Mussels are remarkable creatures, not only in how good they taste steamed and buttered, but also in their ability to cling to rocks that are pounded by ocean waves. Their tenacious grip comes courtesy of byssal holdfast fibers that are secreted by the mussels themselves. Last year, scientists from Germany’s Max Planck Institute for Colloids and Interfaces analyzed these fibers in an effort to determine how they were able to maintain their brute strength, while also giving slightly to avoid snapping. This week, scientists from the University of Chicago announced that they have been able to replicate the fibers, producing an adhesive that could be used on underwater machinery, as a surgical adhesive, or as a bonding agent for implants.

Conventional adhesives typically involve a trade-off between strength and brittleness – they give, but can be ripped, or are hard, but can be snapped. Such substances are linked by covalent bonds, which are held together by two atoms sharing two or more electrons. U Chicago’s synthetic mussel adhesive, however, is linked by metals. This allows it to exhibit both strength and flexibility, as the bonds automatically self-heal if broken, without adding any energy to the system.

One of the keys to the material is a long-chain polymer, developed at Northwestern University. It takes the form of a green solution when combined with metal salts at low pH, but becomes a sticky red gel when mixed with sodium hydroxide to change its pH from high acidity to high alkalinity. This gel can repair tears to itself within minutes. Its stiffness and strength can be tweaked both by altering its pH, or by using different types of metal ions when creating it. The scientists are now trying to determine what other factors might affect its properties.

Besides offering an optimum combination of strength and give, the adhesive should also be environmentally-friendly, as it’s made from natural ingredients. A patent is currently pending.

“Our aspiration is to learn some new design principles from nature that we haven’t yet actually been using in man-made materials that we can then apply to make man-made materials even better,” said Chicago postdoctoral scholar Niels Holten-Andersen.

Sourced & published by Henry Sapiecha

Polymer coatings have self healing qualities

Materials that can repair themselves are generally a good thing, as they increase the lifespan of products created from them, and reduce the need for maintenance. Biorenewable polymers are also pretty likable, as they reduce or even eliminate the need for petroleum products in plastic production, replacing them with plant-derived substances. Michael Kessler, an Iowa State University associate professor of materials science and engineering, and an associate of the U.S. Department of Energy’s Ames Laboratory, is now attempting to combine the two.

Self-healing materials generally incorporate microcapsules containing a liquid healing agent, and catalyst elements, which are embedded within the material’s matrix. As cracks form within the matrix, the microcapsules rupture, releasing the healing agent. As soon as that agent encounters the catalyst, it hardens into three-dimensional polymer chains, thus filling and securing the cracks. Such technology has been used not only to create self-healing plastics, but also self-healing concrete.

Since 2005, Kessler has been working with Iowa State’s Prof. Richard Larock on the development of biorenewable polymers made from vegetable oils. Larock is the inventor of a process wherein bioplastics can be created that consist of 40 to 80 percent inexpensive natural oils – these plastics reportedly have very good thermal and mechanical properties, are good at dampening noises and vibrations, and are also very good at returning to their original shape when heated.

Kessler is now trying to create self-healing versions of these same plastics.

One thing he has deduced so far is that a healing agent for a tung oil-based polymer works too fast. Kessler and his colleagues are now working on slowing down the reactive process of that agent, while also developing biopolymer-friendly encapsulating techniques, and bio-based healing agents.

The big challenge, he says, is to match the 90 percent healing efficiency of standard synthetic composites.

Sourced & published by Henry Sapiecha

Visitors to last year’s World 2010 Expo in Shanghai might have noticed that the outer walls of the Italian pavilion were kind of… DIFFERENT. Although they felt solid, and looked like concrete when viewed from an angle, light was able to pass through them. How could it be possible? They were made from what the Italcementi Group refers to as “transparent cement,” and has trademarked as i.light. It’s definitely a unique substance, as it blurs the line between wall and window.

  • Italcementi's i.light in place at the Italian pavilion at Expo 2010 (Photo: Italcementi)
  • The Italcementi i.light research team (Photo: Italcementi)
  • Italcementi's i.light in place at the Italian pavilion at Expo 2010 (Photo: Italcementi)
  • Italcementi's i.light in place at the Italian pavilion at Expo 2010 (Photo: Italcementi)

The material was created specifically for the pavilion, as architect Giampaolo Imbrighi wanted a building with transparent walls. While the exact fabrication method hasn’t been fully divulged, Italcementi states that it involves “an innovative cement/admixtures mix design.” That mixture reportedly bonds well with thermoplastic polymer resin, which is inserted into a matrix of 2-3 mm holes running through the width of each panel.

