Mineralizing bio-composites with 3D printable bacteria ink


Not all bacteria kill. For the researchers in the Soft Materials Laboratory of the School of Engineering at the Swiss Federal Institute of Technology Lausanne (EPFL), bacteria can restore damaged objects, architecture, and even public artworks such as underwater marine reefs and sculptures. They can rebuild underwater additives or seal the cracks of different items. 


The researchers have developed a 3D printable ink infused with bacteria called Sporosarcina pasteurii. When exposed to a urea-containing solution, this bacterium triggers a mineralization process that produces calcium carbonate. The 3D printer-reader bacteria-loaded ink, or BactoInk as the researchers call it, can materialize any shape from its liquid form and be mineralized, or hardened, after a few days.


‘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 fulfil certain flow conditions,’ explains lab head Esther Amstad. ‘For example, they must behave like a solid when at rest, but still be extrudable through a 3D printing nozzle – sort of like ketchup.’

bacteria ink 3D printer
images courtesy of EPFL | photos © Eva Baur



The researchers believe that their 3D printable bacteria ink can produce mineralized bio-composite. Such a technique results in strong, light, and environmentally friendly objects and can be adapted to a range of applications from art to biomedicine.


The strong and resilient bio-composite, which can be produced using a standard 3D printer and natural materials, may come out well without the extreme temperatures often required for manufacturing ceramics. Final products no longer contain living bacteria, as they are submerged in ethanol at the end of the mineralization process.

bacteria ink 3D printer
the liquid ink can harden and mineralize in a few days



An alternative to restoration processes


Amstad and the EPFL researchers — namely Matteo Hirsch, Lorenzo Lucherini, Ran Zhao, and Alexandra Clarà Saracho — say that 3D printing inks containing microscopic mineral particles have previously been used to match the flow conditions of printing. One issue is that the resulting structures tend to be soft or shrink upon drying, leading to 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. After about four days, the mineralization process triggered by the bacteria in the scaffold leads to a final product with a mineral content of over 90%,’ says Amstad.


Using BactoInk for future 3D production poses several applications. Restoration of damaged, splintered, or due-for-renovation artworks and sculptures may no longer be a hassle since the bacteria ink can be directly injected into a mold, a crack in a vase, or a chip in a statue. 


The method’s use of solely ecologically acceptable ingredients, as well as its capacity to construct a mineralized biocomposite, makes it a good option for creating artificial corals that can assist repair damaged marine reefs. Ultimately, the biocomposite’s structure and mechanical properties are similar to those of bone, which could make it appealing for future biomedical applications.

bacteria ink 3D printer
BactoInk can help regenerate damaged marine reefs



3D printable bacteria ink is versatile


The Soft Materials Lab’s approach has several potential applications across a broad range of fields, from art and ecology to biomedicine. Amstad believes that the restoration of artworks could be greatly facilitated by BactoInk, which can also be directly injected into a mold or target site – a crack in a vase or a chip in a statue, for example.


The ink’s mechanical properties lend it the strength and shrinkage resistance necessary to repair a work of art, as well as prevent further damage during the restoration process. The ink’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 can help regenerate damaged marine reefs.


Biomedicine is also a potential recipient of the bacteria ink since its biocomposite structure and mechanical properties can mimic those of bone. It implies the creation of limbs and other parts of the body that need restructuring.


‘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,’ says Amstad.

bacteria ink 3D printer
because of its bone-like properties, BactoInk can also be used in biomedicine



project info:


name: BactoInk

institution: Swiss Federal Institute of Technology Lausanne (EPFL)

laboratory head: Esther Amstad

research team: Matteo Hirsch, Lorenzo Lucherini, Ran Zhao, Alexandra Clarà Saracho