The Intersection of Information and Energy Technologies

Engineerblogger
April 27, 2012

Smart energy: Entrepreneur Bill Gross amid the solar-thermal concentrators of eSolar’s Sierra SunTower in 2009. Credit: Andres Castañeda

Two talks at the TED conference this year formed, back to back, a sort of debate about the future of our planet. First, Paul Gilding gave a talk entitled "The Earth Is Full," about how we are using up all Earth's resources, with possibly devastating consequences. Next, X Prize creator Peter Diamandis gave a presentation entitled "Abundance," about how we will invent innovative ways to solve the challenges that loom before us.

I believe that we will need great ingenuity to enable our planet to provide successfully for more than seven billion human beings, let alone the nine billion that will probably inhabit it by 2050, and I believe that information technology will make this ingenuity possible. Because of fluid marketplaces and an ever more globalized economy, nearly every important resource is becoming scarcer and more costly. Evidence of this is seen in the price not only of oil but also of aluminum, concrete, wood, water, rare-earth elements, and even common elements like copper. Everything is getting more expensive because billions of people are trying creatively to repackage and consume these materials. But there is one resource whose price has consistently has gone down: computation.

The power, cost, and energy use involved in one unit of computation is declining at a more consistent, dependable rate than we have seen with any other commodity in human history. That declining cost curve must be tapped to lower energy prices—and I believe it will be. This will happen as people ask: To achieve my purpose (in designing whatever device or system), can I use more "atoms" or more "bits" (computation power)? The choice will have to be bits, because atoms are going up in price while bits are going down.

Here are a few examples. When designing a car, one can put a bit more effort into stronger, lighter-weight materials, which will increase energy efficiency but possibly drive up cost; or one can put a lot more effort into using computational power to run simulations that optimize the use of materials. Today, computational fluid dynamics allow a designer to accurately design a new shape of car, put it in a computer wind tunnel instead of a physical one, and test 1,000,000 body designs to improve fuel mileage by significant amounts. This was never before possible for those constructing vehicles.

In solar energy, large fields of mirrors or photovoltaic panels can be optimized to be lighter, more reliable, and more power-efficient by putting a $2 microprocessor in every panel. An onboard computer that lets each panel track the sun independently replaces previous systems that used more steel, bigger gears, and bigger gearboxes—basically, more materials. As little as 10 years ago, the computing power and sensors needed to build a closed-loop, sun-tracking solar panel might have cost $2,000, or more than the panel itself, and thus the system would not have been cost effective. But with computing costs coming down by a factor of 1,000 every 15 years, all kinds of new opportunities arise to improve system design.

At eSolar, one of our companies, we designed and built a utility-scale solar-thermal power plant with a huge amount of computation embedded into the field of mirrors. We reduced the size of the components, cut the installation expense, and drove the cost of the system down to nearly half what had been achieved before. This experience proved to me the feasibility of replacing atoms with bits.

The price reduction curve for computing is not over—it's continuing, and each year will open up further avenues for ingenuity. That is important because our current energy resources are not at all easy to compete with. Fuels that we dig out of the ground and burn are extremely cheap. They are, in effect, the concentrated storage of millions of years of sunlight falling on Earth. Ironically, the biggest component of energy costs is the expense of moving the fuel to consumers from where it's obtained—and transportation costs are mostly fuel, too. So we are in a kind of vicious cycle. The way to break free of fossil fuels is to introduce something new to our energy equation that isn't fuel.

I believe ingenuity in the form of information technology is the only variable that offers sufficient leverage. We need to replace a cheap, unsustainable form of energy with sustainable forms of energy that are equally cheap. The only way to compete with cheap fuels is to be more clever with computation; that is, to use as little of anything else as possible.

