Mechanics of 3D Printed Microbial Hydrogel Composites

The majority of 3D-printed engineered living materials are printed on flat surfaces limiting the complexity and size of the materials. Additionally, the interplay between microbial cell density and hydrogel matrix stiffness has been shown to impact the final mechanical properties of 3D-printed microbial hydrogel composites. However, since these inks of materials are typically extremely soft, they require crosslinking as they are 3D printed. Therefore, the final mechanical properties of these materials are fixed in the 3D printing process. We will overcome these challenges, by utilizing a 3D support media that fixes the ink into place allowing for the cells to grow before crosslinking. Here, we 3D print photocrosslinkable methacrylated hyaluronic acid and Escherichia coli into a 3D support media swollen with liquid growth media. We show how crosslinking after incubating the 3D printed impacts the final cell density and stiffness of the microbial hydrogel composites. Our results thus provide fundamental insights into how the growth of cells in confined environments can affect the mechanics of 3D-printed microbial hydrogel composites.