Tag Archives: Swiss Federal Laboratories for Materials Science and Technology (Empa)

Aerogels that are 3D printed from nanocellulose

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The one on the far right looks a bit like a frog (to me),

Caption: Complexity and lightness: Empa researchers have developed a 3D printing process for biodegradable cellulose aerogel. Credit: Empa

An April 4, 2024 Swiss Federal Laboratories for Materials Science and Technology (EMPA) press release (also on EurekAlert) describes some interesting possibilities for nanocellulose,

At first glance, biodegradable materials, inks for 3D printing and aerogels don’t seem to have much in common. All three have great potential for the future, however: “green” materials do not pollute the environment, 3D printing can produce complex structures without waste, and ultra-light aerogels are excellent heat insulators. Empa researchers have now succeeded in combining all these advantages in a single material. And their cellulose-based, 3D-printable aerogel can do even more.

The miracle material was created under the leadership of Deeptanshu Sivaraman, Wim Malfait and Shanyu Zhao from Empa’s Building Energy Materials and Components laboratory, in collaboration with the Cellulose & Wood Materials and Advanced Analytical Technologies laboratories as well as the Center for X-ray Analytics. Together with other researchers, Zhao and Malfait had already developed a process for printing silica aerogels in 2020. No trivial task: Silica aerogels are foam-like materials, highly open porous and brittle. Before the Empa development, shaping them into complex forms had been pretty much impossible. “It was the logical next step to apply our printing technology to mechanically more robust bio-based aerogels,” says Zhao.

The researchers chose the most common biopolymer on Earth as their starting material: cellulose. Various nanoparticles can be obtained from this plant-based material using simple processing steps. Doctoral student Deeptanshu Sivaraman used two types of such nanoparticles – cellulose nanocrystals and cellulose nanofibers – to produce the “ink” for printing the bio-aerogel.

Over 80 percent water

The flow characteristics of the ink are crucial in 3D printing: Tt must be viscous enough in order to hold a three-dimensional shape before solidification. At the same time, however, it should liquefy under pressure so that it can flow through the nozzle. With the combination of nanocrystals and nanofibers, Sivaraman succeeded in doing just that: The long nanofibers give the ink a high viscosity, while the rather short crystals ensure that it has shear thinning effect so that it flows more easily during extrusion.

In total, the ink contains around twelve percent cellulose – and 88 percent water. “We were able to achieve the required properties with cellulose alone, without any additives or fillers,” says Sivaraman. This is not only good news for the biodegradability of the final aerogel products, but also for its heat-insulating properties. To turn the ink into an aerogel after printing, the researchers replace the pore solvent water first with ethanol and then with air, all while maintaining shape fidelity. “The less solid matter the ink contains, the more porous the resulting aerogel,” explains Zhao.

This high porosity and the small size of the pores make all aerogels extremely effective heat insulators. However, the researchers have identified a unique property in the printed cellulose aerogel: It is anisotropic. This means its strength and thermal conductivity are direction-dependent. “The anisotropy is partly due to the orientation of the nanocellulose fibers and partly due to the printing process itself,” says Malfait. This allows the researchers to control in which axis the printed aerogel piece should be particularly stable or particularly insulating. Such precisely crafted insulating components could be used in microelectronics, where heat should only be conducted in a certain direction.

A lot of potential applications in medicine

Although the original research project, which was funded by the Swiss National Science Foundation (SNSF), was primarily interested in thermal insulation, the researchers quickly saw another area of application for their printable bio-aerogel: medicine. As it consists of pure cellulose, the new aerogel is biocompatible with living tissues and cells. Its porous structure is able to absorb drugs and then release them into the body over a long period of time. And 3D printing offers the possibility of producing precise shapes that could, for instance, serve as scaffolds for cell growth or as implants.

