3D printing with wood-based ink creates packaging-on-demand possibilities

27 Jun 2019 --- Researchers at Chalmers University of Technology, Sweden, have succeeded in 3D printing with a wood-based ink in a way that mimics the unique “ultrastructure” of wood. By emulating the natural cellular architecture of wood, the 3D printing technology could “revolutionize the manufacturing of green products,” including packaging, healthcare and personal care products, and create a manufacture-on-demand system. The researchers believe that the wood-based ink could ultimately replace the metal and plastic ink typically used in 3D printing with a renewable alternative.

The way in which wood grows is controlled by its genetic code. Wood has limitations when it comes to processing – unlike metals and plastics, it cannot be melted and easily reshaped and instead must be sawn, planed or curved. Processes which do involve conversion to make products such as paper, card and textiles destroy the underlying “ultrastructure” of the wood cells. But Chalmers University's new technology allows wood to be grown into exactly the shape desired for the final product through the medium of 3D printing.

Chalmers University's new technology mimics the natural cellular architecture of wood.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 the genetic code of wood so that it can instruct a 3D printer.

The arrangement of the cellulose nanofibrils can now be precisely controlled during the printing process to actually replicate the desirable ultrastructure of wood and replicate its unique properties in terms of porosity, toughness and torsional strength.

“This is a breakthrough in manufacturing technology that allows us to move beyond the limits of nature to create new sustainable products. It means that those products which today are already forest-based can now be 3D printed and designed and “grown” to order in a much shorter timeframe,” Professor Paul Gatenholm, who led the research within Chalmers’ Wallenberg Wood Science Center, tells PackagingInsights.

A honeycomb structure with solid particles encapsulated in the air gaps between the printed walls.A further advance on previous research is the addition of hemicellulose – a natural component of plant cells – to the nanocellulose gel. The 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.

Gatenholm's team has already developed a prototype for an innovative packaging concept. They printed out honeycomb structures, with chambers in between the printed walls and then managed to encapsulate solid particles inside those chambers. Cellulose has excellent oxygen barrier properties, creating the possibility for airtight packaging for foodstuffs or pharmaceuticals.

Professor Paul Gatenholm“Manufacturing products in this way could lead to huge savings in terms of resources and harmful emissions,” Gatenholm explains. “Imagine if we could start printing packaging locally. It would mean an alternative to today's industries with heavy reliance on plastics and C02-generating transport. Packaging could be designed and manufactured to order without any waste.”

Gatenholm adds that 3D printed wood packaging can be made flexible like plastic with the tailored addition of bio-additives such as sorbitol or glycerol. “We can also add lignin – another wood component – to provide dark packaging for light-sensitive products,” he says.

At end-of-life, products manufactured through this 3D printing, packing-on-demand process, can be recycled into new packaging, composted or burned.The microscope images show how the researchers are able to precisely control the orientation of the cellulose nanofibrils, printing in different directions in the same way that natural wood grows.

Paul Gatenholm sees huge potential for the 3D printing technology in space exploration, suggesting that it could offer “the perfect first test bed 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,” he says.

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 notes.

By Joshua Poole