New 3-D printed materials harness the power of bacteria

A new type of 3-D printing ink has a special ingredient: live bacteria.

Materials made with this “living ink” could help clean up environmental pollution, harvest energy via photosynthesis or help make medical supplies, researchers report online December 1 in Science Advances.

This study “shows for the first time that 3-D printed bacteria can make useful materials,” says Anne Meyer, a biologist at Delft University of Technology in the Netherlands who wasn’t involved in the work.

The newly concocted printing ink is a polymer mix called a hydrogel that is blended with bacteria and a broth of nutrients that helps bacterial cells grow and reproduce. Eventually, the bacteria use up all of this built-in sustenance, says study coauthor Manuel Schaffner, a material scientist at ETH Zurich. But the ink is porous, so dipping a 3-D printed structure in more broth can reload it with nutrients, he says.

Schaffner and colleagues printed a grid embedded with a breed of bacteria called Pseudomonas putida, which eats the hazardous chemical phenol. When the researchers placed this lattice in phenol-contaminated water, the bacteria completely purified the water in just a few days.

“This result has big implications for the application of 3-D printing [to] clean up toxic chemicals,” Meyer says. Lattices packing various types of chemical-hungry bacteria could create special water filters or help clean up oil spills. And unlike free-floating bacteria, cells locked in a 3-D grid could be plucked out of cleaned-up water and reused somewhere else.

But the lattices printed for this study are just centimeters across, points out Jürgen Groll, a materials scientist at the University of Würzburg in Germany not involved in the work, so “scaling up is really going to be an issue if you want to deploy these commercially.”

Bacteria-filled 3-D prints could also produce bacterial cellulose — a gelatinous substance used for dressing wounds. Bacterial cellulose is typically grown in sheets, but “imagine if you have a burn on your elbow,” Schaffner says. “You try to wrap flat, wet tissue around this area, it’s prone to detach.” Swathes of cellulose grown on 3-D printed structures could precisely match the contours of specific body parts, curbing the risk of contaminants getting trapped under wrinkles in the cellulose or the material peeling off.

The researchers demonstrated this idea by mixing up a batch of ink laced with the cellulose-producing bacteria Acetobacter xylinum and printing a patch in the precise shape of a doll’s face. Leaving the material in a sealed container for a few days “nicely produced a cellulose film on top of the printed structure,” says study coauthor Patrick Rühs, a food scientist also at ETH Zurich.

Bacteria can be genetically modified to produce various proteins and other substances humans need, so 3-D printed bacterial materials may have many other medical uses, too. Groll imagines a kind of “smart Band-Aid,” for instance, infused with medicine-secreting bacteria to speed healing.