3D-Printed Living Material for Cleaning Contaminated Water

Dubbed an “engineered living material,” a new type of material developed at the University of California San Diego could offer a sustainable and eco-friendly solution to clean pollutants from water.

“It is a 3D-printed gel-based structure containing the bacteria that have been programmed to produce an output that transforms organic pollutants into benign molecules; in our case it is water decontamination,” said Co-First Author Debika Datta, who is a nanoengineering postdoctoral researcher at UCSD. “The bacteria were also programmed to self-destruct in the presence of a molecule called theophylline, which is often found in tea and chocolate. This offers a way to eliminate them after they have done their job.”

The team’s objective, Datta said, was to investigate a category of materials known as engineered living materials, wherein an engineered micro-organism is incorporated into a polymeric substance. There has been minimal research into the integration of cyanobacteria with conventional materials.

To create the living material in this study, the researchers used alginate, a natural polymer derived from seaweed, hydrated it to make a gel, and then mixed it with a type of water-dwelling, photosynthetic bacteria known as cyanobacteria.

“These photosynthetic micro-organisms are relatively resource-efficient, as they primarily require CO2, water, and abundant light,” Datta said. “Initially, we were interested in the creation of scaffolding materials that facilitate the growth of cyanobacteria. We did try a variety of different materials, and among them the natural polymer alginate, which has its source from the seaweed, turned out to provide the best support for growth and survival,” she added.

The mixture was then fed into a 3D printer. After testing various 3D-printed geometries for their material, the researchers found that a grid-like structure was optimal for keeping the bacteria alive. The chosen shape has a high surface-area-to-volume ratio, which places most of the cyanobacteria near the material’s surface to access nutrients, gases, and light. The increased surface area also makes the material more effective at decontamination.

“Certainly, one of the key challenges we encountered was designing the scaffold,” Datta said. “Initially, when we discovered that the alginate material could support cell growth, it was an exciting moment for us. However, our initial alginate hydrogels were in a disk or circular shape, and we observed uneven cell growth within the matrix. The breakthrough came when we realized the importance of incorporating void spaces into the matrix.

According to her, this adjustment was crucial because these micro-organisms rely on gaseous diffusion for their growth. “So, we decided to change the matrix shape to custom designs we created in-house, such as a honeycomb or a grid pattern, and this modification yielded fantastic results. It enabled us to achieve uniform cell growth throughout the matrix. We achieved this by utilizing additive manufacturing 3D printing technique.”

As a proof-of-concept experiment, the team genetically engineered the cyanobacteria in its material to continually produce a decontaminating enzyme called laccase. In this study, the researchers demonstrated that their material can be used to decontaminate the dye-based pollutant indigo carmine, which is a blue dye that is widely used in the textile industry to color denim. In tests, the material decolorized a water solution containing the dye.

“We are also trying to use micro-organisms for production of polymers, taking a biosynthetic approach rather than conventional chemical synthesis in the lab, which could be a potential step toward green chemistry,” Datta said.

This article was written by Andrew Corselli, Digital Content Editor at SAE Media Group. For more information, visit the UC San Diego Materials Research Science and Engineering Center .

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