09 May 2015

New low-cost cerium alloy magnets developed for motors and turbines

motor assembly

Permanent magnets based on neodymium-iron-boron are about the strongest money can buy. The main problem with them is that in order to work above room temperature you need to add significant amounts of the rare element dysprosium. With prices soaring, this situation will likely have to change. Researchers at the Energy Department’s Ames Laboratory have just found that the most abundant rare earth we have, cerium, can substitute for dysprosium when properly co-alloyed with cobalt.

Previously, attempts to use cerium in magnets failed because it actually lowered the Curie temperature. That’s the point above which magnetic properties for the alloy or metal are lost. However, when cobalt is added to the mix, you get an alloy that performs better than anything else above 150° C. Several important variables come into play when spec’ing out a magnet, but its intrinsic coercivity at elevated temperatures is key for many common applications. This is the ability of the material to resist the evil forces of demagnetization.

In addition to the magnet-busting effects of elevated temperature, the forces that degrade motor magnet lifetime and performance include vibration and even radiation. For mining companies that can hardly give cerium away, the robustness of these new cerium alloys to these forces is great news. Compared with the standard dysprosium based magnets now used in many turbine, electric car, and servomotor applications, cerium should chop 20 to 40 percent off the sticker price.

motor stator and rotor magnet

That may not sound like a huge deal, but as demand for larger permanent magnet motors increases, manufacturers may be able to meet it using cerium. Some electric vehicles still use induction-style or other motor designs that lack permanent magnets. But above a certain size, manufacturing big magnets gets progressively more uneconomical. On the other hand, winding the coils of all-electromagnetic motors gets easier when everything gets bigger. For applications like 10 degree-of-freedom robotic arms, you are never going to beat the compactness and power density of permanent magnet motors.

It is estimated that the drive motor in a hybrid typically delivers around 80 horsepower per kilogram of neodymium. With more elite applications like all-electric airplanes now looming, motors will likely be pushed to their extreme. The high temperature capabilities of cerium magnets would let motors made from them run at correspondingly higher temperatures. That means that the currents pushed through their coils can be higher, longer, and stronger.

In a time when China tightly regulates more than 90 percent of the world’s production of rare earth metals, being a little more strategic with our strategic materials would seem like a wise move. Moving to more abundant cerium would certainly be one way to do this.

Extremetech

New Rombertik malware hits hard drives, cleans MBR if recognized

Carbon Crack

The game of cat-and-mouse between malware authors and security white hats may have entered a new phase this week, thanks to an aggressive new malware system that doesn’t just attempt to obfuscate its own operation it aggressively scans for clues that others are monitoring its actions. If it detects that it’s operating within a Virtual Machine, the malware, dubbed Rombertik, will go nuclear and attempt to overwrite the master boot record of the local hard drive.

Cisco’s threat response team has detailed the operation of Rombertik, and the malware’s obfuscation and attack vectors are unique. Once installed, it’s a fairly standard data sniffer that grabs indiscriminately from the information available on an infected PC. What sets Rombertik apart is the way it checks to see if it’s running in a VM-provided sandbox, and the actions it takes if it finds itself in such a mode.

malware compromise flow

The infograph above breaks down how the malware works and what it does. Rombertik contains a great deal of information designed to make it look genuine; Cisco estimates that 97% of the packed file is devoted to images and functions that are never used by the actual malware. Once it starts running, the executable kicks off by writing 960 million random bytes to memory. This serves no useful function, but it does ensure that any application attempting to trace the malware’s activity would be flooded by 100GB+ log files.

Having completed this task, Rombertik makes some specific invalid function calls to check for particular errors (it’s looking for an error that a VM might typically suppress). Once it decides that it isn’t running within a sandbox, the malware starts unpacking itself. The code is deliberately obfuscated with dozens of functions, jumps, and unnecessary (but obfuscating) bloat.

The security checks are on the right, the primary code on the left. 

