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Waterfiltration Photo Manuel Darío Fuentes Hernández , Pixabay
10.11.2024

New filtration material could remove long-lasting chemicals from water

Membranes based on natural silk and cellulose can remove many contaminants, including “forever chemicals” and heavy metals.

Water contamination by the chemicals used in today’s technology is a rapidly growing problem globally. A recent study by the U.S. Centers for Disease Control found that 98 percent of people tested had detectable levels of PFAS, a family of particularly long-lasting compounds also known as “forever chemicals,” in their bloodstream.

A new filtration material developed by researchers at MIT might provide a nature-based solution to this stubborn contamination issue. The material, based on natural silk and cellulose, can remove a wide variety of these persistent chemicals as well as heavy metals. And, its antimicrobial properties can help keep the filters from fouling.

Membranes based on natural silk and cellulose can remove many contaminants, including “forever chemicals” and heavy metals.

Water contamination by the chemicals used in today’s technology is a rapidly growing problem globally. A recent study by the U.S. Centers for Disease Control found that 98 percent of people tested had detectable levels of PFAS, a family of particularly long-lasting compounds also known as “forever chemicals,” in their bloodstream.

A new filtration material developed by researchers at MIT might provide a nature-based solution to this stubborn contamination issue. The material, based on natural silk and cellulose, can remove a wide variety of these persistent chemicals as well as heavy metals. And, its antimicrobial properties can help keep the filters from fouling.

The findings are described in the journal ACS Nano, in a paper by MIT postdoc Yilin Zhang, professor of civil and environmental engineering Benedetto Marelli, and four others from MIT.

PFAS chemicals are present in a wide range of products, including cosmetics, food packaging, water-resistant clothing, firefighting foams, and antistick coating for cookware. A recent study identified 57,000 sites contaminated by these chemicals in the U.S. alone. The U.S. Environmental Protection Agency has estimated that PFAS remediation will cost $1.5 billion per year, in order to meet new regulations that call for limiting the compound to less than 7 parts per trillion in drinking water.

Contamination by PFAS and similar compounds “is actually a very big deal, and current solutions may only partially resolve this problem very efficiently or economically,” Zhang says. “That’s why we came up with this protein and cellulose-based, fully natural solution,” he says.

“We came to the project by chance,” Marelli notes. The initial technology that made the filtration material possible was developed by his group for a completely unrelated purpose — as a way to make a labelling system to counter the spread of counterfeit seeds, which are often of inferior quality. His team devised a way of processing silk proteins into uniform nanoscale crystals, or “nanofibrils,” through an environmentally benign, water-based drop-casting method at room temperature.

Zhang suggested that their new nanofibrillar material might be effective at filtering contaminants, but initial attempts with the silk nanofibrils alone didn’t work. The team decided to try adding another material: cellulose, which is abundantly available and can be obtained from agricultural wood pulp waste. The researchers used a self-assembly method in which the silk fibroin protein is suspended in water and then templated into nanofibrils by inserting “seeds” of cellulose nanocrystals. This causes the previously disordered silk molecules to line up together along the seeds, forming the basis of a hybrid material with distinct new properties.

By integrating cellulose into the silk-based fibrils that could be formed into a thin membrane, and then tuning the electrical charge of the cellulose, the researchers produced a material that was highly effective at removing contaminants in lab tests.

The electrical charge of the cellulose, they found, also gave it strong antimicrobial properties. This is a significant advantage, since one of the primary causes of failure in filtration membranes is fouling by bacteria and fungi. The antimicrobial properties of this material should greatly reduce that fouling issue, the researchers say.

“These materials can really compete with the current standard materials in water filtration when it comes to extracting metal ions and these emerging contaminants, and they can also outperform some of them currently,” Marelli says. In lab tests, the materials were able to extract orders of magnitude more of the contaminants from water than the currently used standard materials, activated carbon or granular activated carbon.

While the new work serves as a proof of principle, Marelli says, the team plans to continue working on improving the material, especially in terms of durability and availability of source materials. While the silk proteins used can be available as a byproduct of the silk textile industry, if this material were to be scaled up to address the global needs for water filtration, the supply might be insufficient. Also, alternative protein materials may turn out to perform the same function at lower cost.

