Markerfuge [expo whiteboard marker reviver]
https://www.youtube.com/watch?v=DPbsY0JJ8rM
All this does is spin whiteboard markers very fast to draw ink to the end of an otherwise pronounced dead marker.
Schools go through hundreds of these, and I know that this is just a temporary solution to the issue. I did this for fun but was more surprised by how effective it was.
It is compatible with lego technic axles, because I don't really have any other motors lying around. You can do any kind of gearing you like to increase the speed.
Press fit the markers into the rings with the ends facing out and put the cap back on to secure it.
Right now this only holds Expo markers, or any others that share the same shape and size would be fine.
All parts are made to be printable with no supports, and no hardware necessary (see video). the small hook-type things on the base are flattened slightly to print on that side. You can use a brim on those if needed.