Alan Turing’s Patterns in Nature, and Beyond
Near the end of his life, the great mathematician Alan Turing wrote his first and last paper on biology and chemistry, about how a certain type of chemical reaction ought to produce many patterns seen in nature.
Called “The Chemical Basis of Morphogenesis,” it was an entirely theoretical work. But in following decades, long after Turing tragically took his own life in 1954, scientists found his speculations to be reality.
First found in chemicals in dishes, then in the stripes and spirals and whorls of animals, so-called Turing patterns abounded. Some think that Turing patterns may actually extend to ecosystems, even to galaxies. That’s still speculation — but a proof published Feb. 11 in Science of Turing patterns in a controlled three-dimensional chemical system are even more suggestion of just how complex the patterns can be.
How Turing Patterns Work
At the heart of any Turing pattern is a so-called reaction-diffusion system. It consists of an “activator,” a chemical that can make more of itself; an “inhibitor,” that slows production of the activator; and a mechanism for diffusing the chemicals.
Many combinations of chemicals can fit this system: What matters isn’t their individual identity, but how they interact, with concentrations oscillating between high and low and spreading across an area. These simple units then suffice to produce very complex patterns.
Proving Their Existence
Even though what appeared to be Turing patterns were immediately evident in nature, it wasn’t easy to be sure they were produced by reaction-diffusion systems, rather than some other mechanism.
The breakthrough came during the 1980s, when chemists were able to produce Turing patterns in the laboratory, on thin slabs of gel. In these controlled systems, the reactions could be closely followed, simulated on computers and unambiguously demonstrated as true Turing patterns.
At left in each photograph is a real seashell. At right is a computer-generated image of a pattern produced by a Turing pattern simulation.
At left in each photograph is the eye of a popper fish. At right is a computer-generated image of a pattern generated by a Turing pattern simulation.
Brent Constantz builds cement like corals do
Biomineralization expert Brent Constantz of Stanford University was inspired to make a new type of cement for buildings by the way corals build reefs. The process of making this cement actually removes carbon dioxide – a greenhouse gas, thought to cause global warming – from the air. The company Constantz founded, called Calera, has a demonstration plant on California’s Monterrey Bay. The installation takes waste CO2 gas from a local power plant and dissolves it into seawater to form carbonate, which mixes with calcium in the seawater and creates a solid. It’s how corals form their skeletons, and how Constantz creates cement.
Ray Baughman creates artificial muscles
Nature has been developing her technologies for many hundreds of millions of years, said Ray Baughman. “By looking at the way in which nature has solved problems like muscles, we can advance our own technologies.” Baughman is director of the NanoTech Institute at the University of Texas at Dallas. His lab creates very tiny artificial muscles by spinning filaments of invisibly small carbon nanotubes into an extraordinary yarn. Pound for pound, this nano-yarn is stronger than steel – yet is so light it almost floats in air.
“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.
A robot that flies like a bird
Plenty of robots can fly, but none can fly like a real bird. That is, until Markus Fischer and his team at Festo built SmartBird, a large, lightweight robot, modeled on a seagull, that flies by flapping its wings. A soaring demo fresh from TEDGlobal 2011.
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.
Humpback whale secret may help helicopters fly faster
DLR Institute of Aerodynamics and Flow Technology / DLR Institute of Aeroelasticity
Helicopters can deliver military troops or rescue the wounded in tight spaces, but their rotating blade design also puts a hard limit on their speed and maneuverability. Now researchers have begun flight-testing an unlikely fix inspired by the underwater ballet of humpback whales.
The potentially cheap solution uses small bumps along the front edge of the helicopter blades similar to bumps found on the large pectoral fins of humpback whales. Such bumps give an aerodynamic edge that delays the moment of “stalling” when there’s not enough lift to keep the whale from sinking — or a helicopter from stalling out at top speeds.
“Stalling is one of the most serious problems in helicopter aerodynamics — and one of the most complex,” said Kai Richter from the DLR Institute of Aerodynamics and Flow Technology in Germany.
Helicopters face a speed limit because their backward-moving rotor blade goes against their forward motion of flight. That problem leads to turbulence and loss of lift, as well as strong forces acting on the rotor, which eventually cause the helicopter to stall out.
German researchers patented the bump idea for helicopters, under the name “Leading-Edge Vortex Generators.” Wind tunnel experiments led to a test flight with a helicopter carrying 186 rubber bumps —each less than a quarter of an inch long — glued to its four rotor blades.
“The pilots have already noticed a difference in the behavior of the rotor blades,” Richter said. “The next step is a flight using special measuring equipment to accurately record the effects.”
If testing goes well, existing helicopters could get a speed boost with simple retrofits. New helicopters could have the design built into their titanium blades during manufacturing.
The natural bump design already helps humpback whales swim at speeds of up to 16.5 miles per hour, or about five times faster than the fastest human swimmer.
“Research has shown that these bumps cause stalling to occur significantly later underwater and increase buoyancy,” said Holger Mai from the DLR Institute of Aeroelasticity in Germany. “Flow phenomena in water are similar to those in air; they just need to be scaled accordingly.”
Source: Innovation News Daily
Insect-inspired Material That Could Solve Our Plastic Problem
“Shrilk,” made from proteins found in crustacean and insect shells, is strong, stretchy, and fully biodegradable. It may be how you carry your groceries home in the future.