Initially, the material would likely be used as a point-of-use filter, something that could be attached to a kitchen faucet, Zhang says. Eventually, it could be scaled up to provide filtration for municipal water supplies, but only after testing demonstrates that this would not pose any risk of introducing any contamination into the water supply. But one big advantage of the material, he says, is that both the silk and the cellulose constituents are considered food-grade substances, so any contamination is unlikely.

“Most of the normal materials available today are focusing on one class of contaminants or solving single problems,” Zhang says. “I think we are among the first to address all of these simultaneously.”

“What I love about this approach is that it is using only naturally grown materials like silk and cellulose to fight pollution,” says Hannes Schniepp, professor of applied science at the College of William and Mary, who was not associated with this work. “In competing approaches, synthetic materials are used — which usually require only more chemistry to fight some of the adverse outcomes that chemistry has produced. [This work] breaks this cycle! ... If this can be mass-produced in an economically viable way, this could really have a major impact.”

The research team included MIT postdocs Hui Sun and Meng Li, graduate student Maxwell Kalinowski, and recent graduate Yunteng Cao PhD ’22, now a postdoc at Yale University. The work was supported by the U.S. Office of Naval Research, the U.S. National Science Foundation, and the Singapore-MIT Alliance for Research and Technology.

Sensors made from ‘electronic spider silk’ printed on human skin (c) Huang Lab, Cambridge
27.05.2024

Sensors made from ‘electronic spider silk’ printed on human skin

Researchers have developed a method to make adaptive and eco-friendly sensors that can be directly and imperceptibly printed onto a wide range of biological surfaces, whether that’s a finger or a flower petal.

The method, developed by researchers from the University of Cambridge, takes its inspiration from spider silk, which can conform and stick to a range of surfaces. These ‘spider silks’ also incorporate bioelectronics, so that different sensing capabilities can be added to the ‘web’.

The fibres, at least 50 times smaller than a human hair, are so lightweight that the researchers printed them directly onto the fluffy seedhead of a dandelion without collapsing its structure. When printed on human skin, the fibre sensors conform to the skin and expose the sweat pores, so the wearer doesn’t detect their presence. Tests of the fibres printed onto a human finger suggest they could be used as continuous health monitors.

Researchers have developed a method to make adaptive and eco-friendly sensors that can be directly and imperceptibly printed onto a wide range of biological surfaces, whether that’s a finger or a flower petal.

The method, developed by researchers from the University of Cambridge, takes its inspiration from spider silk, which can conform and stick to a range of surfaces. These ‘spider silks’ also incorporate bioelectronics, so that different sensing capabilities can be added to the ‘web’.

The fibres, at least 50 times smaller than a human hair, are so lightweight that the researchers printed them directly onto the fluffy seedhead of a dandelion without collapsing its structure. When printed on human skin, the fibre sensors conform to the skin and expose the sweat pores, so the wearer doesn’t detect their presence. Tests of the fibres printed onto a human finger suggest they could be used as continuous health monitors.

This low-waste and low-emission method for augmenting living structures could be used in a range of fields, from healthcare and virtual reality, to electronic textiles and environmental monitoring. The results are reported in the journal Nature Electronics.

Although human skin is remarkably sensitive, augmenting it with electronic sensors could fundamentally change how we interact with the world around us. For example, sensors printed directly onto the skin could be used for continuous health monitoring, for understanding skin sensations, or could improve the sensation of ‘reality’ in gaming or virtual reality application.

While wearable technologies with embedded sensors, such as smartwatches, are widely available, these devices can be uncomfortable, obtrusive and can inhibit the skin’s intrinsic sensations.

Last year, some of the same researchers showed that if the fibres used in smart textiles were coated with materials that can withstand stretching, they could be compatible with conventional weaving processes. Using this technique, they produced a 46-inch woven demonstrator display.

“If you want to accurately sense anything on a biological surface like skin or a leaf, the interface between the device and the surface is vital,” said Professor Yan Yan Shery Huang from Cambridge’s Department of Engineering, who led the research. “We also want bioelectronics that are completely imperceptible to the user, so they don’t in any way interfere with how the user interacts with the world, and we want them to be sustainable and low waste.”