This complexity map shows the anti-analysis code on the right, the executable on the left. While the anti-analysis code might look more daunting, it’s actually a relatively simple flowchart with a huge number of iterations. The left hand graph, in contrast, is a mess of function blocks, checks, and hundreds of nodes all meant to prevent analysts from reading what’s been written.

At the end of this process, Rombertik computes a 32-bit hash, compares it to an unpacked sample and, if it detects that it’s running in a VM, immediately declares war against the Master Boot Record of your hard drive. If it can’t access and overwrite the MBR, it encrypts all files within the C:\Documents and Settings\Administrator folder using an RC4 key. If it can get its hands on the MBR, it overwrites the partition data with null bytes, making it extremely difficult to restore the drive.

So who wrote Rombertik?

What’s odd about Rombertik is that it combines elements of classic malware a poorly written initial phishing attempt and bog-standard data capture from browser sessions with some absolutely first-rate anti-detection methods and a hell of a right hook if caught. The authors of Rombertik have gone to enormous length to ensure the virus arrives on-target and can perform its actions. But this is the kind of obfuscation technique we’d expect to see in products from state actors if not our own government, then someone else’s.

No one is talking about any sort of government initiative attached to Rombertik. In a way, that’s actually more worrying a trojan this complex that was designed by state actors is worrying to begin with, but these techniques becoming mainstream is almost worse. Cisco’s blog post has more details on the malware and its functions give it a read if you want to peek inside one of the most impressive malware projects to date.

Extremetech

CERN scientists tuning Large Hadron Collider ahead of 13 TeV collisions

CERN Large Hadron Collider

We’re getting closer to full power: For the first time in two years, after significant upgrades and repairs, the Large Hadron Collider is now delivering proton-to-proton collisions for four of CERN’s major experiments at energies up to 450 gigaelectronvolts (GeV) per beam, the research organization said in a statement.

The four experiments in progress are ALICE, which is studying quark-gluon plasma thought to have formed just after the big bang; ATLAS, a general-purpose detector looking for fundamental particles; CMS, which employs a giant solenoid magnet to bend the paths of particles; and LHCb, an ongoing study of the differences between matter and antimatter.

Proton beams collide for a total energy of 900 GeV in the ATLAS detector
Proton beams collide for a total energy of 900 GeV in the ATLAS detector. (Credit: ATLAS/CERN)

The lower-energy collisions send “showers of particles flying through an experiment’s many layers,” CERN Web editor Cian O’Luanaigh said. The process ensures researchers can check their subdetectors and ensure they’re firing exactly as they should be. Essentially, researchers are using the current lower-level collisions as a way to tune their detectors, paving the way for the LHC to deliver beams at 6.5 teraelectronvolts (TeV) for collisions at the never-before-achieved level of 13 TeV.

Currently, the LHC is roughly halfway through its eight weeks of scheduled beam commissioning, “during which the accelerator’s many subsystems are checked to ensure that beams will circulate stably and in the correct orbit,” O’Luanaigh said in the statement. “Sensors and collimators around the accelerator’s full 27 kilometres send information to the CERN Control Centre, from where the operators can remotely adjust the beam by fine-tuning the positions and field strengths of hundreds of electromagnets.”

Proton-to-proton collisions at 900 GeV, measured by the inner silicon trackers in the ALICE detector
Proton-to-proton collisions at 900 GeV, measured by the inner silicon trackers in the ALICE detector (Credit: ALICE/CERN)

Ultimately, scientists are hoping that the 17-mile-long Large Hadron Collider will help shed light on the true nature of dark matter, and whether it originates from the Higgs Boson. Dark matter doesn’t seem to emit radiation, so we can’t detect it. But we know it’s there, because of its gravitational pull on matter we can detect, and we know it seems to have something to do with the distribution of galaxies throughout our universe.

