It seems as though we can 3D print with just about anything these days – glass, sand, food substances, human cells, you name it – but one substance I never would have thought to put into a 3D printer is bacteria. The first question that might come into most people’s minds is, “Well, why would you?” As it turns out, there’s a pretty good reason, according to researchers from Delft University of Technology (TU Delft).
If you’re familiar with the 3D printing industry, you’re likely familiar with graphene and how excited everyone is about it. It truly is a brand new material, having been first successfully isolated in 2004 and patented for 3D printing less than two years ago, and its super strength, flexibility and electrical conductivity make it highly desirable for manufacturers in all areas. What the TU Delft researchers discovered was that if you place certain types of bacteria on flat sheets of graphene oxide, they can turn it into a reduced version of the compound by pulling oxygen atoms off the material as they metabolize.
That reduced compound has many of the same properties as graphene, but is easier to produce in large amounts. Reducing graphene oxide isn’t a first; it’s normally done with chemicals or high heat, but using bacteria is a lot cheaper and more environmentally friendly.
“The more you reduce [graphene oxide], the closer it is to graphene,” said Dr. Anne Meyer of TU Delft’s Department of Bionanoscience. “It’s very easy – it takes place at room temperature in some sugar water.”
While the traditional means of reducing graphene with heat or chemicals is still more effective, the bacterial method could be very useful in the production of precise, small-scale graphene structures – such as those produced with a 3D printer. In a paper entitled “A Straightforward Approach for 3D Bacterial Printing,” Dr. Meyer and her colleagues, Benjamin A. E. Lehner and Dominik T. Schmieden, document how they modified a $300 CoLiDo 3D printer by replacing the extruder with a pipet tip and tubing system.
“This alteration allows the liquid biological ink (‘bioink’) to be transported under ambient temperatures that are amenable to microbes, rather than the elevated temperatures that are applied to melt plastic filament,” the team explains. “A secondary pipet tip was affixed to the printhead to allow for rapid alternation between the deposition of different types of bioink. A syringe pump was added to the system to generate continuous but adjustable flows of bioink through the sets of tubing into the pipet tips.”
The bioink was created by combining live E. coli bacteria with an alginate gel that, when extruded onto a calcium ion surface, solidified to form a firm scaffold. It’s similar to the bioprinting technology that we see used in the creation of human tissue, except that it uses the cells of bacteria instead of humans. The TU Delft researchers’ ultimate goal isn’t to 3D print E. coli, thankfully – their initial work has so far only been to show that bacteria can be successfully 3D printed. The real goal is to 3D print a type of graphene oxide-reducing bacteria called Shewanella oneidensis onto 2D sheets of the material in specific patterns that will allow the researchers to carefully tailor its properties.
For example, Dr. Meyer said, eventually it may be possible to carve tiny conductive wires into the surface of the graphene oxide to make certain parts of it conductive while the rest remains non-conductive. They’re not to that point yet; the key now is finding a way to print the bacteria with enough growth medium that it lives long enough to reduce the graphene oxide without losing its precise shape – a difficult balance to strike.
Once they do refine the technique, though, they plan to shoot for the moon. Dr. Meyer and her team intend to find out if it’s possible to use similar technology to modify substances found in lunar dust, which could eventually allow us to 3D print electronic devices in space. Currently, they are working with bacteria to try to turn silica and iron oxide from replicated lunar soil into silicon and iron.
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