I have a pretty specific problem that I'm trying to solve and I'm out of ideas. I can't divulge too many details, so I thought I'd use an example to describe my problem in general terms. I'm not sure if it's really possible to brainstorm using this forum, but I thought I'd give it a shot anyway, so here goes: If you were to design a device, like a salt shaker, that could deliver a very small dose of salt (around 20 mg) at a frequency of once every 10 minutes for 16 hrs, how would you do it? It has to be EXTREMELY small, and cheap and provide precision dosing to around +/-10%. Here's the challenging part, it has to deliver the salt underwater and not allow the salt that remains in the reservoir to get wet. It would be great if it could be completely self-powered and mechanical only (electronics might take up too much space). Any thoughts or ideas would be greatly appreciated and no ideas are too far out there.