Tag Archives: Massachusetts Institute of Technology

Steampower via nanotechnology

It seems that researchers at MIT (Massachusetts Institute of Technology (US) have been inspired by steam punk, of a sort. From a July 21, 2014 news item on Nanowerk,

A new material structure developed at MIT generates steam by soaking up the sun.

The structure — a layer of graphite flakes and an underlying carbon foam — is a porous, insulating material structure that floats on water. When sunlight hits the structure’s surface, it creates a hotspot in the graphite, drawing water up through the material’s pores, where it evaporates as steam. The brighter the light, the more steam is generated.

The new material is able to convert 85 percent of incoming solar energy into steam — a significant improvement over recent approaches to solar-powered steam generation. What’s more, the setup loses very little heat in the process, and can produce steam at relatively low solar intensity. This would mean that, if scaled up, the setup would likely not require complex, costly systems to highly concentrate sunlight.

A July 21, 2014 MIT news release, which originated the news item, details the research,

Hadi Ghasemi, a postdoc in MIT’s Department of Mechanical Engineering, says the spongelike structure can be made from relatively inexpensive materials — a particular advantage for a variety of compact, steam-powered applications.

“Steam is important for desalination, hygiene systems, and sterilization,” says Ghasemi, who led the development of the structure. “Especially in remote areas where the sun is the only source of energy, if you can generate steam with solar energy, it would be very useful.”

Today, solar-powered steam generation involves vast fields of mirrors or lenses that concentrate incoming sunlight, heating large volumes of liquid to high enough temperatures to produce steam. However, these complex systems can experience significant heat loss, leading to inefficient steam generation.

Recently, scientists have explored ways to improve the efficiency of solar-thermal harvesting by developing new solar receivers and by working with nanofluids. The latter approach involves mixing water with nanoparticles that heat up quickly when exposed to sunlight, vaporizing the surrounding water molecules as steam. But initiating this reaction requires very intense solar energy — about 1,000 times that of an average sunny day.

By contrast, the MIT approach generates steam at a solar intensity about 10 times that of a sunny day — the lowest optical concentration reported thus far. The implication, the researchers say, is that steam-generating applications can function with lower sunlight concentration and less-expensive tracking systems.

“This is a huge advantage in cost-reduction,” Ghasemi says. “That’s exciting for us because we’ve come up with a new approach to solar steam generation.”

The approach itself is relatively simple: Since steam is generated at the surface of a liquid, Ghasemi looked for a material that could both efficiently absorb sunlight and generate steam at a liquid’s surface.

After trials with multiple materials, he settled on a thin, double-layered, disc-shaped structure. Its top layer is made from graphite that the researchers exfoliated by placing the material in a microwave. The effect, Chen says, is “just like popcorn”: The graphite bubbles up, forming a nest of flakes. The result is a highly porous material that can better absorb and retain solar energy.

The structure’s bottom layer is a carbon foam that contains pockets of air to keep the foam afloat and act as an insulator, preventing heat from escaping to the underlying liquid. The foam also contains very small pores that allow water to creep up through the structure via capillary action.

As sunlight hits the structure, it creates a hotspot in the graphite layer, generating a pressure gradient that draws water up through the carbon foam. As water seeps into the graphite layer, the heat concentrated in the graphite turns the water into steam. The structure works much like a sponge that, when placed in water on a hot, sunny day, can continuously absorb and evaporate liquid.

The researchers tested the structure by placing it in a chamber of water and exposing it to a solar simulator — a light source that simulates various intensities of solar radiation. They found they were able to convert 85 percent of solar energy into steam at a solar intensity 10 times that of a typical sunny day.

Ghasemi says the structure may be designed to be even more efficient, depending on the type of materials used.

“There can be different combinations of materials that can be used in these two layers that can lead to higher efficiencies at lower concentrations,” Ghasemi says. “There is still a lot of research that can be done on implementing this in larger systems.”

Here’s a link to and a citation for the paper,

Solar steam generation by heat localization by Hadi Ghasemi, George Ni, Amy Marie Marconnet, James Loomis, Selcuk Yerci, Nenad Miljkovic, & Gang Chen. Nature Communications 5, Article number: 4449 doi:10.1038/ncomms5449 Published 21 July 2014

This paper is behind a paywall but a free preview is available via ReadCube Access.

Squishy but rigid robots from MIT (Massachusetts Institute of Technology)

A July 14, 2014 news item on ScienceDaily MIT (Massachusetts Institute of Technology) features robots that mimic mice and other biological constructs or, if you prefer, movie robots,

In the movie “Terminator 2,” the shape-shifting T-1000 robot morphs into a liquid state to squeeze through tight spaces or to repair itself when harmed.

Now a phase-changing material built from wax and foam, and capable of switching between hard and soft states, could allow even low-cost robots to perform the same feat.

The material — developed by Anette Hosoi, a professor of mechanical engineering and applied mathematics at MIT, and her former graduate student Nadia Cheng, alongside researchers at the Max Planck Institute for Dynamics and Self-Organization and Stony Brook University — could be used to build deformable surgical robots. The robots could move through the body to reach a particular point without damaging any of the organs or vessels along the way.

A July 14, 2014 MIT news release (also on EurekAlert), which originated the news item, describes the research further by referencing both octopuses and jello,

Working with robotics company Boston Dynamics, based in Waltham, Mass., the researchers began developing the material as part of the Chemical Robots program of the Defense Advanced Research Projects Agency (DARPA). The agency was interested in “squishy” robots capable of squeezing through tight spaces and then expanding again to move around a given area, Hosoi says — much as octopuses do.

But if a robot is going to perform meaningful tasks, it needs to be able to exert a reasonable amount of force on its surroundings, she says. “You can’t just create a bowl of Jell-O, because if the Jell-O has to manipulate an object, it would simply deform without applying significant pressure to the thing it was trying to move.”

What’s more, controlling a very soft structure is extremely difficult: It is much harder to predict how the material will move, and what shapes it will form, than it is with a rigid robot.

So the researchers decided that the only way to build a deformable robot would be to develop a material that can switch between a soft and hard state, Hosoi says. “If you’re trying to squeeze under a door, for example, you should opt for a soft state, but if you want to pick up a hammer or open a window, you need at least part of the machine to be rigid,” she says.

Compressible and self-healing

To build a material capable of shifting between squishy and rigid states, the researchers coated a foam structure in wax. They chose foam because it can be squeezed into a small fraction of its normal size, but once released will bounce back to its original shape.

The wax coating, meanwhile, can change from a hard outer shell to a soft, pliable surface with moderate heating. This could be done by running a wire along each of the coated foam struts and then applying a current to heat up and melt the surrounding wax. Turning off the current again would allow the material to cool down and return to its rigid state.

In addition to switching the material to its soft state, heating the wax in this way would also repair any damage sustained, Hosoi says. “This material is self-healing,” she says. “So if you push it too far and fracture the coating, you can heat it and then cool it, and the structure returns to its original configuration.”

