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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.

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    I'm voting to close this question as off-topic because it is not about IoT. Microfluidics is its own field that bears researching in proper contexts - common technologies including peristaltic pumps (potentially stepper driven), syringe pumps, micro-pipettes, micro solenoids, etc. Often the biology people are the primary users, as they tend to want to work with smaller sample quantities than physical chemists. For non-medical applications many of these have cruder DIY forms. Once you have your actuator, if there's an IoT control aspect, that might make a suitable question. – Chris Stratton Oct 9 '17 at 21:30
  • Just to toss out an example, some soap bubble blowing toys have a peristaltic pump in them, or you can 3d print one, connect this to a stepper with microstopping drive. Or you can get very fine unidirectional motion with a screw to drive a syringe fixed to a board. – Chris Stratton Oct 9 '17 at 21:35
  • @ChrisStratton - understood; can you suggest which stack exchange site might be more suitable? – askvictor Oct 9 '17 at 22:04
  • There isn't necessarily going to be a stack exchange site for every purpose, and "what can I buy to accomplish X" sort of questions are generally off-topic system wide, except in a few places where explicitly allowed. Ultimately this is probably something you want to pursue via web searching; sometimes that might yield an incidental mention in the context of a more classically fitting question on an SE site. – Chris Stratton Oct 9 '17 at 22:11
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    @ChrisStratton yeah I get you, but I posted here after a lot of web searching didn't yield anything. The bubble toy example was great and I wouldn't have thought of that (I also got a couple of suggestions in /r/engineering ,which is also tenuous), and is the kind of thing that comes up in forums like this. I guess the question to consider is whether a question is in the spirit of the rules. – askvictor Oct 10 '17 at 1:05

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