Tag Archives: MIT

The origins of gold and other precious metals

The link between this research and my side project on gold nanoparticles is a bit tenuous but this work on the origins for gold and other precious metals being found in the stars is so fascinating and I’m determined to find a connection.

An artist's impression of two neutron stars colliding. (Credit: Dana Berry / Skyworks Digital, Inc.) Courtesy: Kavli Foundation

An artist’s impression of two neutron stars colliding. (Credit: Dana Berry / Skyworks Digital, Inc.) Courtesy: Kavli Foundation

From a May 19, 2016 news item on phys.org,

The origin of many of the most precious elements on the periodic table, such as gold, silver and platinum, has perplexed scientists for more than six decades. Now a recent study has an answer, evocatively conveyed in the faint starlight from a distant dwarf galaxy.

In a roundtable discussion, published today [May 19, 2016?], The Kavli Foundation spoke to two of the researchers behind the discovery about why the source of these heavy elements, collectively called “r-process” elements, has been so hard to crack.

From the Spring 2016 Kavli Foundation webpage hosting the  “Galactic ‘Gold Mine’ Explains the Origin of Nature’s Heaviest Elements” Roundtable ,

RESEARCHERS HAVE SOLVED a 60-year-old mystery regarding the origin of the heaviest elements in nature, conveyed in the faint starlight from a distant dwarf galaxy.

Most of the chemical elements, composing everything from planets to paramecia, are forged by the nuclear furnaces in stars like the Sun. But the cosmic wellspring for a certain set of heavy, often valuable elements like gold, silver, lead and uranium, has long evaded scientists.

Astronomers studying a galaxy called Reticulum II have just discovered that its stars contain whopping amounts of these metals—collectively known as “r-process” elements (See “What is the R-Process?”). Of the 10 dwarf galaxies that have been similarly studied so far, only Reticulum II bears such strong chemical signatures. The finding suggests some unusual event took place billions of years ago that created ample amounts of heavy elements and then strew them throughout the galaxy’s reservoir of gas and dust. This r-process-enriched material then went on to form Reticulum II’s standout stars.

Based on the new study, from a team of researchers at the Kavli Institute at the Massachusetts Institute of Technology, the unusual event in Reticulum II was likely the collision of two, ultra-dense objects called neutron stars. Scientists have hypothesized for decades that these collisions could serve as a primary source for r-process elements, yet the idea had lacked solid observational evidence. Now armed with this information, scientists can further hope to retrace the histories of galaxies based on the contents of their stars, in effect conducting “stellar archeology.”

The Kavli Foundation recently spoke with three astrophysicists about how this discovery can unlock clues about galactic evolution as well as the abundances of certain elements on Earth we use for everything from jewelry-making to nuclear power generation. The participants were:

  • Alexander Ji – is a graduate student in physics at the Massachusetts Institute of Technology (MIT) and a member of the MIT Kavli Institute for Astrophysics and Space Research (MKI). He is lead author of a paper in Nature describing this discovery.
  • Anna Frebel – is the Silverman Family Career Development Assistant Professor in the Department of Physics at MIT and also a member of MKI. Frebel is Ji’s advisor and coauthored the Nature paper. Her work delves into the chemical and physical conditions of the early universe as conveyed by the oldest stars.
  • Enrico Ramirez-Ruiz – is a Professor of Astronomy and Astrophysics at the University of California, Santa Cruz. His research explores violent events in the universe, including the mergers of neutron stars and their role in generating r-process elements.

Here’s a link to and citation for Ji’s and Frebel’s paper about r-process elements in the stars,

R-process enrichment from a single event in an ancient dwarf galaxy by Alexander P. Ji, Anna Frebel, Anirudh Chiti, & Joshua D. Simon. Nature 531, 610–613 (31 March 2016) doi:10.1038/nature17425 Published online 21 March 2016

This paper is behind a paywall but you can read an edited transcript of the roundtable discussion on the Galactic ‘Gold Mine’ Explains the Origin of Nature’s Heaviest Elements webpage (keep scrolling past the introductory text).

As for my side project, Steep (2) on gold nanoparticles, that’s still in the planning stages but if there’s a way to include this information, I’ll do it.

Ingestible origami robot gets one step closer

Fiction, more or less seriously, has been exploring the idea of ingestible, tiny robots that can enter the human body for decades (Fantastic Voyage and Innerspace are two movie examples). The concept is coming closer to being realized as per a May 12, 2016 news item on phys.org,

In experiments involving a simulation of the human esophagus and stomach, researchers at MIT [Massachusetts Institute of Technology], the University of Sheffield, and the Tokyo Institute of Technology have demonstrated a tiny origami robot that can unfold itself from a swallowed capsule and, steered by external magnetic fields, crawl across the stomach wall to remove a swallowed button battery or patch a wound.

A May 12, 2016 MIT news release (also on EurekAlert), which originated the news item, provides some fascinating depth to this story (Note: Links have been removed),

The new work, which the researchers are presenting this week at the International Conference on Robotics and Automation, builds on a long sequence of papers on origami robots from the research group of Daniela Rus, the Andrew and Erna Viterbi Professor in MIT’s Department of Electrical Engineering and Computer Science.

“It’s really exciting to see our small origami robots doing something with potential important applications to health care,” says Rus, who also directs MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL). “For applications inside the body, we need a small, controllable, untethered robot system. It’s really difficult to control and place a robot inside the body if the robot is attached to a tether.”

Although the new robot is a successor to one reported at the same conference last year, the design of its body is significantly different. Like its predecessor, it can propel itself using what’s called a “stick-slip” motion, in which its appendages stick to a surface through friction when it executes a move, but slip free again when its body flexes to change its weight distribution.

