Tag Archives: US

More of the ‘blackest black’

There’s a very good November 11, 2019 article by Natalie Angier for the New York Times on carbon nanotubes (CNTs) and the colour black,

On a laboratory bench at the National Institute of Standards and Technology was a square tray with two black disks inside, each about the width of the top of a Dixie cup. Both disks were undeniably black, yet they didn’t look quite the same.

Solomon Woods, 49, a trim, dark-haired, soft-spoken physicist, was about to demonstrate how different they were, and how serenely voracious a black could be.

“The human eye is extraordinarily sensitive to light,” Dr. Woods said. Throw a few dozen photons its way, a few dozen quantum-sized packets of light, and the eye can readily track them.

Dr. Woods pulled a laser pointer from his pocket. “This pointer,” he said, “puts out 100 trillion photons per second.” He switched on the laser and began slowly sweeping its bright beam across the surface of the tray.

On hitting the white background, the light bounced back almost unimpeded, as rude as a glaring headlight in a rearview mirror.

The beam moved to the first black disk, a rondel of engineered carbon now more than a decade old. The light dimmed significantly, as a sizable tranche of the incident photons were absorbed by the black pigment, yet the glow remained surprisingly strong.

Finally Dr. Woods trained his pointer on the second black disk, and suddenly the laser’s brilliant beam, its brash photonic probe, simply — disappeared. Trillions of light particles were striking the black disk, and virtually none were winking back up again. It was like watching a circus performer swallow a sword, or a husband “share” your plate of French fries: Hey, where did it all go?

N.I.S.T. disk number two was an example of advanced ultra-black technology: elaborately engineered arrays of tiny carbon cylinders, or nanotubes, designed to capture and muzzle any light they encounter. Blacker is the new black, and researchers here and abroad are working to create ever more efficient light traps, which means fabricating materials that look ever darker, ever flatter, ever more ripped from the void.

The N.I.S.T. ultra-black absorbs at least 99.99 percent of the light that stumbles into its nanotube forest. But scientists at the Massachusetts Institute of Technology reported in September the creation of a carbon nanotube coating that they claim captures better than 99.995 of the incident light.

… The more fastidious and reliable the ultra-black, the more broadly useful it will prove to be — in solar power generators, radiometers, industrial baffles and telescopes primed to detect the faintest light fluxes as a distant planet traverses the face of its star.

Psychology and metaphors

It’s not all technical, Angier goes on to mention the psychological and metaphorical aspects,

Psychologists have gathered evidence that black is among the most metaphorically loaded of all colors, and that we absorb our often contradictory impressions about black at a young age.

Reporting earlier this year in the Quarterly Journal of Experimental Psychology, Robin Kramer and Joanne Prior of the University of Lincoln in the United Kingdom compared color associations in a group of 104 children, aged 5 to 10, with those of 100 university students.

The researchers showed subjects drawings in which a lineup of six otherwise identical images differed only in some aspect of color. The T-shirt of a boy taking a test, for example, was switched from black to blue to green to red to white to yellow. The same for a businessman’s necktie, a schoolgirl’s dress, a dog’s collar, a boxer’s gloves.

Participants were asked to link images with traits. Which boy was likeliest to cheat on the test? Which man was likely to be in charge at work? Which girl was the smartest in her class, which dog the scariest?

Again and again, among both children and young adults, black pulled ahead of nearly every color but red. Black was the color of cheating, and black was the color of cleverness. A black tie was the mark of a boss, a black collar the sign of a pit bull. Black was the color of strength and of winning. Black was the color of rage.

Art

Then, there is the world of art,

For artists, black is basal and nonnegotiable, the source of shadow, line, volume, perspective and mood. “There is a black which is old and a black which is fresh,” Ad Reinhardt, the abstract expressionist artist, said. “Lustrous black and dull black, black in sunlight and black in shadow.”

So essential is black to any aesthetic act that, as David Scott Kastan and Stephen Farthing describe in their scholarly yet highly entertaining book, “On Color,” modern artists have long squabbled over who pioneered the ultimate visual distillation: the all-black painting.