There are multiple methods for making wearable sensors, but these all have drawbacks. Flexible electronics, for example, are normally printed on plastic films that don’t allow gas or moisture to pass through, so it would be like wrapping your skin in cling film. Other researchers have recently developed flexible electronics that are gas-permeable, like artificial skins, but these still interfere with normal sensation, and rely on energy- and waste-intensive manufacturing techniques.

3D printing is another potential route for bioelectronics since it is less wasteful than other production methods, but leads to thicker devices that can interfere with normal behaviour. Spinning electronic fibres results in devices that are imperceptible to the user, but don't have a high degree of sensitivity or sophistication, and they’re difficult to transfer onto the object in question.

Now, the Cambridge-led team has developed a new way of making high-performance bioelectronics that can be customised to a wide range of biological surfaces, from a fingertip to the fluffy seedhead of a dandelion, by printing them directly onto that surface. Their technique takes its inspiration in part from spiders, who create sophisticated and strong web structures adapted to their environment, using minimal material.

The researchers spun their bioelectronic ‘spider silk’ from PEDOT:PSS (a biocompatible conducting polymer), hyaluronic acid and polyethylene oxide. The high-performance fibres were produced from water-based solution at room temperature, which enabled the researchers to control the ‘spinnability’ of the fibres. The researchers then designed an orbital spinning approach to allow the fibres to morph to living surfaces, even down to microstructures such as fingerprints.

Tests of the bioelectronic fibres, on surfaces including human fingers and dandelion seedheads, showed that they provided high-quality sensor performance while being imperceptible to the host.

“Our spinning approach allows the bioelectronic fibres to follow the anatomy of different shapes, at both the micro and macro scale, without the need for any image recognition,” said Andy Wang, the first author of the paper. “It opens up a whole different angle in terms of how sustainable electronics and sensors can be made. It’s a much easier way to produce large area sensors.”

Most high-resolution sensors are made in an industrial cleanroom and require the use of toxic chemicals in a multi-step and energy-intensive fabrication process. The Cambridge-developed sensors can be made anywhere and use a tiny fraction of the energy that regular sensors require.

The bioelectronic fibres, which are repairable, can be simply washed away when they have reached the end of their useful lifetime, and generate less than a single milligram of waste: by comparison, a typical single load of laundry produces between 600 and 1500 milligrams of fibre waste.

“Using our simple fabrication technique, we can put sensors almost anywhere and repair them where and when they need it, without needing a big printing machine or a centralised manufacturing facility,” said Huang. “These sensors can be made on-demand, right where they’re needed, and produce minimal waste and emissions.”

The research was supported in part by the European Research Council, Wellcome, the Royal Society, and the Biotechnology and Biological Sciences Research Council (BBSRC), part of UK Research and Innovation (UKRI).

Source:

Sarah Collins, University of Cambridge

Bacteria, eating Plastic and producing Multipurpose Spider Silk Photo: Kareni, Pixabay
05.02.2024

Bacteria, eating Plastic and producing Multipurpose Spider Silk

For the first time, researchers have used bacteria to “upcycle” waste polyethylene: Move over Spider-Man: Researchers at Rensselaer Polytechnic Institute have developed a strain of bacteria that can turn plastic waste into a biodegradable spider silk with multiple uses.

Their new study marks the first time scientists have used bacteria to transform polyethylene plastic — the kind used in many single-use items — into a high-value protein product.

That product, which the researchers call “bio-inspired spider silk” because of its similarity to the silk spiders use to spin their webs, has applications in textiles, cosmetics, and even medicine.

For the first time, researchers have used bacteria to “upcycle” waste polyethylene: Move over Spider-Man: Researchers at Rensselaer Polytechnic Institute have developed a strain of bacteria that can turn plastic waste into a biodegradable spider silk with multiple uses.

Their new study marks the first time scientists have used bacteria to transform polyethylene plastic — the kind used in many single-use items — into a high-value protein product.

That product, which the researchers call “bio-inspired spider silk” because of its similarity to the silk spiders use to spin their webs, has applications in textiles, cosmetics, and even medicine.

