took much longer than buying 70 bottles of ketchup) but had the advantage that you could see through it.
One time a group of college students I hung out with got a bulk order of silly putty. This was fun to play with. Until someone had the idea of dropping it from about 6 feet up onto the floor. It shattered. Picking up slivers of silly putty from the carpeted floor was not fun.
Elsefluid ... a different category (shear thinning - https://en.wikipedia.org/wiki/Shear_thinning ) has it so that if you drop something through it, it takes {some time}. If you immediately drop another thing through it at the same spot, it takes {some less time}. One of the chemistry professors wanted to do some experiments with this type of fluid and had his grad students develop a proof of concept. There are some challenges with this - it can't be a thin cylinder of the fluid you drop it through since the distance to the walls is a variable in the speed too. It also needed to be a tall enough cylinder with enough viscosity that you could time it with a stopwatch (initially). One such fluid that has this property is ketchup. They bought 10 gallons of ketchup from the local grocery store (that's all that was on the shelf ... seriously, you need about 7x 20 oz bottles to make one gallon), poured it into a large cylinder... realized that they needed a clear bottom to see it, made a new cylinder with a plexiglass bottom, and did the experiment. They dropped steel ballbearings from height into the the ketchup and timed the duration it took to drop one and the same spot that another had just traveled through vs a new spot. It worked and so they then worked on synthesizing 40 liters of a particular polymer that had that property (another significant effort - took much longer than buying 70 bottles of ketchup) but had the advantage that you could see through it.