To build the material, the researchers simply placed the polyurethane foam in a bath of melted wax. They then squeezed the foam to encourage it to soak up the wax, Cheng says. “A lot of materials innovation can be very expensive, but in this case you could just buy really low-cost polyurethane foam and some wax from a craft store,” she says.

In order to study the properties of the material in more detail, they then used a 3-D printer to build a second version of the foam lattice structure, to allow them to carefully control the position of each of the struts and pores.

When they tested the two materials, they found that the printed lattice was more amenable to analysis than the polyurethane foam, although the latter would still be fine for low-cost applications, Hosoi says.

The wax coating could also be replaced by a stronger material, such as solder, she adds.

Hosoi is now investigating the use of other unconventional materials for robotics, such as magnetorheological and electrorheological fluids. These materials consist of a liquid with particles suspended inside, and can be made to switch from a soft to a rigid state with the application of a magnetic or electric field.

When it comes to artificial muscles for soft and biologically inspired robots, we tend to think of controlling shape through bending or contraction, says Carmel Majidi, an assistant professor of mechanical engineering in the Robotics Institute at Carnegie Mellon University, who was not involved in the research. “But for a lot of robotics tasks, reversibly tuning the mechanical rigidity of a joint can be just as important,” he says. “This work is a great demonstration of how thermally controlled rigidity-tuning could potentially be used in soft robotics.”

Here’s a link to and a citation for the paper,

Thermally Tunable, Self-Healing Composites for Soft Robotic Applications by Nadia G. Cheng, Arvind Gopinath, Lifeng Wang, Karl Iagnemma, and Anette E. Hosoi. Macromolecular Materials and Engineering DOI: 10.1002/mame.201400017 Article first published online: 30 JUN 2014

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Dimpling can be more than cute, morphable surfaces (smorphs) from MIT (Massachusetts Institute of Technology)

A morphable surface developed by an MIT team can change surface texture — from smooth to dimply, and back again — through changes in pressure. When the inside pressure is reduced, the flexible material shrinks, and the stiffer outer layer wrinkles. Increasing pressure returns the surface to a smooth state.

A June 24, 2014 news item on Nanowerk features a story about the origins of the dimpled golf ball, aerodynamics, and some very pink material (Note: A link has been removed),

There is a story about how the modern golf ball, with its dimpled surface, came to be: In the mid-1800s, it is said, new golf balls were smooth, but became dimpled over time as impacts left permanent dents. Smooth new balls were typically used for tournament play, but in one match, a player ran short, had to use an old, dented one, and realized that he could drive this dimpled ball much further than a smooth one.

Whether that story is true or not, testing over the years has proved that a golf ball’s irregular surface really does dramatically increase the distance it travels, because it can cut the drag caused by air resistance in half. Now researchers at MIT are aiming to harness that same effect to reduce drag on a variety of surfaces — including domes that sometimes crumple in high winds, or perhaps even vehicles.

Detailed studies of aerodynamics have shown that while a ball with a dimpled surface has half the drag of a smooth one at lower speeds, at higher speeds that advantage reverses. So the ideal would be a surface whose smoothness can be altered, literally, on the fly — and that’s what the MIT team has developed.

The new work is described in a paper in the journal Advanced Materials (“Smart Morphable Surfaces for Aerodynamic Drag Control”) by MIT’s Pedro Reis and former MIT postdocs Denis Terwagne (now at the Université Libre de Bruxelles in Belgium) and Miha Brojan (now at the University of Ljubljana in Slovenia).

esearchers made this sphere to test their concept of morphable surfaces. Made of soft polymer with a hollow center, and a thin coating of a stiffer polymer, the sphere becomes dimpled when the air is pumped out of the hollow center, causing it to shrink. (Photo courtesy of the MIT researchers)

Researchers made this sphere to test their concept of morphable surfaces. Made of soft polymer with a hollow center, and a thin coating of a stiffer polymer, the sphere becomes dimpled when the air is pumped out of the hollow center, causing it to shrink. (Photo courtesy of the MIT researchers)

A June 24, 2014 MIT (Massachusetts Institute of Technology) news release (also on EurekAlert) by David Chandler, which originated the news item, provides more detail about the work,

The ability to change the surface in real time comes from the use of a multilayer material with a stiff skin and a soft interior — the same basic configuration that causes smooth plums to dry into wrinkly prunes. To mimic that process, Reis and his team made a hollow ball of soft material with a stiff skin — with both layers made of rubberlike materials — then extracted air from the hollow interior to make the ball shrink and its surface wrinkle.

“Numerous studies of wrinkling have been done on flat surfaces,” says Reis, an assistant professor of mechanical engineering and civil and environmental engineering. “Less is known about what happens when you curve the surface. How does that affect the whole wrinkling process?”

The answer, it turns out, is that at a certain degree of shrinkage, the surface can produce a dimpled pattern that’s very similar to that of a golf ball — and with the same aerodynamic properties.

The aerodynamic properties of dimpled balls can be a bit counterintuitive: One might expect that a ball with a smooth surface would sail through the air more easily than one with an irregular surface. The reason for the opposite result has to do with the nature of a small layer of the air next to the surface of the ball. The irregular surface, it turns out, holds the airflow close to the ball’s surface longer, delaying the separation of this boundary layer. This reduces the size of the wake — the zone of turbulence behind the ball — which is the primary cause of drag for blunt objects.

When the researchers saw the wrinkled outcomes of their initial tests with their multilayer spheres, “We realized that these samples look just like golf balls,” Reis says. “We systematically tested them in a wind tunnel, and we saw a reduction in drag very similar to that of golf balls.”

Because the surface texture can be controlled by adjusting the balls’ interior pressure, the degree of drag reduction can be controlled at will. “We can generate that surface topography, or erase it,” Reis says. “That reversibility is why this is pretty interesting; you can switch the drag-reducing effect on and off, and tune it.”

As a result of that variability, the team refers to these as “smart morphable surfaces” — or “smorphs,” for short. The pun is intentional, Reis says: The paper’s lead author — Terwagne, a Belgian comics fan — pointed out that one characteristic of Smurfs cartoon characters is that no matter how old they get, they never develop wrinkles.

Terwagne says that making the morphable surfaces for lab testing required a great deal of trial-and-error — work that ultimately yielded a simple and efficient fabrication process. “This beautiful simplicity to achieve a complex functionality is often used by nature,” he says, “and really inspired me to investigate further.”

Many researchers have studied various kinds of wrinkled surfaces, with possible applications in areas such as adhesion, or even unusual optical properties. “But we are the first to use wrinkling for aerodynamic properties,” Reis says.

The drag reduction of a textured surface has already expanded beyond golf balls: The soccer ball being used at this year’s World Cup, for example, uses a similar effect; so do some track suits worn by competitive runners. For many purposes, such as in golf and soccer, constant dimpling is adequate, Reis says.

