Tech Briefs Magazine - February 2021 - 41

els of resolution. They process light with small advanced computer chips and software and the image is recreated with the
help of small colored LEDs. These technologies have developed
extremely rapidly in recent years due mainly to smaller and
more effective circuit components.
Camera lenses themselves, however, have not changed as much.
The majority of today's lenses are based on the same physical principles and include the same basic limitations as the first prototypes
invented in the 16th century. In the past decade, however,
researchers have begun to work with artificial materials - metasurfaces - that could replace today's lenses.

Currently, certain issues stand in the way of large-scale manufacturing of metasurfaces. Advanced equipment is required
to manufacture them and the process is also very time-consuming. With the new method, the production rate can be
increased several times compared to current state-of-the-art
techniques. The new technology uses harmless chemicals as
well as machines that are already common in nanomanufacturing laboratories, meaning that more researchers could now
begin to study metasurfaces.
For more information, contact Ruggero Verre, Researcher, Department
of Physics, at ruggero.verre@chalmers.se; +46 31 772 80 39.

3D Printing with Wood-Based Ink
By emulating the natural cellular architecture of wood, green products such as clothes,
packaging, and furniture can be manufactured with unique properties.
Chalmers University of Technology, Gothenburg, Sweden

he way in which wood grows is controlled by its genetic
code, which gives it 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 instead must be sawed,
planed, or curved. Processes that involve conversion - to
make products such as paper, cards, and textiles - destroy the
underlying ultrastructure, or architecture, of the wood cells.
A technology was developed that allows wood to be, in effect,
grown into exactly the shape desired for the final product
through the use of 3D printing. By previously converting wood
pulp into a nanocellulose gel, an ink was created that could be
3D-printed. The process interprets and digitizes wood's genetic
code, so that it can instruct a 3D printer.
The arrangement of the cellulose nanofibrils can be precisely controlled during the printing process to actually replicate
the desirable ultrastructure of wood. Being able to manage the
orientation and shape means that the useful properties of natural wood can be captured. Products that are already forestbased can now be 3D-printed in a much shorter time.
Hemicellulose, a natural component of plant cells, was
added 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.

Honeycomb structures were printed with chambers in
between the printed walls; solid particles were then encapsulated inside those chambers. Cellulose has excellent oxygen barrier properties, meaning this could be a promising method for
creating airtight packaging for food or pharmaceuticals.
Prototypes also were developed for healthcare products
and clothing.
For more information, contact Mats Tiborn at mats.tiborn@
chalmers.se; +46 (0)31 772 27 99.

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Printed wood tissue

Mimicking the natural cellular architecture of wood. The printed version is
at a larger scale for ease of handling and display; however, the researchers
are able to print at any scale. (Illustration: Yen Strandqvist/Chalmers
University of Technology)

Tech Briefs, February 2021

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Tech Briefs Magazine - February 2021

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