I need a way of dispensing a drop of water from an electronic signal, and am wondering if there are any devices which can do this cheaply. The volume doesn't need to be particularly precise, but I'm talking about a single drop of water. All the solenoids I've come across are for large volumes (e.g. irrigation), and generally require a certain amount of pressure in the line to activate. Is anyone aware of any low volume solenoids?
I was considering something like a tube that is squeezed by an actuator of some sort to close it (mostly, and rely on surface tension to keep it from otherwise flowing out); might this work? Alternately, something like a syringe pump like they have in hospitals, but I imagine these are pretty expensive.