Two proton beams at 450 GeV collide in the CMS detector, for a total collision energy of 900 GeV
Two proton beams at 450 GeV collide in the CMS detector, for a total collision energy of 900 GeV. (Image: CMS/CERN)

The LHC first came online in 2008, and performed experiments on and off for five years before shutting down in 2013 ahead of a series of upgrades. During that first five-year run, it confirmed the existence of the elusive Higgs Boson particle. The two years of upgrades consisted of reinforcing 10,000 electrical connections between the supercooled magnets inside the LHC. Scientists still expect to run the first record-setting collisions at 13 TeV sometime this summer.

Proton to proton collision at 900 GeV in the LHCb detector
Proton-to-proton collision at 900 GeV in the LHCb detector (Image: LHCb/CERN)

Meanwhile, plans are still a go for the LHC’s successor, a 60-mile-long particle accelerator that could achieve 100 TeV collisions, which we’re assuming at this point will just create a giant black hole and suck the Earth right through it. If that project ends up going through, then excavations won’t begin until sometime in the 2020s.

Extremetech

BitWhisper: Stealing data from non-networked computers using heat

BitWhisper

No matter how secure you think a computer is, there’s always a vulnerability somewhere that a remote attacker can utilize if they’re determined enough. To reduce the chance of sensitive material being stolen, many government and industrial computer systems are not connected to outside networks. This practice is called air-gapping, but even that might not be enough. The Stuxnet worm from several years ago spread to isolated networks via USB flash drives, and now researchers at Ben Gurion University in Israel have shown that it’s possible to rig up two-way communication with an air-gapped computer via heat exchange.

Researchers call this technique of harvesting sensitive data “BitWhisper.” It was developed and tested in a standard office environment with two systems sitting side-by-side on a desk. One computer was connected to the Internet, while the other had no connectivity. This setup is common in office environment where employees are required to carry out sensitive tasks on the air-gapped computer while using the connected one for online activities.

BitWhisper does require some planning to properly execute. Both the connected and air-gapped machines need to be infected with specially designed malware. For the Internet box, that’s not really a problem, but even the air-gapped system can be infected via USB drives, supply chain attacks, and so on. Once both systems are infected, the secure machine without Internet access can be instructed to generate heating patterns by ramping up the CPU or GPU. The internet-connected computer sitting nearby can monitor temperature fluctuations using its internal sensors and interpret them as a data stream. Commands can also be sent from the Internet side to the air-gapped system via heat.

The malware is able to use the heat patterns as a covert data channel between the machines, thus defeating the air-gap. The data rate between the connected and air-gapped computers isn’t particularly fast it’s somewhere around eight bits per hour. Still, that’s enough to snatch passwords and text files over time. Because all the data theft takes place over invisible heat signals, there are almost no signs of intrusion in the secure network.


Once the malware has found a home in the air-gapped network, it can be instructed to spread to other computers in search of more heat-driven communication channels. The researchers say a secure network is vulnerable to BitWhisper anywhere an internet-connected PC is 15-inches or less away from an air-gapped system. BitWhisper can seek out new connections by sending out periodic “thermal pings” to link up nearby computers.

The researchers demonstrated BitWhisper using a computer with a USB missile-launcher toy attached. In the video above, they were able to send heat commands from the connected system over the air-gap to the isolated system and control the missile launcher. There are a lot of things that can go wrong with this system something as small as a desk fan could break the connection. Still, it’s an ingenious proof-of-concept.

Extremetech

25 March 2015

Group creates light-emitting electrochemical cell for use in textiles

light emitting electrochemical cell fiber
Fiber-shaped polymer light-emitting electrochemical cells with tunable colors are twisted together to generate colorful lights. Credit: Zhitao Zhang

A large team of researchers in China has developed a type of light emitting electrochemical cell (LEC) that can be woven into fabric material. As the team notes in their paper published in the journal Nature Photonics, their cells can be used to create wearable electronics. Henk Bolink and Enrique Ortí with the University of Valencia in Spain, offer a News & Views piece on the work done by the team in the same journal issue.