A particular advantage is that the printed aerogel can be rehydrated and re-dried several times after the initial drying process without losing its shape or porous structure. In practical applications, this would make the material easier to handle: It could be stored and transported in dry form and only be soaked in water shortly before use. When dry, it is not only light and convenient to handle, but also less susceptible to bacteria – and does not have to be elaborately protected from drying out. “If you want to add active ingredients to the aerogel, this can be done in the final rehydration step immediately before use,” says Sivaraman. “Then you don’t run the risk of the medication losing its effectiveness over time or if it is stored incorrectly.”

The researchers are also working on drug delivery from aerogels in a follow-up project – with less focus on 3D printing for now. Shanyu Zhao is collaborating with researchers from Germany and Spain on aerogels made from other biopolymers, such as alginate and chitosan, derived from algae and chitin respectively. Meanwhile, Wim Malfait wants to further improve the thermal insulation of cellulose aerogels. And Deeptanshu Sivaraman has completed his doctorate and has since joined the Empa spin-off Siloxene AG, which creates new hybrid molecules based on silicon.

Fascinating work and here’s a link to and a citation for the paper,

Additive Manufacturing of Nanocellulose Aerogels with Structure-Oriented Thermal, Mechanical, and Biological Properties by Deeptanshu Sivaraman, Yannick Nagel, Gilberto Siqueira, Parth Chansoria, Jonathan Avaro, Antonia Neels, Gustav Nyström, Zhaoxia Sun, Jing Wang, Zhengyuan Pan, Ana Iglesias-Mejuto, Inés Ardao, Carlos A. García-González, Mengmeng Li, Tingting Wu, Marco Lattuada, Wim J. Malfait, Shanyu Zhao. Advanced Science DOI: https://doi.org/10.1002/advs.202307921 First published: 13 March 2024

This paper is open access.

You can find Siloxene AG here.

Memristors based on halide perovskite nanocrystals are more powerful and easier to manufacture

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A March 8, 2023 news item on phys.org announces research from Swiss and Italian researchers into a new type of memristor,

Researchers at Empa, ETH Zurich and the Politecnico di Milano are developing a new type of computer component that is more powerful and easier to manufacture than its predecessors. Inspired by the human brain, it is designed to process large amounts of data fast and in an energy-efficient way.

In many respects, the human brain is still superior to modern computers. Although most people can’t do math as fast as a computer, we can effortlessly process complex sensory information and learn from experiences, while a computer cannot – at least not yet. And, the brain does all this by consuming less than half as much energy as a laptop.

One of the reasons for the brain’s energy efficiency is its structure. The individual brain cells – the neurons and their connections, the synapses – can both store and process information. In computers, however, the memory is separate from the processor, and data must be transported back and forth between these two components. The speed of this transfer is limited, which can slow down the whole computer when working with large amounts of data.

One possible solution to this bottleneck are novel computer architectures that are modeled on the human brain. To this end, scientists are developing so-called memristors: components that, like brain cells, combine data storage and processing. A team of researchers from Empa, ETH Zurich and the “Politecnico di Milano” has now developed a memristor that is more powerful and easier to manufacture than its predecessors. The researchers have recently published their results in the journal Science Advances.

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A March 8, 2023 Swiss Federal Laboratories for Materials Science and Technology (EMPA) press release (also on EurekAlert), which originated the news item, provides details about what makes this memristor different,

Performance through mixed ionic and electronic conductivity

The novel memristors are based on halide perovskite nanocrystals, a semiconductor material known from solar cell manufacturing. “Halide perovskites conduct both ions and electrons,” explains Rohit John, former ETH Fellow and postdoctoral researcher at both ETH Zurich and Empa. “This dual conductivity enables more complex calculations that closely resemble processes in the brain.”

The researchers conducted the experimental part of the study entirely at Empa: They manufactured the thin-film memristors at the Thin Films and Photovoltaics laboratory and investigated their physical properties at the Transport at Nanoscale Interfaces laboratory. Based on the measurement results, they then simulated a complex computational task that corresponds to a learning process in the visual cortex in the brain. The task involved determining the orientation of light based on signals from the retina.

