Vehicle body made from cotton, hemp, and wood

bio-based textile fibers

bio-based textile fibers

Carbon and glass fibers reinforce synthetics so that they can be used for vehicle body construction. But in this regard, there is an abundance of potential found in natural fibers – obtained from hemp, cotton, or wood. If you combined bio-based textile and carbon fibers, you can obtain extremely light yet very sturdy components.

“Lightweight” is an important buzzword in automotive engineering, and just as important in the aerospace sector, too. Carmakers are increasingly counting on fiber reinforced synthetics. These fibers, which are embedded into the synthetic matrix, give the material its additional durability. Exactly which material you choose to use depends on its eventual application. Thus, primarily carbon fiber is used in Formula 1 racing. However, one drawback is its high price; even its processing can be tough. These are the reasons why carbon fiber-reinforced plastics (CFRPs) have still not yet found their path into wide-scale serial production so far to date. Glass fibers, on the other hand, are certainly reasonably priced, but heavy by comparison. But this may soon change, thanks to some new research approaches by researchers at the Application Center for Wood Fiber Research HOFZET of the Fraunhofer Institute for Wood Research, the Wilhelm-Klauditz-Institut WKI in Braunschweig.

Combining advantages, eliminating disadvantages

The scientists are relying on natural fibers of botanical origin. Variants derived from hemp, flax, cotton and wood are about as affordable as glass fibers, and moreover have a lower density than the pendants made of glass or carbon. Another advantage: If you incinerate them at the end of their life cycle, they produce additional energy – without leaving residues. Nevertheless, their durability and stability don´t reach that of carbon fibers. ”Depending on the application, we are therefore combining carbon with various bio-based textile fibers,” explains Prof. Dr.-Ing. Hans-Josef Endres, head of the Application Center for Wood Fiber Research. The fibers typically exist as fabrics that are placed on each other accordingly and are embedded by the plastic matrix. “We use carbon fibers in those areas where the part undergoes intense mechanical stress; in other areas, it’s natural fibers. This way, we can leverage the strengths of the respective fibers and get rid of the disadvantages to a great extent. ”The outcome: the parts are cost-effective, have a very high degree of durability, possess excellent acoustic properties and are substantially more ecological than pure carbon components.

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Safer than silver: antibacterial material made with algae

A close-up of the antibacterial fibre created by the KTH scientists. In this 2x2cm swatch of fabric are nearly 200,000 threads running in the same direction.

A close-up of the antibacterial fibre created by the KTH scientists. In this 2x2cm swatch of fabric are nearly 200,000 threads running in the same direction.

Consumers concerned about safety of silver ions in antibacterial and odor-free clothing will soon have a proven safe alternative thanks to ultra-thin thread and a substance found naturally in red algae.

The use of silver ions for antibacterial textiles has been a matter of hot debate worldwide. Sweden’s national agency for chemical inspection is one authority which has ruled silver a health risk, citing possible damage to human genetic material, reproduction and embryonic development.

Mikael Hedenqvist, professor of polymer materials at KTH Royal Institute of Technology, says he and his colleagues, assistant professor Richard Olsson and doctoral student Rickard Andersson, have produced new antibacterial fibres that combine bio-compatible plastics with the antimicrobial compound, lanosol, which is commonly found in seaweeds of the family Rhodophyta, or red algae.

“The substance is a good alternative to particle-based antibacterials for clothing, as well as compresses or bandages,” Hedenqvist says.

Using a process called electrospinning, they have succeeded in creating an ultra-thin thread, which means fabrics can have more contact between the antibacterial fibre and the surrounding area.

“Electrospinning produces quite thin thread, with a thickness on the order of one-hundreth of a human hair,” Hedenqvist says. The result is more effective clean-up of bacteria.

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Super-Stretchable Yarn Is Made of Graphene

Strong, stretchable fibers made of graphene oxide can be knotted like yarn. Credit: Terrones group, Penn State

Researchers at Penn State and Shinshu University in Japan have developed a simple, scalable method of making graphene oxide (GO) fibers that are strong, stretchable and can be easily scrolled into yarns with strengths approaching that of Kevlar.

The researchers made a thin film of graphene oxide by chemically exfoliating graphite into graphene flakes, which were then mixed with water and concentrated by centrifugation into a thick slurry. The slurry was then spread by bar coating – something like a squeegee – across a large plate. When the slurry dries, it becomes a large-area transparent film that can be carefully lifted off without tearing. The film is then cut into narrow strips and wound on itself with an automatic fiber scroller, resulting in a fiber that can be knotted and stretched without fracturing.

“We found this graphene oxide fiber was very strong, much better than other carbon fibers. We believe that pockets of air inside the fiber keep it from being brittle,” says Mauricio Terrones, professor of physics, chemistry and materials science and engineering at Penn State. Terrones and colleagues believe this method opens up multiple possibilities for useful products. For instance, removing oxygen from the GO fiber results in a graphene fiber with high electrical conductivity. Adding silver nanorods to the graphene film would increase the conductivity to the same as copper, which could make it a much lighter weight replacement for copper transmission lines. Many kinds of highly sensitive sensors are imaginable.

“The importance is that we can do almost any material, and that could open up many avenues – it’s a lightweight material with multifunctional properties,” Terrones remarks.

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UT Dallas-led team makes powerful muscles from fishing line and sewing thread

An international team led by The University of Texas at Dallas has discovered that ordinary fishing line and sewing thread can be cheaply converted to powerful artificial muscles.

