Fabrics that resist water are essential for everything from rainwear to military tents, but conventional water-repellent coatings have been shown to persist in the environment and accumulate in our bodies, and so are likely to be phased out for safety reasons. That leaves a big gap to be filled if researchers can find safe substitutes.
Now, a team at MIT has come up with a promising solution: a coating that not only adds water-repellency to natural fabrics such as cotton and silk, but is also more effective than the existing coatings. The new findings are described in the journal Advanced Functional Materials, in a paper by MIT professors Kripa Varanasi and Karen Gleason, former MIT postdoc Dan Soto, and two others.
“The challenge has been driven by the environmental regulators” because of the phaseout of the existing waterproofing chemicals, Varanasi explains. But it turns out his team’s alternative actually outperforms the conventional materials.
“Most fabrics that say ‘water-repellent’ are actually water-resistant,” says Varanasi, who is an associate professor of mechanical engineering. “If you’re standing out in the rain, eventually water will get through.” Ultimately, “the goal is to be repellent—to have the drops just bounce back.” The new coating comes closer to that goal, he says.
Researchers at North Carolina State University have successfully incorporated “photosensitizers” into a range of polymers, giving those materials the ability to render bacteria and viruses inactive using only ambient oxygen and visible-wavelength light. The new approach opens the door to a range of new products aimed at reducing the transmission of drug-resistant pathogens.
“The transmission of antibiotic-resistant pathogens, including so-called ‘superbugs,’ poses a significant threat to public health, with millions of medical cases occurring each year in the United States alone,” says Reza Ghiladi, associate professor of chemistry at NC State and co-corresponding author of a paper on the work. “Many of these infections are caused by surface-transmitted pathogens.
"Our goal with this work was to develop materials that are self-sterilizing, nontoxic and resilient enough for practical use. And we’ve been successful.”
“A lot of work has been done to develop photosensitizer molecules that use the energy from visible light to convert oxygen in the air into biocidal 'singlet’ oxygen, which effectively punches holes in viruses and bacteria,” says Richard Spontak, distinguished professor of chemical and biomolecular engineering, professor of materials science and engineering at NC State and co-corresponding author of the paper. “There is no resistance to this mode of action.
Biological materials from bonetospider-silk and wood are lightweight fibre composites arranged in a complex hierarchical structure, formed by directed self-assembly to demonstrate outstanding mechanical properties. When such bioinspired stiff and lightweight materials are typically developed for applications in aircraft, automobiles and biomedical implants, their manufacture requires energy and labor-intensive fabrication processes. The manufactured materials also exhibit brittle fracture characteristics with difficulty to shapeandrecycle, in stark contrast to the mechanical properties of nature. Existing polymer-based lightweight structure fabrication is limited to 3-D printing, with poor mechanical strength and orientation, while highly oriented stiff polymers are restricted to construct simple geometries. In an effort to combine the freedom of structural shaping with molecular orientation, 3-D printing of liquid-crystal polymers was recently exploited. Although desirable shape-morphing effects were attained, the Young’s modulus of the soft elastomers were lower than high-performance liquid-crystal synthetic fibers due to their molecular structure.
To fully exploit the shaping freedom of 3-D printing and favorable mechanical properties of molecularly oriented liquid-crystal polymers (LCP), a team of scientists at the Department of Materials, ETH Zürich, proposed a novel approach. The strategy followed two design principles that are used in nature to form tough biological materials. Initially, anisotropy was achieved in the printing process via self-assembly of the LCP ink along the print path. Thereafter, complex-shaping capacity offered by the 3-D printing process was exploited to tailor the local stiffness and strength of the structure based on environmental loading conditions. In the study, Silvan Gantenbein and co-workers demonstrated an approach to generate 3-D lightweight, recyclable structures with hierarchical architecture and complex geometries for unprecedented stiffness and toughness. The results are now published in Nature.
Though its technical name is poly(2,6-dimethylphenylene oxide) it is most commonly known as poly(phenylene oxide) or PPO. A condensation polymer, the polymerization of PPO produces water as a byproduct. It is a type of polyphenylene and is often grouped alongside polyphylene ethers as well.
PPO is one of many high-performance polymers known as engineering thermoplastics. These polymers have higher glass transition temperatures, making them temperature resistant. However, these polymers are often more crystalline, and therefore more brittle. In order to help with processing of PPO and to increase the toughness, almost all commercially available forms of the polymer are blended with polystyrene (such as high-impact polystyrene, or HIPS).
