New journal section coming soon!
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One step closer to the Space Pope
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Favourite fact from ScienceWatch this month: the Vatican is a Rising Star in Space Science. True Story: bit.ly/zN7F9l
Beetle-mimetic Velcro?
Most people go through a phase in life where they are fascinated by insects (usually when you’re young and insatiably curious; my cousin’s six-year-old boy was delighted to number an insect vacuum among his gifts from Santa). While some of us then go on to develop phobias and even downright loathing, a few people retain their sense of wonder at the splendors of the natural world, and scientists who study the form and function of biomaterials have produced some incredible synthetic analogues of things that come naturally to our fellow life-forms. Superhydrophobic and self-cleaning surfaces, gecko-foot adhesive patches, mussel-glue, and photonic crystals inspired by weevils are just some of the things we’ve featured on Materials Views, and now we can report on a Velcro-like interlock mechanism inspired by beetles.
In work featured on the latest cover of Advanced Materials, Professor Kahp-Yang Su and his team at Seoul National University have created a synthetic reproduction of the mechanism used by beetles to keep their wings tucked away when not in use. Along the edges of its carapace, a beetle has thousands of tiny, densely packed hairs that slide together and prohibit any sideways slip when the carapace closes over the folding wings. In actual fact, the mechanism is more closely related to the children’s toy Stickle Bricks than to that of Velcro, as it does not use hooks and loops to generate adhesion. Professor Suh’s team mimicked this structure using dense arrays of polymer fibers, where Van der Waal’s interactions between the fibers provide the adhesive force. Simple and elegant, and a very pretty cover picture to highlight an excellent piece of research.
Hemostatic Materials: Anti-hemorrhagic Dressings for Wounds
I’ve been playing a lot of Mass Effect over the holidays. It’s fun, but, as with most games, I’m epically bad at it, and the only thing that keeps me in the missions for any length of time is the convenient convention of health recovery. Skulk behind a wall or crate for a few moments, and you miraculously revitalize. Most RPGs have this convention, justified in this instance by the plot existence of your battle suit, which monitors your condition and distributes treatment as required to get you back up to full speed.
The idea of such powered armor has been hanging around in sci-fi for a good half-century, most notably in Robert A. Heinlein’s novel Starship Troopers, but in recent times has started to make the transition towards science fact through programs such as the US Army’s Future Soldier Initiative. While the complete suit may still be some distance away, some of the concepts and components are the goals of active research programs, as recent work published by Paula Hammond and her team at MIT demonstrates.
The report in Advanced Materials details development of a hemostatic material for use as field dressings in emergency wound treatment. Current practices for staunching bleeding wounds are generally based on compression (for example, tourniquets) but this can be difficult to control or even achieve in the field, depending on where on the body a wound is received. Hemostatic alternatives, which work by enhancing the clotting process) have previously been produced, but suffer from a variety of disadvantages such as expense, impractical application in field conditions, or adverse immune response. Professor Hammond’s team have come up with an alternative that uses a layer-by-layer assembly technique to build films of thrombin (a clotting agent) and tannic acid directly onto absorbent gelatin sponges. Hydrogen bonding between the tannic acid and the thrombin allows the construction of the films without the need for any other ingredients, maximizing the load of the clotting agent, and all the materials used in the study are already approved for clinical use, so could potentially be deployed as a viable treatment system in a short time. The thrombin load, once applied to a wound, was effective in promoting rapid clotting within one minute: a control test using uncoated, regular cotton gauze bandages and compression failed to stop bleeding from a wound over a twelve-minute period, showing this research’s very real potential to save lives in emergency situations and operating theaters.
Image Credit: flickr.com/ arrighi / CC BY 2.0
Shrilk: A Chimera of Chitosan and Fibroin for Biodegradable Plastics
Current plastics technology is overwhelmingly reliant on feedstocks from fossil fuels, and, in many cases, are still non-biodegradable substances (although recycling is able to deal with an ever-increasing range of materials). With declining reserves of resources and the correlated rise in interest in sustainable materials, research towards viable alternatives for plastics in packaging, consumer products and even medical supplies is continuing apace.