But in other uses, the ability to alter a surface could prove useful: For example, many radar antennas are housed in spherical domes, which can collapse catastrophically in very high winds. A dome that could alter its surface to reduce drag when strong winds are expected might avert such failures, Reis suggests. Another application could be the exterior of automobiles, where the ability to adjust the texture of panels to minimize drag at different speeds could increase fuel efficiency, he says.

Delightful is not the first adjective that jumps to my mind when describing this work but I’m not an engineer (from the news release),

John Rogers, a professor of materials research and engineering at the University of Illinois at Urbana-Champaign who was not involved in this work, says, “It represents a delightful example of how controlled processes of mechanical buckling can be used to create three-dimensional structures with interesting aerodynamic properties. The type of dynamic tuning of sophisticated surface morphologies made possible by this approach would be difficult or impossible to achieve in any other way.”

Here’s a link to and a citation for the paper,

Smart Morphable Surfaces for Aerodynamic Drag Control by Denis Terwagne, Miha Brojan, and Pedro M. Reis. Advanced Materials DOI: 10.1002/adma.201401403 Article first published online: 23 JUN 2014

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

The relationship between Valyrian steel (from Game of Thrones), Damascus steel, and nuclear nanotechnology

There’s a very interesting June 20, 2014 posting by Charles Day on his Dayside blog (located on the Physics Today website). Day manages to relate the Game of Thrones tv series to nuclear power and nanotechnology,

The military technology of A Song of Ice and Fire, George R. R. Martin’s series of fantasy novels, is medieval with an admixture of the supernatural. Dragons aside, among the most prized weapons are swords made from Valyrian steel, which are lighter, stronger, and sharper than ordinary steel swords.

Like many of the features in the rich world of the novels and their TV adaptation, Game of Thrones, Valyrian steel has a historical inspiration. Sometime before 300 BC, metalworkers in Southern India discovered a way to make small cakes of high-carbon steel known as wootz. Thanks to black wavy bands of Fe3C particles that pervade the metal, wootz steel was already strong. …

Perhaps because the properties of wootz and Damascus steels depended, in part, on a particular kind of iron ore, the ability of metallurgists to make the alloys was lost sometime in the 18th century. In A Song of Ice and Fire, the plot plays out during an era in which making Valyrian steel is a long-lost art.

Martin’s knowledge of metallurgy is perhaps shaky. …

Interestingly, the comments on the blog posting largely concern themselves with whether George RR Martin knows anything about metallurgy. The consensus being that he does and that the problems in the Game of Thrones version of metallurgy lie with the series writers.

I first came across the Damascus steel, wootz, and carbon nanotube story in 2008 and provided a concise description on my Nanotech Mysteries wiki Middle Ages page,

Damascus steel blades were first made in the 8th century CE when they acquired a legendary status as unlike other blades they were able to cut through bone and stone while remaining sharp enough to cut a piece of silk. They were also flexible which meant they didn’t break off easily in a sword fight. The secret for making the blades died (history does not record how) about 1700 CE and there hasn’t been a new blade since.

 The blades were generally made from metal ingots prepared in India using special recipes which probably put just the right amount of carbon and other impurities into the iron. By following these recipes and following specific forging techniques craftsmen ended up making nanotubes … When these blades were nearly finished, blacksmiths would etch them with acid. This brought out the wavy light and dark lines that make Damascus swords easy to recognize.3

 It turns out part of the secret to the blade is nanotechnology. Scientists discovered this by looking at a Damascus steel blade from 1700 under an electron microscope. It seems those unknown smiths were somehow encasing cementite nanowires in carbon nanotubes then forging them into the steel blades giving them their legendary strength and flexibility.

The reference information I used then seems to be no longer available online but there is this more than acceptable alternative, a Sept. 27, 2008 postiing by Ed Yong from his Not Exactly Rocket Science blog (on ScienceBlogs.com; Note: A link has been removed),

In medieval times, crusading Christian knights cut a swathe through the Middle East in an attempt to reclaim Jerusalem from the Muslims. The Muslims in turn cut through the invaders using a very special type of sword, which quickly gained a mythical reputation among the Europeans. These ‘Damascus blades‘ were extraordinarily strong, but still flexible enough to bend from hilt to tip. And they were reputedly so sharp that they could cleave a silk scarf floating to the ground, just as readily as a knight’s body.

They were superlative weapons that gave the Muslims a great advantage, and their blacksmiths carefully guarded the secret to their manufacture. The secret eventually died out in the eighteenth century and no European smith was able to fully reproduce their method.

Two years ago, Marianne Reibold and colleagues from the University of Dresden uncovered the extraordinary secret of Damascus steel – carbon nanotubes. The smiths of old were inadvertently using nanotechnology.

Getting back to Day, he goes on to explain the Damascus/Valyrian steel connection to nuclear power (Note: Links have been removed),

Valyrian and Damascus steels were on my mind earlier this week when I attended a session at TechConnect World on the use of nanotechnology in the nuclear power industry.

Scott Anderson of Lockheed Martin gave the introductory talk. Before the Fukushima disaster, Anderson pointed out, the principal materials science challenge in the nuclear industry lay in extending the lifetime of fuel rods. Now the focus has shifted to accident-tolerant fuels and safer, more durable equipment.

Among the other speakers was MIT’s Ju Li, who described his group’s experiments with incorporating carbon nanotubes (CNTs) in aluminum to boost the metal’s resistance to radiation damage. In a reactor core, neutrons and other ionizing particles penetrate vessels, walls, and other structures, where they knock atoms off lattice sites. The cumulative effect of those displacements is to create voids and other defects that weaken the structures.

Li isn’t sure yet how the CNTs resist irradiation and toughen the aluminum, but at the end of his talk he recalled their appearance in another metal, steel.

In 2006 Peter Paufler of Dresden University of Technology and his collaborators used high-resolution transmission electron microscopy (TEM) to examine the physical and chemical microstructure of a sample of Damascus steel from the 17th century.

The saber from which the sample was taken was forged in Isfahan, Persia, by the famed blacksmith Assad Ullah. As part of their experiment, Paufler and his colleagues washed the sample in hydrochloric acid to remove Fe3C particles. A second look with TEM revealed the presence of CNTs.

There’s still active interest in researching Damascus steel blades as not all the secrets behind the blade’s extraordinary qualities have been revealed yet. There is a March 13, 2014 posting here which describes a research project where Chinese researchers are attempting (using computational software) to uncover the reason for the blade’s unique patterns,

It seems that while researchers were able to answer some questions about the blade’s qualities, researchers in China believe they may have answered the question about the blade’s unique patterns, from a March 12, 2014 news release on EurekAlert,

Blacksmiths and metallurgists in the West have been puzzled for centuries as to how the unique patterns on the famous Damascus steel blades were formed. Different mechanisms for the formation of the patterns and many methods for making the swords have been suggested and attempted, but none has produced blades with patterns matching those of the Damascus swords in the museums. The debate over the mechanism of formation of the Damascus patterns is still ongoing today. Using modern metallurgical computational software (Thermo-Calc, Stockholm, Sweden), Professor Haiwen Luo of the Central Iron and Steel Research Institute in Beijing, together with his collaborator, have analyzed the relevant published data relevant to the Damascus blades, and present a new explanation that is different from other proposed mechanisms.