Ever since the development of OLEDs, researchers have been hot on the idea of using them to create wearable electronics, such as clothes that light up like an LED screen. But OLEDs proved too difficult to weave into fiber, which led researchers to LECs, which are essentially OLEDs with salt added to overcome some of the limitations of OLEDs. In this new effort the researchers in China have found a way to create LECs that are both strong enough and flexible enough to allow for weaving into textile fabrics.

To make the LECs, the researchers started with a tiny bare wire, which they coated with zinc oxide nanoparticles; that was followed by applying an electroluminescent polymer and than a transparent layer of carbon nanotubes the result is a cell that is long, flexible and thin allowing for weaving into fabric. Currently, fabrics created with the cells emit just blue and yellow light (when subjected to just a few volts of electricity) but the team reports it will be a simple matter to add many more colors. The team also reports that the process for making the cells can be ramped up easily, which means the cells, and clothes with them, could be available for sale in the very near future.

There is still one down side, however, the light generated by the cells only persists for a few hours after that they grow less and less bright. But that problem may be temporary as well, as other ongoing research with LECs suggests that much longer lasting cells may soon be made. If such wearable electronics do become available it could mark a rapid change in clothing, from body suits that show mood by color, to human billboards, to clothes that light up in artistic ways, sort of like glowing tattoos.

light emitting fibre

Prototype of the light-emitting fibre. Credit: Huisheng Peng

A colour-tunable, weavable fibre-shaped polymer light-emitting electrochemical cell, Nature Photonics (2015) DOI: 10.1038/nphoton.2015.37

Abstract
The emergence of wearable electronics and optoelectronics requires the development of devices that are not only highly flexible but can also be woven into textiles to offer a truly integrated solution. Here, we report a colour-tunable, weavable fibre-shaped polymer light-emitting electrochemical cell (PLEC). The fibre-shaped PLEC is fabricated using all-solution-based processes that can be scaled up for practical applications. The design has a coaxial structure comprising a modified metal wire cathode and a conducting aligned carbon nanotube sheet anode, with an electroluminescent polymer layer sandwiched between them. The fibre shape offers unique and promising advantages. For example, the luminance is independent of viewing angle, the fibre-shaped PLEC can provide a variety of different and tunable colours, it is lightweight, flexible and wearable, and it can potentially be woven into light-emitting clothes for the creation of smart fabrics.

Tech Xplore

Can perovskites and silicon team up to boost industrial solar cell efficiencies?

Tandem cell
1 cm2 monolithic perovskite-silicon tandem solar cell. Credit: Rongrong Cheacharoen/Stanford University

Silicon solar cells dominate 90 percent of the global photovoltaic market today, yet the record power conversion efficiency of silicon photovoltaics has progressed merely from 25 percent to 25.6 percent during the past 15 years meaning the industry is keen to explore alternatives.

A collaboration between the Massachusetts Institute of Technology (MIT) and Stanford University may be poised to shake things up in the solar energy world. By exploring ways to create solar cells using low-cost manufacturing methods, the team has developed a novel prototype device that combines perovskite with traditional silicon solar cells into a two-terminal "tandem" device.

As the team reports in the journal Applied Physics Letters, their new tandem cells have the potential to achieve significantly higher energy conversion efficiencies than standard single-junction silicon solar cells.

Perovskite is an inexpensive crystalline material that can easily be produced in labs and, as it turns out, stacking it atop a conventional silicon solar cell forms a tandem that has the potential to improve the cell's overall efficiency, a measure of the amount of sunlight the cell can convert into electricity.

The team focused on tandem solar cells because there was big room for improvement in their cost and market penetration. Tandem solar cells have only garnered a worldwide market share of 0.25 percent compared to silicon solar cells' 90 percent. "Despite having higher efficiency, tandems are traditionally made using expensive processes making it difficult for them to compete economically," said Colin Bailie, a Ph.D. student at Stanford and an author on the new paper.

Designing low-cost perovskite-silicon tandem solar cells

The team's tandem approach focuses on keeping costs low and "integrates perovskite solar cells monolithically building them sequentially in layers onto a silicon solar cell, without significant optical or electrical losses, by using commonly available semiconductor materials and deposition methods," explained Jonathan P. Mailoa, a graduate student in MIT's Photovoltaic Research Laboratory and another co-author on the paper.