“As far as we know, this is only the second time this kind of computation has been performed on memristors,” says Maksym Kovalenko, professor at ETH Zurich and head of the Functional Inorganic Materials research group at Empa. “At the same time, our memristors are much easier to manufacture than before.” This is because, in contrast to many other semiconductors, perovskites crystallize at low temperatures. In addition, the new memristors do not require the complex preconditioning through application of specific voltages that comparable devices need for such computing tasks. This makes them faster and more energy-efficient.

Complementing rather than replacing

The technology, though, is not quite ready for deployment yet. The ease with which the new memristors can be manufactured also makes them difficult to integrate with existing computer chips: Perovskites cannot withstand temperatures of 400 to 500 degrees Celsius that are needed to process silicon – at least not yet. But according to Daniele Ielmini, professor at the “Politecnico di Milano”, that integration is key to the success for new brain-like computer technologies. “Our goal is not to replace classical computer architecture,” he explains. “Rather, we want to develop alternative architectures that can perform certain tasks faster and with greater energy efficiency. This includes, for example, the parallel processing of large amounts of data, which is generated everywhere today, from agriculture to space exploration.”

Promisingly, there are other materials with similar properties that could be used to make high-performance memristors. “We can now test our memristor design with different materials,” says Alessandro Milozzi, a doctoral student at the “Politecnico di Milano”. “It is quite possible that some of them are better suited for integration with silicon.”

Here’s a link to and a citation for the paper,

Ionic-electronic halide perovskite memdiodes enabling neuromorphic computing with a second-order complexity by Rohit Abraham John, Alessandro Milozzi, Sergey Tsarev, Rolf Brönnimann, Simon C. Boehme, Erfu Wu, Ivan Shorubalko, Maksym V. Kovalenko, and Daniele Ielmini. Science Advances 23 Dec 2022 Vol 8, Issue 51 DOI: 10.1126/sciadv.ade0072

This paper is open access.

Cellulose nanofibrils for slow-release fertilizer

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An October 17, 2022 news item on phys.org highlights nanocellulose research from Brazil, Note: A link has been removed,

A research team affiliated with the Laboratory of Polymeric Materials and Biosorbents at the Federal University of São Carlos (UFSCar) in Araras, São Paulo state, Brazil, has produced and is testing cellulose-based materials for enhanced-efficiency fertilizers to improve the supply of nutrients to crops and reduce the release of non-biodegradable chemicals [forever chemicals] into the ecosystem.

The studies were led by Roselena Faez, a professor at the Center for Agricultural Sciences (CCA-UFSCar). The findings have recently been reported in two publications. One is an article published in Carbohydrate Polymers, with Débora França as first author. Here [keep scrolling down] the researchers describe how they used modified nanocellulose to discharge the nutrients contained in fertilizer into the soil slowly and in a controlled manner, given that nitrogen, phosphorus and potassium are highly soluble.

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Caption: The first and third photos show the paper made from phosphorylated sugarcane cellulose. The second shows the 3D structure of the material comprising cellulose and nutrient. The fourth shows the microparticles in powder form and after molding into tablets. Credit: Lucas Luiz Messa/Débora França

An October 19, 2022 Fundação de Amparo à Pesquisa do Estado de São Paulo [FAPESP] press release (also on EurekAlert but published October 17, 2022) by Karina Ninni, originated the phys.org news item. The researchers explain (Note: Links have been removed),

“Potassium is rapidly washed away by rain because of its high ion mobility. It’s the hardest to release in a controlled manner. Nitrogen can be obtained from various sources, such as nitrates, ammonia and urea, but plants get the nitrogen they need most easily from nitrate, which is also easily washed away and doesn’t remain in the soil for long. Phosphorus [as phosphate] is a very large ion and less mobile than the other macronutrients,” said Faez, who coordinates the Polymeric Materials and Biosorbents Research Group at UFSCar Araras.