Also like its predecessor — and like several other origami robots from the Rus group — the new robot consists of two layers of structural material sandwiching a material that shrinks when heated. A pattern of slits in the outer layers determines how the robot will fold when the middle layer contracts.

Material difference

The robot’s envisioned use also dictated a host of structural modifications. “Stick-slip only works when, one, the robot is small enough and, two, the robot is stiff enough,” says Guitron [Steven Guitron, a graduate student in mechanical engineering]. “With the original Mylar design, it was much stiffer than the new design, which is based on a biocompatible material.”

To compensate for the biocompatible material’s relative malleability, the researchers had to come up with a design that required fewer slits. At the same time, the robot’s folds increase its stiffness along certain axes.

But because the stomach is filled with fluids, the robot doesn’t rely entirely on stick-slip motion. “In our calculation, 20 percent of forward motion is by propelling water — thrust — and 80 percent is by stick-slip motion,” says Miyashita [Shuhei Miyashita, who was a postdoc at CSAIL when the work was done and is now a lecturer in electronics at the University of York, England]. “In this regard, we actively introduced and applied the concept and characteristics of the fin to the body design, which you can see in the relatively flat design.”

It also had to be possible to compress the robot enough that it could fit inside a capsule for swallowing; similarly, when the capsule dissolved, the forces acting on the robot had to be strong enough to cause it to fully unfold. Through a design process that Guitron describes as “mostly trial and error,” the researchers arrived at a rectangular robot with accordion folds perpendicular to its long axis and pinched corners that act as points of traction.

In the center of one of the forward accordion folds is a permanent magnet that responds to changing magnetic fields outside the body, which control the robot’s motion. The forces applied to the robot are principally rotational. A quick rotation will make it spin in place, but a slower rotation will cause it to pivot around one of its fixed feet. In the researchers’ experiments, the robot uses the same magnet to pick up the button battery.

Porcine precedents

The researchers tested about a dozen different possibilities for the structural material before settling on the type of dried pig intestine used in sausage casings. “We spent a lot of time at Asian markets and the Chinatown market looking for materials,” Li [Shuguang Li, a CSAIL postdoc] says. The shrinking layer is a biodegradable shrink wrap called Biolefin.

To design their synthetic stomach, the researchers bought a pig stomach and tested its mechanical properties. Their model is an open cross-section of the stomach and esophagus, molded from a silicone rubber with the same mechanical profile. A mixture of water and lemon juice simulates the acidic fluids in the stomach.

Every year, 3,500 swallowed button batteries are reported in the U.S. alone. Frequently, the batteries are digested normally, but if they come into prolonged contact with the tissue of the esophagus or stomach, they can cause an electric current that produces hydroxide, which burns the tissue. Miyashita employed a clever strategy to convince Rus that the removal of swallowed button batteries and the treatment of consequent wounds was a compelling application of their origami robot.

“Shuhei bought a piece of ham, and he put the battery on the ham,” Rus says. [emphasis mine] “Within half an hour, the battery was fully submerged in the ham. So that made me realize that, yes, this is important. If you have a battery in your body, you really want it out as soon as possible.”

“This concept is both highly creative and highly practical, and it addresses a clinical need in an elegant way,” says Bradley Nelson, a professor of robotics at the Swiss Federal Institute of Technology Zurich. “It is one of the most convincing applications of origami robots that I have seen.”

I wonder if they ate the ham afterwards.

Happily, MIT has produced a video featuring this ingestible, origami robot,

Finally, this team has a couple more members than the previously mentioned Rus, Miyashita, and Li,

…  Kazuhiro Yoshida of Tokyo Institute of Technology, who was visiting MIT on sabbatical when the work was done; and Dana Damian of the University of Sheffield, in England.

As Rus notes in the video, the next step will be in vivo (animal) studies.

Tightening the skin (and protecting it and removing wrinkles, temporarily)

“It’s an invisible layer that can provide a barrier, provide cosmetic improvement, and potentially deliver a drug locally to the area that’s being treated. Those three things together could really make it ideal for use in humans,” Daniel Anderson says. Photo: Melanie Gonick/MIT

“It’s an invisible layer that can provide a barrier, provide cosmetic improvement, and potentially deliver a drug locally to the area that’s being treated. Those three things together could really make it ideal for use in humans,” Daniel Anderson says. Photo: Melanie Gonick/MIT

It almost looks like he’s peeling off his own skin and I imagine that’s the secret to this polymer’s success. A May 9, 2016 news item on phys.org describes the work being done at the Massachusetts Institute of Technology (MIT) and elsewhere with collaborators,

Scientists at MIT, Massachusetts General Hospital, Living Proof, and Olivo Labs have developed a new material that can temporarily protect and tighten skin, and smooth wrinkles. With further development, it could also be used to deliver drugs to help treat skin conditions such as eczema and other types of dermatitis.

A May 9, 2016 MIT news release (also on EurekAlert), which originated the news item, provides more detail,

The material, a silicone-based polymer that could be applied on the skin as a thin, imperceptible coating, mimics the mechanical and elastic properties of healthy, youthful skin. In tests with human subjects, the researchers found that the material was able to reshape “eye bags” under the lower eyelids and also enhance skin hydration. This type of “second skin” could also be adapted to provide long-lasting ultraviolet protection, the researchers say.

“It’s an invisible layer that can provide a barrier, provide cosmetic improvement, and potentially deliver a drug locally to the area that’s being treated. Those three things together could really make it ideal for use in humans,” says Daniel Anderson, an associate professor in MIT’s Department of Chemical Engineering and a member of MIT’s Koch Institute for Integrative Cancer Research and Institute for Medical Engineering and Science (IMES).

