The centrifuge was designed in Fusion 360, and was apparently as easy as drawing a few circles and hitting copy and paste. Interestingly, this fidget spinner was designed to be completely 3D printable, including the bearings. The bearing is a standard 608 though, so if you want to get some real performance out of this centrispinner, off-the-shelf bearings are always an option. The design of this fidget spinner holds 2 mL and 1.5 mL vials, but if your lab has 500 μL tubes on hand, there are handy 3D printable adapters.
Still think using a toy to do Real Science™ is dumb? Contain your rage, because a few months ago a few folks at Stanford devised a way to build a centrifuge out of paper. This paperfuge can — at least theoretically — save lives where real commercial centrifuges or even electricity aren’t available. Fidget spinners save humanity once again.