Alright! We have a functioning 2D scanner. But I said that this was a 4-axis motorized microscope, so we still have two more motors to go: A small, linear stepper motor that serves as a Z axis, and a small, rotary stepper motor that actually spins our sample around. In the full version, they work in unison; the Z axis carries the mini stepper motor. The full configuration looks like this:

Like before, we have a 3D-printed main carriage (red) that slides along coupled to our big stepper motor. To this mounts a mini linear stepper motor (black), and optionally a circuit board with connectors and cables (green). Then, with a bolt/nut/washer (not shown), a second 3D printed piece (blue) fits into the linear stepper motor. And then to that, a mini rotary stepper motor (white/orange) snaps/slides into place. Finally, an adapter piece (transparent) is placed on the motor, with a needle (white) for stabbing things.

So first things first, we'll need a mini linear Z motor. This one actually comes from inside the optical pickup of the KES-400a! It's used to move a focusing lens back and forth for reading multi-layer blu-ray disks. All Blu-Ray players have one, but the KES-400a is the only one that I've seen which is so hackable, in that you can actually take it out of the player and run it separately. It has mounting points, a ribbon cable, 1 micron precision at 8th stepping resolution, and incredibly, an embedded optical interrupt switch that allows you to home it, just like the bigger motors. I've been searching for small motors that have all of these features for over a year and have yet to find one commercially, so let me know if you have any leads.

Remove the sheet metal cover on the optical pickup unit and peer inside at the glory of mass production and humankind's domination over the forces of nature. Once you are finished, take out the motor by removing and saving its 3 mounting screws (notice the super tiny washers!). For the next part, you will need an X-acto knife and a willingness to risk cutting yourself...

There is probably a better way to do this, but you will actually cut out the lens by (carefully!) picking at the glue holding it in place. There are three spots, and after you are done the lens should pop out if you pry a bit. But be careful, because the motors are almost as fragile as your fingers. Then save the lens, you can clip it to your smartphone or use it to read tiny messages...

Next, we are going to have to connect to that motor and optical switch. If you have the PCB, just plug it into the board. Otherwise, you are going to have to solder onto those 8 points.

Hoo, boy. Did I destroy a lot of motors. Do not attempt this as your first soldering experience, unless you have dozens to spare. But it absolutely can be done, and now that I know how, the fatality rate is much lower.

I'm going to assume you're an expert (and I'm running out of time to submit this), but quickly: Prepare your work space. Use a good, shiny, fine-tipped iron, thin fluxy solder, and color-coded flexible silicone wire (I've also used magnet wire). Snip and tin your wires and 2x4 sets of pin headers and attach one side of wires. On the other end, trim the wire until just a bit of metal is exposed, and once the motor is gripped in the gentle embrace of a vise, you can solder, following the charts and schematics above.

Great! One way or another, the Z axis is wired into the system. It runs just like our X and Y axes, except it uses that optical endstop instead of a mechanical one, and it has a range of three whole milimeters. You can use it to carry stuff like a coverslip slide or other tiny stage, or (as I assume you want to) you can lift up a rotary motor.