“Spider silk is nature’s Kevlar,” said Helen Zha, Ph.D., an assistant professor of chemical and biological engineering and one of the RPI researchers leading the project. “It can be nearly as strong as steel under tension. However, it’s six times less dense than steel, so it’s very lightweight. As a bioplastic, it’s stretchy, tough, nontoxic, and biodegradable.”

All those attributes make it a great material for a future where renewable resources and avoidance of persistent plastic pollution are the norm, Zha said.

Polyethylene plastic, found in products such as plastic bags, water bottles, and food packaging, is the biggest contributor to plastic pollution globally and can take upward of 1,000 years to degrade naturally. Only a small portion of polyethylene plastic is recycled, so the bacteria used in the study could help “upcycle” some of the remaining waste.

Pseudomonas aeruginosa, the bacteria used in the study, can naturally consume polyethylene as a food source. The RPI team tackled the challenge of engineering this bacteria to convert the carbon atoms of polyethylene into a genetically encoded silk protein. Surprisingly, they found that their newly developed bacteria could make the silk protein at a yield rivaling some bacteria strains that are more conventionally used in biomanufacturing.

The underlying biological process behind this innovation is something people have employed for millennia.

“Essentially, the bacteria are fermenting the plastic. Fermentation is used to make and preserve all sorts of foods, like cheese, bread, and wine, and in biochemical industries it’s used to make antibiotics, amino acids, and organic acids,” said Mattheos Koffas, Ph.D., Dorothy and Fred Chau ʼ71 Career Development Constellation Professor in Biocatalysis and Metabolic Engineering, and the other researcher leading the project, and who, along with Zha, is a member of the Center for Biotechnology and Interdisciplinary Studies at Rensselaer.

To get bacteria to ferment polyethylene, the plastic is first “predigested,” Zha said. Just like humans need to cut and chew our food into smaller pieces before our bodies can use it, the bacteria has difficulty eating the long molecule chains, or polymers, that comprise polyethylene.

In the study, Zha and Koffas collaborated with researchers at Argonne National Laboratory, who depolymerized the plastic by heating it under pressure, producing a soft, waxy substance. Next, the team put a layer of the plastic-derived wax on the bottoms of flasks, which served as the nutrient source for the bacteria culture. This contrasts with typical fermentation, which uses sugars as the nutrient source.

“It’s as if, instead of feeding the bacteria cake, we’re feeding it the candles on the cake,” Zha said.

Then, as a warming plate gently swirled the flasks’ contents, the bacteria went to work. After 72 hours, the scientists strained out the bacteria from the liquid culture, purified the silk protein, and freeze dried it. At that stage, the protein, which resembled torn up cotton balls, could potentially be spun into thread or made into other useful forms.

“What’s really exciting about this process is that, unlike the way plastics are produced today, our process is low energy and doesn’t require the use of toxic chemicals,” Zha said. “The best chemists in the world could not convert polyethylene into spider silk, but these bacteria can. We’re really harnessing what nature has developed to do manufacturing for us.”

However, before upcycled spider silk products become a reality, the researchers will first need to find ways to make the silk protein more efficiently.

“This study establishes that we can use these bacteria to convert plastic to spider silk. Our future work will investigate whether tweaking the bacteria or other aspects of the process will allow us to scale up production,” Koffas said.

“Professors Zha and Koffas represent the new generation of chemical and biological engineers merging biological engineering with materials science to manufacture ecofriendly products. Their work is a novel approach to protecting the environment and reducing our reliance on nonrenewable resources,” said Shekhar Garde, Ph.D., dean of RPI’s School of Engineering.

The study, which was conducted by first author Alexander Connor, who earned his doctorate from RPI in 2023, and co-authors Jessica Lamb and Massimiliano Delferro with Argonne National Laboratory, is published in the journal “Microbial Cell Factories.”

