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EEE / A new image reveals the structure of the cosmic web
« on: February 28, 2020, 09:53:46 PM »
Like an ethereal cosmic spider web, filaments of gas form a complex, interconnected structure that links galaxies to one another. But, just as whisper-thin threads of spider silk can be nearly invisible, this cosmic web is faint and difficult to detect. Now astronomers have made the first detailed picture of light emitted by the gas. The newly revealed filaments extend for millions of light-years, researchers report in the Oct. 4 Science.

Computer simulations predicted the existence of the cosmic web, and astronomers previously have caught glimpses of a single filament (SN: 1/20/14). But scientists hadn’t seen the network stretching between multiple galaxies until now. “Finally, we actually have a picture,” says astrophysicist Michele Fumagalli of Durham University in England.

Fumagalli and colleagues studied a region of the sky that contains a protocluster of galaxies — a region where a large cohort of galaxies is beginning to assemble. Galaxies within the cluster emit ultraviolet light, a result of new stars forming inside or of churning regions around supermassive black holes at the galaxies’ centers. The filaments of gas absorb that light and reemit it. Using the European Southern Observatory’s Very Large Telescope in Chile, the astronomers detected the reemitted light.

After the Big Bang 13.8 billion years ago, scientists believe that gravity caused matter to collapse into sheets and filaments. In regions where the matter was especially dense, galaxies formed, feeding on gas from the cosmic web. The new picture of the filaments supports this origin story.

EEE / A new kind of spray is loaded with microscopic electronic sensors
« on: February 28, 2020, 09:24:20 PM »
alk about cloud-connected devices.

Using tiny 2-D materials, researchers have built microscopic chemical sensors that can be sprayed in an aerosol mist. Spritzes of such minuscule electronic chips, described online July 23 in Nature Nanotechnology, could one day help monitor environmental pollution or diagnose diseases.

Each sensor comprises a polymer chip about 1 micrometer thick and 100 micrometers across (about as wide as a human hair) overlaid with a circuit made with atomically thin semiconducting materials (SN Online: 2/13/18). This superflat circuit includes a photodiode, which converts ambient light into electric current, and a chemical detector. This chemical detector is composed of a 2-D material that conducts electric current more easily if the material binds with a specific chemical in its environment.
Researchers can choose from a vast menu of 2-D materials to fashion detectors that are sensitive to different chemicals, says study coauthor Volodymyr Koman, a chemical engineer at MIT (SN Online: 1/17/18). In lab experiments, Koman and colleagues created a sensor spray that detected toxic ammonia vapor inside a sealed section of piping, as well as a spray that ID’d soot particles sprinkled across a flat surface.

Right now, researchers can determine whether their sensors have come in contact with certain particles only after the fact — by collecting the chips and hooking them up to electrodes. These electrodes test how easily electric current flows through a chip’s chemical detector, which reveals whether it touched a particular chemical after it was sprayed. But future sensors could emit light signals when in contact with target particles, says study coauthor Michael Strano, a chemical engineer at MIT.

The team is also investigating ways to power the circuits without ambient light and to integrate multiple chemical detectors onto a single chip. The simpler, single-chemical detection systems tested so far are “only the beginning,” Koman says.

“It’s very exciting,” says Kourosh Kalantar-Zadeh, an electrical and chemical engineer at the University of New South Wales in Sydney whose commentary on the study appears in the same issue of Nature Nanotechnology. Sprayable sensors could someday detect gas leaks, pollution from power plants, volatile organic compounds and other air and water contaminants (SN: 3/17/18, p. 12).

Being so tiny, the devices could also be injected into a person’s bloodstream to monitor its chemical composition for medical purposes — like a blood test that wouldn’t require drawing any blood, Kalantar-Zadeh says. Or chemical sensors could be taken as nasal spray or swallowed to track digestive health (SN Online: 1/8/18). Unlike silicon-based devices that might pose environmental or health hazards, the polymers and the minute amounts of 2-D materials used to make the new devices are expected to be more biofriendly, he says.

EEE / Strange metals are even weirder than scientists thought
« on: February 28, 2020, 09:23:50 PM »
Curiouser and curiouser: Strange metals are getting a little stranger.

Normal metals such as copper and aluminum are old hat — physicists have a strong grasp on the behavior of the electrons within. But strange metals behave in mysterious ways, and researchers have now uncovered an additional oddity. A type of strange metal called a cuprate behaves unexpectedly when inside a strong magnetic field, the team reports in the Aug. 3 Science.

