There is now a method to make bone-like material with the 3D printer. The researchers see opportunities for medicine, coral restoration, and restoration of artifacts.
Nature has an extraordinary talent for producing composite materials that are light and strong, porous and rigid at the same time, like mollusks or bones. But producing such materials in a lab or factory – especially using environmentally friendly materials and processes – is a huge challenge.
Researchers at the TU’s Soft Materials Laboratory in Lausanne turned to nature for a solution. They have developed a 3D-printable ink that contains Sporosarcina pasteurii: a bacteria that, when exposed to a urea-containing solution, initiates a mineralization process that produces calcium carbonate (CaCO3) produces. As a result, the researchers can use their ink – called BactoInk – to 3D print virtually any shape, which then mineralizes over the course of a few days.
“3D printing in general is becoming increasingly important, but the number of materials that can be 3D printed is limited for the simple reason that inks have to meet certain flow conditions,” says lab head Esther Amstad. “For example, they need to behave like a solid at rest, but still be extrudable through a 3D printing nozzle – a bit like ketchup.”
Amstad says that 3D printing inks with small mineral particles have been used before to meet some of these flow criteria, but the resulting structures are often soft or shrink on drying, leading to cracking and loss of control over the shape of the final product .
polymer structure
“So we came up with a simple trick: instead of printing minerals, we printed a polymer structure with our BactoInk, which is then mineralized in a second step. After about four days, this leads to an end product with a mineral content of more than 90%.”
The result is a strong and resilient biocomposite that can be produced using a standard 3D printer and natural materials, and without the extreme temperatures often required for ceramic manufacturing. End products no longer contain live bacteria, as they are immersed in ethanol at the end of the mineralization process.
The method, which describes the first 3D printing ink that uses bacteria to induce mineralization, is published in the journal Materials Today.
Patch up art, coral reefs or bones
The Soft Materials Lab’s approach has several potential applications in a wide variety of fields from art and ecology to biomedicine. Amstad believes that the restoration of artworks can be greatly facilitated by BactoInk, which can also be injected directly into a mold or target location, such as a crack in a vase or a chip in a statue. The ink’s mechanical properties give it the strength and shrinkage resistance needed to repair an artwork and prevent further damage during the restoration process.
The method’s use of only environmentally friendly materials and its ability to produce a mineralized biocomposite also makes it a promising candidate for building artificial corals, which could be used to help regenerate damaged marine reefs. Finally, the fact that the structure and mechanical properties of the biocomposite mimic those of bone could make it interesting for biomedical applications.
Mid-impact lage
“The versatility of BactoInk processing, combined with the low environmental impact and excellent mechanical properties of the mineralized materials, opens up many new possibilities for manufacturing lightweight, load-bearing composites that are more akin to natural materials than to today’s synthetic composites. ”, summarizes Amstad.