There are approximately 50 holes in each 500 x 1,000 x 50 mm (19.7 x 39 x 2 inch) panel, resulting in an overall transparency of about 20 percent – the pavilion also included semi-transparent panels, which had a transparency of 10 percent created by “modulating the insertion of the resins.”

Past attempts at similar materials have included placing fiber optic cables through a concrete mixture, although the Italcementi researchers claim that their product is much less expensive to produce, and allows light to enter from a greater number of angles.

Although i.light has yet to be made available for commercial use, it has already been suggested that buildings made with the material could save electricity that would otherwise be required for daytime lighting.

Sourced & published by Henry Sapiecha

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Sourced & published by Henry Sapiecha

Smart Tape Like Gecko Feet

Posted on January 30, 2008 by dikidee

gecko feet

Inspired by the gecko feet, University of California, Berkeley have created a new kind of tape.

Conventional adhesive tape sticks when pressed on a surface. A new gecko-inspired synthetic adhesive (GSA) does not stick when it is pressed into a surface, but instead sticks when it slides on the surface. A similar directional adhesion effect allows real geckos to run up walls while rapidly attaching and detaching toes. The gecko-inspired adhesive uses hard plastic microfibers. The plastic is not itself sticky, but the millions of microscopic contacts work together to adhere. The number of contacts automatically increases to handle higher loads. A feature of the hard plastic gecko-inspired adhesive is that no residue is left on surfaces as is left by conventional adhesive tapes.

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Sourced & published by Henry Sapiecha

Ultra-Simple Method for Creating

Nanoscale Gold Coatings Developed

Researchers at Rensselaer have developed a new, ultra-simple method for making layers of gold that measure only billionths of a meter thick. As seen in the research image, drops of gold-infused toluene applied to a surface evaporate within a few minutes and leave behind a uniform layer of nanoscale gold. The process requires no sophisticated equipment, works on nearly any surface, takes only 10 minutes, and could have important implications for nanoelectronics and semiconductor manufacturing. (Credit: Image courtesy of Rensselaer Polytechnic Institute)

Gold plated porche.Munich show.

Science (June 21, 2010) — Researchers at Rensselaer Polytechnic Institute have developed a new, ultra-simple method for making layers of gold that measure only billionths of a meter thick. The process, which requires no sophisticated equipment and works on nearly any surface including silicon wafers, could have important implications for nanoelectronics and semiconductor manufacturing.

Sang-Kee Eah, assistant professor in the Department of Physics, Applied Physics, and Astronomy at Rensselaer, and graduate student Matthew N. Martin infused liquid toluene — a common industrial solvent — with gold nanoparticles. The nanoparticles form a flat, closely packed layer of gold on the surface of the liquid where it meets air. By putting a droplet of this gold-infused liquid on a surface, and waiting for the toluene to evaporate, the researchers were able to successfully coat many different surfaces — including a 3-inch silicon wafer — with a monolayer of gold nanoparticles.

“There has been tremendous progress in recent years in the chemical syntheses of colloidal nanoparticles. However, fabricating a monolayer film of nanoparticles that is spatially uniform at all length scales — from nanometers to millimeters — still proves to be quite a challenge,” Eah said. “We hope our new ultra-simple method for creating monolayers will inspire the imagination of other scientists and engineers for ever-widening applications of gold nanoparticles.”

Results of the study, titled “Charged gold nanoparticles in non-polar solvents: 10-min synthesis and 2-D self-assembly,” were published recently in the journal Langmuir.

Whereas other synthesis methods take several hours, this new method chemically synthesizes gold nanoparticles in only 10 minutes without the need for any post-synthesis cleaning, Eah said. In addition, gold nanoparticles created this way have the special property of being charged on non-polar solvents for 2-D self-assembly.

Previously, the 2-D self-assembly of gold nanoparticles in a toluene droplet was reported with excess ligands, which slows down and complicates the self-assembly process. This required the non-volatile excess ligands to be removed in a vacuum. In contrast, Eah’s new method ensures that gold nanoparticles float to the surface of the toluene drop in less than one second, without the need for a vacuum. It then takes only a few minutes for the toluene droplet to evaporate and leave behind the gold monoloayer.