Strange metals are “really one of the most interesting things to happen in physics” in recent decades, says theoretical physicist Chandra Varma of the University of California, Riverside, who was not involved with the research. The theory that explains the behavior of standard metals can’t account for strange metals, so “a completely new kind of fundamental physics” is needed.
The metallic curios’ idiosyncrasies relate to their resistivity — how difficult it is for electric current to flow through them. As scientists crank up a strange metal’s temperature, its resistivity increases in lockstep: Double the temperature and you double the resistivity. That’s unusual: In most metals, the change in resistivity is more complex. For example, at low temperatures, the resistivity of a normal metal like copper would hardly change as the temperature inched up.

Strange metals’ behavior flouted the norms of physics, attracting scientists’ attention. The materials were “poking in our eye much more than other materials,” says physicist Arkady Shekhter of the National High Magnetic Field Laboratory in Tallahassee, Fla. So he and colleagues studied how the cuprate behaved in extremely strong magnetic fields, up to almost 2 million times the strength of Earth’s magnetic field.

The researchers showed that when the magnetic field is ramped up, the strange metal exhibits similarly weird behavior as it does with temperature. As the magnetic field grows, resistivity in the cuprate increases apace. It’s what’s known as a linear relationship, because it looks like a diagonal straight line when plotted on a graph showing resistivity versus magnetic field. In a normal metal, the change in resistance with the increasing magnetic field would be smaller, and would not be a straight line, instead curving.

Besides being strange metals, cuprates have another claim to fame: Under certain conditions, cuprates become superconducting, transmitting electricity without resistance (SN: 1/20/18, p. 11). While most superconductors have to be cooled to nearly absolute zero, cuprates operate at significantly higher temperatures. That makes the superconductors easier to use in technological applications, where the elimination of resistance could allow for more efficient, better performing electronics. Studying strange metals could help scientists better understand how cuprates superconduct at higher temperatures.

The result is “a really amazing discovery,” says physicist Jiun-Haw Chu of the University of Washington in Seattle, who was not involved with the research. “There’s a symmetric role that is played by temperature and field, and that is really new.”

EEE / A filter that turns saltwater into freshwater just got an upgrade
« on: February 28, 2020, 09:23:13 PM »
Smoothing out the rough patches of a material widely used to filter saltwater could make producing freshwater more affordable, researchers report in the Aug. 17 Science.

Desalination plants around the world typically strain salt out of seawater by pumping it through films made of polyamide — a synthetic polymer riddled with tiny pores that allow water molecules to squeeze through, but not sodium ions. But organic matter, along with some other waterborne particles like calcium sulfate, can accumulate in the pockmarked surfaces of those films, preventing water from passing through the pores (SN: 8/20/16, p. 22). Plant operators must replace the membranes frequently or install expensive equipment to remove these contaminants before they reach the filters.
Now researchers have made a supersmooth version without the divots that trap troublesome particles. That could cut costs for producing freshwater, making desalination more broadly accessible. Hundreds of millions of people already rely on desalinated water for drinking, cooking and watering crops, and the need for freshwater is only increasing (SN: 8/18/18, p. 14).

Manufacturers normally create salt-filtering films by dipping porous plastic sheets into chemical baths that contain the molecular ingredients of polyamide. These molecules glom onto the sheet, building up a thin polymer membrane. But that technique doesn’t allow much control over the membrane’s texture, says Jeffrey McCutcheon, a chemical engineer at the University of Connecticut in Storrs.

McCutcheon and colleagues made their version by spraying the polyamide building blocks, molecular layer by layer, onto sheets of aluminum foil. These polyamide films can be up to 40 times smoother than their commercial counterparts.

Such ultrasmooth surfaces should reduce the amount of gunk that accumulates on the films, McCutcheon says, though his team has yet to test exactly how clean its films stay over time.

EEE / See the ‘periodic table’ of molecular knots
« on: February 28, 2020, 09:22:41 PM »
Like a scouting handbook for the molecular realm, a new chart reveals how to tie molecules up in knots of increasing complexity.

Mathematicians have cataloged billions of distinct knot types, but researchers have been able to make only a few molecular versions. Scientists craft the minuscule knots using a solution filled with building blocks of curved strings of atoms, which glom onto one another.

