Materials
According to Amstad, the range of materials that can be 3D printed is still limited. “One reason is that inks must fulfil certain complex flow conditions,” she says. “They must behave as a solid when at rest, but still be extrudable through a 3D-printing nozzle – with a texture a bit like ketchup.” Small mineral particles that have previously been used to meet some of these flow criteria have resulted in structures that tend to be soft or shrink when drying, which leads to cracking and loss of control over the shape of the final product. “We turned to the natural world for a potential solution,” Amstad adds. “We printed a polymeric scaffold using material laced with Sporosarcina pasteurii, a bacterium that in nature starts the process of mineralisation to calcium carbonate deposition. After four days, the bacteria triggered the mineralisation process in the scaffold, and we were handling a final product with a mineral content of over 90%.” The result was a strong and resilient bio-composite that can be produced using a standard 3D printer and natural materials, without the extreme temperatures often required for manufacturing ceramics. Also, the final products no longer contain living bacteria as they are submerged in ethanol at the end of the mineralisation process.
Regenerative medicine
A visual illustration of high-throughput combinatorial printing.
Amstad is head of the soft materials laboratory at the renowned Federal Institute of Technology. She too is making waves with her bio-ink studies by exploring which types of compounds make useful biomaterials that are also environmentally friendly. “The need to be able to fabricate more sustainable materials and to process them in an energy-efficient, benign way has motivated me to examine 3D-printing options,” she says. “Our technology is paving the way to customised products with minimal material waste. Much useful research has been conducted designing the printing technology, but less has been devoted to ink formulation.” How does Amstad see the long-term prospects for rapidly growing an array or library of bio ink coatings? “It depends on what is meant by long- term,” she says. “Bio-inks we study here help us produce viable and elegant ‘scaffolds’ for tissue engineering. These enable the growth of more functional organoids. But we can use them to test the effect of a variety of active substances, for example in the food and pharma sectors.”
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The aptly named “BactoInk” opens possibilities that cut across many sectors. For biomedical use in particular, Amstad explains that “with additional work and funding, this technology will be a significant stride for personalised medicine”. “It would be marvellous to enable the fabrication of more customisable wound healing and drug delivery systems, open up new possibilities for the real-time monitoring of patients. One day, they might also be used in regenerative medicine, because of their ability to attain customisable shapes and properties.” Unlike in Zhang’s lab, the use of AI to turbocharge the creation of bio-compatible composites has yet to become viable in Amstad’s work. It is only a matter of time and funding, however. “I’m hoping that the addition of AI will lead soon to in-vivo trials using bio-ink coatings taking place in humans and animal models, rather the trials we perform using art statues,” she says.
The work to develop bio-inks and composites using theory and calculation follows the trajectory set by Nikola Tesla almost a century ago, and with machine learning driving the process, researchers no longer have to be a human calculator to reduce their time spent tinkering in the lab. ●
Medical Device Developments /
www.nsmedicaldevices.com
University of Notre Dame
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