Patrick Rühs1

1, Department of Bioengineering, University of California, Berkeley, Berkeley, California, United States

Despite recent advances to control the spatial composition and dynamic functionalities of bacteria embedded in materials, bacterial localization into complex 3D geometries remains a major challenge. Here we demonstrate a 3D printing approach to create bacteria-derived functional materials by combining the natural diverse metabolism of bacteria with the shape design freedom of additive manufacturing (1).
For 3D printing we use a recently developed multimaterial direct ink writing technique (2) which allows us to incorporate bacteria in biocompatible inks within the same 3D printed material. Our bioinks are designed by combining different hydrogels to form a paste-like ink, which after printing is crosslinked by low intensity UV light. To obtain accurate 3D printed structures, we determine the ideal rheological properties prior, during and after printing, demonstrating the effect of the printing steps on the bioink. With this approach we are able to obtain a hydrogel which supports bacteria growth while still maintaining a high shape fidelity in 3D printing.
We embedded bacteria in the biocompatible and functionalized 3D printing ink and printed two types of ‘living materials’ capable of degrading pollutants and of producing medically relevant bacterial cellulose. Furthermore, we demonstrate that bacteria proliferation is a function of viscosity and oxygen availability. By fine-tuning the single ink components, we adjust the viscosity to match the growth profile of our cells. With this printing platform, we envision the use of additive manufacturing materials combined together with cells to be used for new and biomedical applications.

(1) Schaffner, M.*, Rühs, P.A.*, Coulter, F., Kilcher, S., Studart, A.R. 3D printing of bacteria into functional complex materials, Science Advances, Vol. 3, no. 12, eaao6804 (2017)
(2) Kokkinis, D., Schaffner, M. & Studart, A. R. Multimaterial magnetically assisted 3D printing of composite materials. Nature Communications, 6, (2015).