It may seem odd to combine a printer with the bacterium E. coli.
Scientists have melded the virtues of the tool and the toxic microbe to create an ink that is alive. 3D-printed into various tiny shapes, such as a circle, a square, and a cone, hold their form and glisten like Jell-O, thanks to the ink flowing under pressure.
The researchers describe their recipe in a study published in the journal Nature Communications. The ink could be a crucial renewable building material, able to grow and heal itself, and ideal for constructing sustainable homes on Earth and in space, according to the authors.
This is not the first living ink. Scientists have previously created gels that were made frombacteria and polymers. The ink contained agents that made it thicker and more viscous.
The new substance is made from genetically engineered E. colibacteria. The ink is made of livingbacteria cells. When the ink is taken from the liquid culture, it becomes firm and can be plugged into 3D-printers and printed into living structures, which do not grow further and remain in their printed forms.
Sujit Datta, a chemical and biological engineer at Princeton University, was not involved in the research. You just have to feed the microbes and keep them happy.
It may seem like a strange building block. Scientists have already engineered microbes to produce plastic, which is a crucial component of products such as perfumes and vitamins.
An author on a new paper says that a material like a microbial ink has more grandiose ambitions. The field of engineered living materials has an expanding focus on such inks. Living systems cast from concrete or plastic would be able to regenerate, at least, according to Dr. Joshi.
Dr. Datta said to imagine creating buildings that heal themselves.
The best analogy is a seed becoming a tree. A seed has all the information it needs to grow into a tree, and organize its growth and development into something grand. A single engineered cell could function like a seed in an engineered living system.
Microbes are not great at making clearly defined shapes. Dr. Joshi said to think of pond scum. That is the level of complexity thatbacteria are comfortable with, in terms of making shapes.
Microbial inks rely on a scaffold to stiffen their scummy forms. Dr. Datta said that the mechanical properties of the ink can be changed in unwanted ways. The microbes don't die if the polymers are biocompatible. Synthetic polymers are derived from oil.
R. Knane Bay, a soft-matter physicist and an incoming assistant professor at the University of Colorado Boulder, was not involved with the research.
Many engineered living materials are made from hydrogels, structures that can absorb large quantities of water. The authors of the new paper, Dr. Joshi and Anna Duraj-Thatte, created a hydrogel from E. coli that could grow and regenerate.
The hydrogel was not stiff enough to stand on its own. Dr. Duraj-Thatte said you couldn't make structures.
The researchers had to firm up the substance. The team came up with the idea of using a blood-clotting agent called fibrin, which is a type of glue, said team member Avinash Manjula-Basavanna, who completed the work while he was a researcher at Harvard University.
The researchers genetically engineered the E. coli to produce a fibrin-based substance that can be used to link into a meshlike network. The material is stiff enough to print while still being able to flow from the nozzle of the 3-D printer.
The authors used the 3-D printers in the lab of Yu Shrike Zhang, a bioengineer at Harvard Medical School, which uses the printers for tissue-engineering mammalian cells. The lab was one of the few that was brave enough to let thebacteria in.
A lab that is only doing tissue engineering with cells would be hesitant about bringing inbacteria.
Dr. Duraj-Thatte said the lab would try many different things.
The image is.
When printed into a circle or a square, the ink remained stiff and did not swell or ooze.
A lattice grid, a box, a ring, and a cone were all printed into the ink to see if it could hold its shape. The ink was squeezed like toothpaste from the printer, but did not melt or ooze as it was printed.
They put the ink to a fidelity test to see how long a strand of it would last. In the test, the printer's nozzle stretched a half-millimeter-thick strand of ink across a line of pillars, each one a greater distance from the last, to show how far between pillars the ink strand could hold without breaking.
The strand was able to support its own weight between the pillars. They screamed with joy when they recorded the test in the lab. Audio was not included in the video that accompanied the study.
Dr. Duraj-Thatte and Dr. Manjula-Basavanna tested the printed structures against other microbes that had been engineered to perform specific tasks. The printed ink released the drug azurin when it was exposed to a chemical. The printed ink trapped the toxic chemicalBPA in a test, suggesting that the material could potentially remove harmful contaminants from its surroundings.
The ink needs a lot of work. It is not stable enough to be the sole basis of larger constructions, such as a house for a human, and the researchers are working on ways to make more robust printed structures. Researchers see no limits to its future applications.
Dr. Duraj-Thatte hopes that the ink can be combined with tissue engineering to make medical applications. The ink could be used to construct buildings. Dr. Bay wondered if the ink could be created from otherbacteria such as Pseudomonas putida, which can clean up the toxin phenol. Dr. Bay suggested that they could make them into biosensors.
Dr. Manjula-Basavanna wants to use the moon as a satellite because there are no forests to harvest for wood and no easy way to send bulk building materials. He said that the ink could be used as a self-regenerating substance to help build habitats on other planets and places on Earth.
There is a lot of work to be done to make it economically viable. He noted that five years ago creating robust structures out of microbes was unimaginable, and that self-healing buildings could be a reality in our lifetime.
Dr. Datta said it was hard to project into the future. The future looks very bright because of the pace in this area.
