“The thorny devil, a tiny highly specialised lizard from the central Australian desert which lives entirely on ants has each scale enlarged and drawn out to a point in the centre. Few birds could relish such a thorny mouthful and to that extent, they must be a very effective defence, but the shape of the scales also serves another and most unusual function. Each is scored with very thin grooves radiating from the central peak. During cold nights, dew condenses on them and is drawn by capillary action along the grooves and eventually down to the tiny creature’s mouth.” (Attenborough 1979:164)
The Thorny Devil (Moloch horridus) can gather all the water it needs directly from rain, standing water, or from soil moisture, against gravity without using energy or a pumping device. Water is conveyed to this desert lizard’s mouth by capillary action through a circulatory system on the surface of its skin, comprised of semi-enclosed channels 5-150 µm wide running between cutaneous scales. Channel surfaces are heavily convoluted, greatly increasing the effective surface area to which water can hydrogen-bond and hence capillary action force. Passive collection and distribution systems of naturally distilled water could help provide clean water supplies to the 1 billion people estimated to lack this vital resource, reduce the energy consumption required in collecting and transporting water by pump action (e.g., to the tops of buildings), and provide a variety of other inexpensive technological solutions such as managing heat through evaporative cooling systems, protecting structures from fire through on-demand water barriers, etc.
This butterfly could hold the secret to letting you see in the dark
The opalescent wings of the Morpho butterfly embody a perfect marriage of aesthetic beauty and biological functionality. Scientists believe that a better understanding of this creature’s wings and their chemical makeup could have big implications for imaging technologies like night vision goggles that rely on sensing heat, rather than visible light.
Now, a team of GE researchers has taken an important step in accomplishing exactly that.
One of the biggest problems facing thermal imaging technologies is temperature management. The sensors in a heat-sensing device have to be cooled constantly, otherwise the image you see becomes washed out with old, and therefore insignificant, heat measurements. Imagine watching a person walk across a room while wearing thermal imaging goggles — if the thermal sensor’s temperature wasn’t kept in check, you’d be able to see a sort of thermal ghost trailing behind the person as they moved across your field of vision.
Physics World’s Tim Wogan explains the challenges of regulating the heat of thermal sensors:
The most sensitive thermal imagers require liquid-helium refrigeration. Since the heat sinks required are relatively large and power-hungry, this limits the minimum size and efficiency of the sensors. These requirements pose severe challenges for those designing portable equipment, such as thermal-imaging goggles. Indeed, goggles pose a particular problem because an ideal pair would be transparent to visible light, which is difficult to achieve with heat sinks in the way.
This is where the Morpho butterfly swoops in to save the day. The scales that cover the Morpho’s iridescent wings reflect light at some wavelengths, while absorbing it at others; these absorption/reflection properties can even change depending on the wings’ temperature, shifting the color of the wings in the process.
This is a pretty inspired biological feature, and it’s one that scientists believe could be put to use in thermal imaging sensors; but what researchers are really impressed with is the chitin that the scales of the Morpho wings are actually made of.
Chitin has a much lower heat capacity than the materials that are used in contemporary thermal sensors; lower heat capacity, in turn, eliminates the need for bulky, energy-hungry cooling methods. In the thermographic video featured here, you can see a Morpho butterfly responding quickly to heat pulses distributed first across the whole butterfly structure, and then onto localized regions of the wings.
And believe it or not, we can make these wings even more impressive — and with carbon nanotubes, no less! Writes Wogan:
Building on previous work by other researchers that revealed that decorating a material surface with carbon nanotubes enhances its ability to absorb infrared radiation, [a research team led by analytical chemist Radislav Potyrailo] showed that the [Morpho’s wings] absorbed infrared better if carbon nanotubes were added to the exposed surface. As a bonus, because carbon nanotubes have excellent thermal conductivity, the decoration helped to diffuse heat through the chitin away from the site of irradiation, thus providing a molecular heat sink.
In other words, Potyrailo and his colleagues showed that treating Morpho scales with carbon nanotubes not only enhances their ability to absorb radiation at wavelengths relevant to thermal imaging, it actually improves their ability to diffuse heat.
The question that remains is: how do researchers translate the functionality of nanotube-doped butterfly wings into a synthetic thermal sensor? Poryrailo and his team have already created an ersatz version of Morpho wings, but they still need a way to incorporate the chitin that grants them their unique heat-dissipating abilities. Once they do that, however, the researchers believe it could mark a major shift toward cheap, more effective thermal-imaging devices.
Better Body Armor? Piranha-Proof Fish Have Answers
The armor that a massive Amazonian fish evolved against piranhas could lead to better body armor for soldiers, researchers say.
The arapaima (Arapaima gigas) is one of the largest freshwater fish in the world, weighing up to 440 pounds (200 kilograms). It lives in the Amazon, and as the waters of the rivers there recede during the dry season, it gets trapped alongside piranhas, and the latter eventually attack every bird, fish, mammal and reptile they can, save alligators.
“I’ve gone to the Amazon many times — I first spent time there as part of a Peace Corps project when I was 20,” said researcher Marc Meyers, a material scientist at the University of California, San Diego. “I remember being struck by how the arapaima could live in these piranha-infested lakes.”
It turns out the arapaima can thrive in this crowded environment. As such, Meyers and his colleagues wanted to learn how it could coexist with such a ravenous predator, especially one with a guillotine-like bite highly effective at slicing through muscle.
The researchers devised a mechanical version of a fight between a piranha and an arapaima. Piranha teeth were attached to what was essentially an industrial-strength hole punch and pressed down onto arapaima scales up to 4 inches (10 centimeters) long, which were embedded on a soft rubber surface that mimicked the muscle of the fish. They found the cutting and puncturing ability of the piranha teeth could not penetrate the arapaima scales.
The arapaima experiments suggest a number of lessons when it comes to designing advanced materials. For instance, the corrugated, ridged surfaces of the scales, which people in the Amazon sometimes use as nail files, help the scales bend without cracking, a discovery that could be of use when working with brittle materials such as ceramics. In addition, the scales mix soft and hard materials — soft collagen fibers stacked in alternating directions like a pile of plywood lend toughness to the scale, and a very hefty mineralized layer on top lends hardness.
Such flexible, tough, hard materials could be useful in body armor, Meyers said. “I believe that this can be used for flexible armor,” he told InnovationNewsDaily. “I am in the process of contacting funding agencies for support.”
The researchers will continue exploring the natural world for inspiration, “asking, ‘how does nature put these things together?’” Meyers said. Another project will involve the alligator gar, a huge fish from the American South whose scales were used by Native Americans as arrow tips. The researchers are also studying abalone shells and leatherback turtle skin for inspiration.
“The materials that nature has at its disposal are not very strong, but nature combines them in a very ingenious way to produce strong components and strong designs,” Meyers said.
The researchers detailed their findings online Jan. 9 in the journal Advanced Engineering Materials. The work was also detailed in the October 2011 issue of the Journal of the Mechanical Behavior of Biomedical Materials.