Source:

Samantha Murray, Rensselaer

Photo: Sibi Suku, unsplash
29.01.2024

Naturalistic silk spun from artificial spider gland

Researchers led by Keiji Numata at the RIKEN Center for Sustainable Resource Science in Japan, along with colleagues from the RIKEN Pioneering Research Cluster, have succeeded in creating a device that spins artificial spider silk that closely matches what spiders naturally produce. The artificial silk gland was able to re-create the complex molecular structure of silk by mimicking the various chemical and physical changes that naturally occur in a spider’s silk gland. This eco-friendly innovation is a big step towards sustainability and could impact several industries. This study was published January 15 in the scientific journal Nature Communications.

Researchers led by Keiji Numata at the RIKEN Center for Sustainable Resource Science in Japan, along with colleagues from the RIKEN Pioneering Research Cluster, have succeeded in creating a device that spins artificial spider silk that closely matches what spiders naturally produce. The artificial silk gland was able to re-create the complex molecular structure of silk by mimicking the various chemical and physical changes that naturally occur in a spider’s silk gland. This eco-friendly innovation is a big step towards sustainability and could impact several industries. This study was published January 15 in the scientific journal Nature Communications.

Famous for its strength, flexibility, and light weight, spider silk has a tensile strength that is comparable to steel of the same diameter, and a strength to weight ratio that is unparalleled. Added to that, it’s biocompatible, meaning that it can be used in medical applications, as well as biodegradable. So why isn’t everything made from spider silk? Large-scale harvesting of silk from spiders has proven impractical for several reasons, leaving it up to scientists to develop a way to produce it in the laboratory.

Spider silk is a biopolymer fiber made from large proteins with highly repetitive sequences, called spidroins. Within the silk fibers are molecular substructures called beta sheets, which must be aligned properly for the silk fibers to have their unique mechanical properties. Re-creating this complex molecular architecture has confounded scientists for years. Rather than trying to devise the process from scratch, RIKEN scientists took a biomimicry approach. As Numata explains, “in this study, we attempted to mimic natural spider silk production using microfluidics, which involves the flow and manipulation of small amounts of fluids through narrow channels. Indeed, one could say that that the spider’s silk gland functions as a sort of natural microfluidic device.”

The device developed by the researchers looks like a small rectangular box with tiny channels grooved into it. Precursor spidroin solution is placed at one end and then pulled towards the other end by means of negative pressure. As the spidroins flow through the microfluidic channels, they are exposed to precise changes in the chemical and physical environment, which are made possible by the design of the microfluidic system. Under the correct conditions, the proteins self-assembled into silk fibers with their characteristic complex structure.

The researchers experimented to find these correct conditions, and eventually were able to optimize the interactions among the different regions of the microfluidic system. Among other things, they discovered that using force to push the proteins through did not work; only when they used negative pressure to pull the spidroin solution could continuous silk fibers with the correct telltale alignment of beta sheets be assembled.

“It was surprising how robust the microfluidic system was, once the different conditions were established and optimized,” says Senior Scientist Ali Malay, one of the paper’s co-authors. “Fiber assembly was spontaneous, extremely rapid, and highly reproducible. Importantly, the fibers exhibited the distinct hierarchical structure that is found in natural silk fiber.”

The ability to artificially produce silk fibers using this method could provide numerous benefits. Not only could it help reduce the negative impact that current textile manufacturing has on the environment, but the biodegradable and biocompatible nature of spider silk makes it ideal for biomedical applications, such as sutures and artificial ligaments.

“Ideally, we want to have a real-world impact,” says Numata. “For this to occur, we will need to scale-up our fiber-production methodology and make it a continuous process. We will also evaluate the quality of our artificial spider silk using several metrics and make further improvements from there.”

Source:

RIKEN Center for Sustainable Resource Science, Japan

Silk Provides the Building Blocks to Transform Modern Medicine Photo: Jenna Schad
31.10.2023

Silk Provides the Building Blocks to Transform Modern Medicine

Tufts researchers harness protein from silk to make virus-sensing gloves, surgical screws that dissolve in your body, and other next-generation biomedical materials

About a mile northwest of Tufts’ Medford/Somerville campus, on the fourth floor of a refurbished woolen factory, there is a shrine to silk. Glass vases filled with silkworm cocoons and washed silk fibers sit artfully on a shelf across from a colorful drawing of the life cycle of Bombyx mori, the domesticated silk moth. Farther in, more cocoons in wall-mounted cases border a large, close-up image of silk fibers, and displays hold dozens of prototypes made from silk, including smart fabrics, biosensors, a helmet that changes color upon impact, and potential replacements for materials like leather, plastic, and particle board.