Was it the Russian Constructivist Aleksandr Rodchenko, who in 1918 created a series of eight seemingly all-black canvases? No, insisted the American artist Barnett Newman: Those works were very dark brown, not black. He, Mr. Newman, deserved credit for his 1949 opus, “Abraham,” which in 1966 he described as “the first and still the only black painting in history.”

But what about Kazimir Malevich’s “Black Square” of 1915? True, it was a black square against a white background, but the black part was the point. Then again, the English polymath Robert Fludd had engraved a black square in a white border back in 1617.

Clearly, said Alfred H. Barr, Jr., the first director of the Museum of Modern Art, “Each generation must paint its own black square.”

Structural colour

Solomon and his NIST colleagues and the MIT scientists are all trying to create materials with structural colour, in this case, black. Angier goes on to discuss structural colour in nature mentioning bird feathers and spiders as examples of where you might find superblacks. For anyone unfamiliar with structural colour, the colour is not achieved with pigment or dye but with tiny structures, usually measured at the nanoscale, on a bird’s wing, a spider’s belly, a plant leaf, etc. Structural colour does not fade or change . Still, it’s possible to destroy the structures, i.e., the colour, but light and time will not have any effect since it’s the tiny structures and their optical properties which are producing the colour . (Even after all these years, my favourite structural colour story remains a Feb. 1, 2013 article, Color from Structure, by Cristina Luiggi for The Scientist magazine. For a shorter version, I excerpted parts of Luiggi’s story for my February 7, 2013 posting.)

The examples of structural colour in Angier’s article were new to me. However, there are many, many examples elsewhere,. You can find some here by using the terms ‘structural colour’ or ‘structural color’ in the blog’s search engine.

Angier’s is a really good article and I strongly recommend reading it if you have time but I’m a little surprised she doesn’t mention Vantablack and the artistic feud. More about that in a moment,

Massachusetts Institute of Technology and a ‘blacker black’

According to MIT (Massachusetts Institute of Technology), they have the blackest black. It too is courtesy of carbon nanotubes.

The Redemption of Vanity, is a work of art by MIT artist in residence Diemut Strebe that has been realized together with Brian L. Wardle, Professor of Aeronautics and Astronautics and Director of necstlab and Nano- Engineered Composite aerospace STructures (NECST) Consortium and his team Drs. Luiz Acauan and Estelle Cohen. Strebe’s residency at MIT is supported by the Center for Art, Science & Technology (CAST). Image: Diemut Strebe

What you see in the above ‘The Redemption of Vanity’ was on show at the New York Stock Exchange (NYSE) from September 13 – November 29, 2019. It’s both an art piece and a demonstration of MIT’s blackest black.

There are two new releases from MIT. The first is the more technical one. From a Sept. 12, 2019 MIT news release,

With apologies to “Spinal Tap,” it appears that black can, indeed, get more black.

MIT engineers report today that they have cooked up a material that is 10 times blacker than anything that has previously been reported. The material is made from vertically aligned carbon nanotubes, or CNTs — microscopic filaments of carbon, like a fuzzy forest of tiny trees, that the team grew on a surface of chlorine-etched aluminum foil. The foil captures at least 99.995 percent* of any incoming light, making it the blackest material on record.

The researchers have published their findings today in the journal ACS-Applied Materials and Interfaces. They are also showcasing the cloak-like material as part of a new exhibit today at the New York Stock Exchange, titled “The Redemption of Vanity.”

The artwork, conceived by Diemut Strebe, an artist-in-residence at the MIT Center for Art, Science, and Technology, in collaboration with Brian Wardle, professor of aeronautics and astronautics at MIT, and his group, and MIT Center for Art, Science, and Technology artist-in-residence Diemut Strebe, features a 16.78-carat natural yellow diamond from LJ West Diamonds, estimated to be worth $2 million, which the team coated with the new, ultrablack CNT material. The effect is arresting: The gem, normally brilliantly faceted, appears as a flat, black void.

Wardle says the CNT material, aside from making an artistic statement, may also be of practical use, for instance in optical blinders that reduce unwanted glare, to help space telescopes spot orbiting exoplanets.