Materials scientists have once again turned to the lessons of nature in addressing this issue. Javier Fernandez and Donald Ingber of Harvard University took chitosan (commonly found in the shells and carapaces of mollusks and insects) and fibroin (silk), and deposited them sequentially to develop a layered composite material that they christened “shrilk”: a chimera of the shrimp and silkmoths that provided the raw materials. The dry material demonstrates strength and toughness similar to aluminum alloys. When water is added, strength is sacrificed but the elasticity improves. The films can be deposited on patterned molds to impart a specific patterning to the surface, and being able to tune or switch the elasticity allows simple engineering of 3D structures. The materials are biocompatible (and thus feasible for biomedical applications: the authors envision a tissue-engineering scaffold in the paper), biodegradable, and biosourced, presenting a truly sustainable and environmentally friendly wrapper for your next plastics purchase.
Original paper: 10.1002/adma.201104051
Luminescent Solar Concentrators – the Search for Photovoltaic Windows
With an ever-increasing number of column inches being dedicated to renewable energy as the great climate change debate rages, the search for viable, scalable solutions to humanity’s dependence on fossil fuels continues. Often, currently available solutions suffer from bad press regarding aesthetics, efficiency, or just plain bad luck:
The aesthetic argument always plays strongly to the crowd, and so one avenue of research into renewable energy is looking at ways in which energy tech can be incorporated into existing structures and materials, taking advantage of the fact that there are things we need to build anyway. Windows, for example, present a large surface area for trapping light – imagine if every window in the Burj al Khalifa could be photovoltaic – all 26,000 plus of them. One technology that could achieve this is the luminescent solar concentrator (LSC), the topic of a review published recently in Advanced Energy Materials. LSCs are simple devices that use a plastic or glass sheet as a waveguide. The waveguide has lumophore molecules associated with it, either embedded in the material, coated on the top or bottom surface, or entrapped as a liquid layer between two plates. When light hits the glass, it is absorbed by the lumophores and re-emitted at a longer wavelength. Some of the light is then trapped in the waveguide by total internal reflection. At the end of the waveguide, if a photovoltaic cell is attached, the light can be converted to electricity.
Michael Debije and Paul Verbunt take a detailed look in their review at the past thirty years of LSC development, noting that extensive commercialization has not yet taken place, largely hindered by the modest conversion efficiencies when compared to silicon solar cell outputs. However, with more and more types of lumophore becoming available (a particularly interesting approach is the use of quantum dots, which can be tailored simply by adjusting their size), the options are becoming ever-more promising, and it might turn out that maximum efficiency may not be the only guiding light in LSC design. Aesthetics may also have a part to play – what color of window would you prefer? And how about creating energy by painting a little sunshine of your own?
Original paper: 10.1002/aenm.201100554
Advanced Healthcare Materials now online!
I’m pleased to report that the first papers for Advanced Healthcare Materials have just been published online on Wiley Online Library. Head over and check out Mauro Ferarri and co-workers research on nanoparticle-based thermal therapy for breast cancer, and Xingyu Jiang and colleagues’ work on monitoring acetylcholinesterase levels in cerebral spinal fluid, a potential marker for Alzheimer’s disease.
Shrink-Wrap Stem Cell Growth
It’s easy to give a stem cell a goal in life, apparently. Simply placing a cell in contact with a surface can provide sufficient information (a cue) to dictate how the cell will develop, and incredibly, even simple length-scale changes are enough to affect the outcome of the cell development. Far-fetched as this may sound, if you think about the nature of stem cells for a moment, it becomes less surprising that they are so responsive to their environment: how else to explain the extraordinary variety of cell types that derive from a uniform base material?
As stem cells continue to be the focus of much research into the concepts of regenerative medicine and tissue engineering, a corollary challenge for materials science is the design and build for artificial substrates that can mimic biological environments and thereby control the growth and specialization of the cells. For one thing, the subtleties make it easy to grow off in the wrong direction. Growing muscle tissue will need a different set of conditions from, say, a new liver, but the differences in the environment might turn out to be very slight. A small change in the period of a pattern on the substrate might result in completely the wrong kind of tissue. A challenge of a more mechanical nature is the actual fabrication of the substrates. Most cell-growth environments have cues that act over a number of different length scales, with multiple patterns and features of various sizes interacting to produce the end result. Current micro- and nanofabrication techniques don’t mimic this complexity too well, or rather, don’t mimic it too well without complex multi-step procedures, expensive instrumentation, and expertise on fabrication that is not readily available to medical researchers.