Before creating the tandems, the researchers first needed to design an interlayer to facilitate electronic charge carrier recombination without significant energy losses. "Fortunately, the physical concepts already exist for other types of multijunction solar cells, so we simply needed to find the best interlayer material combination for the perovskite-silicon pair," Mailoa said.

To form a connecting layer, known technically as the semiconductor "tunnel junction," between the two sub-cells, the team used degenerately doped p-type and n-type silicon, which facilitates the recombination of positive charge carriers (holes) from the silicon solar cell and negative charge carriers (electrons) from the perovskite solar cell.

Because the two silicon layers are highly doped, "the energy barrier between them is thin enough so that electrons and holes in the semiconductor easily pass through using quantum mechanical tunneling," Mailoa added.

While electrons from a perovskite solar cell won't normally enter this tunnel junction layer, a titanium-dioxide (TiO2) layer commonly used in perovskite solar cells works as an electron-selective contact for silicon. This allows electrons to flow from the perovskite solar cell through the TiO2 layer, eventually passing into the silicon tunnel junction, where they recombine with the holes from the silicon solar cell.

Perovskite

How do perovskite-silicon tandem solar cells work?

Once the tandem is set up, it relies on its multiple absorber layers to absorb different portions of the solar spectrum. "The perovskite absorbs all of the visible photons [higher in energy], for example, while the silicon absorbs the infrared photons [lower in energy]," Bailie said.

Splitting the solar spectrum allows these specialized absorbing layers to convert their range of the spectrum into electrical power much more efficiently than a single absorber can convert the entire solar spectrum on its own.

"This minimizes an undesirable process in solar cells called "thermalization," in which the energy of an absorbed photon is released as heat until it reaches the energy of the absorber's bandgap," Bailie explained. "Using a high-bandgap absorber on top of the low-bandgap absorber recovers some of this energy in the high-energy photons that would otherwise be 'thermalized' if absorbed in the low-bandgap absorber."

Another key part of the tandem's design is that it uses a serial connection, which means that the two solar cells are connected in a manner so that the same amount of current passes through each of the solar cells. In other words, the same amount of light is absorbed in each solar cell and their voltage is added together.

Efficiency evolution ahead

The team's tandem "demonstrated an open-circuit voltage of 1.65 V, which is essentially the sum of top and bottom cells, with very little voltage loss," said Tonio Buonassisi, an associate professor of mechanical engineering at MIT who led the research.

An open-circuit voltage of 1.65 V was the highest best-case scenario the team had predicted, which indicates that their tunnel junction performs very well.

But an efficiency evolution is on the horizon. The efficiency record for single-junction perovskite cells ranges from 16 to 20 percent, depending on the formula used. "By contrast, the perovskite in our tandem is based on a technology that achieves only 13 percent in our lab as a single-junction device," said Bailie. "Improving the quality of our perovskite layer will lead to better tandem devices."

Another area for improving the tandem's efficiency is by "reducing parasitic optical losses in other layers of the multijunction solar cell devices and predicting their efficiency potentials through simulation to determine whether or not this approach is truly cost effective," added Mailoa.

The team also plans "to make improvements to the silicon bottom cell," said Buonassisi. "The back contact isn't well passivated, so we lose power at longer wavelengths. But the photovoltaic industry has developed several solutions for this problem...we just need to incorporate one best practice into our next-generation devices."

While their work is still far from becoming commercially available, it frees other researchers to start to focus their efforts on important aspects of the multijunction device to help further improve both its stability and efficiencies in the future.

"This is the first step in the evolution of a technology that has the potential to disrupt the photovoltaic industry," noted Bailie.