Anderson is one of the authors of a paper describing the polymer in the May 9 online issue of Nature Materials. Robert Langer, the David H. Koch Institute Professor at MIT and a member of the Koch Institute, is the paper’s senior author, and the paper’s lead author is Betty Yu SM ’98, ScD ’02, former vice president at Living Proof. Langer and Anderson are co-founders of Living Proof and Olivo Labs, and Yu earned her master’s and doctorate at MIT.

Mimicking skin

As skin ages, it becomes less firm and less elastic — problems that can be exacerbated by sun exposure. This impairs skin’s ability to protect against extreme temperatures, toxins, microorganisms, radiation, and injury. About 10 years ago, the research team set out to develop a protective coating that could restore the properties of healthy skin, for both medical and cosmetic applications.

“We started thinking about how we might be able to control the properties of skin by coating it with polymers that would impart beneficial effects,” Anderson says. “We also wanted it to be invisible and comfortable.”

The researchers created a library of more than 100 possible polymers, all of which contained a chemical structure known as siloxane — a chain of alternating atoms of silicon and oxygen. These polymers can be assembled into a network arrangement known as a cross-linked polymer layer (XPL). The researchers then tested the materials in search of one that would best mimic the appearance, strength, and elasticity of healthy skin.

“It has to have the right optical properties, otherwise it won’t look good, and it has to have the right mechanical properties, otherwise it won’t have the right strength and it won’t perform correctly,” Langer says.

The best-performing material has elastic properties very similar to those of skin. In laboratory tests, it easily returned to its original state after being stretched more than 250 percent (natural skin can be elongated about 180 percent). In laboratory tests, the novel XPL’s elasticity was much better than that of two other types of wound dressings now used on skin — silicone gel sheets and polyurethane films.

“Creating a material that behaves like skin is very difficult,” says Barbara Gilchrest, a dermatologist at MGH and an author of the paper. “Many people have tried to do this, and the materials that have been available up until this have not had the properties of being flexible, comfortable, nonirritating, and able to conform to the movement of the skin and return to its original shape.”

The XPL is currently delivered in a two-step process. First, polysiloxane components are applied to the skin, followed by a platinum catalyst that induces the polymer to form a strong cross-linked film that remains on the skin for up to 24 hours. This catalyst has to be added after the polymer is applied because after this step the material becomes too stiff to spread. Both layers are applied as creams or ointments, and once spread onto the skin, XPL becomes essentially invisible.

High performance

The researchers performed several studies in humans to test the material’s safety and effectiveness. In one study, the XPL was applied to the under-eye area where “eye bags” often form as skin ages. These eye bags are caused by protrusion of the fat pad underlying the skin of the lower lid. When the material was applied, it applied a steady compressive force that tightened the skin, an effect that lasted for about 24 hours.

In another study, the XPL was applied to forearm skin to test its elasticity. When the XPL-treated skin was distended with a suction cup, it returned to its original position faster than untreated skin.

The researchers also tested the material’s ability to prevent water loss from dry skin. Two hours after application, skin treated with the novel XPL suffered much less water loss than skin treated with a high-end commercial moisturizer. Skin coated with petrolatum was as effective as XPL in tests done two hours after treatment, but after 24 hours, skin treated with XPL had retained much more water. None of the study participants reported any irritation from wearing XPL.

“I think it has great potential for both cosmetic and noncosmetic applications, especially if you could incorporate antimicrobial agents or medications,” says Thahn Nga Tran, a dermatologist and instructor at Harvard Medical School, who was not involved in the research.

Living Proof has spun out the XPL technology to Olivo Laboratories, LLC, a new startup formed to focus on the further development of the XPL technology. Initially, Olivo’s team will focus on medical applications of the technology for treating skin conditions such as dermatitis.

 

This video supplied by MIT shows how to apply the polymer and offers a description and demonstration of its properties once applied,

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

An elastic second skin by Betty Yu, Soo-Young Kang, Ariya Akthakul, Nithin Ramadurai, Morgan Pilkenton, Alpesh Patel, Amir Nashat, Daniel G. Anderson, Fernanda H. Sakamoto, Barbara A. Gilchrest, R. Rox Anderson & Robert Langer. Nature Materials (2016) doi:10.1038/nmat4635 Published online 09 May 2016

This paper is behind a paywall.

One final comment, I wonder who’s lining up to invest in this product.

MIT.nano building update

A few years ago I featured a story (my May 6, 2014 posting) about a new building, the MIT.nano, being constructed on the Massachusetts Institute of Technology campus. Now at about 1/2 way through the construction (the building is due to open in 2018) MIT has issued an update in an April 20, 2016 news release by Leda Zimmerman,

A spectacular show has been going on outside the windows of central-campus buildings all spring. An enormous steel structure has been growing — piece by piece, and bolt by bolt — out of a giant hole in the ground formerly occupied by Building 12. At a March 24 [2016] “tool talk” information session for the MIT community on the construction of MIT.nano, representatives from MIT Facilities and the contractors who are building the new 200,000 square foot nanoscale characterization and fabrication facility gave an overview not only of where things stand with the project, but how they got stood up.

“In our structural-steel erection progress log, we’ve been averaging around 23 tons per day,” said Peter Johnson of Turner Construction. “We’re putting up 2,101 tons total, and we’re 22 percent complete.”