Source: Technology Review

3D Printing Technology: Manufacturing technologies present new opportunities for R&D prototypes and high-end manufacturing facilities

R&D Magazine
April 26, 2012


Flight Testing 3D Printing

For years, aerospace engineers have been inspired by the natural world, and many have built and flown biologically inspired vehicles. Engineers at Lockheed Martin Advanced Technology Laboratories (ATL), Cherry Hill, N.J., are designing, flying, and 3D printing Samarai, a family of unmanned aerial vehicles (UAVs) that mimic the shape of winged maple seeds—samaras—that float to the ground each spring. The vehicles are structurally simple, and inherently stable in flight.

Shahrukh Tarapore, senior research scientist at Lockheed Martin Advanced Technology Laboratories, examines the 3D-printed Samarai as he pulls it from the Stratasys Dimension 3D printer. Image: Lockheed Martin Advanced Technology Laboratories

Since 2009, Lockheed Martin ATL engineers have been producing and flying Samarai using traditional materials and manual manufacturing. However, the team is now investigating 3D printing to produce the vehicles.

The research project has two goals. The team will explore whether or not 3D printing can drastically reduce the time and costs required to design and manufacture the small UAV. Also, the team plans to develop a tool that takes specific mission objectives—such as flight duration—as input and automatically produce a customized vehicle design that meets these objectives. This research could go far beyond the Samarai platform, as the technology could be extended to support other complex systems.

3D printing also helps gain insight into how the Samarai wing design affects flight characteristics. Single wing, or monowing, flight is not well understood, and the rapid manufacturing of different designs through 3D printing, combined with testing the different variants and measuring resulting performance, enables rapid exploration of the flight design space.  To read more click here...

New Life for 3D Printing

The additive manufacturing industry is populated by a broad family of technologies and some high-end systems can achieve impressive results with metals and polymers. Developments in ceramics may soon make a big impact. The low end of the market has recently been shaken up by the entry of some very low-cost systems that are causing a lot of excitement in the hobbyist market. 

The first 3D-printed full jaw replacement was made in laser-sintered titanium by the Belgian company LayerWise. Image: LayerWise

Metal parts made by laser sintering of powders top the list in performance. A wide range of stainless and tool steels, titanium and nickel alloys, and cobalt-chrome, as well as copper, aluminum, and precious metals can all be formed in machines built by companies such as EOS (Munich), Concept Laser (Lichtenfels, Germany), Renishaw Inc. (Wotton-under-Edge, U.K.), and Phenix Systems (Riom, France). Metal parts are fully dense, with a uniform microstructure due to the localized melting of a static powder bed. Titanium parts meet American Society for Testing and Materials (ASTM) standards for wrought titanium and exceed the strength and toughness of cast materials.

Laser cladding systems, such as those built by Optomec (Albuquerque, N.M.) and POM Group Inc. (Auburn Hills, Mich.), operate by jetting metal powders through a nozzle directed at a focused laser spot. These systems are able to build up parts from different metals in different locations, and are also able to effect repairs on damaged parts.

Medical implants are a very lively market for additive manufacturing metal parts. Recently, a complete lower jaw was fabricated in titanium by the Belgian company LayerWise on an EOS machine, and subsequently coated with a bioceramic by plasma spraying. Smaller custom-fit cranial implants, as well as dental implants and copings, are becoming more and more common.

More than 30 different systems make plastic parts of some type. Unlike laser-sintered metals, polymeric parts generally don't meet the same standards as conventionally processed materials. This shortcoming has relegated most processes to design prototyping and display models.

The additive manufacturing industry was founded in the mid-1980s by 3D Systems, Rock Hill, S.C., with a technology called stereolithography, which is still one of the most widely used and profitable methods. It is moderately fast, accurate, and very reliable. It is also laser-based, but rather than directing the laser onto a bed of powder, the laser is focused on the surface of a bath of photopolymer that is selectively cured in layers. The resulting parts—mostly epoxies and acrylics—are transparent and relatively tough. Stereolithography parts are useful for displaying the internal components of assemblies.  To read more click here...

Source: R&D Magazine

Project looks to develop robots for precise machine milling

Engineerblogger
April 26, 2012

COMET Machine Tool

Industrial robots could be used for more precise machine milling for things such as aerospace components, after recent trials of new technology.

