An armorlike arapaima fish scale resists being fractured by a piranha tooth that is slowly pressed into it. In fact, it is the tooth that fails. Credit: Meyers Group: Credit: UCSD Jacobs Sch. of Eng.

If you ever watch cable TV’s River Monsters (and, honestly, who doesn’t!), you might be familiar with a large Amazonian “living fossil” fish that goes by the name arapaima.

The arapaima have a reputation for being one of the few animals in the Amazon that hungry piranha don’t bother. Why? Apparently it is because evolution has draped the arapaima in a flexible skin of “armor” that is effectively impenetrable to the piranhas’ teeth. The fish has “scales,” but there aren’t many other species among fish that come close to the defenses of the arapaima.

Researcher Marc Meyers, an expert on bio-inspirational design and a professor at the Jacobs School of Engineering at University of California, San Diego, knew of this reputation and speculated that if the arapaima are indeed protected from piranhas’ bites, maybe insights from the structure of the arapaima’s scales could provide ideas for engineering new materials, such as flexible ceramics.

(Meyers’ name may be familiar to some. He was one of the stars in one of the episodes of Nova’s “Making Stuff” TV series, in which he discussed the strength of mullosk shells.)

As can be seen in the above video, Meyers, along with his students and colleagues, set up a simple desktop test. They attach an arapaima scale to a soft rubber base (to simulate the fish’s soft muscle and tissue under the scale) and mounted a single piranha tooth in a press. The tooth is then pressed into the scale. In each case, the tooth can partially penetrate the scale, but the tooth cracks before the scale suffers a total fracture.

Credit: Meyers Group; UCSD.

Meyers says in a UC San Diego release that the structure of the scale is combination of a mineralized outer layer with a clever and tough internal design (see diagram from the press release). This tough inner layer has collagen fibers stacked in alternating directions “like a pile of plywood.” He says the mix of materials in the scale is similar to the hard enamel of a tooth deposited over softer dentin.

Implications? Meyers says that the arapaima’s design should serve as bioinspiration for lots of things that need to be both tough and flexible, for example body armor, fuel cells, insulation and aerospace designs.

Some lessons for engineers are from this work are:

• Combine hard and soft materials
• Stack the materials in the underlying layer with different orientations
• Texture is key, and a varying surface provides more capability.

On this last point, Meyers notes that each scale has an exterior that is “corrugated.” According to the story, “the corrugated surface keeps the scales’ thick mineralized surface intact while the fish flexes as it swims. Ceramic surfaces of constant thickness are strained when forced to follow a curved surface. The corrugations allow the scales to ‘be bent more easily without cracking,’ Meyers said.”

Meyers says he will also be studying the scales of another unusual fish, the alligator gar whose scales were reportedly used as arrow tips.

Corrugated texture of arapaima scales. Credit: Meyers Group; UCSD Jacobs Sch. of Eng.

Meyers et al. have written about their studies in the The Journal of the Mechanical Behavior of Biomedical Materials in the paper, “Biological materials: A materials science approach” (doi:10.1016/j.jmbbm.2010.08.005).

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A year ago, Corning published a promotional video, “A Day Made of Glass… Made possible by Corning” that provide an intriguing peek into some of the technologies the company is considering—and how it may affect our lifestyles. It proved to be a popular video, racking up well over 17 million views as of today.

As those of us old enough to remember Walt Disney’s movies about the future of communities, transportation and space, these visionary presentations are more informed guesswork than prophecy. Sometimes (most times?) these ideas just don’t work out for a number of reasons, but the exercise of compiling and publishing these visions helps bring excitement and motivation, especially to young people contemplating careers in science and engineering.

However, smart tech-oriented companies tend to be cautious about sharing their “visions” with the public (Steve Jobs was and Apple still is among those at the most secretive end of the spectrum) because they are both concerned about tipping their hand to competitors and, well, being embarrassed by being wrong about the future.

Corning, however, seems to be closer to the other end of the spectrum and has clearly decided that there is value in teasing the public with how high-tech glass products may disrupt a lot of technologies in our future. Now today, nearly on the anniversary of its first “A Day Made of Glass” video, the company has published an update,  ”A Day Made of Glass, Part 2″ that fleshes out more of Corning’s vision and also incorporates some of the market trends over the last year, such as the huge success of the iPad.

Some of the concepts illustrated in the new video include durable, multitouch screens; colossal- and large-scale edge-to-edge displays; ubiquitous electrochromic windows; entire dashboard surfaces made of soft, flexible glass displays; lightweight auto and sunroof glass; designer-friendly photovoltaic units; antimicrobial glass services for medical applications; and even advances in glass fiber optics.

Corning admits that a lot of these products aren’t right around the corner and acknowledges that there is still a lot of RD&D work that is needed to address existing problems with scalability and price.

To be clear, Corning is smart enough not to reveal all of its product and technology bets in this video. Furthermore, the Apple/Gorilla Glass story underlines how even Corning and other top-tier companies cannot always anticipate what external disruptions of the marketplace will rock their corporate world. Nevertheless, ADMOG Part 2 is an fascinating vision and I predict the number of views in the next year will easily exceed the 17 million of Part 1.

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A bacteria-induced mineral deposit. Credit: Paramita Mondal.

Concrete is tough, but whether its a sidewalk, driveway, roadway or a structural part of a building, the material is subjected to many temperature, chemical and mechanical stresses. Over time, these stresses induce microscopic cracks and fissures that can grow in length and depth. By the time they are visible, these cracks are a signal of impending material failure and possibly irreversible damage. But researchers are developing tantalizing solutions that can stop — nearly as soon as it starts — concrete crack formation and initiate a “healing” mechanism in the material.