"A 2-terminal perovskite/silicon multijunction solar cell enabled by a silicon tunnel junction," by Jonathan P. Mailoa, Colin D. Bailie, Eric C. Johlin, Eric T. Hoke, Austin J. Akey, William H. Nguyen, Michael D. McGehee and Tonio Buonassisi. Applied Physics Letters, March 24, 2015. DOI: 10.1063/1.4914179

American Institute of Physics

phys

24 March 2015

Researchers working on to bring back wooly mammoth

wooly mammoth

A team of researchers working at Harvard University has taken yet another step towards bringing to life a reasonable facsimile of a woolly mammoth a large, hairy elephant like beast that went extinct approximately 3,300 years ago. The work by the team has not been published as yet, because as team lead George Church told The Sunday Times, recently, they believe they have more work to do before they write up their results.

Church is quick to point out that his team is not cloning the mammoth, instead they are rebuilding the genome of the ancient animal by studying its DNA, replicating it and then inserting the copy into the genome of an Asian elephant the closest modern day equivalent. They are not bringing forth a new mammoth yet either all of their work is confined to simple cells in their lab. What they have done, however, is build healthy living elephant cells with mammoth DNA in them. Their work is yet another step towards that ultimate goal, realizing the birth of a wooly mammoth that is as faithful to the original as is humanly possible.

Talk of cloning a mammoth began not long after scientists learned how to actually do cloning mammoth carcasses have been found in very cold places which preserved remains, which of course, included DNA. But not everyone has been onboard with the idea some claim it is stepping into God's territory, others suggest it seems ridiculous considering all of the species that are nearing extinction, including those of elephants. Why not use those financial resources that are now going towards bringing back something that has gone extinct, to saving those that are still here?

The technique the team is using is called Crispr, it allows for reproducing exact copies of genes in this case 14 mammoth genes, which are then inserted into elephant genes. As Church explains, the team prioritizes which genes are replicated and inserted, based on such factors as hairiness, ear size, and subcutaneous fat, which the animal needed to survive in its harsh cold environment.

Not clear as yet is when or if the team at Harvard has plans to produce an actual living mammoth, or if they will leave that to other teams working on similar projects.

Phys

23 March 2015

Man uses 3D printer to create "world's smallest" power drill

teeny-tiny drill made with an Ultimaker 2 3D printer

The teeny-tiny drill, made with an Ultimaker 2 3D printer (Photo: Lance Abernethy)

Should you ever feel the need to carefully bore a hole through the top layer of skin on your finger, there's now a drill that can do it. Using his Ultimaker 2 3D printer, Auckland, New Zealand maintenance engineer Lance Abernethy has created what is unofficially the world's smallest working power drill.

According to a report on 3DPrint.com, Abernethy started out by creating a computer model using Onshape 3D software, utilizing his full-size drill for reference. He then proceeded to print out the two halves of the drill's body, along with its chuck. The whole printing process took about 25 minutes.

teeny-tiny drill made with an Ultimaker 2 3D printer

It subsequently took Lance about three hours to stuff in a tiny motor, power button, hearing aid battery, and wiring from a stripped headphone cable.

The finished product measures 17 x 7.5 x 13 mm, uses a 0.5-mm bit, and can reportedly drill through soft objects. Abernethy says that he's seen other drills claimed to be the world's smallest, but that his is smaller. Not one to rest on his laurels, though, he already has plans to make an even tinier drill, using a smaller battery that he has on hand.

In the meantime, you can see his existing drill in action, in the video below.



Source: 3DPrint.com via gizmag

New mobile system concept captures high-resolution images inside the eye

Retina smartphone image

It’s crunch time for smartphones to prove what they can do in the medical world. The second killer app, the one to follow the Alivecor heart monitor, has yet to decisively emerge. For many reasons the next device to take its place within the tricorder trinity handhelds that combine sensing, computing, and recording might be expected to use fancy optics to see inside the body. Few better places for a first application exist than the eye. Seizing upon these truths, researchers at Rice have developed a smartphone peripheral they call Mobilevision to image the most sensitive part of the eye in high definition.