One of the key goals of the near-complete European COMET project is to develop robots that can compete against five-axis machine tools.

‘Up to now the problem with robots has been that they’re not quite accurate enough; they’re somewhere in the 2–5mm range,’ said Roland Krain of project partner TEKS. ‘If you calibrate it you can probably get down to a millimetre but it’s still not quite good enough for machining.’

The major current obstacles for fully automated machining are play, mechanical flexibility, thermal effects and particularly backlash.

‘A lot of companies have got robots that handle parts that need to be milled, but if they want to do milling they have to spend between £90,000 and £150,000 on a five-axis machine tool,’ Krain said. ‘If we can add a high-quality spindle into the mix, the robot is already there and so suddenly you’ve got a milling solution for a fraction of the cost — if we can get the accuracy of course.

The cornerstone of this accuracy will be adaptive tracking, which is being developed in collaboration with COMET partner Nikon Metrology of Tamworth. It has devised a stepwise solution for increasing accuracy.

The first offline solution involves measuring the robot in more than 300 poses to determine where it deviates from where it should have been. That information is then fed back into the CAM software. When running, the software then compensates for backlash by driving the robot to what it thinks is the ‘wrong position’.

This can be complemented by an online, real-time system comprising three linear built-in charge coupled device (CCD) cameras with cylindrical lenses that measure the location of infrared LEDs mounted on the robot head. Essentially, it measures where the robot is, then checks where it should be and sends a compensation down to the robot controller in milliseconds.

Preliminary tests of these systems were performed last week in the UK demonstrating sub-1mm accuracy. The final phase of testing will be delivering case studies later this year such as machining the final leading edge of an aircraft wing and deburring parts on the turbine disk.

Meanwhile, TEKS is now exploring applications of COMET technology outside of industrial machining. One comes from the civil engineering sector for surveying quarries and mines using long-range laser scanning.

The new technology has proved difficult in that large amounts of rather unmanageable date are produced, which is difficult to visualise with existing computer hardware and software.

Using COMET technology, TEKS bypassed the computer to machine lightweight models of sites in polystyrene.

The main partners of the COMET project are BTU, Delcam, Nikon Metrology, Fraunhofer IPA, TEKS, SIR and AMRC Manufacturing.



Find out about the progress of the COMET project, which aims to overcome the challenges facing European manufacturing industries by developing innovative robot machining systems that are flexible, reliable and predictable with an average of 30% cost efficiency savings in comparison to machine tools.

 Source: The Engineer

Additional Information:

• Machining with Robots - COMET Project Update
• COMET Project Website 
• Youtube Channel 

Through a glass: Researchers find a way to make glass that’s anti-fogging, self-cleaning and free of glare

Engineerblogger
April 26, 2012

Through a process involving thin layers of material deposited on a surface and then selectively etched away, the MIT team produced a surface covered with tiny cones, each five times taller than their width. This pattern prevents reflections, while at the same time repelling water from the surface.
Image: Hyungryul Choi and Kyoo-Chul Park

One of the most instantly recognizable features of glass is the way it reflects light. But a new way of creating surface textures on glass, developed by researchers at MIT, virtually eliminates reflections, producing glass that is almost unrecognizable because of its absence of glare — and whose surface causes water droplets to bounce right off, like tiny rubber balls.

The new “multifunctional” glass, based on surface nanotextures that produce an array of conical features, is self-cleaning and resists fogging and glare, the researchers say. Ultimately, they hope it can be made using an inexpensive manufacturing process that could be applied to optical devices, the screens of smartphones and televisions, solar panels, car windshields and even windows in buildings.

The technology is described in a paper published in the journal ACS Nano, co-authored by mechanical engineering graduate students Kyoo-Chul Park and Hyungryul Choi, former postdoc Chih-Hao Chang SM ’04, PhD ’08 (now at North Carolina State University), chemical engineering professor Robert Cohen, and mechanical engineering professors Gareth McKinley and George Barbastathis.