There is a Canadian connection,

Working with Ontario-based steel fabricator, Canatal, Johnson and his colleagues at Turner developed a four-dimensional plan for steel engineering, delivery, and installation. “We went through a painstaking process to maximize efficiency of this sequence,” says Johnson. “This allows us to avoid times when a crane is down because it’s waiting” for a delivery of steel.

There are some very interesting details in the news release but if you don’t have the time, there is this picture,

MIT.nano steel structure, looking northwest. Photo: Lillie Paquette/School of Engineering

MIT.nano steel structure, looking northwest. Photo: Lillie Paquette/School of Engineering

The colours are quite striking (I suspect they have been enhanced).

New kind of long-range particle interactions found by Massachusetts Institute of Technology (MIT) team

A team from the Massachusetts Institute of Technology (MIT) found unexpected long-range interactions amongst particles in a liquid medium according to an April 12, 2016 news item on ScienceDaily,

Moving bodies can be attracted to each other, even when they’re quite far apart and separated by many other objects: That, in a nutshell, is the somewhat unexpected finding by a team of researchers at MIT.

Scientists have known for a long time that small particles of matter, from the size of dust to sand grains, can exert influences on each other through electrical, magnetic, or chemical effects. Now, this team has found a new kind of long-range interaction between particles, in a liquid medium, that is based entirely on their motions. And these interactions should apply to any kind of particles that move, whether they be living cells or metal particles whirled by magnetic fields.

An April 11, 2016 MIT news release (also on EurekAlert), which originated the news item, describes the work in more detail,

The discovery, which holds for both living and nonliving particles, is described in a paper by Alfredo Alexander-Katz, the Walter Henry Gale Associate Professor of Materials Science and Engineering at MIT, and his co-researchers, in the Proceedings of the National Academies of Sciences.

Alexander-Katz describes the kind of interactions his team found as being related to the research field of active matter. Example of active systems are the flocking behavior of birds or the schooling of fish. Each individual member of the system may be responding just to others in its vicinity, but the result is a coherent overall pattern of movement that can span a large region. Cells in a fluid medium, or even tiny structures moving within a cell, exhibit similar kinds of motion, he says.

The researchers studied magnetic particles a few micrometers (millionths of a meter) across, comparable to the size of some cells. A small number of these magnetic metal microparticles were interspersed with a much larger quantity of inert particles of comparable size, all suspended in water. When a rotating magnetic field was applied, the metal particles would begin to spin, simulating the movements of living cells in the midst of nonliving or relatively inert objects — such as when cells migrate through tissues or move in a crowded environment.

They found that the spinning particles, even when separated by distances tens of times their size, would ultimately migrate toward each other. Though that attraction progressed through a slow and apparently random series of motions, the particles would in the end almost always come together.

While there has been a lot of research on interactions among active particles, Alexander-Katz says, this is one of the few studies that has looked at the way such particles interact when they are surrounded by inactive particles. “In the absence of the inactive particles there are essentially no interactions,” he says.

The unexpected finding might ultimately lead to a better understanding of the behavior of some natural biological systems or new methods for creating synthetic active materials which could be useful for selectively delivering drugs into certain parts of the body, Alexander-Katz suggests. It could also end up finding applications in electronics or energy-harvesting systems, for example providing a way to flip a crystal structure between two different configurations.

“What we’re addressing is collective excitations of the system, or coherent excitations,” he explains. “What we’re looking at is, what are the interactions as a function of activity” of the individual particles.

The faster the particles spin, the greater the attraction between them, the team found. Below a certain speed the effect stops altogether. But the amount of inert matter also makes a difference, they found.

With no inert particles — if the moving particles are suspended in clear water — there is no motion-based attraction. But when the nonspinning particles are added and their concentration reaches a certain point, “there is attraction!” Alexander-Katz says.

One unexpected aspect of the findings was how far the effect extended. “What was really surprising was that the range of the interactions is gigantic,” he says. By way of comparison, he says, imagine you’re in a crowd, and you start to move a bit, and someone else also starts to move, while everyone else tries to stand still. “I would be able to sense, even 20 people away or more, that that person is also active — assuming that the other folks around us are not active.”

The attraction, he says, “is not chemical, it is not magnetic, it is not electrostatic, it’s just based on activity.” And because the range is so long, these interactions could not be modeled in simulations but required physical experiments to be uncovered. The tests by Alexander-Katz and his team used two-dimensional films, similar to particle sediments that form on a rock surface, he says.

He speculates that some biological organisms may use this phenomenon as a way of sensing parts of their environment, though this has not yet been tested.

There is an MIT video illustrating the work,

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

Emergent ultra–long-range interactions between active particles in hybrid active–inactive systems by Joshua P. Steimel, Juan L. Aragones, Helen Hu, Naser Qureshi, and Alfredo Alexander-Katz. Proceedings of the National Academy of Sciences,  2016; 201520481 doi: 10.1073/pnas.1520481113

This paper is behind a paywall.

Solar cells and soap bubbles

The MIT team has achieved the thinnest and lightest complete solar cells ever made, they say. To demonstrate just how thin and lightweight the cells are, the researchers draped a working cell on top of a soap bubble, without popping the bubble. Photo: Joel Jean and Anna Osherov

The MIT team has achieved the thinnest and lightest complete solar cells ever made, they say. To demonstrate just how thin and lightweight the cells are, the researchers draped a working cell on top of a soap bubble, without popping the bubble. Photo: Joel Jean and Anna Osherov

That’s quite a compelling image and it comes to us courtesy of researchers at MIT (Massachusetts Institute of Technology). From a Feb. 25, 2016 MIT news release (also on EurekAlert),

Imagine solar cells so thin, flexible, and lightweight that they could be placed on almost any material or surface, including your hat, shirt, or smartphone, or even on a sheet of paper or a helium balloon.

