I think its paint (might be watered down) and its a very different process to waterdrops. This one is done with sound - a plastic "skin" stretched thin over a speaker - you then make a central blob of the paint and then turn on the sound The paint jumps up as the skin vibrates and you capture the shot.
If you really want to go serious with it a sound trigger plus some measure of being able to delay the shot after the trigger is set should allow for easier control.
Cornstarch slurry is a non-newtonian fluid, meaning it becomes solid when you exert force on it. I've seen those subwoofer demonstrations with it as well.. hard to tell if it's actually what's in this pic.
Ahh could be either material - though I'm fairly sure the examples I've seen done were with paint. Then again I'm sure varying the material and such will give different results so lots to experiment with.