Building a Micromanipulator

Over the last month of so I have built a micromanipulator that should be capable of single cell work. I say should be as I still lack much of the equipment to test it properly. That said, it can move in all the directions it is meant to as well as being able to inject and aspirate liquid. I built it with the intention of cloning frogs and it should be more than precise enough to do that. I'm not confident that I could use it for mamalian somatic cell nuclear transfer but I also have a laundry list of improvements to make before giving up on the idea.

I won't pretend that I had the basic idea for this. I followed this paper for sourcing parts and cad. I've made some substantial modifications but the general form is the same. The cad I did from scratch although many of the parts were heavily inspired by theirs. I'm not sure if they had slightly different stepper motors or just access to a more capable set of tool than I do, but I couldn't use their modified stage which required a fair bit of novel design work to get around. I also made some changes to the circuit design to accommodate my only having an arduino uno instead of a mega as they used. It arguably has less functionality in this respect but it has the same number of degrees of freedom and precision so I consider it a success.

I would make my designs available, but I would strongly recommend just working from the paper or making more substantial modifications than I did. In either case, my cad is probably not the best starting point. That said, if I get around to my version two with all the upgrades I'm imagining, that I will certainly release.

Here's a not especially good video showing off the basic functionality.

The four buttons on each side control movement in some direction, x, y, z, or the injector. The black button in the middle toggles the resolution. The LED indicates what resolution mode the system is in. The potentiometer controls how much liquid is moved. Sorry the video isn't overly clear. Trying to film through the microscope is challenging and I haven't gotten around to getting a better microscope or even printing some kind of adapter. The whole thing works but I haven't tested it as well as I would like. I think the minimum step size is something like 3 micrometers and the minimum volume of liquid is around half a nanoliter. That's in an ideal case, there's spring and friction in the system so I have to work on bringing those down. Still, the original goal was to clone frogs and I'm confident that this is good enough for that.

So what do I need to test it properly? I need a better microscope so that both the sample and the microinjector are in focus simultanesouly. As it stands, the working distance of my microscope won't allow this. The highest magnification also can't be used since the objective interferese with the microinjector. An inverted scope should fix both these issues. I need some manner of cell culture to move around. Bacterial cells are relatively easy to get but it is my understanding that their much smaller. They also aren't something I have just lying around my apartment and biolabs are full well intentioned rules that keep strange folks like me from asking for their cells. I could buy and culture them with relative ease but it is a rather large diversion just to test the project. Mamalian cells would be nice but you often need trypsin or some other enzyme to free things up from tissue samples. I tried taking my own blood but red blood cells are some of the smallest in the body, white blood cells are rare. I don't want the test run to be when I actually try and clone frogs but it might have to be. I don't really have the time or space to do good cell work right now.

As for improvements, I've thought of many. The biggest one by far is the rigidity of the frame. I don't know the best way to accomplish this but I have some ideas. As shown in the video, the whole thing shakes. This isn't from the 3D printed parts not being rigid enough, although that probably doesn't help. No, the steel shafts that came with the stepper motors are flexible. I can bend them with my finger and thumb. The first order of business is buying larger diameter shafts or proper linear rails. If you decide to make a similar project I would recommend starting there as the added cost is not be substantial. I'd like some more precision, especially on the injector. The x, y, and z are ok. They're a little jerky from microstepping but they get the job done. The minimum injector volume is still probably two or three orders of magnitude more than the volume of a single cell. I don't need it to be exactly one cell's volume, especially because that's pretty variable, but I would like it a little lower. They sell smaller micro syringes so I have an easy place to start. Other than that I would just need better stepper drivers and finer pitch threads. All of these are still affordable relative to the commercial micromanipulators. I'm actually pretty happy with the controls but I'd like to move everything to a custom pcb so it isn't so ugly.

If you want to recreate this but want to source the components from more familiar sources than listed in the paper, here are some of the stranger components that can be found on Amazon. Actually, everything in the paper can be replaced with something on Amazon with various degrees of success.
Micro Syringe
Stepper
Glass tubing for micro needles
Small bore silicone tubing
One of my biggest complaints is with the steppers. They work but they are really not precision instruments and I would strongly recommend making your own linear stage, I'm sure you can do a better job.