Introducing: The Bioprinter

3D Printing has risen to an undeniable level of popularity in the last years. From something that was hardly known to be possible to the public, 3D printing has made it to public access. Projects like the RepRap and the Makerbot have gained some momentum. My own project team, Fab@Home has done its part to contribute to this community.

So here’s where I enter. My main interest with 3D printing technology was to apply it to bioengineering. Take some cells from various tissues you want to reproduce, and culture them in a bio reactor. When the cells are sufficient in quantity, load them up in some form of semisolid gel and extrude them with extreme accuracy. Under the right biotic culturing conditions, and with the right blueprints and precision, you can reproduce tissues. Combine those tissues, and voila! ORGANS.

But it doesn’t just stop there. Of course you can satisfy the organ donor waiting list and help hundreds of thousands of people live normal lives again. But there is more. Say you have vestigial features you have in an organ that you could be better off without. Why not harvest some cells and rebuild a new, better organ to accomplish what you need more efficiently? With organs made with your own cells, there would be no chance of rejection. Organ printing can do things impossible to achieve with regular evolution.

There’s more. My brother suggested this one to me. In agriculture, highly developed breeds of corn are developed through genetic modification. Each corn plant must be propagated by hand by trained technicians. But with 3D bioprinting, there is so much more you can do. Engineer a convenient capsule to house the plant and artificially create your own seed packets for an otherwise fragile sterile plant! Print these out in mass quantities to grow crops that are otherwise unreasonable to use. Of course it’s a stretch in development, but I’m sure engineers will not fail to impress with their innovations.

Now imagine layering cells from different organisms together so closely that they develop in unison and equal to one another. Imagine a chimeral tree that produced different fruits at different times throughout the year, or an animal that contained the genetic material of different species that were otherwise incompatible. Imagine silicon printed with living cells. Transistors and neurons printed together to form viable human/machine neural networks! You can tell I’m excited about the possibilities with this technology.

So here’s my first 3D printer:

Only the chassis is shown + motors. If may not be the most efficient mechanically, but I’m proud to say that this printer was entirely of my design. Only if you count the current extrusion tool too, which I modified and developed as my assignment on the Fab@Home team. The whole thing is made of acrylic, which I got cut since I don’t own a laser cutter (though it would be nice considering the reasonable cost of these lasers).

Here are some of my CAD drawings in designing this thing. On and off, acquiring the parts (it’s surprising how difficult it is to find accurate 3/8″ aluminum rods) and designing the printer took part of my fall semester. I didn’t have time to get the acrylic and assemble the whole thing until winter break when I got home.

First iteration concept. I tried to make the extrusion surface independent of the 3-axis gantry to make sure vibrations from the motors wouldn’t perturb the printed object.

Second iteration (I discovered the scene/render option in SolidWorks)

With the stepper motors and the 1/4″-20 standard (not the expensive Acme stuff) threaded rod, the setup can theoretically reach tens of microns of resolution with microstepping. However, due to the inaccuracy of my extruder, that resolution probably won’t make much of a difference. The extruder I have is a syringe with a plunger that is driven by a drive screw that is driven by a continuous rotation servo motor.

Comically, the syringe tubes were taken from the sharps disposal section of my lab (it probably wasn’t that wise of an idea). Good thing the lab wasn’t dealing with anything medical. I will have to replace them with sterile tubes once I begin wet testing, since contamination is a huge issue.

Here’s the extruder:

Clear acrylic looks nice, but it’s terrible to photograph effectively.

I’m using EasyStepperDrivers from Sparkfun to drive the stepper motors in this project. Coupled to an Arduino coupled to ReplicatorG (for now until i develop my own), I’ll have to make a custom .xml file for the servo extrusion configuration.

The next challenge for this project is to get viable structures to print. It’s a difficult problem right now for bioprinting, as finding a 3D blueprint of an organ or biological structure requires identifying hundreds of different materials. My two material setup probably won’t be able to accomplish that, so for now I’m stuck printing with two materials.

I’m ordering sodium alginate + calcium chloride to experiment with. When mixed, the calcium causes the alginate to form closer bonds and become more solid-like. With some living cells in between, I can hopefully build up some reasonably sized structures. I intended to use the cells from a rosebush on my lawn, but my winter break is proving to be too short for me to culture the cells now. Added with an internship at an electrical/civil firm I’m working for right now, it’ll have to wait till the semester. I hope I have time.

I was debating between two styles of approaching bioprinting. Some scholars researching bioprinting use inkjet technology to deposit bio-ink laden with living cells to deposit many small layers of living cells to build up tissues. Since the volume of the drop of liquid ejected from an ink-jet is reasonably close to the volume of a cell, the inkjet can reliably deposit cells to their target. However, inkjets use bubbles generated by heat from a resistor or by mechanical shock to create such precise droplets of ink. Therefore, cell survivability is an issue. The other approach is to bundle many cells into workable unit voxels. The larger units could be placed accurately while maintaining cell survival. I’ve decided to make both systems.

Coming up next semester, (if I can get access to a biolab) actual printed cells! And a belt drive inkjet system.


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