Controlled-release products are available on the market, she added, but most are made of synthetic polymers, which are non-biodegradable. “Fertilizer grains are about the size of grains of coarse sea salt. To make sure the nutrients are released slowly, they’re coated with layers of polymer that last about two months each, so the manufacturer applies two, three or four coats, according to the desired length of time for controlled release,” Faez explained, noting that the polymers in question are plastics and remain in the soil, eventually degrading into microparticles that last virtually forever.

The researchers at UFSCar developed an entirely different product in which the chemical reaction between the modified nanocellulose and mineral salts keeps the nutrients in the soil. “We focused on the worst problems, which are nitrate and potassium. The material we developed is totally biodegradable and releases these nutrients at about the same slow rate as the available synthetic materials,” Faez said.

The nanocellulose was obtained from pure cellulose donated by a paper factory. The nanofibrils were functionalized with positive and negative charges to enhance polymer-nutrient interaction. “Because the salts are also made up of positively or negatively charged particles and highly soluble, we hypothesized that negatively charged nanocellulose would react with positive ions in the salts, while positively charged nanocellulose would interact with negative ions, reducing the solubility of the salts. This proved to be the case, and the group succeeded in modulating nutrient release in accordance with the type of particle in the material,” França said.

Evaluation in soil

The group fabricated the product in the form of tablets and evaluated its performance in terms of nutrient release into the soil. Evaluation of release into water is the usual method, and water is a very different system from soil. This part of the research was conducted in partnership with Claudinei Fonseca Souza, a professor at CCA-UFSCar’s Department of Natural Resources and Environmental Protection in Araras.

“We evaluated nutrient release into the soil and biodegradation of the material at the site for 100 days. But we deliberately used very poor soil with little organic matter, because this enables us to see the physical effects of release more easily,” Faez said.

The researchers used two techniques to obtain tablets: atomization and spray drying to encapsulate the nutrients with the nanocellulose, followed by heat processing of the resulting powder, which was pressed in a mold. This work was completed with the help of colleagues at the Cellulose and Wood Materials Laboratory belonging to EMPA (Swiss Federal Laboratories for Materials Science and Technology) and in collaboration with UFSCar’s Water, Soil and Environment Engineering Research Group, led by Souza. França performed the cellulose modifications at EMPA while on an internship there with support from FAPESP. She was also supported by a doctoral scholarship in Brazil.

Self-fertilization

The second recent article by the group was published in Industrial Crops and Products, with chemist Lucas Luiz Messa as first author. The goal of the study was to extract cellulose from sugarcane bagasse and modify it with a surface negative charge by phosphorylation (addition of a phosphorus group) to allow controlled release of potassium. In theory, delivery of plant nutrition would be slowed by cellulose phosphorylation, which would create surface anionic charges that would bind to macronutrient and micronutrient cations. 

The group prepared three types of structure with the phosphorylated cellulose: oven-dried paper-like film; spray-dried powder; and freeze-dried porous bulk similar to polystyrene foam. Freeze drying, or lyophilization, was seen to leave nutrients in the voids left by water removal. 

“Technologically speaking, the paper-like structure was the best material we produced for controlled delivery of nutrients. Several products can be created using this paper,” Faez said.

The results obtained in the research led by Messa enabled the group to develop small propagation pots for seedling cultivation. When this material degrades, the phosphorus it contains is released. According to Faez, cellulose phosphorylation is cheap, and the cost of the end product is relatively low. “It’s more or less BRL 0.27 per gram of paper produced. The propagation pot must be about 1 gram. Unit cost is therefore about BRL 0.30 in terms of laboratory costs,” she said.

Biodegradable propagation pots are already available on the market. “But our product has built-in fertilizer, which is a major competitive advantage. Indeed, we’ve filed a patent application,” she said.