At the time the researchers were hoping to have someone donate a piece of genuine Damascus steel blade. From my March 13, 2014 posting,

Note from the authors: It would be much appreciated if anyone would like to donate a piece of genuine Damascus blade for our research.

Corresponding Author:

LUO Haiwen
Email: [email protected]

Perhaps researchers will manage to solve the puzzle of how medieval craftsman were once able to create extraordinary steel blades.

Swelling sensors and detecting gases at the nanoscale

A June 17, 2014 news item on Nanowerk features a new approach to sensing gases from the Massachusetts Institute of Technology (MIT),

Using microscopic polymer light resonators that expand in the presence of specific gases, researchers at MIT’s Quantum Photonics Laboratory have developed new optical sensors with predicted detection levels in the parts-per-billion range. Optical sensors are ideal for detecting trace gas concentrations due to their high signal-to-noise ratio, compact, lightweight nature, and immunity to electromagnetic interference.

Although other optical gas sensors had been developed before, the MIT team conceived an extremely sensitive, compact way to detect vanishingly small amounts of target molecules.

A June 17, 2014 American Institute of Physics (AIP) news release by John Arnst, which originated the news item, describes the new technique in some detail,

The researchers fabricated wavelength-scale photonic crystal cavities from PMMA, an inexpensive and flexible polymer that swells when it comes into contact with a target gas. The polymer is infused with fluorescent dye, which emits selectively at the resonant wavelength of the cavity through a process called the Purcell effect. At this resonance, a specific color of light reflects back and forth a few thousand times before eventually leaking out. A spectral filter detects this small color shift, which can occur at even sub-nanometer level swelling of the cavity, and in turn reveals the gas concentration.

“These polymers are often used as coatings on other materials, so they’re abundant and safe to handle. Because of their deformation in response to biochemical substances, cavity sensors made entirely of this polymer lead to a sensor with faster response and much higher sensitivity,” said Hannah Clevenson. Clevenson is a PhD student in the electrical engineering and computer science department at MIT, who led the experimental effort in the lab of principal investigator Dirk Englund.

PMMA can be treated to interact specifically with a wide range of different target chemicals, making the MIT team’s sensor design highly versatile. There’s a wide range of potential applications for the sensor, said Clevenson, “from industrial sensing in large chemical plants for safety applications, to environmental sensing out in the field, to homeland security applications for detecting toxic gases, to medical settings, where the polymer could be treated for specific antibodies.”

The thin PMMA polymer films, which are 400 nanometers thick, are patterned with structures that are 8-10 micrometers long by 600 nanometers wide and suspended in the air. In one experiment, the films were embedded on tissue paper, which allowed 80 percent of the sensors to be suspended over the air gaps in the paper. Surrounding the PMMA film with air is important, Clevenson said, both because it allows the device to swell when exposed to the target gas, and because the optical properties of air allow the device to be designed to trap light travelling in the polymer film.

The team found that these sensors are easily reusable since the polymer shrinks back to its original length once the targeted gas has been removed.

The current experimental sensitivity of the devices is 10 parts per million, but the team predicts that with further refinement, they could detect gases with part-per-billion concentration levels.

The researchers have provided an image illustrating the sensor’s response to a target gas,

High-sensitivity detection of dilute gases is demonstrated by monitoring the resonance of a suspended polymer nanocavity. The inset shows the target gas molecules (darker) interacting with the polymer material (lighter). This interaction causes the nanocavity to swell, resulting in a shift of its resonance. CREDIT: H. Clevenson/MIT

High-sensitivity detection of dilute gases is demonstrated by monitoring the resonance of a suspended polymer nanocavity. The inset shows the target gas molecules (darker) interacting with the polymer material (lighter). This interaction causes the nanocavity to swell, resulting in a shift of its resonance.
CREDIT: H. Clevenson/MIT

Here’s a link to and a citation for the paper,

High sensitivity gas sensor based on high-Q suspended polymer photonic crystal nanocavity by  Hannah Clevenson, Pierre Desjardins, Xuetao Gan, and Dirk Englund. Appl. Phys. Lett. 104, 241108 (2014); http://dx.doi.org/10.1063/1.4879735

This is an open access paper.

Harvest water from desert air with carbon nanotube cups (competition for NBD Nano?)

It’s been a while since I’ve seen Pulickel Ajayan’s name in a Rice University (Texas) news release and I wonder if this is the beginning of a series. I’ve noticed that researchers often publish a series of papers within a few months and then become quiet for two or more years as they work in their labs to gather more information.

This time the research from Pulickel’s lab has focused on the use of carbon nanotubes to harvest water from desert air. From a June 12, 2014 news item on Azonano,

If you don’t want to die of thirst in the desert, be like the beetle. Or have a nanotube cup handy.

New research by scientists at Rice University demonstrated that forests of carbon nanotubes can be made to harvest water molecules from arid desert air and store them for future use.

The invention they call a “hygroscopic scaffold” is detailed in a new paper in the American Chemical Society journal Applied Materials and Interfaces.

Researchers in the lab of Rice materials scientist Pulickel Ajayan found a way to mimic the Stenocara beetle, which survives in the desert by stretching its wings to capture and drink water molecules from the early morning fog.

Here’s more about the research from a June 11, 2014 Rice University news release (by Mike Williams?), which originated the news item,

They modified carbon nanotube forests grown through a process created at Rice, giving the nanotubes a superhydrophobic (water-repelling) bottom and a hydrophilic (water loving) top. The forest attracts water molecules from the air and, because the sides are naturally hydrophobic, traps them inside.

“It doesn’t require any external energy, and it keeps water inside the forest,” said graduate student and first author Sehmus Ozden. “You can squeeze the forest to take the water out and use the material again.”

The forests grown via water-assisted chemical vapor deposition consist of nanotubes that measure only a few nanometers (billionths of a meter) across and about a centimeter long.

The Rice team led by Ozden deposited a superhydrophobic layer to the top of the forest and then removed the forest from its silicon base, flipped it and added a layer of hydrophilic polymer to the other side.

In tests, water molecules bonded to the hydrophilic top and penetrated the forest through capillary action and gravity. (Air inside the forest is compressed rather then expelled, the researchers assumed.) Once a little water bonds to the forest canopy, the effect multiplies as the molecules are drawn inside, spreading out over the nanotubes through van der Waals forces, hydrogen bonding and dipole interactions. The molecules then draw more water in.

The researchers tested several variants of their cup. With only the top hydrophilic layer, the forests fell apart when exposed to humid air because the untreated bottom lacked the polymer links that held the top together. With a hydrophilic top and bottom, the forest held together but water ran right through.