Now, using computer simulations, physicist Cristian Micheletti of the International School for Advanced Studies in Trieste, Italy, and colleagues have created a “periodic table” of the molecular pretzels. The table reveals which molecular knots are able to be created and arranges them in order of increasing complexity, the researchers report August 3 in Nature Communications.
The team organized the table based on the realization that two characteristics predict how difficult it is to create a molecular knot: the number of molecular building blocks needed to construct each pretzel shape and the number of times each knot’s strands loop around the knot’s center.

Lots of knots
In the “periodic table” below, knots that scientists have already synthesized are in orange and knots yet to be made are in blue. Knots increase in complexity as you go down the table and to the right, offering a road map to creating more knots. Ellipses indicate that the table continues.

Hover over the black circles for 3-D knot renderings and/or images of created knots’ molecular structures.
Fashioning these knots is a challenge, and provides a way for chemists to strengthen their skills for manipulating molecules. The new table offers those scientists a blueprint to figuring out which molecular knots to make next.

These knots eventually could lead to useful new materials. For example, the tiny knots could serve as nanocages, structures that could store chemicals such as drugs for release when needed.

EEE / Here’s how to bend spaghetti to your will
« on: February 28, 2020, 09:22:06 PM »
imply bending a stick of spaghetti in half typically shatters it into three or more fragments. That’s because when the stick breaks, vibrations wrack the remaining halves, causing smaller pieces to splinter off (SN: 11/12/05, p. 315). To avoid this problem, give the spaghetti stick a twist before bending it, researchers report online August 13 in Proceedings of the National Academy of Sciences.
Vishal Patil, a mathematician at MIT, and colleagues discovered this technique by breaking hundreds of pieces of pasta with a custom-made spaghetti-snapping device. These observations, along with computer simulations of the system, reveal that when a spaghetti stick is twisted, it doesn’t bend as far before breaking. As a result, the vibrations that rattle the spaghetti halves post-snap aren’t strong enough to cause further fracturing.

The exact amount of twist required to give pasta a clean break depends on the length of the rod, but for a typical stick 24 centimeters long to crack neatly in two, it’s at least 250 degrees.

This strategy may not be much practical help in the kitchen; Patil and colleagues aren’t selling their spaghetti snapper for $19.95 — and even if they were, meticulously twisting and bending pieces of pasta one-by-one is hardly efficient meal prep. Still, the discovery of the bend-and-twist technique may lend new insight into controlling the breakage of all kinds of brittle rods, from pole vault sticks to nanotubes.

EEE / A new material harnesses light to deice surfaces
« on: February 28, 2020, 09:21:33 PM »
A new material that converts light into heat could be laminated onto airplanes, wind turbines, rooftops and offshore oil platforms to help combat ice buildup.

This deicer, called a photothermal trap, has three layers: a top coating of a ceramic-metal mix that turns incoming light into thermal energy, a middle layer of aluminum that spreads this heat across the entire sheet — warming up even areas not bathed in light — and a foam insulation base. The photothermal trap, described online August 31 in Science Advances, can be powered by sunshine or LEDs.

Engineer Susmita Dash of the Indian Institute of Science in Bengaluru and colleagues laid a 6.3-centimeter-wide sheet of the deicing material out in the sun on a day averaging about –3.5° Celsius, alongside a sheet of aluminum. Within four minutes, the photothermal trap heated to about 30° C, while the aluminum warmed to only about 6° C. After five minutes, snow on the surface of the photothermal trap had mostly melted off, but snow remained caked on the aluminum.

Deicing surfaces typically involves energy-intensive heating systems or environmentally unfriendly chemical sprays. By harnessing light to melt ice away, the new photothermal trap may provide a more sustainable means of keeping surfaces ice-free. “This is a new direction for anti-icing,” says Kevin Golovin, a materials scientist and engineer at the University of British Columbia in Kelowna not involved in the work.

EEE / A new hydrogen-rich compound may be a record-breaking superconductor
« on: February 28, 2020, 09:21:10 PM »
Superconductors are heating up, and a world record-holder may have just been dethroned.

Two studies report evidence of superconductivity — the transmission of electricity without resistance — at temperatures higher than seen before. The effect appears in compounds of lanthanum and hydrogen squeezed to extremely high pressures.

