Nature can create biocomposites with high structural complexity and mechanical integrity from a small number of elements. Natural materials have unparalleled mechanical properties due to the unique interplay of hierarchical structure and locally varying composition.
It has an extraordinary talent for creating composite materials that are both light and strong, porous and rigid, such as mollusk shells or bone. However, producing such materials in a lab or factory is extremely difficult, especially when using environmentally friendly materials and processes.
Nature provided a solution to researchers in the School of Engineering’s Soft Materials Laboratory. They are the first to develop a 3D printable ink containing Sporosarcina pasteurii, a bacterium that, when exposed to a urea-containing solution, initiates a mineralization process that results in calcium carbonate (CaCO3). As a result, the researchers’ ink, dubbed BactoInk, can be used to 3D-print virtually any shape, which will then gradually mineralize over the course of a few days.
Lab head Esther Amstad said, “3D printing is gaining increasing importance in general, but the number of materials that can be 3D printed is limited for the simple reason that inks must fulfill certain flow conditions,”
“For example, they must behave like a solid at rest while still being extrudable through a 3D printing nozzle – sort of like ketchup. 3D printing inks containing small mineral particles have previously been used to meet some flow criteria. However, the resulting structures tend to be soft or shrink upon drying, resulting in cracking and loss of control over the final product’s shape.”
“So, we came up with a simple trick: instead of printing minerals, we printed a polymeric scaffold using our BactoInk, which is then mineralized in a second, separate step. The mineralization process triggered by the bacteria in the scaffold results in a final product with a mineral content of more than 90% after about four days.”
As a result, a strong and resilient bio-composite can be created using a standard 3D printer and natural materials, without the extreme temperatures required for ceramic manufacturing. The final products are submerged in ethanol at the end of the mineralization process; hence they no longer contain living bacteria.
The procedure was recently described in the journal Materials today. It describes the first 3D printing ink that used bacteria to induce mineralization.
The concept presented by the Soft Materials Lab has several potential applications ranging from art and ecology to biomedicine. Amstad believes that BactoInk, which can also be directly injected into a mold or target site – such as a crack in a vase or a chip in a statue – could greatly simplify the restoration of artworks. The mechanical properties of the ink provide the strength and shrinkage resistance required to repair a work of art while also preventing further damage during the restoration process.
Amstad said, “The versatility of the BactoInk processing, combined with the low environmental impact and excellent mechanical properties of the mineralized materials, opens up many new possibilities for fabricating lightweight, load-bearing composites that are more akin to natural materials than to today’s synthetic composites,”
The environmentally friendly components used in this procedure, along with its capacity to create a mineralized biocomposite. It is a promising candidate for creating artificial corals to help regenerate damaged marine reefs. Finally, the biocomposite’s structure and mechanical properties are similar to those of bone which could make it appealing for future biomedical applications.
The result shows that they were present 3D printable bacteria-loaded microgels that can be converted into macroscopic organic solid/inorganic composites with mineral contents by using an energy-efficient MICP process.
Journal Reference:
- Hirsch, M., et al. 3D printing of living structural biocomposites. Materials Today. DOI: 10.1016/j.mattod.2023.02.001
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