Posts Tagged ‘Material’

Posted: December 2, 2012 by Wildcat in Uncategorized
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Research by MIT’s Markus Buehler — together with David Kaplan of Tufts University and Joyce Wong of Boston University — has synthesized new variants on silk’s natural structure, and found a method for making further improvements in the synthetic material. The work stems from a collaboration of civil and environmental engineers, mathematicians, biomedical engineers and musical composers. The results are reported in a paper published in the journal Nano Today. “We’re trying to approach making materials in a different way,” Buehler explains, “starting from the building blocks” — in this case, the protein molecules that form the structure of silk. “It’s very hard to do this; proteins are very complex.” Other groups have tried to construct such protein-based fibers using a trial-and-error approach, Buehler says. But this team has approached the problem systematically, starting with computer modeling of the underlying structures that give the natural silk its unusual combination of strength, flexibility and stretchiness. Pound for pound, spider silk is one of the strongest materials known: has helped explain that this strength arises from silk’s unusual hierarchical arrangement of protein building blocks. Buehler’s previous research has determined that fibers with a particular structure — highly ordered, layered protein structures alternating with densely packed, tangled clumps of proteins (ABABAB) — help to give silk its exceptional properties. For this initial attempt at synthesizing a new material, the team chose to look instead at patterns in which one of the structures occurred in triplets (AAAB and BBBA). Making such structures is no simple task. Kaplan, a chemical and biomedical engineer, modified silk-producing genes to produce these new sequences of proteins. Then Wong, a bioengineer and materials scientist, created a microfluidic device that mimicked the spider’s silk-spinning organ, which is called a spinneret. (via The music of the silks | KurzweilAI)

Posted: November 11, 2012 by Wildcat in Uncategorized
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You’re not just imagining it, objects really are harder to shift the longer they sit there. A pair of scientists think they have discovered why. Have you ever had the impression that heavy items of furniture start to take root – that after years standing in the same place, they’re harder to slide to a new position? Do your best wine glasses, after standing many months unused in the cabinet, seem slightly stuck to the shelf? Has the fine sand in the kids’ play tray set into a lump? If so, you’re not just imagining it. The friction between two surfaces in contact with each other does slowly increase over time. But why? A paper by two materials scientists at the University of Wisconsin in Madison, USA, suggests that the surfaces could actually be slowly chemically bonding together. There are already several other explanations for this so-called “frictional ageing” effect. One is simply that two surfaces get squashed closer together. But a curious thing about friction is that the frictional force opposing sliding doesn’t depend on the area of the contacting surfaces. You’d expect the opposite to be the case: more contact should create more friction. But in fact two surfaces in apparent contact are mostly not touching at all, because little bumps and irregularities, called asperities, prop them apart. That’s true even for apparently smooth surfaces like glass, which are still rough at the microscopic scale. It’s only the contacts between these asperities that cause friction. (via BBC – Future – Science & Environment – The power of science friction)

Posted: September 6, 2012 by Wildcat in Uncategorized
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A team of experts in mechanics, materials science, and tissue engineering at Harvard have created an extremely stretchy and tough gel that may pave the way to replacing damaged cartilage in human joints or spinal disks. Called a hydrogel, because its main ingredient is water, the new material is a hybrid of two weak gels that combine to create something much stronger. This new gel can stretch to 21 times its original length, but it is also exceptionally tough, self-healing, and biocompatible — a valuable collection of attributes that opens up new opportunities in medicine and tissue engineering. It could also be used in soft robotics, optics, artificial muscle, as a tough protective covering for wounds, or “any other place where we need hydrogels of high stretchability and high toughness,” the researchers suggest. “Conventional hydrogels are very weak and brittle — imagine a spoon breaking through jelly,” explains lead author Jeong-Yun Sun, a postdoctoral fellow at the Harvard School of Engineering and Applied Sciences (SEAS). “But because they are water-based and biocompatible, people would like to use them for some very challenging applications like artificial cartilage or spinal disks. For a gel to work in those settings, it has to be able to stretch and expand under compression and tension without breaking.” (via Tough super-stretchable gel is tougher than cartilage and heals itself | KurzweilAI)

Posted: June 13, 2012 by Wildcat in Uncategorized
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Scientists have developed a porous material with unique carbon dioxide adsorption properties.The findings, published in Nature Materials, form part of ongoing efforts to develop new materials for gas storage applications and could have an impact in the advancement of new carbon capture products for reducing emissions from fossil fuel processes.

  • Microscopic bumps on a lotus leaf transform its waxy surface into an extremely water repellent, or superhydrophobic, material. Raindrops roll easily across such a surface, removing any dirt.
  • Researchers have developed synthetic self-cleaning materials, some of which are based on this “lotus effect,” whereas others employ the opposite property—superhydro­philicity—as well as catalytic chemical reactions.
  • Future products may combine the two water affinity properties or use substances that can be switched back and forth to control the flow of liquids through microfluidic components.
  • The story of self-cleaning materials begins in nature with the sacred lotus (Nelumbo nucifera), a radiantly graceful aquatic perennial that has played an enormous role in the religions and cultures of India, Myanmar, China and Japan. The lotus is venerated because of its exceptional purity. It grows in muddy water, but its leaves, when they emerge, stand meters above the water and are seemingly never dirty. Drops of water on a lotus leaf have an unearthly sparkle, and rainwater washes dirt from that leaf more readily than from any other plant.It is this last property that drew Barthlott’s attention. In the 1970s he became excited by the possibilities of the scanning electron microscope, which had become commercially available in 1965 and offered vivid images down to the nanometer realm. At that scale of magnification, specks of dirt can ruin the picture, and so the samples have to be cleaned. But Barthlott noticed that some plants never seemed to need washing, and the prince of these was the lotus.
  • source: Scientific American