Photovoltaic panels, Park explains, can lose as much as 40 percent of their efficiency within six months as dust and dirt accumulate on their surfaces. But a solar panel protected by the new self-cleaning glass, he says, would have much less of a problem. In addition, the panel would be more efficient because more light would be transmitted through its surface, instead of being reflected away — especially when the sun’s rays are inclined at a sharp angle to the panel. At such times, such as early mornings and late afternoons, conventional glass might reflect away more than 50 percent of the light, whereas an anti-reflection surface would reduce the reflection to a negligible level.

While some earlier work has treated solar panels with hydrophobic coatings, the new multifunctional surfaces created by the MIT team are even more effective at repelling water, keeping the panels clean longer, the researchers say. In addition, existing hydrophobic coatings do not prevent reflective losses, giving the new system yet another advantage.

Other applications could include optical devices such as microscopes and cameras to be used in humid environments, where both the antireflective and anti-fogging capabilities could be useful. In touch-screen devices, the glass would not only eliminate reflections, but would also resist contamination by sweat.

Ultimately, if the cost of such glass can be lowered sufficiently, even car windows could benefit, Choi says, cleaning themselves of dirt and grit on the exterior surface of the windows, eliminating glare and reflections that can impair visibility, and preventing fogging on the interior surface.

The surface pattern — consisting of an array of nanoscale cones that are five times as tall as their base width of 200 nanometers — is based on a new fabrication approach the MIT team developed using coating and etching techniques adapted from the semiconductor industry. Fabrication begins by coating a glass surface with several thin layers, including a photoresist layer, which is then illuminated with a grid pattern and etched away; successive etchings produce the conical shapes. The team has already applied for a patent on the process.

Since it is the shape of the nanotextured surface — rather than any particular method of achieving that shape — that provides the unique characteristics, Park and Choi say that in the future glass or transparent polymer films might be manufactured with such surface features simply by passing them through a pair of textured rollers while still partially molten; such a process would add minimally to the cost of manufacture.

The researchers say they drew their inspiration from nature, where textured surfaces ranging from lotus leaves to desert-beetle carapaces and moth eyes have developed in ways that often fulfill multiple purposes at once. Although the arrays of pointed nanocones on the surface appear fragile when viewed microscopically, the researchers say their calculations show they should be resistant to a wide range of forces, ranging from impact by raindrops in a strong downpour or wind-driven pollen and grit to direct poking with a finger. Further testing will be needed to demonstrate how well the nanotextured surfaces hold up over time in practical applications.

Andrew Parker, a senior visiting research fellow at Oxford University’s Green Templeton College in the U.K. who was not involved in this work, says, “Multifunctional surfaces in animals and plants are common. For the first time, as far as I am aware, this paper learns a lesson in manufacturing efficiency from nature by making an optimized antireflective and anti-fogging device. … This is the way that nature works, and may well be the future of a greener engineering where two structures, and two manufacturing processes, are replaced by one.”

The research was funded by the Army Research Office through MIT’s Institute for Soldier Nanotechnology; the Air Force Office of Scientific Research; Singapore’s National Research Foundation through the Singapore-MIT Alliance for Research and Technology (SMART) Centre, and the Xerox Foundation. Park and Choi are recipients of fellowships from Samsung and the Kwanjeong Educational Foundation/STX Scholarship Foundation, respectively.



Source: MIT

Defects make catalysts perfect: process which converts carbon dioxide into methanol could make it possible to recycle greenhouse gas

Engineerblogger
April 26, 2012

Defect as a recipe for success: The images of the high-resolution transmission electron microscope show the arrangement of the individual atoms in a copper particle. The arrows indicate stacking faults and twin boundaries. In the detailed image, the stacking fault can be recognized by the fact that the atoms (white dots) deviate from the blue line from a certain position. How strongly is indicated by the red arrow on the yellow line in the lower part of the image. The defects in the crystal structure are also noticeable on the surface of the particles and increase the activity of the catalyst.