All known superconductors must be chilled to function, which makes them difficult to use in real-world applications. If scientists found a superconductor that worked at room temperature, the material could be integrated into electronic devices and transmission wires, potentially saving vast amounts of energy currently lost to electrical resistance. So scientists are constantly on the lookout for higher-temperature superconductors. The current record-holder, hydrogen sulfide, which also must be compressed, works below 203 kelvins, or about −70° Celsius (SN: 12/26/15, p. 25).
The new evidence for superconductivity is based on a dramatic drop in the resistance of the lanthanum-hydrogen compounds when cooled below a certain temperature. One team of physicists found that their compound’s resistance plummeted at a temperature of 260 kelvins (−13° C), the temperature of a very cold winter day. The purported superconductivity occurred when the material had been crushed with almost 2 million times the pressure of Earth’s atmosphere by squeezing it between two diamonds. Some samples even showed signs of superconductivity at higher temperatures, up to 280 kelvins (about 7° C), physicist Russell Hemley of George Washington University in Washington, D.C., and colleagues report in a study posted online August 23 at Hemley first reported signs of the compound’s superconductivity in May in Madrid at a symposium on superconductivity and pressure.

EEE / Here’s how graphene could make future electronics superfast
« on: February 28, 2020, 09:20:35 PM »
New experiments show that this single layer of carbon atoms can transform electronic signals at gigahertz frequencies into higher-frequency terahertz signals — which can shuttle up to 1,000 times as much information per second.

Electromagnetic waves in the terahertz range are notoriously difficult to create, and conventional silicon-based electronics have trouble handling such high-frequency signals (SN: 3/28/09, p. 24). But graphene-based devices could. These future electronics would work much faster than today’s devices, researchers report online September 10 in Nature.
Physicist Dmitry Turchinovich of the University of Duisburg-Essen in Germany and colleagues tested graphene’s terahertz-producing prowess by injecting a sheet of this atom-thick material with 300-gigahertz radiation. When these electromagnetic waves hit the graphene, electrons in the material rapidly heated and cooled off, releasing electromagnetic waves with frequencies up to seven times as high as the incoming radiation.“This is yet another amazing result for graphene,” says Orad Reshef, a physicist at the University of Ottawa not involved in the work. The 2-D material has been hailed as a supermaterial for its extraordinary abilities, such as conducting electric current with no resistance (SN: 3/31/18, p. 13).

The graphene converted more than a thousandth, a ten-thousandth and a hundred-thousandth of the original 300-gigahertz signal into waves at 0.9, 1.5 and 2.1 terahertz, respectively. That conversion rate may seem small, but it’s remarkably high for a lone layer of atoms, says Tsuneyuki Ozaki, a physicist at the National Institute of Scientific Research in Quebec City not involved in the work.

Graphene-based computer components that can deal in terahertz “could be used, not in a normal Macintosh or PC, but perhaps in very advanced computers with high processing rates,” Ozaki says. This 2-D material could also be used to make extremely high-speed nanodevices, he adds.

EEE / High-tech ‘skins’ turn everyday objects into robots
« on: February 28, 2020, 09:20:05 PM »
Robotic skin that bends, stretches and contracts can wrap around inanimate objects like stuffed animals, foam tubes or balloons to create flexible, lightweight robots. Removable, reusable sheets of this artificial skin, described online September 19 in Science Robotics, could also be used to build grippers or wearable devices.

“It’s an interesting approach,” says Christopher Atkeson, a roboticist at Carnegie Mellon University in Pittsburgh who wasn’t involved in the work. In some cases, it may be simpler to use a soft robot ready-made for a specific purpose, like squeezing through tight spaces (SN Online: 7/19/17) or gently grabbing objects (SN: 9/16/17, p. 8). But robotic skins could come in handy for search-and-rescue operations or space exploration — missions where a user might not know in advance what kind of robotic helpers they’ll need, but where packing light is key, Atkeson says.
Each piece of robotic skin is composed of elastic polymer or fabric, embedded with either air pouches that inflate when pumped full of gas or with nickel titanium coils that contract when heated by electric current. These gas pouches and coils allow the robotic skin to move and change shape.

Rebecca Kramer-Bottiglio, an engineer at Yale University, and colleagues used the skin to build several robots. The researchers achieved different types of motion by altering the layout of air pouches or coils in the skin and by attaching pieces of skin to an object in various configurations.

For instance, wrapping the skin around foam tubes in different orientations created robots that either scooted like inchworms or paddled forward on two ends. Patches of robotic skin around three foam fingers animated a soft robot grabber.

EEE / This reflective paint could keep sunbaked buildings cool
« on: February 28, 2020, 09:19:38 PM »
A new polymer-based paint that reflects nearly all incoming sunlight could help keep buildings, cars, airplanes and other sunbaked structures cool.