But with a hydrophobic bottom and hydrophilic top, the forest remained intact even after collecting 80 percent of its weight in water.

The amount of water vapor captured depends on the air’s humidity. An 8 milligram sample (with a 0.25-square-centimeter surface) pulled in 27.4 percent of its weight over 11 hours in dry air, and 80 percent over 13 hours in humid air. Further tests showed the forests significantly slowed evaporation of the trapped water.

If it becomes possible to grow nanotube forests on a large scale, the invention could become an efficient, effective water-collection device because it does not require an external energy source, the researchers said.

Ozden said the production of carbon nanotube arrays at a scale necessary to put the invention to practical use remains a bottleneck. “If it becomes possible to make large-scale nanotube forests, it will be a very easy material to make,” he said.

This is not the first time researchers have used the Stenocara beetle (also known as the Namib desert beetle) as inspiration for a water-harvesting material. In a Nov. 26, 2012 posting I traced the inspiration  back to 2001 while featuring the announcement of a new startup company,

… US startup company, NBD Nano, which aims to bring a self-filling water bottle based on Namib desert beetle to market,

NBD Nano, which consists of four recent university graduates and was formed in May [2012], looked at the Namib Desert beetle that lives in a region that gets about half an inch of rainfall per year.

Using a similar approach, the firm wants to cover the surface of a bottle with hydrophilic (water-attracting) and hydrophobic (water-repellent) materials.

The work is still in its early stages, but it is the latest example of researchers looking at nature to find inspiration for sustainable technology.

“It was important to apply [biomimicry] to our design and we have developed a proof of concept and [are] currently creating our first fully-functional prototype,” Miguel Galvez, a co-founder, told the BBC.

“We think our initial prototype will collect anywhere from half a litre of water to three litres per hour, depending on local environments.”

You can find out more about NBD Nano here although they don’t give many details about the material they’ve developed. Given that MIT (Massachusetts Institute of Technology) researchers published a  paper about a polymer-based material laced with silicon nanoparticles inspired by the Namib beetle in 2006 and that NBD Nano is based Massachusetts, I believe NBD Nano is attempting to commercialize the material or some variant developed at MIT.

Getting back to Rice University and carbon nanotubes, this is a different material attempting to achieve the same goal, harvesting water from desert air. Here’s a link to and a citation for the latest paper inspired by the Stenocara beetle (Namib beetle),

Anisotropically Functionalized Carbon Nanotube Array Based Hygroscopic Scaffolds by Sehmus Ozden, Liehui Ge , Tharangattu N. Narayanan , Amelia H. C. Hart , Hyunseung Yang , Srividya Sridhar , Robert Vajtai , and Pulickel M Ajayan. ACS Appl. Mater. Interfaces, DOI: 10.1021/am5022717 Publication Date (Web): June 4, 2014

Copyright © 2014 American Chemical Society

This paper is behind a paywall.

One final note, the research at MIT was funded by DARPA (US Defense Advanced Research Projects Agency). According to the news release the Rice University research held interest for similar agencies,

The U.S. Department of Defense and the U.S. Air Force Office of Scientific Research Multidisciplinary University Research Initiative supported the research.

Music on the web, a spider’s web, that is

I was expecting to see Markus Buehler and MIT (Massachusetts Institute of Technology) mentioned in this latest work on spiderwebs and music. Surprise! This latest research is from three universities in the UK as per a June 3, 2014 news item on ScienceDaily,

Spider silk transmits vibrations across a wide range of frequencies so that, when plucked like a guitar string, its sound carries information about prey, mates, and even the structural integrity of a web.

The discovery was made by researchers from the Universities of Oxford, Strathclyde, and Sheffield who fired bullets and lasers at spider silk to study how it vibrates. They found that, uniquely, when compared to other materials, spider silk can be tuned to a wide range of harmonics. The findings, to be reported in the journal Advanced Materials, not only reveal more about spiders but could also inspire a wide range of new technologies, such as tiny light-weight sensors.

A June 3, 2014 University of Oxford news release (also on EurekAlert), which originated the news item, explains the research and describes how it was conducted (firing bullets?),

‘Most spiders have poor eyesight and rely almost exclusively on the vibration of the silk in their web for sensory information,’ said Beth Mortimer of the Oxford Silk Group at Oxford University, who led the research. ‘The sound of silk can tell them what type of meal is entangled in their net and about the intentions and quality of a prospective mate. By plucking the silk like a guitar string and listening to the ‘echoes’ the spider can also assess the condition of its web.’

‘Most spiders have poor eyesight and rely almost exclusively on the vibration of the silk in their web for sensory information,’ said Beth Mortimer of the Oxford Silk Group at Oxford University, who led the research. ‘The sound of silk can tell them what type of meal is entangled in their net and about the intentions and quality of a prospective mate. By plucking the silk like a guitar string and listening to the ‘echoes’ the spider can also assess the condition of its web.’

This quality is used by the spider in its web by ‘tuning’ the silk: controlling and adjusting both the inherent properties of the silk, and the tensions and interconnectivities of the silk threads that make up the web. To study the sonic properties of the spider’s gossamer threads the researchers used ultra-high-speed cameras to film the threads as they responded to the impact of bullets. [emphasis mine] In addition, lasers were used to make detailed measurements of even the smallest vibration.

‘The fact that spiders can receive these nanometre vibrations with organs on each of their legs, called slit sensillae, really exemplifies the impact of our research about silk properties found in our study,’ said Dr Shira Gordon of the University of Strathclyde, an author involved in this research.

‘These findings further demonstrate the outstanding properties of many spider silks that are able to combine exceptional toughness with the ability to transfer delicate information,’ said Professor Fritz Vollrath of the Oxford Silk Group at Oxford University, an author of the paper. ‘These are traits that would be very useful in light-weight engineering and might lead to novel, built-in ‘intelligent’ sensors and actuators.’

Dr Chris Holland of the University of Sheffield, an author of the paper, said: ‘Spider silks are well known for their impressive mechanical properties, but the vibrational properties have been relatively overlooked and now we find that they are also an awesome communication tool. Yet again spiders continue to impress us in more ways than we can imagine.’

Beth Mortimer said: ‘It may even be that spiders set out to make a web that ‘sounds right’ as its sonic properties are intimately related to factors such as strength and flexibility.’

The research paper has not yet been published in Advanced Materials (I checked this morning, June 4, 2014).

However, there is this video from the researchers,

As for Markus Buehler’s work at MIT, you can find out more in my Nov. 28, 2012 posting, Producing stronger silk musically.

MIT.nano: new nanotechnology research hub for 2018 and the Self-Assembly Lab

MIT (Massachusetts Institute of Technology) has released an unheard of (as far as I’m concerned) two announcements about a new building, MIT.nano. The shorter announcement mentions priorities (from an April 30, 2014 news item on Azonano),

“If you have your hands on the right tools,” says MIT President L. Rafael Reif, “we believe even big problems have answers.” And, he adds, “A state-of-the-art nano facility is the highest priority for MIT, because nanoscience and nanotechnology are omnipresent in innovation today.”

