Mimicking wood’s cellular structure with 3D printing

Researcher at Chalmers University of Technology in Sweden succeeded in 3D printing with a wood-based ink in a way that mimics the cellular architecture of wood.

Wood’s growth is controlled by its genetic code, which gives the material unique properties in terms of porosity, toughness and torsional strength. However, these properties can only be maintained if the wood is sawn, planed or curved. For wood-based products like paper and textile, the wood is converted, destroying the underlying ‘ultrastructure’, or the architecture of the wood cells.

The new research allows wood to be ‘grown’ in the desired shape of the final product through 3D printing. The ink is made from wood pulp, which is converted into nanocellulose gel. To this gel, hemicellulose is added, a natural component of plant cells. This hemicellulose acts as a glue, giving the cellulose sufficient strength to be useful, similar to the natural process of cell walls being built.

The innovative part of the research lies in it successfully interpreting and digitising wood’s genetic code so that it can instruct a 3D printer. This means that the arrangement of the cellulose nanofibrils can be precisely controlled during the printing process, replicating the ultrastructure of wood and thus capturing the useful properties of natural wood.

“This is a breakthrough in manufacturing 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,” says Professor Paul Gatenholm, who led this research within Chalmers University of Technology’s Wallenberg Wood Science Centre.

The team developed a prototype of an innovative packaging concept. They printed out honeycomb structures, with chambers in between the printed walls, and encapsulated solid particles inside those chambers. As cellulose has excellent oxygen barrier properties, this type of packaging could be promising for the airtight packaging for foodstuffs or pharmaceuticals.

In addition, the researchers developed prototypes for healthcare products and clothing. Space could also potentially an area in which this technology is deployed.

Image: Chalmers University of Technology