“There are optical and space science applications for very black materials, and of course, artists have been interested in black, going back well before the Renaissance,” Wardle says. “Our material is 10 times blacker than anything that’s ever been reported, but I think the blackest black is a constantly moving target. Someone will find a blacker material, and eventually we’ll understand all the underlying mechanisms, and will be able to properly engineer the ultimate black.”

Wardle’s co-author on the paper is former MIT postdoc Kehang Cui, now a professor at Shanghai Jiao Tong University.

Into the void

Wardle and Cui didn’t intend to engineer an ultrablack material. Instead, they were experimenting with ways to grow carbon nanotubes on electrically conducting materials such as aluminum, to boost their electrical and thermal properties.

But in attempting to grow CNTs on aluminum, Cui ran up against a barrier, literally: an ever-present layer of oxide that coats aluminum when it is exposed to air. This oxide layer acts as an insulator, blocking rather than conducting electricity and heat. As he cast about for ways to remove aluminum’s oxide layer, Cui found a solution in salt, or sodium chloride.

At the time, Wardle’s group was using salt and other pantry products, such as baking soda and detergent, to grow carbon nanotubes. In their tests with salt, Cui noticed that chloride ions were eating away at aluminum’s surface and dissolving its oxide layer.

“This etching process is common for many metals,” Cui says. “For instance, ships suffer from corrosion of chlorine-based ocean water. Now we’re using this process to our advantage.”

Cui found that if he soaked aluminum foil in saltwater, he could remove the oxide layer. He then transferred the foil to an oxygen-free environment to prevent reoxidation, and finally, placed the etched aluminum in an oven, where the group carried out techniques to grow carbon nanotubes via a process called chemical vapor deposition.

By removing the oxide layer, the researchers were able to grow carbon nanotubes on aluminum, at much lower temperatures than they otherwise would, by about 100 degrees Celsius. They also saw that the combination of CNTs on aluminum significantly enhanced the material’s thermal and electrical properties — a finding that they expected.

What surprised them was the material’s color.

“I remember noticing how black it was before growing carbon nanotubes on it, and then after growth, it looked even darker,” Cui recalls. “So I thought I should measure the optical reflectance of the sample.

“Our group does not usually focus on optical properties of materials, but this work was going on at the same time as our art-science collaborations with Diemut, so art influenced science in this case,” says Wardle.

Wardle and Cui, who have applied for a patent on the technology, are making the new CNT process freely available to any artist to use for a noncommercial art project.

“Built to take abuse”

Cui measured the amount of light reflected by the material, not just from directly overhead, but also from every other possible angle. The results showed that the material absorbed at least 99.995 percent of incoming light, from every angle. In other words, it reflected 10 times less light than all other superblack materials, including Vantablack. If the material contained bumps or ridges, or features of any kind, no matter what angle it was viewed from, these features would be invisible, obscured in a void of black.  

The researchers aren’t entirely sure of the mechanism contributing to the material’s opacity, but they suspect that it may have something to do with the combination of etched aluminum, which is somewhat blackened, with the carbon nanotubes. Scientists believe that forests of carbon nanotubes can trap and convert most incoming light to heat, reflecting very little of it back out as light, thereby giving CNTs a particularly black shade.

“CNT forests of different varieties are known to be extremely black, but there is a lack of mechanistic understanding as to why this material is the blackest. That needs further study,” Wardle says.

The material is already gaining interest in the aerospace community. Astrophysicist and Nobel laureate John Mather, who was not involved in the research, is exploring the possibility of using Wardle’s material as the basis for a star shade — a massive black shade that would shield a space telescope from stray light.

“Optical instruments like cameras and telescopes have to get rid of unwanted glare, so you can see what you want to see,” Mather says. “Would you like to see an Earth orbiting another star? We need something very black. … And this black has to be tough to withstand a rocket launch. Old versions were fragile forests of fur, but these are more like pot scrubbers — built to take abuse.”

[Note] An earlier version of this story stated that the new material captures more than 99.96 percent of incoming light. That number has been updated to be more precise; the material absorbs at least 99.995 of incoming light.