Applications of PPO (or, more commonly, blends of PPO and polystyrene) include those shown on the chart above. PPO is often used in applications where a polymer is desired but high heat resistance is also necessary, such as certain structural applications, electronics, and medical equipment (such as sterilizable instruments). Another common usage is in air separation membranes for the generation of nitrogen, an application which uses hollow fibers to create a membrane.
In the world of catalytic reactions, polymers created through electropolymerization are attracting renewed attention. A group of Chinese researchers recently provided the first detailed characterization of the electrochemical properties of polyaniline and polyaspartic acid (PASP) thin films. In AIP Advances, the team used a wide range of tests to characterize the polymers, especially their capacity for catalyzing the oxidation of popularly used materials, hydroquinone and catechol.
This new paper marks one of the first pairings of standard electrochemical tests with nuclear magnetic resonance (NMR) analysis in such an application. “Because these materials can be easily prepared in an electric field and are cost-effective and environmentally friendly, we think they have the potential to be widely used,” said Shuo-Hui Cao, an author on the paper.
Although PASP has shown excellent electrocatalytic responses to biological molecules, newer areas of inquiry have explored the material’s ability to lower the oxidational potential in oxidation-reduction reactions. Reducing the oxidation potential is key for finding further uses for two materials used extensively as raw materials and synthetic intermediates in pharmaceuticals, hydroquinone and catechol.
In the 17th Century two giants of science, Isaac Newton and Robert Hooke, were both trying to understand how the wings of butterflies and peacocks, which are made of the same material as our fingernails and hair, could colors of such brilliant quality. They both came to the same conclusion, the color was a result of tiny structures on the wing, structures so small that they could not observe it themselves but had deduced must exist.
Science and technology have progressed far in those 300 years and not only can we easily observe the structure of a butterfly’s wing that produces such brilliant color, but we can readily create them ourselves. Inspired by this kind of structural color, researchers at Kyoto University’s Institute for Integrated Cell-Material Science (iCeMS), led by Prof. Easan Sivaniah, in collaboration with researchers from Semmelweis University and Kyoto University Medical School, have produced a structural color device for measuring the beating of heart cells which they hope will help speed up the process of pharmaceutical testing.
Like the wing of a butterfly, this device produces structural color from micro-patterns developed on the surface of a polymer gel. Heart cells beating on the device cause the structural color to change which can be detected easily with low power microscopes.
Researchers have developed a highly robust gel that includes large amounts of ionic liquid. The research team was led by Professor MATSUYAMA Hideto and Assistant Professor KAMIO Eiji (Kobe University Graduate School of Science, Center for Membrane and Film Technology). These findings were published on November 8 in Advanced Materials.
Ionic liquid is a substance made solely from ions, and it has unique properties – for example, it does not evaporate at normal temperatures or pressures, and it has high thermal stability. Gels that contain ionic liquid are known as ion gels. With the same properties as ionic liquids, as well as their ability to retain liquid form, they can potentially be used as electrolytes for rechargeable batteries and as membranes for gas separation. However, the low mechanical strength of typical ion gels limits their practical applications.
Authored by Kenny Walter, Digital Reporter, R&D Magazine
Thanks to 3D printing, customers across the country can now order a customized loafer, sneaker or sandal designed specifically to fit their exact foot— and receive it in less than 24 hours.
Feetz, a San Diego-based company founded by Lucy and Nigel Beard, creates a shoe that is almost entirely printed, with approximately 90 percent of each shoe created with a 3D printer. The only part of the shoe that is not made from the 3D printer is the fabric lining, which is produced using traditional methods because 3D printers are currently unable to print fabrics.
A new form of 3-D-printed material made by combining commonly-used plastics with carbon nanotubes is tougher and lighter than similar forms of aluminium, scientists say.
The material could lead to the development of safer, lighter and more durable structures for use in the aerospace, automotive, renewables and marine industries.
In a new paper published in the journal Materials & Design, a team led by University of Glasgow engineers describe how they have developed a new plate-lattice cellular metamaterial capable of impressive resistance to impacts.
Metamaterials are a class of artificially-created cellular solids, designed and engineered to manifest properties which do not occur in the natural world.
Researchers in the labs of Christopher Bates, an assistant professor of materials at UC Santa Barbara, and Michael Chabinyc, a professor of materials and chair of the department, have teamed to develop the first 3-D-printable “bottlebrush” elastomer. The new material results in printed objects that have unusual softness and elasticity—mechanical properties that closely resemble those of human tissue.