Some researchers, such as Victor Li, have proposed self-healing approaches for concrete that rely, for example, on excess or encapsulated unhydrated cement materials in the concrete mix that springs into action when a crack is exposed to moisture and carbon dioxide in the atmosphere.

One concern about many of the self-healing approaches is that there may be limits to the number of self-healing cycles in a particular location within the concrete.

But, a group from the Civil and Environmental Engineering Department at the University of Illinois at Urbana-Champaign, has a novel idea about how to create a renewable form of self-healing concrete based on exploiting the biomineralization characteristics of some bacteria.

The CEE researchers, which include ACerS members Paramita Mondal, Leslie Struble and Bin Zhang, along with Ashna Chopra and Wen-Tso Liu, are investigating the possible use of the common Bacillus pasteurii (also named Sporosarcina pasteurii) to add a self-healing component to concrete.

In a news release from the school, Mondal explains, “The work we are doing puts bacteria in concrete, to mimic the way limestone forms in nature. In nature, bacteria that form calcium carbonate are known to influence the rock formation process of carbonate rocks and sediments such as limestone. The list of bacteria capable of forming calcium carbonate is extensive, but the challenge was finding one that would be active in concrete’s environment of high alkalinity and low oxygen.” She says the B. pasteurii met their requirements.

In the CEE laboratory, the group did some initial testing of the concept. ”We provided the bacteria, the food and the right environment. We could see that it was depositing the minerals, which are the basic building block of limestone,” says Mondal.

“Then we made a cement specimen and applied the bacteria with food. We saw the same kind of deposition. We did a chemical analysis of it, and it is the same calcium carbonate that’s forming,” she continues.

At larger scale, the group’s renewable self-healing concept is that once the bacteria are spread into concrete during mixing, they will form spores and go dormant in the highly alkaline condition inside the concrete. Then, if a crack is initiated, the pH drop combined with moisture and gases from the atmosphere will stir the bacteria back to life.

As they awaken, it is hoped that the microorganisms deposit calcium carbonate and fill the crack. Finally, once the crack is sealed, the microorganisms again go dormant until another crack forms.

The chemistry of what should happen is fairly well understood, but the challenge for this team is to test and characterize the “healed” concrete and determine if it will still perform as needed. Filling pores and microcracks via the bacterial process does not necessarily mean that the strength of the concrete has been restored. “That is the specific goal of our project,” Mondal says. “We are testing the specimen to see whether the crack is going through the filling material, through the original material, or through the interface. That will tell us which part is the weakest. … Conceptually, all of this should work, but there is lots more research to be done. It’s an innovative concept—definitely outside the box.”

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Rediheal borate glass fibers are successfully being used to treat injured green sea turtles and other animals. Credit: Avalon Medical Ltd.

One topic I and other ACerS staff frequently get asked about relates to a story from last April about the special healing borate-based glass fiber pads developed by glass scientists Delbert Day and Steve Jung in conjunction with MoSci Corp., a Rolla, Mo.-based glass products company. The news last year was that the glass fiber product, dubbed DermaFuse by MoSci, helped speed the healing of venous stasis ulcers in a majority of patients enrolled in a small human clinical test group of adult diabetics supervised by the internal review board of the Phelps County Regional Medical Center.

Most of the inquiries that come to me are from people who either are suffering with hard-to-heal skin ulcers or sores themselves or are reaching out to me on behalf of friends or family members who have the condition. Their questions are all pretty much along the lines of, “How can I or my doctors get my/their hands on DermaFuse?”

Up until just recently, I had to disappoint a lot of people because MoSci mainly does the R&D for glass products, and then licenses or reaches a supply agreement with third-party commercial companies and institutions, which then shepherd the products through regulatory processes and handle marketing and distribution. And, from what I understand, there are still testing, certification and agreements with distributors that need to be completed before it is authorized for human use.

However, the significant news is that Avalon Medical Ltd. has arranged for the DermaFuse material to be classified as “veterinary medical device” and is now marketing the product under the Rediheal brand to the veterinary and animal care marketplace.

According to the Rediheal website, the company is making the product for various size animals (”Equine version now available”) and is also offering a putty-like version of the product that can be shaped for bone healing.

While the story I originally wrote focused on a case study of human patients with venous stasis ulcers, it appears that Dermifuse/Rediheal material works shockingly well on many types of wounds. For example, the Rediheal website has several amazing animal case studies including large and small lacerations, dental void packing and gunshot wounds. (Warning - photos are not for the squeamish!)

In regard the gunshot wound case, a dog sustained at 42-square-inch wound in its back that was treated with Rediheal. According the company, the wound shrunk rapidly, and 40 days later it was nearly healed.

For me, one of the most jarring things about the gunshot wound is that there appears to be almost no scarring (see for yourself), and the dog’s fur seems to have completely regrown (albeit in a lighter color).

More information and case studies are on a special Rediheal/Avalon Facebook page, including successful efforts to heal injured green sea turtles at Jekyll Island, Ga.

One final note: Day and Jung (along with Mohamed N. Rahaman, B. Sonny Bal, Qiang Fu, Lynda F. Bonewald and Antoni P. Tomsia) also published a paper on this topic last summer in Acta Biomaterialia (doi:10.1016/j.actbio.2011.03.016), titled “Bioactive glass in tissue engineering.”

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Magnetic memory miniaturized to just 12 atoms

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New thermal diodes: Jumping droplets take a lot of heat, as long as it comes in a cool way

Microscopic water droplets jumping between surfaces that repel and attract moisture could hold the key to a wide array of more energy efficient products, ranging from large solar panels to compact laptop computers. Duke University engineers have developed a new way of producing thermal diodes, devices which regulate heat to preferentially flow in a certain direction, effectively creating a thermal conductor in the forward direction and an insulator in the reverse direction.

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