Mind-Boggling Materials

March 13, 2007

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Spray and Bomb-Resist, Scented Tires, Stretchable Wonder Thread, Black Hole Coating, Modern-Day Dark Age Technique, NASCAR Lifesaver, Tips from the Twinkie and "Cheerio, Silicon?" The more materials and their applications advance, the wilder they get. What follows is an assortment of far-out material developments.

Stretchable Wonder Thread A wonder material that seems to defy the laws of physics has been developed at Bolton University. The more it is stretched, the thicker the fabric gets.

The material is part of a group known as auxetics (first discovered in the late 1980s in America), which work in direct opposition to other stretchable substances.

According to The Manchester Evening News:

If an item made out of auxetic material was struck by a hammer it would expand rather than contract, helping cushion the blow and absorb more of the impact.

The material could be used to create responsive aircraft wings — to change shape in mid-flight. Among some of the examples given for application of this material: it could be used for bulletproof vests that expand to absorb the blow of a bullet; or a range of super-responsive mattresses capable of stopping bedsores in hospital patients; or to create super-strong car bumpers that would be more capable of absorbing the impact of a low-speed crash.

Professor Andy Alderson, a material physics expert at the university, and his wife Dr. Kim Alderson are part of a team of experts studying the material at the university, and were among the first to create a usable form of the material. Dr. Alderson was one of the first scientists in Britain to work with these materials and, in 1999, was the first person to develop an auxetic fabric, resulting in a nomination for the Female Inventor of the Year award. Her discovery was hailed as the first practical example of an auxetic material — paving the way for auxetic bandages and medical sutures that are currently under development.

Spray-on Polymer for Bomb-Resistant Buildings Last year, we touched on earthquake-proofing buildings. Now, while designers and civil engineers have been working for quite some time to make buildings bomb-resistant, a company called Line-X — which makes pickup truck bed liners — offers a spray-on polymer coating called Paxcon to reinforce buildings against such damage.

Popular Mechanics recently pointed out:

Derived from Line-X's bed liners, Paxcon can be sprayed on existing structures. It is designed to reduce or eliminate damage caused by fragmentation, or possibly delay a building's collapse until it can be evacuated. Paxcon is being applied to commercial and government buildings [including the Pentagon] around the world.

Brighter LEDs from Black Holes A team of researchers from Rensselaer Polytechnic Institute has created the world's first material that reflects virtually no light.

Reporting in the March issue of Nature Photonics, the team described an optical coating made from the material that enables vastly improved control over the basic properties of light. The research could open the door to much brighter LEDs, more efficient solar cells and a new class of "smart" light sources that adjust to specific environments, among a number of other potential applications, according to PhysOrg.

Speaking of light and dark... .

Dark Age High-Tech The metallurgical technique now known as shot peening goes all the way back to the swordsmiths of the Dark Ages, according to Davis L. Baughman in the Winter 2007 issue of American Heritage's Invention & Technology magazine. The technique involves peppering the surface of a part with thousands of tiny steel balls to keep metal fatigue from starting.

During the time of the Crusades, the blacksmiths of Toledo had developed blades that were thin and lightweight, but they were also tough enough that they could be bent almost double, repeatedly, without breaking, making them virtually indestructible in battle. The process remained a secret for a millennium.

Today it helps keep your car out of the repair shop. If you flex a part many times, it will ultimately fail, and the failure will occur where the tension loads are highest. The first tiny crack will originate at some minute discontinuity (such as a scratch or dent) on the part's surface. Another name for such a flaw is a stress riser. A failure crack will propagate from a stress riser because it reduces the cross-sectional area of the part, thus raising the tension load at that point.

According to Baughman:

Shot peening prevents this kind of metal failure because it pre-stresses a part's surface with permanent compressive stresses. These counteract the tension stresses that result from loading the part. In addition, the shot-peening process nullifies stress risers because it applies a layer of compressive stresses to the total part's surface. This prevents a failure crack from starting.

Yet as important as its anti-failure effects are, Baughman noted, shot peening can do much more. In one of its most powerful applications, shot peening can actually mold the shape of a part — for example, forming aircraft wing skins to the required aerodynamic contours. This process is called peen forming.

