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Nanocellulose structure from bacteria

Bacteria used to ‘print’ intricate 3D objects

Image credit: Valeria Azovskaya

Researchers from Aalto University have used bacteria to manufacture detailed 3D designs from nanocellulose, with great control over the physical characteristics of the objects.

The technique allows the researchers to guide the growth of bacterial colonies, using moulds with superhydrophobic (extremely water repellent) surfaces. These moulds are produced by simply embedding hydrophobic particles in silicone.

Unlike the fibrous objects made using conventional 3D-printing methods, the technique allows for fibres – with a diameter 1,000 times thinner than a human hair – to be aligned in any orientation, across layers, and in various gradients of thickness and topology by controlling wetting, incubation time, and nutrient availability. This opens up a world of possible applications in fields such as tissue regeneration; the physical characteristics of these objects are crucial for supporting materials in the growth and regeneration of certain tissues found in muscles and the brain.

“It’s like having billions of tiny 3D printers that fit inside a bottle,” said Luiz Greca, a PhD student at Aalto University. “We can think of the bacteria as natural microrobots that take the building blocks provided to them and, with the right input, create complex shapes and structures.”

Once the bacteria (Komagataeibacter medellinensis) have been placed in a superhydrophobic mould with water and nutrients, they produce nanocellulose. The surface repels water, trapping a thin layer of air, which encourages the bacteria to create a fibrous film replicating the surface and shape of the mould. As the film grows thicker, the object becomes stronger.

Using this technique, the researchers have created objects with pre-designed features: these range from one-tenth the diameter of a hair to 15-20cm.

The nanofibres do not cause adverse reactions when placed in contact with human tissues. The researchers suggest that the technique could be used to grow realistic models of organs for doctors undergoing training in surgery, as well as to improve the accuracy of in-vitro testing.

“It’s really exciting to expand this area of biofabrication that takes advantage of strong cellulose nanofibres and the networks they form,” said research group leader Professor Orlando Rojas. “We’re exploring applications for age-related tissue degeneration, with this method being a step forward in this and other directions.”

The bacteria can be removed or left in the final material, allowing the objects to “evolve” as a living organism over time.

Dr Blaise Tardy said: “Our research really shows the need to understand both the fine details of bacteria interaction at interfaces and their ability to make sustainable materials. We hope that these results will also inspire scientists working on both bacteria-repelling surfaces and those making materials from bacteria.”

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