Circuits from renewable raw materials for "green" electronics

From wood pulp or agricultural waste sustainable and "easy" electronic products as well as useful for multiple purposes thanks to EMPA and OST

"Green" electronics: housing elements for computer mice starting from cellulose fibers
Thomas Geiger, scientist at EMPA, has experimentally produced housing elements for computer mice from cellulose fibers: the surfaces shine like precious ivory and the components are completely compostable
(Photo: EMPA)

Is it possible to produce ecologically sustainable printed circuit boards for the electronics industry from cellulose fibers?
It is Thomas Geiger, researcher of theEMPA, which in Switzerland has undertaken to answer this question.
Now it is included in a multinational project of the European Union called “Hypelignum”. Indeed, its goal is biodegradable electronics.
For many years, Thomas Geiger has been conducting research in the field of cellulose fibrils, fine fibers that can be produced, for example, from wood pulp or agricultural waste.

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"Green" electronics: Thomas Geiger, EMPA researcher
At 150 tons of pressure, the cellulose fibers are first dehydrated and then consolidated in a second operation, which proceeds almost by itself: Thomas Geiger, EMPA researcher, in front of his special press for "green" electronics
(Photo: EMPA)

From nature with zero CO2 emissions, residue-free and even compostable fuels

Cellulose fibrils have great potential for sustainable production and the decarbonisation of industry: they grow in nature with zero CO2 emissions, burn without residues and are even compostable.
They can be used for multiple purposes, for example as a reinforcing fiber in technical rubber products, such as pump membranes.
But can cellulose fibrils also be used to make printed circuit boards that reduce the ecological footprint of computers?
Printed circuits or PCBs, in particular, are anything but "innocent" from an ecological point of view: they usually consist of glass fibers soaked in epoxy resin.
This composite material is not recyclable and so far can only be properly disposed of in special pyrolysis plants.

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"Green" electronics: housing elements for computer mice starting from cellulose fibers
Thomas Geiger, scientist at EMPA, has experimentally produced housing elements for computer mice from cellulose fibers: the surfaces shine like precious ivory and the components are completely compostable
(Photo: EMPA)

Computer mice the same feel and look as ivory, but too "expensive"

Thomas Geiger had already produced printed circuit boards from cellulose fibrils and had studied their biodegradation.
Mixed with water, the biofibrils produce a thick sludge which can be dewatered and compacted in a special press.
Together with a colleague, he produced 20 experimental boards, which were subjected to various mechanical tests and finally equipped with electronic components.
The test was successful and the cellulose board released the welded components after a few weeks of testing in natural soil.
Thomas Geiger had already been involved in an Innosuisse project together with theEastern Switzerland University of Applied Sciences (OST) of Rapperswil in the Canton of St. Gallen, which manufactured housing components for computer mice.
The housing parts have a silky sheen and are similar in color and feel to pieces of ivory.
But it was not possible to find any manufacturer who wanted to adopt this method.
Price competition for small electronics is still too strong and conventional plastic injection molding processes have a clear advantage in this respect.

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Carbon nanotubes make cellulose electrically conductive, allowing the creation of "green" electronic components

Computer circuit boards? In wood wool or cellulose fibrils

Recently, the opportunity to build on existing findings has arisen: Claudia Som, sustainability specialist at EMPA, was asked to collaborate on the EU's 'Hypelignum' research project.
This project is led by the Swedish Materials Research Institute RISE and is looking for new ways to produce electronics in a sustainable way. Claudia Som enlisted the help of colleague Thomas Geiger.
The project started in October 2022 and the research consortium, with participants from Austria, Slovenia, Spain, the Netherlands, Sweden and Switzerland, plans to produce and evaluate green electronic boards made from different materials.
In addition to nanofibrillated cellulose (CNF), wood wool and wood pulp are being studied as a base; wood veneer is also used as a base for the circuits.
Veneering is an operation that is performed in carpentry and consists in covering a non-precious wood or a panel with a very thin slice of wood called veneer.

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"Green" electronics: EMPA headquarters in St. Gallen (St. Gallen)
The headquarters of the Federal Materials Testing and Research Laboratory (EMPA) in St. Gallen in the canton of the same name

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Two laboratories of EMPA collaborate on the project: firstly, the sustainability specialists led by Claudia Som of the Laboratory Technology e Society.
SOM will use materials databases to calculate the ecological footprint of eco-circuits and compare individual concepts with each other.
Thomas Geiger, from EMPA's Cellulose & Wood Materials laboratory, will produce the circuits with renewable raw materials.
Green electronics has long been a research goal of the laboratory, directed by Gustav Nystrom.
The team directed by the latter has already developed several electronic components printed with biodegradable materials, such as batteries and displays.
The requirements for industrially produced circuit boards, however, are not trivial: not only must they have high mechanical strength, but they must also avoid swelling in humid conditions or cracking in very low humidity.

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"Green" electronics: organic waste for electronics
Organic waste: an experimental table after the composting of electronic components made starting from cellulose fibrils
(Photo: EMPA)

The dehydrated nanofibrillated cellulose particles stick together by themselves without additives

“Cellulose fibers can be an excellent alternative to fiberglass composites”Geiger explains.
“We dehydrate the material in a special press with a pressure of 150 tons. Then the cellulose fibrils join together by themselves, without any additives. We call this process 'cornification'…”.
The key is at what pressure, temperature and for how long the pressing process must occur to produce optimal results.

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"Green" electronics: housing elements for computer mice starting from cellulose fibers
Thomas Geiger, scientist at EMPA, has experimentally produced housing elements for computer mice from cellulose fibers: the surfaces shine like precious ivory and the components are completely compostable
(Photo: EMPA)

There are four demonstrators already planned, starting with… conductive inks

The EU project "Hypelignum" has ambitious objectives: it does not only propose to study printed circuits made with renewable and compostable raw materials, but also to develop conductive inks for the electrical connections between the individual components.
These inks are often based on silver nanoparticles.
Researchers are looking for cheaper and less scarce substitute materials as well as an environmentally friendly production method for these nanoparticles.
At the end of the project, four demonstrators should show the obtained results.
An ecologically exemplary printed circuit board, a large wooden construction element that will be equipped with sensors and actuators, pieces of furniture that will be equipped with sensors in an automated production line and, finally, a demonstrator that will illustrate the recyclability of all these components.

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"Green" electronics: Thomas Geiger, EMPA researcher
At 150 tons of pressure, the cellulose fibers are first dehydrated and then consolidated in a second operation, which proceeds almost by itself: Thomas Geiger, EMPA researcher, in front of his special press for "green" electronics
(Photo: EMPA)

Display and batteries in electrically conductive cellulose thanks to carbon nanotubes

In 2022, a research team from EMPA led by Gustav Nyström succeeded in building a biodegradable display based on hydroxypropyl cellulose (HPC).
They used HPC as a substrate and added a small amount of carbon nanotubes, making the cellulose electrically conductive.
By mixing cellulose nanofibers (CNF), they made the ink printable. In this way, the display changes color according to the applied electrical voltage.
Furthermore, it can also serve as a pressure or voltage sensor and has the potential to play the role of a biodegradable user interface in future eco-electronics.

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The site of the Federal Materials Testing and Research Laboratory (EMPA) in Dübendorf in the Canton of Zurich