In the 1970s, a group of engineers familiar with the history of weapons began to wonder if some sort of peening was the secret to the Toledo blacksmiths' technique. They knew that steel shot did not exist back then, but they felt the idea was worth investigating. So they re-examined a Toledo sword using modern techniques. X-ray diffraction detected an induced compressive stress layer at the surface. Acid etching removed extremely thin layers, beneath which electron microscope surveys showed subsurface compression patterns that would have been made with a ball-peen hammer. The Toledo blades had not been peened with shot, but they had been peened, and that was the secret to their strength and durability.

NASCAR's Material of Tomorrow NASCAR is rolling out its "Car of Tomorrow" this spring, when it will make its official racing debut at the Bristol Motor Speedway in Tennessee. Even fans and drivers who dislike the boxy look and high cost of the new commonly called COT admit that safety is more important than style, and these new cars are certainly safer.

Unseen to racing fans is a layer of protection between the door and roll cage (the special metal frame surrounding the driver), compliments of Dow Automotive, where employees worked to develop potentially life-saving material — IMPAXX energy-absorbing foam — for NASCAR's new vehicles.

The Oakland Business Review reported:

The IMPAXX foam is made up of microscopic cells that collapse in on one another during impact, absorbing energy and hopefully reducing the impact on the driver. Dow produces the foam through a proprietary manufacturing process involving the use of blowing agents in the raw mix. Once the IMPAXX foam is extruded, the cell structure appears.

Eighteen months ago, NASCAR had already looked at about 200 different energy-absorbing materials, but it was not satisfied with any of them; some were too heavy, others too expensive.

Dow Automotive specializes in fast, flexible design done without cumbersome tools, so development of IMPAXX came fast and furious, according to Todd Wodzinski, the marketing development manager at Dow Automotive who led the team that produced IMPAXX.

What the Dow team produced was the low-cost, lightweight, energy-absorbing material that NASCAR needed.

Scented Tires Have you ever gone car shopping, found a car you really liked with all the features and functions you could ever hope for, and then decided against the purchase because the tires, well, smelled too much like rubber? Good news for you, then.

In January (and already one of the stranger tech stories of the year), Kumho Tire USA announced it developed the world's first scented tire, targeted at female buyers who drive such vehicles as the Chrysler Sebring, Ford Taurus, Honda Accord, Subaru Outback and Toyota Camry.

The company said that the aromatic tire came after more than a year's worth of R&D to deliver "an alluring aroma tire that replaces the normal 'black rubber' smell with heat-resistant oils in the scent of lavender, and in later versions, neroli [orange] and jasmine."

Prussian Polymer In a quest for more compact memory storage, researchers at the University of Paris have tweaked 18th-century colormaker Heinrich Diesbach's formula for the color Prussian blue a bit and found that, when tickled with light, the pigment becomes magnetic and remains so until heated. Then it reverts to its nonmagnetic state. This ability to switch between two states is how memory devices store information, recently noted The Christian Science Monitor. The team was able to image the modified compound and found that when red light struck it, the atoms in Prussian blue realigned in ways that led to the material becoming magnetic.

The work is exploratory at this point, and the material must be chilled to -238 ˚F before red light magnetizes it. Yet it indicates the range of materials researchers are exploring as they try to shrink memory devices without sacrificing capacity.

Polymer Fish Clot-Removal An engineering graduate at the University of Wollongong (Australia) has developed a polymer actuator fish that may one day be able to travel through a human vein to remove a clot.

According to Future Materials:

Laleh Bayat Sarmadi developed the tiny device to mimic the exact movements of fish. It's currently being refined so it can propel itself through liquid such as water and blood.

Thermoplastic covers will soon be placed on the polymer actuator to allow the device to propel through any solution. Amplified voltages generated by a computer program and released into the polymers allow it to "swim."

From the Twinkie Deconstructor: Did You Know? Chapter by chapter, Steve Ettlinger's new book "deconstructs" a Hostess Twinkie and decodes all 39 ingredients in the little cr

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