Conventional elastomers, i.e. rubbers, are stiffer than many biological tissues. That’s due to the size and shape of their constituent polymers, which are long, linear molecules that easily entangle like cooked spaghetti. In contrast, bottlebrush polymers have additional polymers attached to the linear backbone, leading to a structure more akin to a bottle brush you might find in your kitchen. The bottlebrush polymer structure imparts the ability to form extremely soft elastomers.
The ability to 3-D-print bottlebrush elastomers makes it possible to leverage these unique mechanical properties in applications that require careful control over the dimensions of objects ranging from biomimetic tissue to high-sensitivity electronic devices, such as touch pads, sensors and actuators.
Ozone is a problematic air pollutant that causes serious health problems. A newly developed material not only quickly and selectively indicates the presence of ozone, but also simultaneously renders the gas harmless. As reported by Chinese researchers in Angewandte Chemie, the porous “two-in-one systems” also function reliably in very humid air.
Ozone (O3) can cause health problems, such as difficulty breathing, lung damage, and asthma attacks. Relevant occupational safety regulations therefore limit the concentrations of ozone allowable in the workplace. Previous methods for the detection of ozone, such as those based on semiconductors, have a variety of disadvantages, including high power consumption, low selectivity, and malfunction due to humid air. Techniques aimed at reducing the concentration of ozone have thus far been based mainly on activated charcoal, chemical absorption, or catalytic degradation.
A team led by Zhenjie Zhang at Nankai University (Tianjin, China) set themselves the goal of developing a material that can both rapidly detect and efficiently remove ozone. Their approach uses materials known as covalent organic frameworks (COFs). COFs are two- or three-dimensional organic solids with extended porous crystalline structures; their components are bound together by strong covalent bonds. COFs can be tailored to many applications through the selection of different components.
The speed of light has come to 3-D printing. Northwestern University engineers have developed a new method that uses light to improve 3-D printing speed and precision while also, in combination with a high-precision robot arm, providing the freedom to move, rotate or dilate each layer as the structure is being built.
Most conventional 3-D printing processes rely on replicating a digital design model that is sliced into layers with the layers printed and assembled upwards like a cake. The Northwestern method introduces the ability to manipulate the original design layer by layer and pivot the printing direction without recreating the model. This “on-the-fly” feature enables the printing of more complicated structures and significantly improves manufacturing flexibility.
“The 3-D printing process is no longer a way to merely make a replica of the designed model,” said Cheng Sun, associate professor of mechanical engineering at Northwestern’s McCormick School of Engineering. “Now we have a dynamic process that uses light to assemble all the layers but with a high degree of freedom to move each layer along the way.”
Plastics are among the most successful materials of modern times. However, they also create a huge waste problem. Scientists from the University of Groningen (The Netherlands) and the East China University of Science and Technology (ECUST) in Shanghai produced different polymers from lipoic acid, a natural molecule. These polymers are easily depolymerized under mild conditions. Some 87 percent of the monomers can be recovered in their pure form and re-used to make new polymers of virgin quality. The process is described in an article that was published in the journal Matter on 4 February.
A problem with recycling plastics is that it usually results in a lower-quality product. The best results are obtained by chemical recycling, in which the polymers are broken down into monomers. However, this depolymerization is often very difficult to achieve. At the Feringa Nobel Prize Scientist Joint Research Center, a collaboration between the University of Groningen and ECUST, scientists developed a polymer that can be created and fully depolymerized under mild conditions.
Ingestion of degrading ocean plastics likely poses a substantial risk to the survival of post-hatchling sea turtles because the particles can lead to blockages and nutritional deficiencies, according to new research from Loggerhead Marinelife Center and the University of Georgia. This puts the survival of all sea turtle populations at risk, because sea turtles may take decades to become sexually mature. The study also suggests that micronizing plastics could have tremendous negative implications for the ocean’s food web.
“We may be in the early phases of the first micronized plastic waste-associated species population decline or extinction event,” said co-author Branson W. Ritchie, a veterinarian with more than 30 years of experience in exotic and wildlife medicine and the director of technology development and implementation for the UGA New Materials Institute. “But, an even bigger issue is what micronizing plastics are doing to the ocean’s ecosystem. As ocean plastics continue to micronize, smaller and smaller particles are being consumed by the smallest creatures in our oceans, which compromises the entire food chain, because the plastic in these animals inhibits their ability to uptake the nutrients they need to survive. If the level of mortality we have observed in post-hatchling sea turtles also occurs for zoo plankton, baby fish and crustaceans, then we will witness a complete disruption in our ocean life cycle.”