This polymer paint, described online September 27 in Science, can be applied to various surfaces, including plastics, metals and wood. It also could be fashioned into recyclable tarpaulins for covering homes, cars or other enclosed spaces.

Materials scientist Yuan Yang of Columbia University and colleagues made the heat-resistant paint using water, acetone and a polymer called poly(vinylidene fluoride-co-hexafluoropropene). When the paint dries, the evaporated acetone and water leave behind a polymer film riddled with air pockets. These tiny cavities, ranging from hundreds of nanometers to several micrometers across, reflect more than 96 percent of incoming sunlight. Other cool-roof white paints have been able to deflect only about 85 percent of sunshine.
The film’s porous structure also allows any heat the material does absorb to escape into the air more easily than it could from a solid polymer sheet, says study coauthor Nanfang Yu, an applied physicist at Columbia. In field tests, a coating of this polymer paint under a clear sky in Phoenix stayed about 6 degrees Celsius cooler than surrounding air.

Using the paint to create heat shields could curb the use of energy-intensive air conditioning systems that often require air-polluting coolants, as well as offer protection from heat waves to people who don’t have electricity in the first place (SN: 4/14/18, p. 18).

EEE / Vanadium dioxide’s weird phase transition just got weirder
« on: February 28, 2020, 09:19:11 PM »
For the first time, researchers have gotten a detailed view of how atoms in a compound called vanadium dioxide move when an ultrafast laser pulse transforms the material from an electrical insulator to a conductor — and it’s nothing like scientists expected.

Rather than switching from one crystal formation to another in a direct, synchronized manner, like choreographed ballerinas, the atoms shift around in a disordered manner, more like clumsy partygoers doing the Cha Cha Slide. This new insight into the inner workings of vanadium dioxide, reported in the Nov. 2 Science, may inform engineers who are trying to harness the dual nature of the compound and others like it for new technologies.
Scientists have been fascinated for decades by the nature of vanadium dioxide’s insulator-to-metal transition, which happens when the material is heated above about 67° Celsius or hit with an ultrafast laser pulse. But that electrical about-face is difficult to study, because it happens in about 150 femtoseconds, or quadrillionths of a second.

Other experiments that involved tickling vanadium dioxide’s atoms with laser light have measured only the average motions of atoms during this transformation. These general trends suggested a smooth shift from one crystal formation to another, but were not detailed enough to reveal small deviations in the atoms’ movement.

Mariano Trigo, a physicist at SLAC National Accelerator Laboratory in Menlo Park, Calif., and colleagues got a closer look at the compound using ultrashort pulses of X-ray radiation. After hitting a sample of vanadium dioxide with a superfast flash of laser light to trigger its insulator-to-metal transition, the researchers zapped the compound with a series of X-ray pulses, each a few tens of femtoseconds long.

This X-ray radiation scattered off atoms in the material, revealing the particles’ positions at the time of each pulse, explains study coauthor Olivier Delaire, a materials scientist at Duke University. The pulses were so rapid and intense that they tracked atoms’ movements much more precisely, and at shorter time intervals, than other experiments.

“It’s extremely cool” to see these atomic motions in such fine detail, says Ralph Ernstorfer, a physicist at the Fritz Haber Institute of the Max Planck Society in Berlin not involved in the study.

These atomic snapshots exposed the vanadium atoms’ discombobulated movement from one crystal structure to the next. Supercomputer simulations of vanadium atoms rejiggering themselves in this way reproduced almost the exact same X-ray scattering patterns as the experiment.

Vanadium dioxide’s ultrafast insulator-to-metal transition may someday form the basis of super speedy electronic components, or devices that exploit vanadium dioxide’s weird relationship with light and electricity for camouflage or efficient heating and cooling (SN Online: 10/25/13). Understanding this material’s internal structure could help engineers wrest better control over its properties, says Richard Averitt, a physicist at the University of California, San Diego not involved in the work.

The technique Trigo’s team used to investigate vanadium dioxide may also help researchers probe other materials that change characteristics under the influence of laser light, Averitt says. These may include materials that switch magnetic properties or become superconductors that transmit electricity with no resistance. “It’s got a very bright future” for revealing the atomic goings-on in such two-faced materials, he says.

EEE / Questions about toxic red tides, and more reader feedback
« on: February 28, 2020, 09:18:43 PM »
A new material that converts sunlight into heat could someday melt ice off airplane wings, wind turbines and rooftops, Maria Temming reported in “A new material harnesses light to deice surfaces” (SN: 9/29/18, p. 17).