Researchers at MIT have now demonstrated just such a technology: the thinnest, lightest solar cells ever produced. Though it may take years to develop into a commercial product, the laboratory proof-of-concept shows a new approach to making solar cells that could help power the next generation of portable electronic devices.

Bulović [Vladimir Bulović ], MIT’s associate dean for innovation and the Fariborz Maseeh (1990) Professor of Emerging Technology, says the key to the new approach is to make the solar cell, the substrate that supports it, and a protective overcoating to shield it from the environment, all in one process. The substrate is made in place and never needs to be handled, cleaned, or removed from the vacuum during fabrication, thus minimizing exposure to dust or other contaminants that could degrade the cell’s performance.

“The innovative step is the realization that you can grow the substrate at the same time as you grow the device,” Bulović says.

In this initial proof-of-concept experiment, the team used a common flexible polymer called parylene as both the substrate and the overcoating, and an organic material called DBP as the primary light-absorbing layer. Parylene is a commercially available plastic coating used widely to protect implanted biomedical devices and printed circuit boards from environmental damage. The entire process takes place in a vacuum chamber at room temperature and without the use of any solvents, unlike conventional solar-cell manufacturing, which requires high temperatures and harsh chemicals. In this case, both the substrate and the solar cell are “grown” using established vapor deposition techniques.

One process, many materials

The team emphasizes that these particular choices of materials were just examples, and that it is the in-line substrate manufacturing process that is the key innovation. Different materials could be used for the substrate and encapsulation layers, and different types of thin-film solar cell materials, including quantum dots or perovskites, could be substituted for the organic layers used in initial tests.

But already, the team has achieved the thinnest and lightest complete solar cells ever made, they say. To demonstrate just how thin and lightweight the cells are, the researchers draped a working cell on top of a soap bubble, without popping the bubble. The researchers acknowledge that this cell may be too thin to be practical — “If you breathe too hard, you might blow it away,” says Jean [Joel Jean, doctoral student] — but parylene films of thicknesses of up to 80 microns can be deposited easily using commercial equipment, without losing the other benefits of in-line substrate formation.

A flexible parylene film, similar to kitchen cling-wrap but only one-tenth as thick, is first deposited on a sturdier carrier material – in this case, glass. Figuring out how to cleanly separate the thin material from the glass was a key challenge, explains Wang [Annie Wang, research scientist], who has spent many years working with parylene.

The researchers lift the entire parylene/solar cell/parylene stack off the carrier after the fabrication process is complete, using a frame made of flexible film. The final ultra-thin, flexible solar cells, including substrate and overcoating, are just one-fiftieth of the thickness of a human hair and one-thousandth of the thickness of equivalent cells on glass substrates — about two micrometers thick — yet they convert sunlight into electricity just as efficiently as their glass-based counterparts.

No miracles needed

“We put our carrier in a vacuum system, then we deposit everything else on top of it, and then peel the whole thing off,” explains Wang. Bulović says that like most new inventions, it all sounds very simple — once it’s been done. But actually developing the techniques to make the process work required years of effort.

While they used a glass carrier for their solar cells, Jean says “it could be something else. You could use almost any material,” since the processing takes place under such benign conditions. The substrate and solar cell could be deposited directly on fabric or paper, for example.

While the solar cell in this demonstration device is not especially efficient, because of its low weight, its power-to-weight ratio is among the highest ever achieved. That’s important for applications where weight is important, such as on spacecraft or on high-altitude helium balloons used for research. Whereas a typical silicon-based solar module, whose weight is dominated by a glass cover, may produce about 15 watts of power per kilogram of weight, the new cells have already demonstrated an output of 6 watts per gram — about 400 times higher.

“It could be so light that you don’t even know it’s there, on your shirt or on your notebook,” Bulović says. “These cells could simply be an add-on to existing structures.”

Still, this is early, laboratory-scale work, and developing it into a manufacturable product will take time, the team says. Yet while commercial success in the short term may be uncertain, this work could open up new applications for solar power in the long term. “We have a proof-of-concept that works,” Bulović says. The next question is, “How many miracles does it take to make it scalable? We think it’s a lot of hard work ahead, but likely no miracles needed.”

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

In situ vapor-deposited parylene substrates for ultra-thin, lightweight organic solar cells by Joel Jean, Annie Wang, Vladimir Bulović. Organic Electronics Volume 31, April 2016, Pages 120–126 doi:10.1016/j.orgel.2016.01.022

This paper is behind a paywall.

Graphene like water

This is graphene research from Harvard University and Raytheon according to a Feb. 11, 2016 news item on phys.org (Note: Links have been removed),

It’s one atom thick [i.e., two-dimensional], stronger than steel, harder than diamond and one of the most conductive materials on earth.

But, several challenges must be overcome before graphene products are brought to market. Scientists are still trying to understand the basic physics of this unique material. Also, it’s very challenging to make and even harder to make without impurities.

In a new paper published in Science, researchers at the [sic] Harvard and Raytheon BBN Technology have advanced our understanding of graphene’s basic properties, observing for the first time electrons in a metal behaving like a fluid.

A Feb. 11, 2016 Harvard University press release by Leah Burrows (also on EurekAlert), which originated the news item, provides more detail,

In order to make this observation, the team improved methods to create ultra-clean graphene and developed a new way measure its thermal conductivity. This research could lead to novel thermoelectric devices as well as provide a model system to explore exotic phenomena like black holes and high-energy plasmas.