© Malte Behrens / Fritz Haber Institute of the MPG

There is now one less mystery in chemical production plants. For many decades industry has been producing methanol on a large scale from a mixture of carbon dioxide and carbon monoxide, as well as hydrogen. An international team, including chemists from the Fritz Haber Institute of the Max Planck Society in Berlin, has now clarified why the catalyst used in this process - copper and zinc oxide particles and a small portion of aluminium oxide - works so well. They also discovered why this reaction accelerator has to be produced in the tried and tested way. The researchers established that defects in an as yet unknown combination with mixing of copper and zinc oxide at the catalyst’s surface are the reason why the catalysts are so active. These findings could make a contribution to further improving the catalyst, and also help researchers develop catalysts that convert pure carbon dioxide efficiently. These could be used to recycle the greenhouse gas that is produced when fossil fuels burn.

Recycling could provide an elegant way of, for example, solving the problem of the carbon dioxide emission from coal-fired power stations. It is not only the fact that the gas would then no longer heat up the climate; methanol could be used to replace at least part of fossil raw materials, but above all could be used to store regenerative energy. “A changeover to green energies is not possible without energy storage systems,” says Robert Schlögl, Director at the Fritz Haber Institute of the Max Planck Society. This is because the electricity generated by wind turbines and solar installations varies strongly and does not follow demand. The findings of the chemists at the Fritz Haber Institute and their team of researchers could contribute to the development of catalysts that efficiently convert carbon dioxide produced in the combustion of coal, gas or oil with hydrogen into methanol or other chemical energy storage systems.

The Berlin-based Max Planck researchers were joined by scientists from the Helmholtz Zentrum Berlin für Materialien und Energie (HZB), the SLAC National Accelerator Laboratory in Menlo Park, California, Stanford University and Südchemie AG in carrying out the work. The researchers studied the catalyst which industry is already using to produce 50 million tonnes of methanol annually. However, industry uses a mixture of carbon dioxide and carbon monoxide for the process, which is produced especially for this purpose from natural gas or coal. “Only when we understand why this catalyst works so well and why it must be produced in the tried and tested way will we be able to optimise it and further develop it for the conversion of pure carbon dioxide,” says Malte Behrens, who played a crucial role in clarifying the catalyst’s mystery.

Where do the molecules team up?

The industrial catalyst is composed of innumerable nanoparticles, some made of copper, some of zinc oxide and a small proportion of aluminium oxide; together they form a type of nanosponge. Malte Behrens and his colleagues have now identified the sites in the aggregate where carbon dioxide and carbon monoxide molecules combine with their hydrogen partners via various intermediate steps. Using images from a high-resolution transmission electron microscope (HRTEM) and neutron diffraction, which provides information on the crystal structure, the scientists discovered defects in the arrangement of the copper atoms in the nanoparticles. They subsequently employed quantum chemical computations to prove that some of the intermediate products preferred to adsorb at these defects. This means: The defects increase the catalyst’s activity, as its exact task is to promote the formation of these intermediate products.

In addition, the scientists discovered why the zinc oxide plays an important role in the mixture. They investigated the nanosponge with the synchrotron radiation from the Bessy II electron storage ring at the Helmholtz-Zentrum Berlin für Materialien und Energie using equipment which the Max Planck researchers had developed especially for the investigation of catalysts. They used the X-ray portion of this extremely intense radiation to follow what was happening chemically on the surface of the reaction accelerator when it came into contact with the reaction partners. In these analyses, and also on HRTEM images, they ascertained that zinc oxide also creeps over parts of the copper particles, and that some atoms in the copper surface are even replaced by zinc. This also makes the catalyst very active: calculations showed that some intermediate products of the reaction - in this case those containing oxygen - are more likely to bond to the zinc than to the copper.

It had long been assumed that the copper was the only catalytically active component. The catalysis research therefore concentrated on increasing its surface, as more molecules find room for the chemical transformation on the larger surface. For a long time, chemists assumed that the zinc oxide’s only role was as a spacer; it was to prevent the copper particles fusing with each other in the heat of the reaction. The zinc oxide particles also fulfil this role, but it has been known for some years that zinc oxide also exerts another influence. This is because, although similar sponge-like structures from copper and metals other than zinc also have a large surface, they come nowhere near to achieving the activity of the copper-zinc-aluminium system. “Different effects of the zinc oxide were discussed,” says Malte Behrens. “Our investigations are now helping to finally explain its role.”