An international team of researchers, affiliated UNIST has introduced an exiting new organic network structure that shows pure organic ferromagnetic property at room temperature. As described in the CHEM journal this pure organic material exhibits ferromagnetism from pure p-TCNQ without any metal contamination.
This breakthrough has been led by by Professor Jong-Beom Baek and his research team in the School of the Energy and Chemical Engineering at UNIST. In the study, the research team has synthesized a network structure from the self polymerization of tetracyanoquinodimethane (TCNQ) monomer. The designed organic network structure generates stable neutral radicals.
For over two decades, there has been widespread scepticism around claims of organic plastic ferromagnetism, mostly due to contamination by transition metals. Extensive effort has been devoted to developing magnets in purely organic compounds based on free radicals, driven by both scientific curiosity and the potential applications of a ‘plastic magnet’. Excluding the contamination issues and realizing magnetic properties from pure organic plastics must occur to revive the quest for plastic magnetism.
Twenty years ago, researchers made the accidental discovery that the now infamous plastics ingredient known as bisphenol A or BPA had inadvertently leached out of plastic cages used to house female mice in the lab, causing a sudden increase in chromosomally abnormal eggs in the animals. Now, the same team is back to report in the journal Current Biology on September 13 that the array of alternative bisphenols now used to replace BPA in BPA-free bottles, cups, cages, and other items appear to come with similar problems for their mice.
“This paper reports a strange déjà vu experience in our laboratory,” says Patricia Hunt of Washington State University.
The new findings were uncovered much as before as the researchers again noticed a change in the data coming out of studies on control animals. Again, the researchers traced the problem to contamination from damaged cages, but the effects this time, Hunt says, were more subtle than before. That’s because not all of the cages were damaged and the source of contamination remained less certain.
However, she and her colleagues were able to determine that the mice were being exposed to replacement bisphenols. They also saw that the disturbance in the lab was causing problems in the production of both eggs and sperm.
A green method for producing crystalline supramolecular fibers promises to make polymer production more sustainable.
A polymer that catalyzes its own formation in an environmentally friendly solvent-free process has been developed by an all-RIKEN team of chemists. The discovery could lead to the development of inherently recyclable polymer materials that are made using a sustainable process.
Polymers are ubiquitous today, but they are detrimental to the environment through the accumulation of plastic waste and the unsustainable nature of conventional polymer manufacture. Polymers are generally made by linking together strings of building blocks, known as monomers, using covalent bonds. But these strong bonds make it difficult to take used, end-of-life plastic items and de-polymerize them to recover the monomers for reuse.
Researchers have created a stretchy transistor that can be elongated to twice its length with only minimal changes in its conductivity. The development is a valuable advancement for the field of wearable electronics. To date, it has been difficult to design a transistor using inherently stretchable materials that maintains its conductivity upon being stretched.
Here, Jie Xu and devise a clever and scalable way to confine organic conductors inside a rubbery polymer to create stretchy transistors. They took a semiconducting polymer, called DPPT-TT, and confined it inside another polymer, SEBS, which has elastic properties.
As the two polymers don’t like to mix with each other, the DPPT-TT forms thin bundles within the SEBS matrix. Testing and analysis of this new combination reveal that it works as an effective transistor, even as it is repeatedly stretched up to 100% of its length. While the material demonstrated a normal conductivity of 0.59 cm2/Vs on average, this dropped only slightly to 0.55 cm2/Vs when being stretched to twice its length.
Most current plastics are made from oil, which is unsustainable. However, scientists from the Centre for Sustainable Chemical Technologies (CSCT) at the University of Bath have developed a renewable plastic from a chemical called pinene found in pine needles.
Pinene is the fragrant chemical from the terpene family that gives pine trees their distinctive “Christmas smell” and is a waste product from the paper industry.
The researchers hope the plastic could be used in a range of applications, including food packaging, plastic bags and even medical implants.
Making renewable plastics from trees
Degradable polyesters such as PLA (polylactic acid) are made from crops such as corn or sugar cane, but PLA can be mixed with a rubbery polymer called caprolactone to make it more flexible. Caprolactone is made from crude oil, and so the resulting plastic isn’t totally renewable.