“The extension of this droplet 2-D self-assembly method to other kinds of nanoparticles, such as magnetic and semiconducting particles, is challenging but holds much potential,” Eah said. “Monolayer films of magnetic nanoparticles, for instance, are important for magnetic data storage applications. Our new method may be able to help inform new and exciting applications.”

Co-authors on the paper are former Rensselaer undergraduate researchers James I. Basham ’07, who is now a graduate student at Pennsylvania State University, and Paul Chando ’09, who will begin graduate study in the fall at the City College of New York.

The research project was supported by Rensselaer, the Rensselaer Summer Undergraduate Research Program, the National Science Foundation (NSF) Research Experiences for Undergraduates, and the NSF’s East Asia and Pacific Summer Institutes and Japan Society for the Promotion of Science.

Watch a video demonstration of this new fabrication process at:

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Sourced and Published by Henry Sapiecha 5th June 2010

Shark-Inspired Boat Surface

Materials Engineers Turn to Ferocious

Fish for Nonstick Ship Coating

May 1, 2005 — Researchers are using shark skin as a model for creating new coatings that prevent adhesion of algae and barnacles to boats. The new coating is modeled after sharks’ placoid scales, which have a rectangular base embedded in the skin with tiny spines or bristles that poke up from the surface that prevent things from attaching to the shark’s skin.

GAINESVILLE, Fla.–In the boating industry, a huge problem exists that can be summed up in three words — algae, barnacles and slime. Until now, the only way to prevent these organisms from growing was toxic paint. But researchers are studying a more natural approach that’s inspired by the ocean’s fiercest predator.

In movies, they’re the enemy, but in the world of science, sharks are allies.

Materials engineer Tony Brennan, of University of Florida in Gainesville, uses shark skin as a model for creating new surfaces. “The shark scales have a roughness that approximates the roughness that we had predicted would be a good roughness to stop adhesion,” he says.

Brennan designed the surfaces to prevent algae and barnacles from growing on boats. He says, “We started making surfaces that are mimicking the shark’s skin.”

A computer program helped researchers create the pattern and structure…

“Whatever we can draw, we can make into a surface,” says UF graduate student, Jim Schumacher.

And just like shark skin, spores can’t fit in the ridges and don’t want to balance on top of the surface Brennan and his team designed in the lab. “That’s a tremendous benefit to energy consumption, dollars and maintenance,” Brennan says.

Getting rid of those barnacles and other organisms would mean less cleaning and not having to drag around the extra weight would lower fuel costs.

“If it’s effective, it would tremendously affect the industry,” Emerson says.

When the surface hits the market in the next year, it could impact private boaters and Navy vessels, too. Researchers are also studying the shark-coated surface for medical applications.

In addition to being very thick — as much as four inches in some species — shark skin is made up of tiny rectangular scales topped with even smaller spines or bristles, making the skin rough to the touch.

Shark skin was used in the past as an abrasive, for polishing wood. In Asia, it was used to decorate sword hilts. In the South Pacific, natives used it for the membranes on drums. Even today, because shark skin is so tough and pliable, it is used to make fine leather goods, including purses, shoes, boots and wallets.

Shark skin is covered with tiny scales, known as placoid scales. These scales resemble small shark teeth in both appearance and structure: there is an outer layer of enamel, dentine, and a central pulp cavity. (Biologists call them “dermal denticles,” which literally translates into “tiny skin teeth.”)

Sharks essentially have a built-in suit of chain mail armor that doesn’t make them too stiff to move. The scales move and flex as the shark swims.

The shark skin’s dentine layer is made of a hard, crystalline material, which is embedded in a soft protein. This is important because embedding a hard material inside a softer one combines the best properties of both: a material that is rigid without being brittle.

The structure of shark skin has another function besides protection. The streamlined shape of the scales decreases the friction of the water flowing along the shark’s body by channeling it through grooves. The grooves are so closely spaced, they prevent eddies from coming into contact with the surface of the shark’s moving body. This reduces the amount of “drag” as the shark swims, enabling the creature to glide farther on a given amount of energy. Scientists have found that the ridges created by shark scales can reduce drag in the water by as much as 8 percent. Golf balls and many military aircraft and vessels employ similar drag-reducing principles.

Sourced and published by Henry Sapiecha 9th April 2010

Resbond™ Alumina Adhesive Protects Electronic Components to 3000º F Resbond™ 989 offers continuous protection to 3000°F.

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Sourced and published by Henry Sapiecha 25th March 2010