Search for catalysts no longer trial and error

Since the scientists now know which structural details characterise the tried and tested catalyst for methanol synthesis, they now understand why it is so difficult to prepare the reaction accelerator. The catalyst is produced from solutions of copper and zinc salts in several steps. Chemists first produce a precursor of the catalyst by precipitating both metals as carbonates. “The pH value and the temperature at which the precursor is produced decide on the activity of the catalyst,” says Malte Behrens. “The catalyst has a chemical memory.” Now the chemist can also explain what the catalyst remembers: Only in the tried and tested process does the copper crystallise with small defects, and the zinc creep over and into the copper.

These results are not only relevant because they can assist in improving the methanol synthesis and trim it for the recycling of emissions. “Our work also shows that we will only really understand catalysts when we look at them in all their complexity,” says Robert Schlögl. Researchers have often studied the catalytic process of methanol synthesis, but always on idealised model systems. These are easier to investigate and to describe theoretically. However, it is precisely the decisive details, such as defects, that do not exist in them. Moreover, the findings represent a paradigm change in catalysis research. “Until now, new catalysts have usually been found using the trial and error method,” says Robert Schlögl. “Our work shows that we can understand catalysts and their manufacture in detail. This allows us to develop catalysts in the future in a rational way, namely on the drawing board, as well.”

Source: Max Planck Society

Additional Information:

•  The Active Site of Methanol Synthesis over Cu/ZnO/Al2O3 Industrial Catalysts ScienceExpress, 19 April 2012; doi: 10.1126/science.1219831

Future Electronics: Scientists Predict Paradoxical Laser Effect

Engineerblogger
April 26, 2012

Two coupled microlasers.

Two lamps are brighter than one. This simple truism does not necessarily apply to lasers, as a team of scientists, led by the Vienna University of Technology found out. When one laser is shining and next to it another laser is turned on gradually, complex interactions between the two lasers can lead to a total shutdown and no light is emitted anymore. For technologies connecting the fields of electronics and photonics, this result may be very important. The new findings have now been published in the journal “Physical Review Letters”.

When switching on means switching off
“Imagine two light bulbs right next to each other, one of which is switched on. As you gradually turn on the second bulb by adjusting a dimmer switch, you expect the room to get brighter”, says Matthias Liertzer. He studied the behavior of coupled micro-lasers using computer simulations, together with Professor Stefan Rotter at the Institute for Theoretical Physics (TU Vienna). They were assisted by scientists from Princeton University, Yale University and the ETH Zurich.

To make a laser shine, it has to be “pumped” – it has to be supplied with energy, using light or electric current. If only one of two micro-lasers is pumped, only the pumped laser emits light. Surprisingly, pumping the second laser too does not necessarily increase the brightness of the coupled system. Supplying more energy can even reduce the brightness, until both lasers become dark. “When we saw that the two lasers can switch each other off completely, due to the coupling between them, we knew: either we made a mistake or this is a spectacular result”, says Stefan Rotter. In the meantime, the effect was confirmed in independent calculations by the co-authors from Yale.

Connecting Physics, Math and Electrical Engineering
Light consists of waves, and it is well known that waves can interfere and cancel each other out. The interplay between the two lasers, however, is more complicated than that: “This effect is not just about wave interference. It is a combination of interference and light amplification, which can lead to seemingly paradoxical effects”, says Matthias Liertzer. New methods, some of which were developed by mathematicians at TU Vienna, were necessary to solve the complicated equations which describe this problem. “The phenomenon is based on what mathematicians call exceptional points”, says Stefan Rotter. Exceptional points are special intersections of surfaces in complex spaces. “The appearance of such exceptional points in our laser equations can lead to a laser blackout. In this way we could connect a rather abstract mathematical structure to a measurable phenomenon”, says Rotter.