The pot is about to be trialed by a flower producer in Holambra, São Paulo state. Several batches produced in the laboratory have been shipped there. Nutrient release has so far been tested only in water. “We call this an accelerated ion release assessment method because it’s faster in water, but even in water we found the release rate to be 40%-50% slower compared with the behavior of the ion in the material and without the material. Even in water, therefore, we succeeded in retaining these ions. We assume delivery will be even slower in the substrate,” she said.

The research was also supported by FAPESP via a Doctoral Scholarship in Brazil and a Research Internship Abroad Scholarship awarded to Messa, and a Regular Research Grant awarded to Faez.

Messa was assisted by a colleague at the University of California Davis (USA), where he worked as a research intern.

About São Paulo Research Foundation (FAPESP)

The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. You can learn more about FAPESP at www.fapesp.br/en and visit FAPESP news agency at www.agencia.fapesp.br/en to keep updated with the latest scientific breakthroughs FAPESP helps achieve through its many programs, awards and research centers. You may also subscribe to FAPESP news agency at http://agencia.fapesp.br/subscribe

I have links and citations for both papers mentioned in the press release,

Sugarcane bagasse derived phosphorylated cellulose as substrates for potassium release induced by phosphates surface and drying methods by Lucas Luiz Messa, You-Lo Hsieh, Roselena Faez. Industrial Crops and Products Volume 187, Part A, 1 November 2022, 115350 DOI: https://doi.org/10.1016/j.indcrop.2022.115350 Available online 20 July 2022, Version of Record 20 July 2022

This paper is behind a paywall.

Charged-cellulose nanofibrils as a nutrient carrier in biodegradable polymers for enhanced efficiency fertilizers by Débora França, Gilberto Siqueira, Gustav Nyström, Frank Clemens, Claudinei Fonseca Souza, Roselena Faez. Carbohydrate Polymers Volume 296, 15 November 2022, 119934 DOI: https://doi.org/10.1016/j.carbpol.2022.119934 Available online 1 August 2022, Version of Record 3 August 2022

This paper is behind a paywall.

Nanoplastics in the air we breathe

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Most of the research I’ve seen about polluting nanoplastics it concerns the ocean; this time it concerns the air. This research dates from November 2021 but I didn’t stumble across it until this February 2, 2022 article by Talib Visram for Fast Company (Note: Links have been removed),

By some estimates, people have discarded 4,900 million tonnes of plastic have into the environment. Once in nature, that plastic starts to degrade, fragmenting into microplastics about the size of a sesame seed, which are inadvertently ingested by humans and animals through eating them in seafood and drinking them in water. Some reports suggest that we all consume five grams a week–about the weight of a bottle cap.

But, we may be taking more plastics into our systems through our respiratory systems. There’s been less investigation of nanoplastics: particles smaller than microplastics, so small that they can move huge distances in the air and be more easily inhaled into the bloodstream. A new study looks at the travel of those lighter particles, finding them abundant in the atmosphere, and carried, via aerosol transmission, even to remote areas. As far as the scientists know, it’s “the most accurate record of air pollution by nanoplastics ever made.”

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A February 1, 2022 news item on SciTechDaily.com highlights some of the concerns raised by the research,

In a new study, Empa [Swiss Federal Laboratories for Materials Science and Technology] researcher Dominik Brunner, together with colleagues from Utrecht University and the Austrian Central Institute for Meteorology and Geophysics, is investigating how much plastic is trickling down on us from the atmosphere.

According to the study, some nanoplastics travel over 2000 kilometers through the air. According to the figures from the measurements about 43 trillion miniature plastic particles land in Switzerland every year. Researchers still disagree on the exact number. But according to estimates from the study, it could be as much as 3,000 tonnes of nanoplastics that cover Switzerland every year, from the remote Alps to the urban lowlands. These estimates are very high compared to other studies, and more research is needed to verify these numbers.