An electron super highway

In ordinary, three-dimensional metals, electrons hardly interact with each other. But graphene’s two-dimensional, honeycomb structure acts like an electron superhighway in which all the particles have to travel in the same lane. The electrons in graphene act like massless relativistic objects, some with positive charge and some with negative charge. They move at incredible speed — 1/300 of the speed of light — and have been predicted to collide with each other ten trillion times a second at room temperature.  These intense interactions between charge particles have never been observed in an ordinary metal before.

The team created an ultra-clean sample by sandwiching the one-atom thick graphene sheet between tens of layers of an electrically insulating perfect transparent crystal with a similar atomic structure of graphene.

“If you have a material that’s one atom thick, it’s going to be really affected by its environment,” said Jesse Crossno, a graduate student in the Kim Lab [Philip Kim, professor of physics and applied physics] and first author of the paper.  “If the graphene is on top of something that’s rough and disordered, it’s going to interfere with how the electrons move. It’s really important to create graphene with no interference from its environment.”

The technique was developed by Kim and his collaborators at Columbia University before he moved to Harvard in 2014 and now have been perfected in his lab at SEAS [Harvard School of Engineering and Applied Sciences].

Next, the team set up a kind of thermal soup of positively charged and negatively charged particles on the surface of the graphene, and observed how those particles flowed as thermal and electric currents.

What they observed flew in the face of everything they knew about metals.

A black hole on a chip

Most of our world — how water flows or how a curve ball curves —  is described by classical physics. Very small things, like electrons, are described by quantum mechanics while very large and very fast things, like galaxies, are described by relativistic physics, pioneered by Albert Einstein.

Combining these laws of physics is notoriously difficult but there are extreme examples where they overlap. High-energy systems like supernovas and black holes can be described by linking classical theories of hydrodynamics with Einstein’s theories of relativity.

But it’s difficult to run an experiment on a black hole. Enter graphene.

When the strongly interacting particles in graphene were driven by an electric field, they behaved not like individual particles but like a fluid that could be described by hydrodynamics.

“Instead of watching how a single particle was affected by an electric or thermal force, we could see the conserved energy as it flowed across many particles, like a wave through water,” said Crossno.

“Physics we discovered by studying black holes and string theory, we’re seeing in graphene,” said Andrew Lucas, co-author and graduate student with Subir Sachdev, the Herchel Smith Professor of Physics at Harvard. “This is the first model system of relativistic hydrodynamics in a metal.”

Moving forward, a small chip of graphene could be used to model the fluid-like behavior of other high-energy systems.

Industrial implications

So we now know that strongly interacting electrons in graphene behave like a liquid — how does that advance the industrial applications of graphene?

First, in order to observe the hydrodynamic system, the team needed to develop a precise way to measure how well electrons in the system carry heat.  It’s very difficult to do, said co-PI Kin Chung Fong, scientist with Raytheon BBN Technology.

Materials conduct heat in two ways: through vibrations in the atomic structure or lattice; and carried by the electrons themselves.

“We needed to find a clever way to ignore the heat transfer from the lattice and focus only on how much heat is carried by the electrons,” Fong said.

To do so, the team turned to noise. At finite temperature, the electrons move about randomly:  the higher the temperature, the noisier the electrons. By measuring the temperature of the electrons to three decimal points, the team was able to precisely measure the thermal conductivity of the electrons.

“This work provides a new way to control the rate of heat transduction in graphene’s electron system, and as such will be key for energy and sensing-related applications,” said Leonid Levitov, professor of physics at MIT [Massachusetts Institute of Technology].

“Converting thermal energy into electric currents and vice versa is notoriously hard with ordinary materials,” said Lucas. “But in principle, with a clean sample of graphene there may be no limit to how good a device you could make.”

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

Observation of the Dirac fluid and the breakdown of the Wiedemann-Franz law in graphene by Jesse Crossno, Jing K. Shi, Ke Wang, Xiaomeng Liu, Achim Harzheim, Andrew Lucas, Subir Sachdev, Philip Kim, Takashi Taniguchi, Kenji Watanabe, Thomas A. Ohki, Kin Chung Fong.Science  11 Feb 2016: pp. DOI: 10.1126/science.aad0343

This paper is behind a paywall.

Here’s an image illustrating the research,

Caption: In a new paper published in Science, researchers at the Harvard and Raytheon BBN Technology have advanced our understanding of graphene's basic properties, observing for the first time electrons in a metal behaving like a fluid. Credit: Peter Allen/Harvard SEAS

Caption: In a new paper published in Science, researchers at the Harvard and Raytheon BBN Technology have advanced our understanding of graphene’s basic properties, observing for the first time electrons in a metal behaving like a fluid. Credit: Peter Allen/Harvard SEAS

Handling massive digital datasets the quantum way

A Jan. 25, 2016 news item on phys.org describes a new approach to analyzing and managing huge datasets,

From gene mapping to space exploration, humanity continues to generate ever-larger sets of data—far more information than people can actually process, manage, or understand.

Machine learning systems can help researchers deal with this ever-growing flood of information. Some of the most powerful of these analytical tools are based on a strange branch of geometry called topology, which deals with properties that stay the same even when something is bent and stretched every which way.

Such topological systems are especially useful for analyzing the connections in complex networks, such as the internal wiring of the brain, the U.S. power grid, or the global interconnections of the Internet. But even with the most powerful modern supercomputers, such problems remain daunting and impractical to solve. Now, a new approach that would use quantum computers to streamline these problems has been developed by researchers at [Massachusetts Institute of Technology] MIT, the University of Waterloo, and the University of Southern California [USC}.

