Quote Originally Posted by kb3lms View Post
I 've made myself a hand crank syringe pump and use 18 gauge needles and nylon (I think) tubing. The tubing came from empty hair spray bottles. It's not really not that hard to control delivery rate.

Since I've worked in analytical chemistry labs, I have experience with peristaltic pumps.

From Wikipedia: A peristaltic pump is a type of positive displacement pump used for pumping a variety of fluids. The fluid is contained within a flexible tube fitted inside a circular pump casing (though linear peristaltic pumps have been made). A rotor with a number of "rollers", "shoes", "wipers", or "lobes" attached to the external circumference of the rotor compresses the flexible tube. As the rotor turns, the part of tube under compression is pinched closed (or "occludes") thus forcing the fluid to be pumped to move through the tube. Additionally, as the tube opens to its natural state after the passing of the cam ("restitution" or "resilience") fluid flow is induced to the pump. This process is called peristalsis and is used in many biological systems such as the gastrointestinal tract. Typically, there will be two or more rollers, or wipers, occluding the tube, trapping between them a body of fluid. The body of fluid is then transported, at ambient pressure, toward the pump outlet. Peristaltic pumps may run continuously, or they may be indexed through partial revolutions to deliver smaller amounts of fluid.

They have a nice animation the Wikipedia page in case you are a visual person... http://en.wikipedia.org/wiki/Peristaltic_pump

I think peristaltic pumps work better for this type of application, especially for flows in the 1 ml or so per minute range compared to syringe pumps. The stepper motor in a syringe pump is not running continuously, so it's constantly squirting out little bits of fluid, like a discrete automotive fuel injection system (not a CIS system) or like a ink jet printer. Little drops, not continously, over time. Also, a peristaltic pump is not limited by the size of the syringe. (Although you can replace the syringe in a syringe pump to get volumes larger than what 1 syringe can hold.)

A peristaltic pump has a motor that runs in a much smoother fashion, and it is constantly pushing liquid out. You control the flow in a peristaltic pump by varying the motor speed and the diameter of the pump tubing. You can get a pretty wide range of flow from a peristatlic pump depending on the setup, from 0.001 ml/minute to hundreds of mls per minute. It just depends on the model of pump, the speed, and the tubing size.

Here's some photos of the set-ups I had been working on a couple years ago:

First Photo -
This set-up for a single channel pump. The stirplate has a built-in heater, and there is a temp controller (reading 41C mounted onto a ring stand that attaches to the back of the hot plate. Also attached to the ring stand, is a clamp that hold a stainless tube that I have a thinner teflon tube inserted through and then the bottom end goes into the solution in the beaker.

That teflon tube is connected to a silicone peristaltic pump tube by merely inserting the teflon tube into the silicone pump tube. The other end of the silicone pump tube goes into the graduated cylinder which is holding the silver nitrate solution.

The 3rd thing in the beaker is a kitchen temp meter (the one with the right-angel bend at the top) and you can see it reads 40C on its display.

I use a large, X-shaped, teflon-coated stirbar to get as much turbulance and mixing as posible.

Second photo -
Here's a close-up of the beaker and pump. You can see the end of the teflon tube that goes through the stainless tube. The stainless tube is just to hold the thin trflon tube. (I think the teflon is 24 or 28 ga. I have some that goes down to 36 ga. but I never tried it.) Since the teflon tube that thin is not stiff at all, it needed something for support. I had the stainless tube sitting around, so I used that. Otherwise, I would have taken some glass tubing and used it. I preferred the stainless as I didn't have to worry about breaking it!

You can see the teflon coming down from the end of the stainless tube (off frame to the top) and into the polyvinylchloride peristaltic pump tube, which is a larger diameter. The little teflon tube is just butt-connected to the larger pump tubing merely by pressing it into the pump tube. If the difference in size between the two tubes is too great to do this, an intermediate size of pump tube can be used to go between the bigger and smaller tubes. No fittings are required using this technique.

You can see the little lever on the pump platten that is used to apply pressure to the tube to firmly bring it into contact with the pump rollers. This pump has 8 rollers, which will give a smoother flow than a pump that uses say 2 rollers.

Below - The tip of the dual solution nozzle. The tubing is 24 or 28 ga teflon tubing. One of the tubes is inserted into a long stainless tube for rigidity, the second teflon tube is strung on the outside of the stainless tube. They are held in place with short sections of PVC tubing, a smaller one to keep the teflon tube that's inside the stainless from pulling up into the stainless tube, and a larger one around the stainless tube and the second teflon tube.

Note that the teflon tubes have very small opening. I have them mounted so that they are as close to each other as I can get them. They are also open perpendicular to the flow of the liquid past them to get the liquid to shear off the tip of the nozzles so the solutions get dispirsed into the make as quickly as possible.

Below - Peristaltic pump set-up with two pump channels bring used. One for silver nitrate, the other for halide. You can see there pump nozzle in the beaker and behind it is the temp probe for the stirring hotplate. The two channels are loaded into the peristaltic pump, the close one has the platten for the pump tube tightened down so the liquid would flow, and back one has the platten loose to the pump is not flowing in that channel.

Note the hemostat is being used to pinch the back pump tube shut so it does not siphon liquid out of the beaker! To put the back pump into operation, all that needs to be done is flip the plastic lever on the platten down and to the left to tighten the platten against the pump tube and release the hemostat.

Below - The full setup in the darkroom. Red LED lights with rubylith over them just because... Laptop with rubylith of the screen - spreadsheet with all calcs and times for the make pulled up so it can bee seen and consulted during the run (and to play music - I was in there for hours...) Clipboard to make notes and record timing/addition times. Stirplate with temp controller, peristaltic pump, reagents prepped in plastic cups, darkroom timer running in 24 hr clock mode so I could easily see and record times.