Materials

3D Printing With Bacteria Promises Revolutionary New Materials

A team of researchers has developed an inexpensive method for 3D bacterial printing, a technique that could be used to develop mother-of-pearl fake teeth, powerful microlenses, and graphene.

A team of researchers in Holland have pioneered an inexpensive method for 3D printing bacteria into shapes and patterns, opening the door to a wide range of potential real-world applications from mother-of-pearl fake teeth to powerful new microlenses that boost the effectiveness of solar panels or cameras.

The lab is already using the technique to 3D print plaque onto cow's teeth as a potential avenue for studying oral hygiene.

The technique could also be used in the bacterial production of graphene, the one-atom-thick material that is both the thinnest and the strongest compound ever discovered, with over 100 times the strength of steel.

"The possibilities are really wide-ranging — I could imagine materials in so many different categories," said Dr. Anne Meyer of the Delft University of Technology in the Netherlands, one of the lead scientists of the team and an author of a paper on the technique.

Once viewed as something of a novelty, 3D printing has found a widening variety of applications from the production of artificial bones and organs to a candy store in Chicago that lets customers 3D print gummy bears into any shape they want. In 2014, astronauts 3D printed a special wrench in space to repair their spaceship after NASA sent only a digital design file for the tool to the craft.

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The team in Holland developed their method by modifying a $300 commercial 3D printer.

That low price tag is significant, because it makes the approach widely reproducible. Techniques for cellular printing for biological or medical applications are generally much more expensive, ranging from $5,000 to $200,000.

Over-the-counter commercial 3D printers operate by heating plastic to make it liquid enough to be patterned by the print-head. But that kind of heat kills bacteria.

So the team removed the heater from the print-head, and affixed a syringe filled with liquid bacteria. They used a syringe pump controlled by a custom computer program to control output.

"Then we had to develop some chemistry to make sure the bacteria stays where you print it," Meyer said.

That involved mixing the live bacteria with a polymer called alginate, which solidifies when it touches calcium ions.

"As long as we have calcium on the surface, then as soon as the bacteria hits it, our stripe of bacteria becomes a rigid scaffold," said Dr. Meyer.

Internal structure of printed layers. Modified strains of E. coli expressing two different fluorescent proteins were printed one on top of the other in a 2-layered square. After 24 hours of incubation, the internal structure of the printed bacterial layers was inspected by confocal microscopy.

Once in place, bacteria can carry out advanced chemical reactions to create a wide range of materials, many of which could be modeled from the natural world.

"There are several species of animal that can make bioglass," said Dr. Meyer, including sea sponges that use it for internal skeletons.

Borrowing that technique could lead to microlenses that increase the efficiency of light collection, from photography to photovoltaic electricity production.

The team is already 3D printing plaque, the bacterial biofilm that grows inside the mouth, onto teeth β€” with an eye towards helping those who study oral hygiene figure out how to get rid of it.

Rather than use fake teeth, the researches opted for the genuine article. "My student went down to the butcher and got some cow teeth," Dr. Meyer said. "It's kind of funny, because he's a vegan."

"Our engineered bacteria stick much better to the cow teeth than non-engineered bacteria," Meyer said.

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Their approach to 3D printing bacteria may also prove effective in constructing objects out of graphene β€” the buzzy supermaterial that, as a sheet of carbon atoms, is harder than diamonds and conducts electricity more efficiently than copper.

One approach to making graphene starts with another chemical precursor called graphene oxide, and then chemically reduces it.

"Chemical reduction approaches are typically very energy intensive, and can make a lot of chemical waste," Meyer said.

A specific strain of bacteria, on the other hand, can serve as a reducing agent, stripping away oxygen atoms from the material.

"We can mix up graphene oxide with this bacteria, leave it on the counter overnight, and when we come back the next day, it has made graphene by reducing the graphene oxide," Meyer said. "You don't have to have a chemical lab to do it."

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