It’s this challenge that Michelle Khine and her team at the University of California, along with colleagues from the University of Hong Kong and the Mount Sinai School of Medicine in New York, have made some headway in addressing with their latest research. Khine’s previous research has focused on creating ordered wrinkle patterns through heat-shrinking layers of plastic and metal by using the stiffness mismatch between the materials to buckle the metal layer in a controlled and ordered manner. Now, by using plasma pre-treatment, the team have found they can do away with the metal layer; oxidizing the surface of the plastic results in a thin, stiff layer that buckles in the same fashion. The wrinkles that form are ordered and occur on several different length scales; in the reported research, the substrate structure after shrinking was similar to that of collagen. The properties of the wrinkles can be adjusted depending on the plasma treatment time, and such fine control over the structure opens up the possibility of systematic testing of the effect of different length scales on the differentiation of the cells. Since the material is thermoplastic, is can also be molded easily into shapes that more closely mimic real environments. The fabrication is achieved using commercially available polyethylene film, can be adapted to large-scale roll-to-roll plasma treatment systems, and takes only ten minutes to perform, all key factors in developing fast, low-cost production of experimental substrates and enabling the wider and more systematic studies of stem cell behavior that are required in order to develop a thorough understanding of such potentially life-changing research.
dx.doi.org/10.1002/adma.201103643
Article first published on www.Materialsviews.com
Cover Story: Little Green Men
Materials science has much to offer the field of healthcare; things have moved on quite a way from the original wooden peg leg; recent breakthroughs are to be found across a wide range of medical applications. There are improved drug delivery systems, and nanoparticles for cancer treatment and detection. There are antibiotic coatings for wound–healing and anti-inflammatory coatings for brain electrodes and cardiac stents. New contrast agents for imaging. New materials for tissue-engineering scaffolds, and platforms for custom growing stem-cells, and perhaps someday soon, replacement organs. For diagnostics, there are flexible, wearable electronic devices, and nanogenerators capable of powering monitoring systems from muscle movement. And while all of these discoveries are still fledgling, they offer a tantalizing glimpse into the future of healthcare, where one can imagine personalized medicine, diagnostic and monitoring devices incorporated into clothing, regenerative medicine to provide replacement organs, and real gains made in treating some of the most lethal diseases of our time.
The materials we need to achieve such goals are myriad, requiring properties tailored to suit a very specific set of conditions, and there is lots of work to be done, and lots of work already being done. Publishing trends in the last few years in materials science have seen the rise to prominence of biomedical materials research, and it’s fitting that healthcare be the subject of a new section in Advanced Materials, highlighting just how important a contribution materials can make.
An illustration of that contribution provided us with an awesome cover for the inaugural section. Shoji Takeuchi and his colleagues in Tokyo reported a clever, building-block approach to tissue engineering allowing the molding of a scaffold material into pretty well any form you can think of. The team used a microfluidic system to produce uniform, monodisperse collagen beads that can be seeded with a desired cell material (internally or externally) and then compressed together in a mold to form the desired tissue shape. The cells then grow and multiply, consuming the collagen and building into a solid tissue. Nutrients can be fed into the system via the cavities between the beads, and the production method is quick and scalable. The researchers demonstrated the technique by building different shapes, and by far the most striking was the little green chap you see on the cover. This is a great bit of cover art, not only for the impact of the picture, but for the science it represents; the image is a cell viability assay of the structure, and all that green is good news for the technique’s potential use in tissue engineering. Great research, great cover, great start for Advanced Healthcare Materials!
Cover Story: Monitor your Money
Great covers come in many flavors, but it always tickles my fancy to see real-life demos of applied research; snapshots of science in action, if you will. One of the great challenges in science communication is the ability to answer people’s basic questions: what does it do, how does it work, and what can you use it for? If you’ve ever tried explaining your research to your mum, you’ll know that it can be pretty tricky to boil down to a few simple phrases.
Pictures are much better at this sort of thing. It’s said that the front cover of a magazine has 2.5 seconds to catch your attention – that’s how long your eye will rest on the image, and that’s enough time for you to identify what it is and interpret whether or not it holds any interest for you. Try doing the same thing in words, with a time limit of 2.5 seconds. It’s almost impossible to get the identification done, far less any interpretation.
So, with that in mind, on to the cover of Issue 5 of Advanced Materials. The cover features a newly developed technique for depositing electronic circuits on delicate materials such as paper. As Ute Zschieschang and her team reported, the deposition is gentle enough to produce printed circuits on banknotes, providing a potential route to smarter methods of tracking the circulation of individual notes, and better anti-theft and anti-counterfeiting systems. And there’s no better way to visualize that concept than to show the real thing, which is what we have on the cover: a five Euro banknote with the circuitry clearly visible at the bottom left, making the foil anticounterfeit strip on the right look gaudy, invasive, and outdated. No window dressing required – a simple picture, a simple concept, a great piece of science and a great cover!