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A January 25, 2022 EMPA [Swiss Federal Laboratories for Materials Science and Technology] press release by Noé Waldmann, which originated the news item, provides some technical details,

In a large-scale fundraising campaign, popular YouTubers like Mister Beast and Mark Rober are currently trying to rid the oceans of almost 14,000 tonnes of plastic waste. That’s about 0.15 per cent of the amount that ends up in the oceans every year. But it’s not just our waters that are full of plastic. A new study shows that the spread of nanoplastic through the air is a more widespread problem than previously thought.

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Extreme conditions

The scientists studied a small area at an altitude of 3106 meters at the top of the mountain “Hoher Sonnenblick” in the “Hohe Tauern” National Park in Austria. An observatory of the Central Institute for Meteorology and Geodynamics has been located here since 1886. The observatory is run by meteorologist and Arctic researcher Elke Ludewig. Since research began here in the late 19th century, the observatory has only been non-operational on four days. The research station also served as a base for the study on the spread of nanoplastics in remote areas.

Every day, and in all weather conditions, scientists removed a part of the top layer of snow around a marker at 8 AM and carefully stored it. Contamination of the samples by nanoplastics in the air or on the scientists’ clothes was a particular challenge. In the laboratory, the researchers sometimes had to remain motionless when a colleague handled an open sample.

The origin of the tiny particles was traced with the help of European wind and weather data. The researchers could show that the greatest emission of nanoplastics into the atmosphere occurs in densely populated, urban areas. About 30% of the nanoplastic particles measured on the mountain top originate from a radius of 200 kilometers, mainly from cities. However, plastics from the world’s oceans apparently also get into the air via the spray of the waves. Around 10% of the particles measured in the study were blown onto the mountain by wind and weather over 2000 kilometers – some of them from the Atlantic.

Nanoparticles in the bloodstream

It is estimated that more than 8300 million tonnes of plastic have been produced worldwide to date, about 60% of which is now waste. This waste erodes through weathering effects and mechanical abrasion from macro- to micro- and nanoparticles. But discarded plastic is far from the only source. Everyday use of plastic products such as packaging and clothing releases nanoplastics. Particles in this size range are so light that their movement in the air can best be compared to gases.

Besides plastics, there are all kinds of other tiny particles. From Sahara sand to brake pads, the world is buzzing through the air as abrasion. It is as yet unclear whether this kind of air pollution poses a potential health threat to humans. Nanoparticles, unlike microparticles, do not just end up in the stomach. They are sucked deep into the lungs through respiration, where their size may allow them to cross the cell-blood barrier and enter the human bloodstream. Whether this is harmful or even dangerous, however, remains to be researched.

Included here because of its compelling story is Utrecht University’s November 1, 2021 press release conveying the researchers’ excitement, (Note: Links have been removed)

Nanoplastics found in the Alps, transported by air from Frankfurt, Paris and London

A team of researchers have found nanoplastics at the pristine high-altitude Sonnblick Observatory in the Alps. This is the first time that nanoplastics were found in this area. The researchers were originally looking for certain organic particles, but found nanoplastics by chance, discovering a new analysis method for detecting nanoplastics in the process. …

The researchers were looking for organic particles by taking samples of snow or ice, evaporating them, and then burning the residue to detect and analyse the vapours. “Our detection method is a bit like a mechanical nose. And unexpectedly, it smelled burning plastics in our snow samples,” lead researcher Dušan Materić explains. The detector found the smell of several types of plastic, mostly polypropylene (PP) and polyethylene terephthalate (PET).

The detected plastic particles turned out to be less than 200 nm in size, about one hundredth the width of a human hair. That is significantly smaller than plastic particles detected in previous studies. “With this detection method, we are the first group to quantify nanoplastics in the environment,” says Materić. “Since the high Alps are a very remote and pristine area, we were quite shocked and surprised to find such a high concentration of nanoplastics there.” The results suggest that in addition to microplastics, there might be as much nanoplastics present in these remote places.