The longer announcement (from an April 30,2014 news item on Azonano) gives more details about the proposed building,

MIT.nano will house two interconnected floors of cleanroom laboratories containing fabrication spaces and materials growth laboratories, greatly expanding the Institute’s capacity for research involving components that are measured in billionths of a meter — a scale at which cleanliness is paramount, as even a single speck of dust vastly exceeds the nanoscale. The building will also include the “quietest” space on campus — a floor optimized for low vibration and minimal electromagnetic interference, dedicated to advanced imaging technologies — and a floor of teaching laboratory space. Finally, the facility will feature an innovative teaching and research space, known as a Computer-Aided Visualization Environment (CAVE), allowing high-resolution views of nanoscale features.

The longer announcement made in this April 30, 2014 MIT news release which provides more details about the building, the thinking that went into its location, and its special requirements,

The four-level MIT.nano will replace the existing Building 12, and will retain its number, occupying a space alongside the iconic Great Dome. It will be interconnected with neighboring buildings, and accessible from MIT’s Infinite Corridor — meaning, Bulović [electrical engineering professor Vladimir Bulović] says, that the new facility will be just a short walk from the numerous departments that will use its tools.

Users of the new facility, he adds, are expected to come from more than 150 research groups at MIT. They will include, for example, scientists who are working on methods to “print” parts of human organs for transplantation; who are creating superhydrophobic surfaces to boost power-plant efficiency; who work with nanofluids to design new means of locomotion for machines, or new methods for purifying water; who aim to transform the manufacturing of pharmaceuticals; and who are using nanotechnology to reduce the carbon footprint of concrete, the world’s most ubiquitous building material.

Cleanroom facilities, by their nature, are among the most energy-intensive buildings to operate: Enormous air-handling machinery is needed to keep their air filtered to an extraordinarily high standard. Travis Wanat, the senior project manager at MIT who is overseeing the MIT.nano project, explains that while ventilation systems for ordinary offices or classrooms are designed to exchange the air two to six times per hour, cleanroom ventilation typically requires a full exchange 250 times an hour. The fans and filters necessary to handle this volume of air require an entire dedicated floor above each floor of cleanrooms in MIT.nano.

But MIT.nano will incorporate many energy-saving features: Richard Amster, director of campus engineering and construction, has partnered with Julie Newman, MIT’s director of sustainability. Together, they are working within MIT, as well as with the design and contracting teams, “to develop the most efficient building possible for cleanroom research and imaging,” Amster says.

Toward that end, MIT.nano will use heat-recovery systems on the building’s exhaust vents. The building will also be able to sense the local cleanroom environment and adjust the need for air exchange, dramatically reducing MIT.nano’s energy consumption. Dozens of other features aim to improve the building’s efficiency and sustainability.

Despite MIT.nano’s central location, the floor devoted to advanced imaging technology will have “more quiet space than anywhere on campus,” Bulović says: The facility is situated as far as possible from the noise of city streets and subway and train lines that flank MIT’s campus.

Indeed, protection from these sources of noise and mechanical vibration dictated the building’s location, from among five campus sites that were considered. According to national standards on ambient vibration, Bulović says, parts of MIT.nano will rate two levels better than the standard typically used for such high-quality imaging spaces.

Another important goal of the building’s design — by Wilson Architects in Boston — is the creation of environments that foster interactions among users, including those from different disciplines. The building’s location at a major campus “crossroads,” its extensive use of glass walls that allow views into lab and cleanroom areas, and its soaring lobbies and other common areas are all intended to help foster such interactions.

“Nanoscale research is inherently interdisciplinary, and this building was designed to encourage collaboration,” Bulović says.

The choice of MIT.nano’s central location is not without compromise, Bulović says: There is very limited access to the construction site — only three access roads, each with limited headroom — so planning for the activities of construction and delivery vehicles, and for the demolition of the current Building 12 and construction of MIT.nano, will present a host of logistical challenges. “It’s like building a ship in a bottle,” Bulović says.

But addressing those challenges will ultimately be well worth it, he says, pointing out that an estimated one-quarter of MIT’s graduate students and 20 percent of its researchers will make use of the facility. The new building “signifies the centrality of nanotechnology and nanomanufacturing for the needs of the 21st century. It will be a key innovation hub for the campus.”

All current occupants of Building 12 will be relocated by June, when underground facilities work, to enable building construction, will commence; at that point, fences will be erected around the constriction zone. The existing Building 12 will be demolished in spring 2015 and construction of MIT.nano is slated to begin in summer 2015.

An April 25, 2014 news item on Nanowerk features an MIT researcher and research that seems ideally suited to this building initiative (Note: A link has been removed),

Skylar Tibbits … was constructing a massive museum installation with thousands of pieces when he had an epiphany. “Imagine yourself facing months on end assembling this thing, thinking there’s got to be a better way,” he says. A designer and architect, Tibbits was accustomed to modeling and fabricating his complex, architecturally sophisticated sculptures with computation. It suddenly struck him: “With all this information that was used to design the structure and communicate with fabrication machines, there’s got to be a way these parts can build themselves.”

This idea propelled Tibbits to enroll at MIT for dual master’s degrees in computer science, and design and computation — in pursuit of the idea, Tibbits says, “that you could program everything from bits, to atoms, and even large-scale structures.”

Today, Tibbits is breathing life into this vision. A research scientist in the Department of Architecture, and a TED2012 Senior Fellow, Tibbits has launched the Self-Assembly Lab at MIT, where like-minded engineers, scientists, designers, and architects transform commonplace materials into responsive, “smart” materials that can coalesce to form structures, all on their own. Deploying such novel techniques as 4-D printing in collaboration with Stratasys, a firm at the forefront of three-dimensional modeling, Tibbits is experimenting with new products and processes from nano to human scale. [emphasis mine]

An April 24, 2014 MIT news release expands on this “nano to human scale” research,

Although still in its infancy, Tibbits’s research might someday make a profound impact on building and construction. One project, called Logic Matter, encodes simple decision-making in a materials, using only that substance’s properties, shape, and geometry. Bricks, for instance, could be programmed to analyze their own loading conditions or orientation and might contain blueprints to build a wall or guide someone in the construction process. “We don’t have to change what we build with,” Tibbits says. “We take seemingly dumb materials and make them more responsive by combining them in elegant ways with geometry and activation energy.”

Natural processes — such as the replication of DNA, protein folding, and the growth of geometrically perfect crystals — inspired Tibbits. He knew these systems — which build complex structures extremely efficiently and can replicate and repair themselve — depend on a common formula: a simple sequence of instructions, programmable parts, energy, and some type of error correction. Mastering this recipe opens up a world of useful applications, Tibbits believes.