The new muscles can lift a hundred times more weight and generate a hundred times higher mechanical power than the same length and weight of human muscle. Per weight, they can generate 7.1 horsepower per kilogram, about the same mechanical power as a jet engine.

In a paper published Feb. 21 in the journal Science, researchers explain that the powerful muscles are produced by twisting and coiling high-strength polymer fishing line and sewing thread. Scientists at UT Dallas’s Alan G. MacDiarmid NanoTech Institute teamed with scientists from universities in Australia, South Korea, Canada, Turkey and China to accomplish the advances.

The muscles are powered thermally by temperature changes, which can be produced electrically, by the absorption of light or by the chemical reaction of fuels. Twisting the polymer fiber converts it to a torsional muscle that can spin a heavy rotor to more than 10,000 revolutions per minute. Subsequent additional twisting, so that the polymer fiber coils like a heavily twisted rubber band, produces a muscle that dramatically contracts along its length when heated, and returns to its initial length when cooled. If coiling is in a different twist direction than the initial polymer fiber twist, the muscles instead expand when heated.

Compared to natural muscles, which contract by only about 20 percent, these new muscles can contract by about 50 percent of their length. The muscle strokes also are reversible for millions of cycles as the muscles contract and expand under heavy mechanical loads.

“The application opportunities for these polymer muscles are vast,” said corresponding author Dr. Ray Baughman, the Robert A. Welch Distinguished Chair in Chemistry at UT Dallas and director of the NanoTech Institute. “Today’s most advanced humanoid robots, prosthetic limbs and wearable exoskeletons are limited by motors and hydraulic systems, whose size and weight restrict dexterity, force generation and work capability.”

Baughman said the muscles could be used for applications where superhuman strengths are sought, such as robots and exoskeletons. Twisting together a bundle of polyethylene fishing lines, whose total diameter is only about 10 times larger than a human hair, produces a coiled polymer muscle that can lift 16 pounds. Operated in parallel, similar to how natural muscles are configured, a hundred of these polymer muscles could lift about 0.8 tons, Baughman said.

On the opposite extreme, independently operated coiled polymer muscles having a diameter less than a human hair could bring life-like facial expressions to humanoid companion robots for the elderly and dexterous capabilities for minimally invasive robotic microsurgery. Also, they could power miniature “laboratories on a chip,” as well as devices for communicating the sense of touch from sensors on a remote robotic hand to a human hand.

The polymer muscles are normally electrically powered by resistive heating using the metal coating on commercially available sewing thread or by using metal wires that are twisted together with the muscle. For other applications, however, the muscles can be self-powered by environmental temperature changes, said Carter Haines, lead author of the study.

“We have woven textiles from the polymer muscles whose pores reversibly open and close with changes in temperature. This offers the future possibility of comfort-adjusting clothing,” said Haines, who started his research career in Baughman’s lab as a high school student doing summer research through the NanoExplorers program, which Baughman initiated. Haines earned an undergraduate physics degree from UT Dallas and is now a doctoral student in materials science and engineering.

The research team also has demonstrated the feasibility of using environmentally powered muscles to automatically open and close the windows of greenhouses or buildings in response to ambient temperature changes, thereby eliminating the need for electricity or noisy and costly motors.

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Paralysis promises smart silk technology

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A major step towards the large-scale production of silks with tailor-made properties

Oxford University researchers have harnessed the natural defence mechanism of silkworms, which causes paralysis, in what is a major step towards the large-scale production of silks with tailor-made properties.

Professor Fritz Vollrath and colleagues from the Oxford Silk Group at Oxford University’s Department of Zoology collected silk directly from paralysed silkworms by injecting a chemical that is naturally produced by the animal. In the wild silkworms produce this hormone when they are injured since, as they move their bodies through hydrostatic pressure, without this self-induced paralysis their wounds would get worse and they would risk ‘bleeding out’.

The team’s report in the journal Biomacromolecules this week concludes that, in comparison to unparalysed silkworms, paralysis allows longer and more consistent silks to be collected by eliminating the ability of the silkworm to break and alter its silk fibre.

The direct ‘forced reeling’ of silk has been used in spiders for many years. However, reeling large amounts of silk directly from silkworms has not previously been possible. By tricking the silkworm into performing its natural response to injury and becoming paralysed the Oxford scientists show that it is possible to reel hundreds of meters of silk under full control.

Unlike unravelling cocoons, as in the silk textile industry, silkworm forced reeling allows the silk properties to be modified to suit particular purposes. This has important implications for the large-scale reeling of silkworms for industrial production of environmentally-friendly fibres for use in a range of applications – from biomedical implants through to super-tough composite panels.

Silkworm paralysis may open the door to a range of silk technologies, using these animals which, unlike spiders, can be farmed at high-densities. Reeling of silk from paralysed worms is the subject of a recent patent, which also highlights the exciting potential for genetically modifying silkworms to induce paralysis ‘on-demand’, a particularly useful feature for mass-rearing.

‘This is an interesting result as the paralysis prevents the silkworms breaking the fibre, but still allows silk spinning and collection,’ said Beth Mortimer of the Oxford Silk Group, an author of the report.

‘The commercial implications of this process are self evident: now we can make silks to order by manipulating the mechanical properties while at the same time adding functionality,’ said Professor Vollrath.

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