Light and Microelectronics
Electrical engineers at the Vienna University of Technology are now working on experiments with micro lasers, in which the theoretical predictions should be verified. Laser effects like this one are especially interesting, as they show new ways to connect microelectronics and laser technology. In today’s computers, information is transmitted by electric signals. Adding laser light could open up exciting new possibilities.

Source:  Vienna University of Technology


Additional Information:

• Pump-Induced Exceptional Points in Lasers published April 24, 2012 in the Physical Review Letters 
   To read the free arxiv version: http://arxiv.org/abs/1109.0454 

Texas A&M engineers develop fire-resistant, environmentally friendly coating

Engineerblogger
April 25, 2012

Cotton fabric after a vertical flame test, where a flame touches the fabric for 12 seconds. Credit: Texas A&M

A thin polymer coating developed by materials engineers at Texas A&M University could keep cotton clothing and polyurethane-foam-based furniture from going up in flames.

And the coating is environmentally friendly, too.

Dr. Jaime Grunlan, an associate professor in the Department of Mechanical Engineering, works with polymer nanocomposites that have properties similar to those of metals and ceramics — conducting electricity, for instance — while maintaining properties of polymers, such as low density.

In 2010, Grunlan’s development of a flame-resistant polymer coating got him some attention, as he fielded calls from the United States military, the cotton industry, mattress manufacturers and the Federal Aviation Administration, and from companies around the world.

New advancements in the area, however, should garner even more attention.

“We can now make cotton fabric that doesn’t burn at all,” Grunlan says.

Grunlan's technology — which has been reported in Science News, Chemical and Engineering News, Nature and Advanced Materials — involves covering every microscopic fiber in a fabric with a thin composite coating of two polymers that exhibit an intumescent effect, producing a protective carbon foam coating when exposed to high temperatures.

The thin films are about one-tenth of a micron thick, or about one-thousandth the thickness of a human hair, and are created with the layer-by-layer assembly technique in which the coating is deposited onto the surface of the fiber being coated. This layer-by-layer process allows Grunlan to control the thickness of the coating down to the nanometer level.

Grunlan says the technology will be suitable for clothing, including children's clothing; lab coats; and medical clothing for both doctors and patients. It can even be used in military camps, where a fire in a single tent can wipe out an entire camp.

But the technology's applications go far beyond just clothing and fabric. The coating could be used in foams, such as those found in sofas, mattresses, theatre and auditorium seats, airplane seat cushions, and building insulation.

Foam cut through the middle after being exposed to fire from a butane torch. Credit: Texas A&M

On polyurethane foam, a coating of chitosan (a natural material extracted from shrimp and lobster shells) and clay is deposited to eliminate melt dripping during burning. The nanocomposite mixture coats the interior walls of foam. The result is that when burned, the treated foam keeps its shape instead of puddling at high temperatures like untreated polyurethane foam does. This quality eliminates the “melt-dripping” effect that further spreads fires.

"It's like we're building a nano-brick wall within each cell of the foam," Grunlan says.

That brick wall keeps the foam from being destroyed. And the coating is so thin that it adds only 4 to 5 weight-percent to the foam and does not negatively alter its color, texture or flexibility.

"A lot of anti-flammables degrade fabric and foam properties," Grunlan says.

But with Grunlan's technique, each thread can be individually coated, in the case of cotton fabric. In fact, his coating could potentially strengthen fabric. The researchers are also looking at ways to make the coating softer and more durable to washing.

Current flame-retardant materials rely on brominated compounds, many of which have been banned due to concerns over their potential toxicity. The Texas A&M researchers were searching for an alternative to these toxic chemicals, and had previously been using a commonly known clay and a commercial synthetic polymer to make their coatings. But in order to make the coatings more sustainable, Grunlan switched to chitosan.

“Based on initial results,” he says, “I really think this is going to become a widely adopted, environmentally benign alternative to current flame retardant treatments.

"Anywhere you want to make fabric or foam anti-flammable, you can use this technology," he says.

Source: Texas A&M University