One illustrative project underway in Tibbits’s lab may lead to more resilient and efficient infrastructure. He is trying to program a type of peristalsis in water pipes, so they contract and relax like muscles. Unlike current pipes, which tend to break and require constant monitoring and energy input, Tibbits’s pipes can expand and shrink in response to changes in water volume, and could eventually undulate to abet flow. The goal is a “self-regulating system,” where pipes could even repair themselves in case of a puncture.

Self-assembling technologies may eventually help build space structures whose components deposit themselves in zero gravity environments without human intervention, and edifices that become more resilient in response to “noisy and potentially dangerous energies” from phenomena like earthquakes, hurricanes, and tsunamis, Tibbits says. These ideas may seem hard to believe, but “there are structures we can’t build today” that demand new approaches, Tibbits says. “We must ask where self-assembly can solve some of the world’s biggest challenges.”

I can’t resist the image MIT has provided,

Skylar Tibbits’s fluid crystallization project: Self-assembly holds the promise of breakthroughs in many fields. Photo: Len Rubenstein Courtesy: MIT

Skylar Tibbits’s fluid crystallization project: Self-assembly holds the promise of breakthroughs in many fields.
Photo: Len Rubenstein Courtesy: MIT

You can visit Tibbits’s MIT Self-Assembly Lab here.

Your smartphone can be an anti-counterfeiting device thanks to the Massachusetts Institute of Technology

MIT (Massachusetts Institute of Technology) has announced an anti-counterfeiting technology, from an April 29, 2014 article by Mark Wilson for Fast Company (Note: Links have been removed),

Most of us [in the United States] know the Secret Service as the black-suited organization employed to protect the President. But in reality, the service was created toward the end of the Civil War, before Lincoln was assassinated, to crack down on counterfeit currency. Because up to a third of all money at the time was counterfeit.

Fast-forward 150 years:  … the Secret Service reports that they expect counterfeiting to increase. And counterfeiting is no longer a problem for money alone. [emphasis mine] Prescription drugs are also counterfeited–with potentially deadly side effects.

As I noted in an April 28, 2014 posting (How do you know that’s extra virgin olive oil?) about a Swiss anti-counterfeiting effort involving nanoscale labels/tags, foodstuffs and petrol can also be counterfeited.

An April 13, 2014 MIT news release describes the project further,

Led by MIT chemical engineering professor Patrick Doyle and Lincoln Laboratory technical staff member Albert Swiston, the researchers have invented a new type of tiny, smartphone-readable particle that they believe could be deployed to help authenticate currency, electronic parts, and luxury goods, among other products. The particles, which are invisible to the naked eye, contain colored stripes of nanocrystals that glow brightly when lit up with near-infrared light.

These particles can easily be manufactured and integrated into a variety of materials, and can withstand extreme temperatures, sun exposure, and heavy wear, says Doyle, the senior author of a paper describing the particles in the April 13 issue of Nature Materials. They could also be equipped with sensors that can “record” their environments — noting, for example, if a refrigerated vaccine has ever been exposed to temperatures too high or low.

The new particles are about 200 microns long and include several stripes of different colored nanocrystals, known as “rare earth upconverting nanocrystals.” [emphasis mine] These crystals are doped with elements such as ytterbium, gadolinium, erbium, and thulium, which emit visible colors when exposed to near-infrared light. By altering the ratios of these elements, the researchers can tune the crystals to emit any color in the visible spectrum.

The researchers have produced a video where they describe the counterfeiting problem and their solution in nontechnical terms,

For anyone who prefers to read their science, there’s this more technically detailed description (than the one in the video), from the MIT news release ,

To manufacture the particles, the researchers used stop-flow lithography, a technique developed previously by Doyle. This approach allows shapes to be imprinted onto parallel flowing streams of liquid monomers — chemical building blocks that can form longer chains called polymers. Wherever pulses of ultraviolet light strike the streams, a reaction is set off that forms a solid polymeric particle.

In this case, each polymer stream contains nanocrystals that emit different colors, allowing the researchers to form striped particles. So far, the researchers have created nanocrystals in nine different colors, but it should be possible to create many more, Doyle says.

Using this procedure, the researchers can generate vast quantities of unique tags. With particles that contain six stripes, there are 1 million different possible color combinations; this capacity can be exponentially enhanced by tagging products with more than one particle. For example, if the researchers created a set of 1,000 unique particles and then tagged products with any 10 of those particles, there would be 1030 possible combinations — far more than enough to tag every grain of sand on Earth.

“It’s really a massive encoding capacity,” says Bisso, who started this project while on the technical staff at Lincoln Lab. “You can apply different combinations of 10 particles to products from now until long past our time and you’ll never get the same combination.”

“The use of these upconverting nanocrystals is quite clever and highly enabling,” says Jennifer Lewis, a professor of biologically inspired engineering at Harvard University who was not involved in the research. “There are several striking features of this work, namely the exponentially scaling encoding capacities and the ultralow decoding false-alarm rate.”

Versatile particles

The microparticles could be dispersed within electronic parts or drug packaging during the manufacturing process, incorporated directly into 3-D-printed objects, or printed onto currency, the researchers say. They could also be incorporated into ink that artists could use to authenticate their artwork.

The researchers demonstrated the versatility of their approach by using two polymers with radically different material properties — one hydrophobic and one hydrophilic —to make their particles. The color readouts were the same with each, suggesting that the process could easily be adapted to many types of products that companies might want to tag with these particles, Bisso says.

“The ability to tailor the tag’s material properties without impacting the coding strategy is really powerful,” he says. “What separates our system from other anti-counterfeiting technologies is this ability to rapidly and inexpensively tailor material properties to meet the needs of very different and challenging requirements, without impacting smartphone readout or requiring a complete redesign of the system.”

Another advantage to these particles is that they can be read without an expensive decoder like those required by most other anti-counterfeiting technologies. [emphasis mine] Using a smartphone camera equipped with a lens offering twentyfold magnification, anyone could image the particles after shining near-infrared light on them with a laser pointer. The researchers are also working on a smartphone app that would further process the images and reveal the exact composition of the particles.

Before giving a link to and a citation for the paper, I’m going to make an observations.  ‘Rare earths’ the source from which these nanocrystals are derived is concerning since China, the main supplier of rare earths, is limiting the supply made available outside the country and seems intent on continuing to do so. While I appreciate the amount of rare earth needed in the laboratory is minor, should this technology be commercialized and adopted there may be a problem given that ‘rare earths’ are used extensively in smartphones, computers, etc. and that China is limiting the supply.

That said, here’s a link to and a citation for the paper,

Universal process-inert encoding architecture for polymer microparticles by Jiseok Lee, Paul W. Bisso, Rathi L. Srinivas, Jae Jung Kim, Albert J. Swiston, & Patrick S. Doyle. Nature Materials 13, 524–529 (2014) doi:10.1038/nmat3938 Published online 13 April 2014

This article  is behind a paywall.