A Jan. 25, 2016 MIT news release (*also on EurekAlert*), which originated the news item, describes the theory in more detail,

… Seth Lloyd, the paper’s lead author and the Nam P. Suh Professor of Mechanical Engineering, explains that algebraic topology is key to the new method. This approach, he says, helps to reduce the impact of the inevitable distortions that arise every time someone collects data about the real world.

In a topological description, basic features of the data (How many holes does it have? How are the different parts connected?) are considered the same no matter how much they are stretched, compressed, or distorted. Lloyd [ explains that it is often these fundamental topological attributes “that are important in trying to reconstruct the underlying patterns in the real world that the data are supposed to represent.”

It doesn’t matter what kind of dataset is being analyzed, he says. The topological approach to looking for connections and holes “works whether it’s an actual physical hole, or the data represents a logical argument and there’s a hole in the argument. This will find both kinds of holes.”

Using conventional computers, that approach is too demanding for all but the simplest situations. Topological analysis “represents a crucial way of getting at the significant features of the data, but it’s computationally very expensive,” Lloyd says. “This is where quantum mechanics kicks in.” The new quantum-based approach, he says, could exponentially speed up such calculations.

Lloyd offers an example to illustrate that potential speedup: If you have a dataset with 300 points, a conventional approach to analyzing all the topological features in that system would require “a computer the size of the universe,” he says. That is, it would take 2300 (two to the 300th power) processing units — approximately the number of all the particles in the universe. In other words, the problem is simply not solvable in that way.

“That’s where our algorithm kicks in,” he says. Solving the same problem with the new system, using a quantum computer, would require just 300 quantum bits — and a device this size may be achieved in the next few years, according to Lloyd.

“Our algorithm shows that you don’t need a big quantum computer to kick some serious topological butt,” he says.

There are many important kinds of huge datasets where the quantum-topological approach could be useful, Lloyd says, for example understanding interconnections in the brain. “By applying topological analysis to datasets gleaned by electroencephalography or functional MRI, you can reveal the complex connectivity and topology of the sequences of firing neurons that underlie our thought processes,” he says.

The same approach could be used for analyzing many other kinds of information. “You could apply it to the world’s economy, or to social networks, or almost any system that involves long-range transport of goods or information,” says Lloyd, who holds a joint appointment as a professor of physics. But the limits of classical computation have prevented such approaches from being applied before.

While this work is theoretical, “experimentalists have already contacted us about trying prototypes,” he says. “You could find the topology of simple structures on a very simple quantum computer. People are trying proof-of-concept experiments.”

Ignacio Cirac, a professor at the Max Planck Institute of Quantum Optics in Munich, Germany, who was not involved in this research, calls it “a very original idea, and I think that it has a great potential.” He adds “I guess that it has to be further developed and adapted to particular problems. In any case, I think that this is top-quality research.”

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

Quantum algorithms for topological and geometric analysis of data by Seth Lloyd, Silvano Garnerone, & Paolo Zanardi. Nature Communications 7, Article number: 10138 doi:10.1038/ncomms10138 Published 25 January 2016

This paper is open access.

ETA Jan. 25, 2016 1245 hours PST,

Shown here are the connections between different regions of the brain in a control subject (left) and a subject under the influence of the psychedelic compound psilocybin (right). This demonstrates a dramatic increase in connectivity, which explains some of the drug’s effects (such as “hearing” colors or “seeing” smells). Such an analysis, involving billions of brain cells, would be too complex for conventional techniques, but could be handled easily by the new quantum approach, the researchers say. Courtesy of the researchers

Shown here are the connections between different regions of the brain in a control subject (left) and a subject under the influence of the psychedelic compound psilocybin (right). This demonstrates a dramatic increase in connectivity, which explains some of the drug’s effects (such as “hearing” colors or “seeing” smells). Such an analysis, involving billions of brain cells, would be too complex for conventional techniques, but could be handled easily by the new quantum approach, the researchers say. Courtesy of the researchers

*’also on EurekAlert’ text and link added Jan. 26, 2016.

Getting back to incandescent light (recycling the military way)

MIT (Massachusetts Institute of Technology) issued two news releases about this research into reclaiming incandescent light or as they call it “recycling light.” First off, there’s the Jan. 11, 2016 MIT Institute of Soldier Nanotechnologies news release by Paola Rebusco on EurekAlert,

Humanity started recycling relatively early in its evolution: there are proofs that trash recycling was taking place as early as in the 500 BC. What about light recycling? Consider light bulbs: more than one hundred and thirty years ago Thomas Edison patented the first commercially viable incandescent light bulb, so that “none but the extravagant” would ever “burn tallow candles”, paving the way for more than a century of incandescent lighting. In fact, emergence of electric lighting was the main motivating factor for deployment of electricity into every home in the world. The incandescent bulb is an example of a high temperature thermal emitter. It is very useful, but only a small fraction of the emitted light (and therefore energy) is used: most of the light is emitted in the infrared, invisible to the human eye, and in this context wasted.

Now, in a study published in Nature Nanotechnology on January 11th 2016 (online), a team of MIT researchers describes another way to recycle light emitted at unwanted infrared wavelengths while optimizing the emission at useful visible wavelengths. …

“For a thermal emitter at moderate temperatures one usually nano-patterns its surface to alter the emission,” says Ilic [postdoc Ognjen Ilic], the lead author of the study. “At high temperatures” – a light bulb filament reaches 3000K! – “such nanostructures deteriorate and it is impossible to alter the emission spectrum by having a nanostructure directly on the surface of the emitter.” The team solved the problem by surrounding the hot object with special nanophotonic structures that spectrally filter the emitted light, meaning that they let the light reflect or pass through based on its color (i.e. its wavelength). Because the filters are not in direct physical contact with the emitter, temperatures can be very high.