Here’s an August 29, 2019 news release from MIT announcing the then upcoming show. Usually I’d expect to see a research paper associated with this work but this time it seems to an art exhibit only,

The MIT Center for Art, Science &Technology (CAST) and the New York Stock Exchange (NYSE) will present The Redemption of Vanity,created by artist Diemut Strebe in collaboration with MIT scientist Brian Wardle and his lab, on view at the New York Stock Exchange September 13, 2019 -November 25, 2019. For the work, a 16.78 carat natural yellow diamond valued at $2 million from L.J.West was coated using a new procedure of generating carbon nanotubes (CNTs), recently measured to be the blackest black ever created, which makes the diamond seem to disappear into an invisible void. The patented carbon nanotube technology (CNT) absorbs more than 99.96% of light and was developed by Professor Wardle and his necstlablab at MIT.

“Any object covered with this CNT material loses all its plasticity and appears entirely flat, abbreviated/reduced to a black silhouette. In outright contradiction to this we see that a diamond,while made of the very same element (carbon) performs the most intense reflection of light on earth.Because of the extremely high light absorbtive qualities of the CNTs, any object, in this case a large diamond coated with CNT’s, becomes a kind of black hole absent of shadows,“ explains Strebe.“The unification of extreme opposites in one object and the particular aesthetic features of the CNTs caught my imagination for this art project.”

“Strebe’s art-science collaboration caused us to look at the optical properties of our new CNT growth, and we discovered that these particular CNTs are blacker than all other reported materials by an order of magnitude across the visible spectrum”, says Wardle. The MIT team is offering the process for any artist to use. “We do not believe in exclusive ownership of any material or idea for any artwork and have opened our method to any artist,” say Strebe and Wardle.“

The project explores material and immaterial value attached to objects and concepts in reference to luxury, society and to art. We are presenting the literal devaluation of a diamond, which is highly symbolic and of high economic value.It presents a challenge to art market mechanisms on the one hand, while expressing at the same time questions of the value of art in a broader way. In this sense it manifests an inquiry into the significance of the value of objects of art and the art market,” says Strebe. “We are honored to present this work at The New York Stock Exchange, which I believe to be a most fitting location to consider the ideas embedded in The Redemption of Vanity.”

“The New York Stock Exchange, a center of financial and technological innovation for 227 years, is the perfect venue to display Diemut Strebe and Professor Brian Wardle’s collaboration. Their work brings together cutting-edge nanotube technology and a natural diamond, which is a symbol of both value and longevity,” said John Tuttle, NYSE Group Vice Chairman & Chief Commercial Officer.

“We welcome all scientists and artists to venture into the world of natural color diamonds. The Redemption of Vanity exemplifies the bond between art, science, and luxury. The 16-carat vivid yellow diamond in the exhibit spent millions of years in complete darkness, deep below the earth’s surface. It was only recently unearthed —a once-in-a-lifetime discovery of exquisite size and color. Now the diamond will relive its journey to darkness as it is covered in the blackest of materials. Once again, it will become a reminder that something rare and beautiful can exist even in darkness,”said Larry West.

The “disappearing” diamond in The Redemption of Vanity is a $2 Million Fancy Vivid Yellow SI1 (GIA), Radiant shape, from color diamond specialist, L.J. West Diamonds Inc. of New York.

The Redemption of Vanity, conceived by Diemut Strebe, has been realized with Brian L. Wardle, Professor of Aeronautics and Astronautics and Director of necstlab and Nano-Engineered Composite aerospace STructures (NECST) Consortium and his team Drs. Luiz Acauan and Estelle Cohen, in conjunction with Strebe’s residency at MIT supported by the Center for Art, Science & Technology (CAST).

ABOUT THE ARTISTS

Diemut Strebe is a conceptual artist based in Boston, MA and a MIT CAST Visiting Artist. She has collaborated with several MIT faculty, including Noam Chomsky and Robert Langer on Sugababe (2014), Litmus (2014) and Yeast Expression(2015); Seth Lloyd and Dirk Englund on Wigner’s Friends(2014); Alan Guth on Plötzlich! (2018); researchers in William Tisdale’s Lab on The Origin of the Works of Art(2018); Regina Barzilay and Elchanan Mossel on The Prayer (2019); and Ken Kamrin and John Brisson on The Gymnast (2019). Strebe is represented by the Ronald Feldman Gallery.