Tufts researchers harness protein from silk to make virus-sensing gloves, surgical screws that dissolve in your body, and other next-generation biomedical materials

About a mile northwest of Tufts’ Medford/Somerville campus, on the fourth floor of a refurbished woolen factory, there is a shrine to silk. Glass vases filled with silkworm cocoons and washed silk fibers sit artfully on a shelf across from a colorful drawing of the life cycle of Bombyx mori, the domesticated silk moth. Farther in, more cocoons in wall-mounted cases border a large, close-up image of silk fibers, and displays hold dozens of prototypes made from silk, including smart fabrics, biosensors, a helmet that changes color upon impact, and potential replacements for materials like leather, plastic, and particle board.

The only things missing are the silkworms themselves, but Fiorenzo Omenetto, the director of Silklab and the Frank C. Doble Professor of Engineering at Tufts, said they will be arriving soon. The lab is building a terrarium so that visitors can view the animals.
“We’re going to have a celebration of silkworms and moths,” Omenetto said.

Silk has been cultivated and harvested for thousands of years. It is best known for the strong, shimmering fabric that can be woven from its fibers, but it also has a long history of use in medicine to dress injuries and suture wounds. At Silklab, Omenetto and his colleagues are building on silk’s legacy, proving that this ancient fiber could help create the next generation of biomedical materials.

Silk moth caterpillars, known as silkworms, extrude a single sticky strand of silk from their mouths to form cocoons, which are harvested by silk farmers to make silk thread. At its core, silk is a mixture of two proteins: fibroin, which provides the fiber’s structure, and sericin, which binds it together. With a few steps in the lab, Tufts researchers can remove the sericin and dissolve the fibers, turning a dry cocoon into a fibroin-filled liquid.

“Nature builds structural proteins that are very tough and very strong,” Omenetto said. “Your bricks are these fibroin proteins floating in water. From there, you can build whatever you want.”
Starting with shipments of dried cocoons from silk farms, Omenetto and his colleagues have been able to create gels, sponges, clear plastic-like sheets, printable inks, solids that look like amber, dippable coatings, and much more.

“Each of the materials that you make can contain all these different functions, and there’s only 24 hours in a day,” Omenetto said with a laugh. “This is why I don’t sleep.”

Biocompatible and Biodegradable
When Omenetto arrived at Tufts almost two decades ago, his research was focused on lasers and optics—silk wasn’t in the picture. But a chance conversation with David Kaplan, the Stern Family Professor of Engineering and chair of the biomedical engineering department, set him on a new path.

Kaplan, who has been working with silk since the early ’90s, was designing a silk scaffold that would help rebuild a person’s cornea, allowing cells to grow between the layers. He needed a way to ensure that the growing cells would have enough oxygen and showed the small, transparent sheet to Omenetto, who was immediately intrigued by the material. Omenetto was able to use his lab’s lasers to put tiny holes in Kaplan’s silk cornea. More collaborations quickly followed.
“We’ve worked together incessantly since then,” Kaplan said.

One of those lines of research has been finding ways to use silk to help repair and regrow bone, blood vessels, nerves, and other tissue. Silk is biocompatible, meaning it doesn’t cause harm in the body and breaks down in predictable ways. With the right preparation, silk materials can provide necessary strength and structure while the body is healing.

“You can mold and shape silk to whatever you need, and it will hold that volume while the native tissue regrows into the space and the silk material degrades,” Kaplan said. “Eventually it’s 100 percent gone, and you’re back to your normal tissue.”

Some of this work has already been approved for use by the U.S. Food and Drug Administration. A company called Sofregen, which spun out of Kaplan and Omenetto’s research, is using an injectable silk-based gel to repair damaged vocal cords, the tissues that regulate air flow and help us speak.