To showcase this idea, the team picked one of the highest temperature thermal emitters available – an incandescent light bulb. The authors designed nanofilters to recycle the infrared light, while allowing the visible light to go through. “The key advance was to design a photonic structure that transmits visible light and reflects infrared light for a very wide range of angles,” explains Ilic. “Conventional photonic filters usually operate for a single incidence angle. The challenge for us was to extend the desired optical properties across all directions,” a feat the authors achieved using special numerical optimization techniques.

However, for this scheme to work, the authors had to redesign the incandescent filament from scratch. “In a regular light bulb, the filament is a long and curly piece of tungsten wire. Here, the filament is laser-machined out of a flat sheet of tungsten: it is completely planar,” says Bermel [professor Peter Bermel now at Purdue University]. A planar filament has a large area, and is therefore very efficient in re-absorbing the light that was reflected by the filter. In describing how the new device differs from previously suggested concepts, Soljačić [professor Marin Soljačić], the project lead, emphasizes that “it is the combination of the exceptional properties of the filter and the shape of the filament that enabled substantial recycling of unwanted radiated light.”

In the new-concept light bulb prototype built by the authors, the efficiency approaches some fluorescent and LED bulbs. Nonetheless, the theoretical model predicts plenty of room for improvement. “This experimental device is a proof-of-concept, at the low end of performance that could be ultimately achieved by this approach,” argues Celanovic [principal research scientist Ivan Celanovic]. There are other advantages of this approach: “An important feature is that our demonstrated device achieves near-ideal rendering of colors,” notes Ilic, referring to the requirement of light sources to faithfully reproduce surrounding colors. That is precisely the reason why incandescent lights remained dominant for so long: their warm light has remained preferable to drab fluorescent lighting for decades.

Some practical questions need to be addressed before this technology can be widely adopted. “We will work closely with our mechanical engineering colleagues at MIT to try to tackle the issues of thermal stability and long-lifetime,” says Soljačić. The authors are particularly excited about the potential for producing these devices cheaply. “The materials we need are abundant and inexpensive,” Joannopoulos [professor John Joannopoulos] notes, “and the filters themselves–consisting of stacks of commonly deposited materials–are amenable to large-scale deposition.”

Chen [professor Gang Chen] comments further: “The lighting potential of this technology is exciting, but the same approach could also be used to improve the performance of energy conversion schemes such as thermo-photovoltaics.” In a thermo-photovoltaic device, external heat causes the material to glow, emitting light that is converted into an electric current by an absorbing photovoltaic element.

The last point captures the main motivation behind the work. “Light radiated from a hot object can be quite useful, whether that object is an incandescent filament or the Sun,” Ilic says. At its core, this work is about recycling thermal light for a specific application; “a 3000-degree filament is one of the hottest and the most challenging sources to work with,” Ilic continues. “It’s also what makes it a crucial test of our approach.”

There are a few more details in the 2nd Jan. 11, 2016 MIT news release on EurekAlert,

Light recycling

The key is to create a two-stage process, the researchers report. The first stage involves a conventional heated metal filament, with all its attendant losses. But instead of allowing the waste heat to dissipate in the form of infrared radiation, secondary structures surrounding the filament capture this radiation and reflect it back to the filament to be re-absorbed and re-emitted as visible light. These structures, a form of photonic crystal, are made of Earth-abundant elements and can be made using conventional material-deposition technology.

That second step makes a dramatic difference in how efficiently the system converts light into electricity. The efficiency of conventional incandescent lights is between 2 and 3 percent, while that of fluorescents (including CFLs) is currently between 7 and 13 percent, and that of LEDs between 5 and 13 percent. In contrast, the new two-stage incandescents could reach efficiencies as high as 40 percent, the team says.

The first proof-of-concept units made by the team do not yet reach that level, achieving about 6.6 percent efficiency. But even that preliminary result matches the efficiency of some of today’s CFLs and LEDs, they point out. And it is already a threefold improvement over the efficiency of today’s incandescents.

The team refers to their approach as “light recycling,” says Ilic, since their material takes in the unwanted, useless wavelengths of energy and converts them into the visible light wavelengths that are desired. “It recycles the energy that would otherwise be wasted,” says Soljačić.

Bulbs and beyond

One key to their success was designing a photonic crystal that works for a very wide range of wavelengths and angles. The photonic crystal itself is made as a stack of thin layers, deposited on a substrate. “When you put together layers, with the right thicknesses and sequence,” Ilic explains, you can get very efficient tuning of how the material interacts with light. In their system, the desired visible wavelengths pass right through the material and on out of the bulb, but the infrared wavelengths get reflected as if from a mirror. They then travel back to the filament, adding more heat that then gets converted to more light. Since only the visible ever gets out, the heat just keeps bouncing back in toward the filament until it finally ends up as visible light.

I appreciate both MIT news release writers for “Thomas Edison patented the first commercially viable incandescent light bulb” (Rebusco) and the unidentified writer of the 2nd MIT news release for this, from the news release, “Incandescent bulbs, commercially developed by Thomas Edison (and still used by cartoonists as the symbol of inventive insight) … .” Edison did not invent the light bulb. BTW, the emphases are mine.

For interested parties, here’s a link to and a citation for the paper,

Tailoring high-temperature radiation and the resurrection of the incandescent source by Ognjen Ilic, Peter Bermel, Gang Chen, John D. Joannopoulos, Ivan Celanovic, & Marin Soljačić. Nature Nanotechnology  (2016) doi:10.1038/nnano.2015.309 Published online 11 January 2016

This paper is behind a paywall.