Printing with living inks

Researchers have used functional living inks, which they call Flinks, containing bacteria with useful reactive chemical properties for three-dimensional printing. André R. Studart, Patrick A. Rühs, Manuel Schaffner, and coworkers at ETH Zurich embedded the functional bacteria in hydrogels that can be used in 3-D printers to make a variety of structures for various applications (Sci. Adv. 2017, DOI: 10.1126/sciadv.aao6804). The hydrogel consists of hyaluronic acid, κ-carrageenan, and fumed silica at a 1:1:1 ratio. Increasing the weight percent of those components while maintaining the same ratio allows the researchers to adjust the viscosity and elasticity of the hydrogel. After chemically replacing the hyaluronic acid with glycidyl methacrylate hyaluronic acid after the printing step, the team used ultraviolet light to cross-link the hydrogel to form self-supporting structures. The researchers used a Flink loaded with Pseudomonas putida to make devices that can degrade phenols for bioremediation applications. They demonstrated potential biomedical applications using a Flink embedded with Acetobacter xylinum, a bacterium that produces cellulose. Bacterial cellulose is being developed as a material for skin repair and as a tissue envelope for organ transplantation. The researchers showed that they can controllably use the ink to make complex shapes by printing a scaffold in the shape of a miniature T-shirt and by depositing a film on a doll’s face as a model for a human face. In both cases, the bacteria produced a cellulosic biofilm.