When the researchers talked to eye care specialists about what is needed in the business, the response they typically got was “Can you image the macula?” The macula is the sensitive part of the eye, the part that includes the both the fovea and adjacent regions with a high density of photoreceptors. Patients with diabetes or other issues that lead to degeneration in the eye need regular scans to catch issues before they snowball. In reality, few folks adhere to the strict monthly maintenance plan their condition requires.

The main problem is that not only does the patient have to go to the instrument for a scan, but they also need to have their eyes dilated with drugs in order to get a decent picture. A smarter way for everyone involved is to not have to do either of those things. A smartphone accessory that can go instead to the patient fixes the first problem, and letting the pupil dilate in the dark on its own time solves the second. While it sounds like a no-brainer to do this, the instrument has to at least be fast enough (within a few hundred milliseconds) to snap some decent images during the brief illumination pulse before the pupil re-contracts.


The Rice instrument not only can do all this automatically, but it lets the user, ‘the patient one,’ do this on their own time. As the video shows, the device gives a visual cue when everything is in focus. Then the user presses a button to trigger the action. The device itself, likely a prototype, looks like it could be shrunk even further by replacing the optical hardware that holds critical components (lens, beamsplitters, or whatever else one might expect) in place with a mass-produced casting.

The researchers note that the eye is the only region of the body where you can do direct, noninvasive imaging of internal blood vessels. While we see why they claim that, there are perhaps other potential portals to consider for the future. Over a decade ago, I went to a small startup company in the Northeast area to demo a unique device. It was a fiber-optic wand bearing blue light that, if placed on the tissue below the tongue, could image individual red blood cells squeezing through your capillaries. It was incredible to see: your own working cells large as life, right on the screen right in front of you.

I don’t fully know how that particular gadget worked, and whether it has been commercialized since. But once a couple of these devices are out there, we may quickly see a whole new era of medical diagnostics unfold before us.

(Retinal image credit: Adam Samaniego/Rice University)

Extremetech

New materials theory for predicting strength of composites

new material

To most of us, the mother-of-pearl found in the shells of mollusks is just a decorative leftover. But material scientists see something else when they look at it. Mother-of-pearl (more formally known as nacre) is an organic-inorganic composite material with excellent mechanical properties that are hard to replicate in artificially produced composites. This inspired researchers from Rice University to develop a better way to judge the usefulness of composite materials before they’re ever produced.

There are a multitude of considerations that go into the design of a new composite material. Different use cases require a different mixture of toughness, strength, and stiffness. While these terms are often used interchangeably in casual conversation, to material scientists they have very different and specific meanings.

For example, the strength of a material indicates how well it holds up to being stretched or compressed. Stiffness describes a material’s ability to resist deformation. As for toughness, that is a measure of how much energy a material can absorb before failing. It’s tricky to judge the performance of a new man-made composite in each of these categories before you make it, but the Rice University team used nacre as a starting point to do just that.

Rice researchers Rouzbeh Shahsavari and Navid Sakhavand studied the structure of nacre under the microscope. Nacre is known as a platelet-matrix composite, which means it’s composed of overlapping disk-like structures held together with natural polymers. It’s like a brick wall on the microscopic scale with high strength and toughness.


Designing similar platelet-matrix materials in the lab has proven difficult, because there hasn’t been any good way to evaluate the relationship between structure and materials. The design map created by Shahsavari and Sakhavand provides the necessary guide.

If you need something with high stiffness and strength, for example, you can plug the design variables into equations and see where it falls on the map. It took three years of intensive calculations to create this map, which accurately predicts the mechanical properties of a variety of composites. How do they know the theory is accurate? Shahsavari and Sakhavand evaluated a number of synthetic and natural materials to see if the real-world performance matched the theoretical predictions made by the map. They found a very close match between theory and practice.

The Rice University design map could become a useful tool in many manufacturing industries. Any time engineers need a material that has specific properties, they could test a variety of designs virtually without actually going to the trouble of making them. The design map basically guides material scientists to the right composite without all the trial and error.

Extremetech
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