I have been working on several low cost tools for biology, and yesterday it occurred to me to try to make a vacuum manifold. a vacuum manifold is used to facilitate large volume DNA preparations by applying vacuum to the bottom of the filter column. They are quite expensive, but simple devices; they are just a gang valve that hooks up to a vacuum pump, generally via luer lock. As a note, you still have to centrifuge the tubes after you filter them (even in commercial models), but this might be helpful if you have a tiny centrifuge and a lot of preps to do.
My version is simple and cheap, and it works! There are two main components: the vacuum pump and the manifold.
The first manifold was manufactured from POM, aka Delrin. A few notes on delrin: it is incredibly tough, and smells like fish when machined. The manifold was basically three holes drilled perpendicular to the axis of a 3″ piece of delrin. The axis was drilled to a depth of about 2.75, and a hose barb was connected to the end, where I applied the vacuum. This iteration was a big fail, because the seals on the tubes were not soft or, the right size (I just had them lying around). This meant that there was a lot of leakage, and that made it not work, despite looking nice.
While I was testing various parts of the system to find the leak, I found out that 3/16″ tubing, or “standard airline tubing” for fish tanks is the perfect fit for the little nipple on the bottom of silica prep columns! This led me to a less mechanically stable, but totally working connection.
I happened to have a 5-way gang valve (teal thing) from an aquarium in the lab, from the algae bioreactor project. I rigged up four tubes to fit hypothetical silica columns, and one that went to a water intake. This is used to help purge air bubbles from the system.
This setup worked surprisingly well! If I had a vise big enough to clamp down the gang valve, it would be a totally functional manifold. Unfortunately, it was just a hair too big for the vise and the pump was not ergonomic enough to prevent the pumping from moving the manifold around.
Here is the vaccum pump. Nothing fancy- it is just two aquarium check valves, some aquarium tubing, a T connector, and a syringe (for feeding babies formula/medicine) from CVS. The tubing just slips on the tip!
I have considered rebuilding this by replacing the gang valve with a bunch of T connectors, or by upgrading the delrin part, but there are two problems. First, you would have to re-plumb the whole system if you wanted to do a different number of preps than last time. Two, the first prep to drain through the system is going to start to suck a bunch of the air into the system. Much like a hole with a straw in it, or two unequal resistors in parallel, most of flow will be coming through the path of least resistance, reducing the draw on the other samples. With such a sucky (haha, couldn’t help myself) vacuum system, this is going to make the device useless.
This vacuum setup is good for anyone who is interested in DIYBIO and cannot get access to an autoclave, of a large centrifuge. This can be used to filter sterilize media, and bleach can do the sterilizing on the other end. As you can see here, it can take some of the load off the centrifuge. I don’t know if small centrifuges are significantly slower at filtering than large ones, but I do know that they can’t hold as many samples, so something like this could speed that process up!