Transported by air

“We were quite gripped by these findings,” Materić continues. “It’s highly unlikely that these nanoplastics originated from local pristine Alpine areas. So where did they come from? We completely turned around our research project to study this further.”

The researchers found a striking correlation between high concentrations of nanoplastics and winds coming from the direction of major European cities, most notably Frankfurt and the industrial Ruhr area (Germany), but also the Netherlands, Paris, and even London.

“Advanced modelling supported the idea that nanoplastics are indeed transported by air from these urban places,” says Materić. “That’s potentially alarming, because that could mean that there are hotspots of nanoplastics in our cities, and indeed in the very air we’re breathing. We are currently studying this in more detail.” Since working on the current publication, Materić has already received an additional NWO [Dutch Research Council] grant of 50,000 Euros to study the size distribution of nanoplastics in indoor, urban and rural air.

Here’s a link to and a citation for the paper,

Nanoplastics transport to the remote, high-altitude Alps by Dušan Materić,
Elke Ludewig, Dominik Brunner, Thomas Röckmann, Rupert Holzinger. Environmental Pollution Volume 288, 1 November 2021, 117697 DOI: https://doi.org/10.1016/j.envpol.2021.117697

This paper is open access.

Nanocellulose sensors: 3D printed and biocompatible

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I do like to keep up with nanocellulose doings, especially when there’s some Canadian involvement, and an October 8, 2019 news item on Nanowerk alerted me to a newish application for the product,

Physiological parameters in our blood can be determined without painful punctures. Empa researchers are currently working with a Canadian team to develop flexible, biocompatible nanocellulose sensors that can be attached to the skin. The 3D-printed analytic chips made of renewable raw materials will even be biodegradable in future.

The idea of measuring parameters that are relevant for our health via the skin has already taken hold in medical diagnostics. Diabetics, for example, can painlessly determine their blood sugar level with a sensor instead of having to prick their fingers.

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An October 8, 2019 Empa (Swiss Federal Laboratories for Materials Science and Technology) press release, which originated the news item, provides more detail,

A transparent foil made of wood

Nanocellulose is an inexpensive, renewable raw material, which can be obtained in form of crystals and fibers, for example from wood. However, the original appearance of a tree no longer has anything to do with the gelatinous substance, which can consist of cellulose nanocrystals and cellulose nanofibers. Other sources of the material are bacteria, algae or residues from agricultural production. Thus, nanocellulose is not only relatively easy and sustainable to obtain. Its mechanical properties also make the “super pudding” an interesting product. For instance, new composite materials based on nanocellulose can be developed that could be used as surface coatings, transparent packaging films or even to produce everyday objects like beverage bottles.

Researchers at Empa’s Cellulose & Wood Materials lab and Woo Soo Kim from the Simon Fraser University [SFU] in Burnaby, Canada, are also focusing on another feature of nanocellulose: biocompatibility. Since the material is obtained from natural resources, it is particularly suitable for biomedical research.

With the aim of producing biocompatible sensors that can measure important metabolic values, the researchers used nanocellulose as an “ink” in 3D printing processes. To make the sensors electrically conductive, the ink was mixed with silver nanowires. The researchers determined the exact ratio of nanocellulose and silver threads so that a three-dimensional network could form.

Just like spaghetti – only a wee bit smaller

It turned out that cellulose nanofibers are better suited than cellulose nanocrystals to produce a cross-linked matrix with the tiny silver wires. “Cellulose nanofibers are flexible similar to cooked spaghetti, but with a diameter of only about 20 nanometers and a length of just a few micrometers,” explains Empa researcher Gilberto Siqueira.

The team finally succeeded in developing sensors that measure medically relevant metabolic parameters such as the concentration of calcium, potassium and ammonium ions. The electrochemical skin sensor sends its results wirelessly to a computer for further data processing. The tiny biochemistry lab on the skin is only half a millimeter thin.

