These microscope images of real wood tissue and the 3D printed version show how the researchers mimicked the real wood's cellular architecture. The printed version is at a larger scale for ease of handling and display, but the researchers are able to print at any scale. Image: Yen Strandqvist/Chalmers University of Technology.
These microscope images of real wood tissue and the 3D printed version show how the researchers mimicked the real wood's cellular architecture. The printed version is at a larger scale for ease of handling and display, but the researchers are able to print at any scale. Image: Yen Strandqvist/Chalmers University of Technology.

Researchers at Chalmers University of Technology in Sweden have developed a wood-based ink for 3D printing that mimics the unique ‘ultrastructure’ of wood. Their research, reported in a paper in Applied Materials Today, could revolutionize the manufacturing of green products.

Through emulating the natural cellular architecture of wood, the researchers present the ability to create green products with unique properties – everything from clothes, packaging and furniture to healthcare and personal care products.

The way in which wood grows is controlled by its genetic code, which provides it with unique properties in terms of porosity, toughness and torsional strength. But wood has limitations when it comes to processing. Unlike metals and plastics, it cannot be melted and easily reshaped, and must instead be sawn, planed or curved. More extensive processing, such as required to make products such as paper, card and textiles, destroys the underlying ultrastructure, or architecture, of the wood cells. But the new 3D printing technology allows wood to be, in effect, grown into exactly the shape desired for the final product.

By previously converting wood pulp into a nanocellulose gel, researchers at Chalmers had already succeeded in creating a type of ink that could be 3D printed. Now, they present a major progression – successfully interpreting and digitizing wood’s genetic code, so that it can instruct a 3D printer.

This means precisely controlling the arrangement of the cellulose nanofibrils during the printing process, to replicate the desirable ultrastructure of wood. Being able to control the orientation and shape of these nanofibrils allows the researchers to capture the useful properties of natural wood.

“This is a breakthrough in manufacturing technology,” says Paul Gatenholm, who led this research at the Wallenberg Wood Science Centre at Chalmers University of Technology. “It allows us to move beyond the limits of nature, to create new sustainable, green products. It means that those products which today are already forest-based can now be 3D printed, in a much shorter time. And the metals and plastics currently used in 3D printing can be replaced with a renewable, sustainable alternative.”

A further advance on previous research is the addition of hemicellulose, a natural component of plant cells, to the nanocellulose gel. Hemicellulose acts as a glue, giving the cellulose sufficient strength to be useful, in a similar manner to the natural process of lignification, through which cell walls are built.

The new technology opens up a whole new range of possibilities. Wood-based products could now be designed and ‘grown’ to order – at a vastly reduced timescale compared with natural wood.

Gatenholm's group has already used the technology to develop a prototype for an innovative packaging concept. They printed honeycomb structures with chambers in between the printed walls, and then encapsulated solid particles inside those chambers. Cellulose has excellent oxygen barrier properties, meaning this could be a promising method for creating airtight packaging for foodstuffs or pharmaceuticals.

“Manufacturing products in this way could lead to huge savings in terms of resources and harmful emissions,” explains Gatenholm. “Imagine, for example, if we could start printing packaging locally. It would mean an alternative to today's industries, with heavy reliance on plastics and CO2-generating transport. Packaging could be designed and manufactured to order without any waste.”

The researchers have also developed prototypes for healthcare products and clothing. Another area where Gatenholm sees huge potential for the technology is in space, believing that it offers the perfect testbed to develop the technology further. “The source material of plants is fantastically renewable, so the raw materials can be produced on site during longer space travel, or on the moon or on Mars. If you are growing food, there will probably be access to both cellulose and hemicellulose.”

The researchers have already successfully demonstrated their technology at a workshop at the European Space Agency (ESA), and are also working with Florida Tech and NASA on another project, including tests of materials in microgravity. “Traveling in space has always acted as a catalyst for material development on Earth,” Gatenholm says.

This story is adapted from material from Chalmers University of Technology, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.