Brian L. Wardle is a Professor of Aeronautics and Astronautics at MIT and the director of the necstlab research group and MIT’s Nano-Engineered Composite aerospace STructures (NECST) Consortium. Wardle previously worked with CAST Visiting Artist Trevor Paglen on The Last Picturesproject (2012).

ABOUT THE MIT CENTER FOR ART, SCIENCE & TECHNOLOGY

A major cross-school initiative, the MIT Center for Art, Science & Technology (CAST) creates new opportunities for art, science and technology to thrive as interrelated, mutually informing modes of exploration, knowledge and discovery. CAST’s multidisciplinary platform presents performing and visual arts programs, supports research projects for artists working with science and engineering labs, and sponsors symposia, classes, workshops, design studios, lectures and publications. The Center is funded in part by a generous grant from the Andrew W. Mellon Foundation. Evan Ziporyn is the Faculty Director and Leila W. Kinney is the Executive Director.Since its inception in 2012, CAST has been the catalyst for more than 150 artist residencies and collaborative projects with MIT faculty and students, including numerous cross-disciplinary courses, workshops, concert series, multimedia projects, lectures and symposia. The visiting artists program is a cornerstone of CAST’s activities, which encourages cross-fertilization among disciplines and intensive interaction with MIT’s faculty and students. More info at https://arts.mit.edu/cast/ .

HISTORY OF VISITING ARTISTS AT MIT

Since the late 1960s, MIT has been a leader in integrating the arts and pioneering a model for collaboration among artists, scientists and engineers in a research setting. CAST’s Visiting Artists Program brings internationally acclaimed artists to engage with MIT’s creative community in ways that are mutually enlightening for the artists and for faculty, students and research staff at the Institute. Artists who have worked extensively at MIT include Mel Chin, Olafur Eliasson, Rick Lowe, Vik Muniz, Trevor Paglen, Tomás Saraceno, Maya Beiser, Agnieszka Kurant, and Anicka Yi.

ABOUT L.J. WEST DIAMONDS

L.J. West Diamonds is a three generation natural color diamond whole sale rfounded in the late 1970’s by Larry J. West and based in New York City. L.J. West has established itself as one of the world’s prominent houses for some of the most rare and important exotic natural fancy color diamonds to have ever been unearthed. This collection includes a vast color spectrum of rare pink, blue, yellow, green, orange and red diamonds. L.J. West is an expert in every phase of the jewelry process –from sourcing to the cutting, polishing and final design. Each exceptional jewel is carefully set to become a unique work of art.The Redemption of Vanity is on view at the New York Stock Exchange by appointment only.

Press viewing: September 13, 2019 at 3pmNew York Stock Exchange, 11 Wall Street, New York, NY 10005RSVP required. Please check-in at the blue tent at 2 Broad Street(at the corner of Wall and Broad Streets). All guests are required to show a government issued photo ID and go through airport-like security upon entering the NYSE.NYSE follows a business casual dress code -jeans & sneakers are not permitted.

No word yet if there will be other showings.

An artistic feud (of sorts)

Earlier this year, I updated a story on Vantablack. It was the blackest black, blocking 99.8% of light when I featured it in a March 14, 2016 posting. The UK company making the announcement, Surrey NanoSystems, then laid the groundwork for an artistic feud when it granted exclusive rights to their carbon nanotube-based coating, Vantablack, to Sir Anish Kapoor mentioned here in an April 16, 2016 posting.

This exclusivity outraged some artists notably, Stuart Semple. In his first act of defiance, he created the pinkest pink. Next, came a Kickstarter campaign to fund Semple’s blackest black, which would be available to all artists except Anish Kapoor. You can read all about the pinkest pink and blackest black as per Semple in my February 21, 2019 posting. You can also get a bit of an update in an Oct. 17, 2019 Stuart Semple proffile by Berenice Baker for Verdict,

… so I managed to hire a scientist, Jemima, to work in the studio with me. She got really close to a super black, and we made our own pigment to this recipe and it was awesome, but we couldn’t afford to put it into manufacture because it cost £25,000.”