While the tiny biochemistry lab on the skin – which is only half a millimeter thin – is capable of determining ion concentrations specifically and reliably, the researchers are already working on an updated version. “In the future, we want to replace the silver [nano] particles with another conductive material, for example on the basis of carbon compounds,” Siqueira explains. This would make the medical nanocellulose sensor not only biocompatible, but also completely biodegradable.

I like the images from Empa better than the ones from SFU,

Using a 3D printer, the nanocellulose “ink” is applied to a carrier plate. Silver particles provide the electrical conductivity of the material. Image: Empa
Empa researcher Gilberto Siqueira demonstrates the newly printed nanocellulose circuit. After a subsequent drying, the material can be further processed. Image: Empa

SFU produced a news release about this work back in February 2019. Again, I prefer what the Swiss have done because they’re explaining/communicating the science, as well as , communicating benefits. From a February 13, 2019 SFU news release (Note: Links have been removed),

Simon Fraser University and Swiss researchers are developing an eco-friendly, 3D printable solution for producing wireless Internet-of-Things (IoT) sensors that can be used and disposed of without contaminating the environment. Their research has been published as the cover story in the February issue of the journal Advanced Electronic Materials.

SFU professor Woo Soo Kim is leading the research team’s discovery, which uses a wood-derived cellulose material to replace the plastics and polymeric materials currently used in electronics.

Additionally, 3D printing can give flexibility to add or embed functions onto 3D shapes or textiles, creating greater functionality.

“Our eco-friendly, 3D-printed cellulose sensors can wirelessly transmit data during their life, and then can be disposed without concern of environmental contamination,” says Kim, a professor in the School of Mechatronic Systems Engineering. The SFU research is being carried out at PowerTech Labs in Surrey, which houses several state-of-the-art 3D printers used to advance the research.

“This development will help to advance green electronics. For example, the waste from printed circuit boards is a hazardous source of contamination to the environment. If we are able to change the plastics in PCB to cellulose composite materials, recycling of metal components on the board could be collected in a much easier way.”

Kim’s research program spans two international collaborative projects, including the latest focusing on the eco-friendly cellulose material-based chemical sensors with collaborators from the Swiss Federal Laboratories for Materials Science.

He is also collaborating with a team of South Korean researchers from the Daegu Gyeongbuk Institute of Science and Technology’s (DGIST)’s department of Robotics Engineering, and PROTEM Co Inc, a technology-based company, for the development of printable conductive ink materials.

In this second project, researchers have developed a new breakthrough in the embossing process technology, one that can freely imprint fine circuit patterns on flexible polymer substrate, a necessary component of electronic products.

Embossing technology is applied for the mass imprinting of precise patterns at a low unit cost. However, Kim says it can only imprint circuit patterns that are imprinted beforehand on the pattern stamp, and the entire, costly stamp must be changed to put in different patterns.

The team succeeded in developing a precise location control system that can imprint patterns directly resulting in a new process technology. The result will have widespread implications for use in semiconductor processes, wearable devices and the display industry.

This paper was made available online back in December 2018 and then published in print in February 2019. As to why there’d be such large gaps between the paper’s publication dates and the two institution’s news/press releases, it’s a mystery to me. In any event, here’s a link to and a citation for the paper,

3D Printed Disposable Wireless Ion Sensors with Biocompatible Cellulose Composites by Taeil Kim, Chao Bao, Michael Hausmann, Gilberto Siqueira, Tanja Zimmermann, Woo Soo Kim. Advanced Electronic Materials DOI: https://doi.org/10.1002/aelm.201970007 First published online December 19, 2018. First published in print: 08 February 2019 (Adv. Electron. Mater. 2/2109) Volume 5, Issue 2 February 2019 1970007

This paper is behind a paywall.