“What happens when the object (such as an airplane wing) to which the material has been applied is subjected to the sun on a hot summer day?” asked online reader Nell Kroeger. “Could the object dangerously overheat?”

The material can heat up to tens of degrees Celsius above the ambient temperature, says Susmita Dash, an engineer at the Indian Institute of Science in Bangalore. A coated airplane wing on a hot summer day will heat up, she says, but “I don’t think it will reach a dangerously high temperature.”
Dash suggests one way to avoid potential overheating: use the material only during the cold season. “In the case of rooftops … I think it can be used as a laminate during winters and can be easily removed and stored during the summers,” she says.

Bloom food
Scientists around the United States are developing programs that can predict in advance toxic red tides, like one that’s ravaging Florida’s coast, as well as other harmful algal blooms, Leah Rosenbaum reported in “As algae blooms increase, scientists seek better ways to predict these toxic tides” (SN: 9/29/18, p. 14).

“Coastal states plagued with blooms … seem to be spiraling toward disaster from global warming and runoff from agriculture,” reader Enrique Petrovich wrote. “Would agricultural chemical runoff cause these toxic algal blooms if the farms were converted to organic?” he asked.

 Excess nutrients — such as nitrate and phosphate — whether organic, inorganic or synthetic are all usable by algae and can lead to rapid growth, says oceanographer Clarissa Anderson of the Scripps Institution of Oceanography in La Jolla, Calif.

Unless organic farms are better at controlling runoff, Rosenbaum adds, they can still contribute to blooms.

EEE / A new fabric becomes more breathable as you work up a sweat
« on: February 28, 2020, 09:17:39 PM »
Someday, the same shirt could be part of your summer and winter wardrobe, using fabric that alternates between breathable and insulating.

Unlike other heat-accommodating cloth, which has to be flipped inside out to switch from warm to cool (SN: 2/17/18, p. 5), the new dual-use fabric adapts to how much the wearer is sweating. This material may be useful for making sportswear or clothing for babies who can’t articulate when they’re too hot or too cold, says study coauthor YuHuang Wang, a chemist at the University of Maryland in College Park.
The fabric, described in the Feb. 8 Science, is knitted from yarn composed of many polymer fibers coated in tiny, carbon nanotubes. The closer these nanotubes are together, the better the fabric conducts the heat a person’s body sheds as infrared radiation.

Under cool, dry conditions, the fibers are loosely wound, and the fabric traps much of the heat radiating off the wearer’s body. But if the person starts to sweat, that humidity causes the polymer fibers in the yarn to constrict into tight bundles. This brings the carbon nanotubes on neighboring fibers closer together, making the material more breathable.
Wang and colleagues found that increasing the humidity inside a chamber containing a piece of the fabric could increase the amount of heat that passed through the material up to about 35 percent. The fabric’s dependence on water in the surrounding air means that even on a cool, muggy day when the user isn’t necessarily sweating, humidity in the surrounding air could make the fabric less insulating. In the future, Wang imagines making the yarn fibers with materials that respond directly to temperature changes, so the fabric can accommodate a person’s skin temperature as well as sweat levels.

Human-made metamaterials with messy internal designs may be more resistant to damage than those with neatly patterned structures.

Metamaterial lattices, usually composed of struts that form identical, repeating “unit cells,” can exhibit properties that normal solids don’t (SN: 1/19/19, p. 5). But under heavy loads, overstressed struts can collapse, and that breakage quickly splinters through the whole grid, causing it to crumble.

Materials scientist Minh-Son Pham of Imperial College London and colleagues realized that this kind of collapse is similar to the way metallic crystals with atoms arranged in identical unit cells deform under heavy loads. In these materials, defects in the crystal can travel freely through its atomic lattice like dominoes falling in a row, weakening the crystal (SN: 9/11/10, p. 22).
o create more resilient metamaterials, Pham and colleagues drew inspiration from the irregular atomic arrangements inside crystalline metals. In these materials, described in the Jan. 17 Nature, different regions contain unit cells with different orientations, sizes or types of crystals. The boundaries between these regions serve as roadblocks to stop defects from moving. Metamaterial lattices patterned after these atomic setups could make more reliable components for cars and airplanes, Pham says.

Pham’s team 3-D printed lattices with unit cells arranged either in perfect order, as in conventional metamaterials, or in motley groups of different atomic structures. When the researchers squeezed lattices between metal plates, the mixed lattices proved sturdier than those with regular unit cell arrangements.

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