Tag Archives: Gilberto Siqueira

Aerogels that are 3D printed from nanocellulose

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.

Cellulose nanofibrils for slow-release fertilizer

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.

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.


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.

Nanocellulosic 3D-printed ears

It’s been a while since I’ve had a story abut cellulose nanocrystals (CNC) and this one comes from Switzerland’s Empa (Swiss Federal Laboratories for Materials Science and Technology) in a January 15, 2019 news item on Nanowerk (Note: A link has been removed),

Cellulose obtained from wood has amazing material properties. Empa researchers are now equipping the biodegradable material with additional functionalities to produce implants for cartilage diseases using 3D printing (ACS Nano, “Dynamics of Cellulose Nanocrystal Alignment during 3D Printing”).

It all starts with an ear. Empa researcher Michael Hausmann removes the object shaped like a human ear from the 3D printer and explains: “In viscous state cellulose nanocrystals can easily be shaped together with nother biopolymers into complex 3-dimensional structures using a 3D printer, such as the Bioplotter.”

Once cross-linked, the structures remain stable despite their soft mechanical properties. Hausmann is currently investigating the characteristics of the nanocellulose composite hydrogels in order to further optimize their stability as well as the printing process. The researcher already used X-ray analysis to determine how cellulose is distributed and organized within the printed structures.

At this point in time the printed ear is entirely and solely made of cellulose nanocrystals and a biopolymer. However, the objective is to incorporate both human cells and therapeutics into the base structure in order to produce biomedical implants.

Here’s one of the researchers (Michael Hausmann) showing off their ‘ear’,

A 3D-printed ear: Empa researcher Michael Hausmann uses nanocellulose as the basis for novel implants (Image: Empa)

Doesn’t look like much does, eh? It’s scaffolding or, you could say, a kind of skeleton and a January 15, 2019 Empa press release, which originated the news item, describes it and explains how it will house new cells,

A new project is currently underway, looking into how chondrocytes (cartilage cells) can be integrated into the scaffold to yield artificial cartilage tissue. As soon as the colonization of the hydrogel with cells is established, nanocellulose based composites in the shape of an ear could serve as an implant for children with an inherited auricular malformation as for instance, in microtia, where the external ears are only incompletely developed. A reconstruction of the auricle can esthetically and medically correct the malformation; otherwise the hearing ability can be severely impaired. In the further course of the project, cellulose nanocrystals containing hydrogels will also be used for the replacement of articular cartilage (e.g. knee) in cases of joint wear due to, for example, chronic arthritis.

Once the artificial tissue has been implanted in the body, the biodegradable polymer material is expected to degrade over time. The cellulose itself is not degradable in the body, but biocompatible. However, it is not only its biocompatibility that makes nanocellulose the perfect material for implant scaffolds. “It is also the mechanical performance of cellulose nanocrystals that make them such promising candidates because the tiny but highly stable fibers can extremely well reinforce the produced implant,” said Hausmann.

Moreover, nanocellulose allows the incorporation of various functions by chemical modifications into the viscous hydrogel. Thus, the structure, the mechanical properties and the interactions of the nanocellulose with its environment can be specifically tailored to the desired end product. “For instance, we can incorporate active substances that promote the growth of chondrocytes or that sooth joint inflammation into the hydrogel,” says the Empa researcher.

And last but not least, as raw material cellulose is the most abundant natural polymer on earth. Therefore, the use of cellulose nanocrystals not only benefits from the mere elegance of the novel process but also from the availability of the raw material.

The white nanocellulose ear lies glossy on the glass carrier. Just out of the Bioplotter, it is already robust and dimensionally stable. Hausmann can give the go-ahead for the next steps. 

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

Dynamics of Cellulose Nanocrystal Alignment during 3D Printing by Michael K. Hausmann, Patrick A. Rühs, Gilberto Siqueira, Jörg Läuger, Rafael Libanori, Tanja Zimmermann, and André R. Studart. ACS Nano, 2018, 12 (7), pp 6926–6937 DOI: 10.1021/acsnano.8b02366 Publication Date (Web): July 5, 2018

Copyright © 2018 American Chemical Society

This paper is behind a paywall.