What if you could come back from the store, extract your haul, and throw your grocery bag in the garden to compost away? Scientists have created a sturdy, versatile, completely biodegradable alternative to plastic that could just make this crazy dream real. And it’s made from insect skeletons.
Javier Fernandez, a Spanish materials scientist, and his collaborators at the Wyss Institute, have created the material they’re calling “Shrilk,” which mimics the architecture of arthropod exoskeletons. Grasshoppers and other similar bugs have an exoskeleton that is strong enough to support their innards, but light enough to allow the insect to fly. Shrilk, made from the proteins in these natural materials, also adopts a similar duality: It has the strength of an aluminum alloy, but is half its weight. It’s also completely biodegradable.
Fernandez was experimenting with chitin—found in insect shells— for use in bio-compatible microelectronics. When he recreated the complete micro architecture of the shell, with proteins layered like plywood, the result was Shrilk: strong, light, supple, surprising. “We got mechanical properties that were completely crazy and very unexpected,” Fernandez tells Co.Exist.
Fernandez found that Shrilk’s elasticity changed from stretchy to stiff depending on how it was hydrated. And in addition to its spectacular strength and lightness, Shrilk biodegrades completely in a matter of months when in presence of moisture, breaking down into compounds that can be used as nitrogen fertilizer.
Shrilk is a shoe-in for use in medicine, Fernandez says. In the human body, the material has a lifetime of a few months. This makes it an excellent candidate for use in surgical sutures, or as a scaffold for regenerating tissues. Synthetic materials usually go through rigorous and lengthy tests before the FDA approves them for use in people. But, both the materials that form the Shrilk microstructure—chitosan and fibroin—are already individually approved.
Shrilk could also be sold as an eco-conscious stand-in for disposable plastics. If appropriately hydrated, its structure can vary from stretchy to stiff, so it could be used as either the shell of your cellphone or to replace the ubiquitous and wasteful grocery bags.
There are still several next steps that Fernandez and his colleagues must go through before Shrilk is ready to be manufactured commercially. But if it does hit the market, it would require a huge supply of the raw material that goes into it. Extracting the components from natural sources wouldn’t keep up. So, Fernandez and his team are researching ways to genetically engineer bacterial farms to mass-produce the necessary proteins. “If we want this to be realistic, we need to do the next step.”
Slime Mold Grows Network Just Like Tokyo Rail System
Talented and dedicated engineers spent countless hours designing Japan’s rail system to be one of the world’s most efficient. Could have just asked a slime mold.
When presented with oat flakes arranged in the pattern of Japanese cities around Tokyo, brainless, single-celled slime molds construct networks of nutrient-channeling tubes that are strikingly similar to the layout of the Japanese rail system, researchers from Japan and England report Jan. 22 in Science. A new model based on the simple rules of the slime mold’s behavior may lead to the design of more efficient, adaptable networks, the team contends.
Every day, the rail network around Tokyo has to meet the demands of mass transport, ferrying millions of people between distant points quickly and reliably, notes study coauthor Mark Fricker of the University of Oxford. “In contrast, the slime mold has no central brain or indeed any awareness of the overall problem it is trying to solve, but manages to produce a structure with similar properties to the real rail network.”
The yellow slime mold Physarum polycephalum grows as a single cell that is big enough to be seen with the naked eye. When it encounters numerous food sources separated in space, the slime mold cell surrounds the food and creates tunnels to distribute the nutrients. In the experiment, researchers led by Toshiyuki Nakagaki, of Hokkaido University in Sapporo, Japan, placed oat flakes (a slime mold delicacy) in a pattern that mimicked the way cities are scattered around Tokyo, then set the slime mold loose.
Initially, the slime mold dispersed evenly around the oat flakes, exploring its new territory. But within hours, the slime mold began to refine its pattern, strengthening the tunnels between oat flakes while the other links gradually disappeared. After about a day, the slime mold had constructed a network of interconnected nutrient-ferrying tubes. Its design looked almost identical to that of the rail system surrounding Tokyo, with a larger number of strong, resilient tunnels connecting centrally located oats. “There is a remarkable degree of overlap between the two systems,” Fricker says.
The researchers then borrowed simple properties from the slime mold’s behavior to create a biology-inspired mathematical description of the network formation. Like the slime mold, the model first creates a fine mesh network that goes everywhere, and then continuously refines the network so that the tubes carrying the most cargo grow more robust and redundant tubes are pruned.
The behavior of the plasmodium “is really difficult to capture by words,” comments biochemist Wolfgang Marwan of Otto von Guericke University in Magdeburg, Germany. “You see they optimize themselves somehow, but how do you describe that?” The new research “provides a simple mathematical model for a complex biological phenomenon,” Marwan wrote in an article in the same issue of Science.
Fricker points out that such a malleable system may be useful for creating networks that need to change over time, such as short-range wireless systems of sensors that would provide early warnings of fire or flood. Because these sensors are destroyed when disaster strikes, the network needs to efficiently re-route information quickly. Decentralized, adaptable networks would also be important for soldiers in battlefields or swarms of robots exploring hazardous environments, Fricker says.
The new model may also help researchers answer biological questions, such as how blood vessels grow to support tumors, Fricker says. A tumor’s network of vessels start out as a dense, unstructured tangle, and then refine their connections to be more efficient.