On their own, sturdy silk structures can keep their size, shape, and function for years before degrading. But in some instances, such as those involving surgical screws and plates intended for use in rapidly growing children, this pace would be too slow. The researchers had to find a way to speed up the time it takes for dense silk biomaterials to break down. They introduced an enzyme that our bodies produce naturally into the silk to hasten the breakdown process. The idea is that the enzyme would sit dry and inactive within the silk device until the structure is installed in a person, then the device would hydrate and activate the enzyme to digest the material more rapidly.

“We can titer in just the right amount of enzyme to make a screw go away in a week, a month, a year,” Kaplan said. “We have control over the process.”

Currently, Kaplan and his lab are working on other small, degradable medical devices that would help cut down on the number of surgeries that patients need. Ear tubes, for example, are often surgically implanted to help alleviate chronic ear infections and then need to be surgically removed. Kaplan and his colleagues have designed silk-based ear tubes that degrade on their own and can even carry antibiotics.

“As someone with a daughter who went through six surgeries on her ear, I know how helpful this could be,” Kaplan said.

Source:

Laura Castañón, Tufts University, Massachusetts USA

(c) DITF
20.12.2022

New 3D printing process for sustainable fiber composite components

Nature works often with fiber composites. The construction principles of nature require little material and energy and thus ensure the survival of animals and plant species. Examples include wood, plant stalks, chitinous shells, bones or tissues such as tendons and skin. Mussel shells or spider silk are also composite tissues. We can take advantage of these principles to design and manufacture bio-based, sustainable fiber reinforced composites, which are currently in high demand. Bio-based fiber reinforced composites consist of natural fibers or cellulose fibers embedded in a bio-based matrix. The bio-based components offer properties comparable to those of commonly used glass fiber composites. The German Institutes of Textile and Fiber Research (DITF), together with Arburg GmbH + Co KG, are developing an energy- and material-efficient 3D printing process for manufacturing of such lightweight bio-based fiber composites.

Nature works often with fiber composites. The construction principles of nature require little material and energy and thus ensure the survival of animals and plant species. Examples include wood, plant stalks, chitinous shells, bones or tissues such as tendons and skin. Mussel shells or spider silk are also composite tissues. We can take advantage of these principles to design and manufacture bio-based, sustainable fiber reinforced composites, which are currently in high demand. Bio-based fiber reinforced composites consist of natural fibers or cellulose fibers embedded in a bio-based matrix. The bio-based components offer properties comparable to those of commonly used glass fiber composites. The German Institutes of Textile and Fiber Research (DITF), together with Arburg GmbH + Co KG, are developing an energy- and material-efficient 3D printing process for manufacturing of such lightweight bio-based fiber composites.

In fiber composites, which occur naturally, reinforcing fibers such as collagen or cellulose fibrils are embedded in a matrix of lignin, hemicellulose or collagen. The fiber strands align with the stress patterns. Tissues are formed mostly via solution-based physio-chemical processes that take place at ambient temperature. Similar to nature, new 3D printing processes with continuous fiber reinforcement also allow the deposition of fiber strands in the right place (topology optimization) and in the appropriate direction in accordance to the load. However, natural fibers such as cellulose fibers are sensitive to higher temperatures. Therefore, they cannot be processed in the commonly employed thermoplastic 3D printing process.

The result of the research work is 3D-printed fiber composite components consisting of cellulose continuous fibers embedded in a cellulose-based matrix. Newly developed 3D-printing process enables to manufacture the composites at ambient temperature. This means that - as in nature - the material and component can be produced simultaneously in a single operation at ambient temperature.

The cellulose fiber strand is first stabilized with a binder for processing in the printer. The specially designed print head transforms the binder into a matrix with which the cellulose continuous fibers are encased. Since the cellulose fibers and the matrix have similar chemical structures, the composite component is particularly stable. The mechanical properties, such as breaking strength, are exceptionally good. The solution-based and energy-efficient manufacturing method developed by the research team can also be used in other composite materials manufacturing processes. It is particularly suitable for processing temperature-sensitive materials that are in high demand, such as natural or cellulose fibers.

The " CellLoes-3D-Druck" research project is funded by the German Federal Ministry of Education and Research as part of the "Biologisierung der Technik" ideas competition.

Source:

Deutsche Institute für Textil- und Faserforschung Denkendorf