DNA damage from engineered nanoparticles (zinc oxide, silver, silicon dioxide, cerium oxide and iron oxide)

Before launching into this research, there are a few provisos. This work was done in a laboratory, a highly specialized environment that does not mimic real-life conditions, and performed on animal cells (a hamster’s). As well, naturally occurring nanoparticles were not included (my Nov. 24, 2011 post has some information about naturally occurring nanomaterials including nanosilver which we have been ingesting for centuries).

That said, the studies from the Massachusetts Institute of Techology (MIT) and the Harvard School of Public Health (HSPH; last mentioned here in an April 2, 2014 post) are concerning (from an April 9, 2014 news item on Azonano).

A new study from MIT and the Harvard School of Public Health (HSPH) suggests that certain nanoparticles can also harm DNA. This research was led by Bevin Engelward, a professor of biological engineering at MIT, and associate professor Philip Demokritou, director of HSPH’s Center for Nanotechnology and Nanotoxicology.

The researchers found that zinc oxide nanoparticles, often used in sunscreen to block ultraviolet rays, significantly damage DNA. Nanoscale silver, which has been added to toys, toothpaste, clothing, and other products for its antimicrobial properties, also produces substantial DNA damage, they found.

The findings, published in a recent issue of the journal ACS Nano, relied on a high-speed screening technology to analyze DNA damage. This approach makes it possible to study nanoparticles’ potential hazards at a much faster rate and larger scale than previously possible.

More details about current testing requirements and the specific nanoparticles studied can be found in the April 8, 2014 MIT news release, which originated the news item,

The Food and Drug Administration does not require manufacturers to test nanoscale additives for a given material if the bulk material has already been shown to be safe. However, there is evidence that the nanoparticle form of some of these materials may be unsafe: Due to their immensely small size, these materials may exhibit different physical, chemical, and biological properties, and penetrate cells more easily.

“The problem is that if a nanoparticle is made out of something that’s deemed a safe material, it’s typically considered safe. There are people out there who are concerned, but it’s a tough battle because once these things go into production, it’s very hard to undo,” Engelward says.

The researchers focused on five types of engineered nanoparticles — silver, zinc oxide, iron oxide, cerium oxide, and silicon dioxide (also known as amorphous silica) — that are used industrially. Some of these nanomaterials can produce free radicals called reactive oxygen species, which can alter DNA. Once these particles get into the body, they may accumulate in tissues, causing more damage.

“It’s essential to monitor and evaluate the toxicity or the hazards that these materials may possess. There are so many variations of these materials, in different sizes and shapes, and they’re being incorporated into so many products,” says Christa Watson, a postdoc at HSPH and the paper’s lead author. “This toxicological screening platform gives us a standardized method to assess the engineered nanomaterials that are being developed and used at present.”

The researchers hope that this screening technology could also be used to help design safer forms of nanoparticles; they are already working with partners in industry to engineer safer UV-blocking nanoparticles. Demokritou’s lab recently showed that coating zinc oxide particles with a nanothin layer of amorphous silica can reduce the particles’ ability to damage DNA.

Given that Demokritou was part of a team that recently announced a new testing platform (Volumetric Centrifugation Method [VCM]) for nanoparticles as mentioned in my April 2, 2014 post, I was a little curious about the  platform for this project ( the CometChip) and, as always, curious about the results for all the tested engineered nanoparticles (Note: A link has been removed), from the news release,

Until now, most studies of nanoparticle toxicity have focused on cell survival after exposure. Very few have examined genotoxicity, or the ability to damage DNA — a phenomenon that may not necessarily kill a cell, but one that can lead to cancerous mutations if the damage is not repaired.

A common way to study DNA damage in cells is the so-called “comet assay,” named for the comet-shaped smear that damaged DNA forms during the test. The procedure is based on gel electrophoresis, a test in which an electric field is applied to DNA placed in a matrix, forcing the DNA to move across the gel. During electrophoresis, damaged DNA travels farther than undamaged DNA, producing a comet-tail shape.

Measuring how far the DNA can travel reveals how much DNA damage has occurred. This procedure is very sensitive, but also very tedious.

In 2010, Engelward and MIT professor Sangeeta Bhatia developed a much more rapid version of the comet assay, known as the CometChip. Using microfabrication technology, single cells can be trapped in tiny microwells within the matrix. This approach makes it possible to process as many as 1,000 samples in the time that it used to take to process just 30 samples — allowing researchers to test dozens of experimental conditions at a time, which can be analyzed using imaging software.

Wolfgang Kreyling, an epidemiologist at the German Research Center for Environmental Health who was not involved in the study, says this technology should help toxicologists catch up to the rapid rate of deployment of engineered nanoparticles (ENPs).

“High-throughput screening platforms are desperately needed,” Kreyling says. “The proposed approach will be not only an important tool for nanotoxicologists developing high-throughput screening strategies for the assessment of possible adverse health effects associated with ENPs, but also of great importance for material scientists working on the development of novel ENPs and safer-by-design approaches.”

Using the CometChip, the MIT and HSPH researchers tested the nanoparticles’ effects on two types of cells that are commonly used for toxicity studies: a type of human blood cells called lymphoblastoids, and an immortalized line of Chinese hamster ovary cells.

Zinc oxide and silver produced the greatest DNA damage in both cell lines. At a concentration of 10 micrograms per milliliter — a dose not high enough to kill all of the cells — these generated a large number of single-stranded DNA breaks.

Silicon dioxide, which is commonly added during food and drug production, generated very low levels of DNA damage. Iron oxide and cerium oxide also showed low genotoxicity.

Happily the researchers are taking a pragmatic approach to the results (from the news release),

More studies are needed to determine how much exposure to metal oxide nanoparticles could be unsafe for humans, the researchers say.

“The biggest challenge we have as people concerned with exposure biology is deciding when is something dangerous and when is it not, based on the dose level. At low levels, probably these things are fine,” Engelward says. “The question is: At what level does it become problematic, and how long will it take for us to notice?”

One of the areas of greatest concern is occupational exposure to nanoparticles, the researchers say. Children and fetuses are also potentially at greater risk because their cells divide more often, making them more vulnerable to DNA damage.

The most common routes that engineered nanoparticles follow into the body are through the skin, lungs, and stomach, so the researchers are now investigating nanoparticle genotoxicity on those cell types. They are also studying the effects of other engineered nanoparticles, including metal oxides used in printer and photocopier toner, which can become airborne and enter the lungs.

Kudos to the writer for the clarity and care shown here (I think it’s Anne Trafton but MIT is not including bylines as it did previously, so I’m uncertain).

Here’s a link to and a citation for the research paper,

High-Throughput Screening Platform for Engineered Nanoparticle-Mediated Genotoxicity Using CometChip Technology by Christa Watson, Jing Ge, Joel Cohen, Georgios Pyrgiotakis, Bevin P. Engelward, and Philip Demokritou. ACS Nano, 2014, 8 (3), pp 2118–2133 DOI: 10.1021/nn404871p Publication Date (Web): March 11, 2014
Copyright © 2014 American Chemical Society

This article is behind a paywall.