Tell us about yourself!
One of the variations on the "aspirin in the thermostat" gig is to put metal thumbtacks on either side of a clothespin with an aspirin in between the tacks. When water hits the aspirin, it dissolves and the thumbtacks touch. Viola, a flood water detector. (Right now Houston needs a boxcar of aspirins.)
Easy 3D Printing
Ferric Chloride is nasty stuff AND it stains whatever it touches poop brown --- hands, shirts, jeans ...Much better etchant AND locally available is swimming pool muriatic acid from the home improvement store. Mix it 2 parts water to one part muriatic acid. Throw in about 5% by volume hydrogen peroxide if you want to etch faster.Alcohol is the recommended solvent for magic marker. Don't use the tequila afterwards in a margarita!!