A paper published in Advanced Functional Materials demonstrates a method for creating, and 3D printing, inks made from plant cellulose. 3D printed grids made from the ink exhibit mechanical properties similar to those found in wood, opening up the possibilities of creating strong, lightweight and sustainable structures.

A 3D printed grid of cellulose nanocrystal ink. Image via Siqueira, Kokkinis, Libanori, Hausmann, Gladman, Neels, Tingaut, Zimmermann, Lewis and Studart

A 3D printed grid of cellulose nanocrystal ink. Image via Siqueira, Kokkinis, Libanori, Hausmann, Gladman, Neels, Tingaut, Zimmermann, Lewis and Studart

The trouble with cellulose

As previously reported on 3D Printing Industry, one of the chief challenges to 3D printing with cellulose is getting the material to behave like a liquid. Based in plant matter, it cannot be melted using heat, and so other methods have to be investigated for that purpose.

In this study, researchers create inks by extracting particles extracted from wood pulp and mixing them with water. The cellulose nanocrystal particles are mixed with the water using a planetary speed mixer. By combining the two at such high speeds, the mixer eliminates air bubbles that could cause imperfections in an object when 3D printed.

Going against the grain

The cellulose nanocrystal ink is 3D printed in a uniform grid design through a needle-like nozzle. To formally asses the properties of the material, printing is done at rate between 1 and 8 layers. Water is then evaporated from the layer(s) to leave a pure, and solid, cellulose nanocrystal structure.

Rainbow iridescence reveals the structure of 3D printed cellulose nanocrystal inks. Image via Siqueira, Kokkinis, Libanori, Hausmann, Gladman, Neels, Tingaut, Zimmermann, Lewis and Studart

Rainbow iridescence reveals the structure of 3D printed cellulose nanocrystal inks. Image via Siqueira, Kokkinis, Libanori, Hausmann, Gladman, Neels, Tingaut, Zimmermann, Lewis and Studart

Iridescence from the grids confirm that the cellulose particles maintain the same structure as when they were 3D printed. That is to say, the particles align to give anisotropic properties like those exhibited by the grain in wood – easier to break with the grain, and harder to break against it.

Wood splits more easily when an axe hits going with the grain. Photo by Paul Fosselman, pfos on Flickr

Wood splits more easily when an axe hits going with the grain. Photo by Paul Fosselman, pfos on Flickr

Identifying the anisotropic properties of the material is the key discovery in this research, leading to the conclusion that the ink provides “an important step forward toward the development of sustainable materials for 3D printing of cellular architectures with tailored mechanical properties.”

Standing on institutional expertise in materials science and biological engineering

Cellulose Nanocrystal Inks for 3D Printing of Textured Cellular Architectures is published online in the journal Advanced Functional Materials, Volume 27, Issue 12. It is co-authored by Gilberto Siqueira, Dimitri Kokkinis, Rafael Libanori, Michael K. Hausmann, Amelia Sydney Gladman, Antonia Neels, Philippe Tingaut, Tanja Zimmermann, Jennifer A. Lewis, and André R. Studart.

These authors can be respectively attributed to the Swiss Federal Laboratories for Materials Science and Technology, ETH Zürich, behind recent 4D printing research, and the Wyss Institute for Biologically Inspired Engineering at Harvard University, home to the Lewis Lab.

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Featured image: Microscopic inspection of a 3D printed cellulose nanocrystal ink grid. Image via Siqueira, Kokkinis, Libanori, Hausmann, Gladman, Neels, Tingaut, Zimmermann, Lewis and Studart

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