Semple launched a Kickstarter campaign and was amazed to raise half a million pounds, making it the second most-supported art Kickstarter of all time.

The ‘race to the blackest’ is well underway, with MIT researchers recently announcing a carbon nanotube-based black whose light absorption they tested by coasting a diamond. But Semple is determined that his black should be affordable by all artists and work like a paint, not only perform in laboratory conditions. He’s currently working with Jemima and two chemists to upgrade the recipe for Black 3.2.

I don’t know how Semple arrived at his blackest black. I think it’s unlikely that he achieved the result by working with carbon nanotubes since my understanding is that CNTs aren’t that easy to produce.

Finally

Interesting, eh? In just a few years scientists have progressed from achieving a 99.8% black to 99.999%. It doesn’t seem like that big a difference to me but with Solomon Woods, at the beginning of this post, making the point that our eyes are very sensitive to light, an artistic feud, and a study uncovering deep emotions, getting the blackest black is a much more artistically fraught endeavour than I had imagined.

Human-machine interfaces and ultra-small nanoprobes

We’re back on the cyborg trail or what I sometimes refer to as machine/flesh. A July 3, 2019 news item on ScienceDaily describes the latest attempts to join machine with flesh,

Machine enhanced humans — or cyborgs as they are known in science fiction — could be one step closer to becoming a reality, thanks to new research Lieber Group at Harvard University, as well as scientists from University of Surrey and Yonsei University.

Researchers have conquered the monumental task of manufacturing scalable nanoprobe arrays small enough to record the inner workings of human cardiac cells and primary neurons.

The ability to read electrical activities from cells is the foundation of many biomedical procedures, such as brain activity mapping and neural prosthetics. Developing new tools for intracellular electrophysiology (the electric current running within cells) that push the limits of what is physically possible (spatiotemporal resolution) while reducing invasiveness could provide a deeper understanding of electrogenic cells and their networks in tissues, as well as new directions for human-machine interfaces.

The Lieber Group at Harvard University provided this image illustrating the work,

U-shaped nanowires can record electrical chatter inside a brain or heart cell without causing any damage. The devices are 100 times smaller than their biggest competitors, which kill a cell after recording. Courtesy: University of Surrey

A July 3, 2019 University of Surrey press release (also on EurekAlert), which originated the news item, provides more details about this UK/US/China collaboration,

In a paper published by Nature Nanotechnology, scientists from Surrey’s Advanced Technology Institute (ATI) and Harvard University detail how they produced an array of the ultra-small U-shaped nanowire field-effect transistor probes for intracellular recording. This incredibly small structure was used to record, with great clarity, the inner activity of primary neurons and other electrogenic cells, and the device has the capacity for multi-channel recordings.

Dr Yunlong Zhao from the ATI at the University of Surrey said: “If our medical professionals are to continue to understand our physical condition better and help us live longer, it is important that we continue to push the boundaries of modern science in order to give them the best possible tools to do their jobs. For this to be possible, an intersection between humans and machines is inevitable.

“Our ultra-small, flexible, nanowire probes could be a very powerful tool as they can measure intracellular signals with amplitudes comparable with those measured with patch clamp techniques; with the advantage of the device being scalable, it causes less discomfort and no fatal damage to the cell (cytosol dilation). Through this work, we found clear evidence for how both size and curvature affect device internalisation and intracellular recording signal.”

Professor Charles Lieber from the Department of Chemistry and Chemical Biology at Harvard University said: “This work represents a major step towards tackling the general problem of integrating ‘synthesised’ nanoscale building blocks into chip and wafer scale arrays, and thereby allowing us to address the long-standing challenge of scalable intracellular recording.

“The beauty of science to many, ourselves included, is having such challenges to drive hypotheses and future work. In the longer term, we see these probe developments adding to our capabilities that ultimately drive advanced high-resolution brain-machine interfaces and perhaps eventually bringing cyborgs to reality.”

Professor Ravi Silva, Director of the ATI at the University of Surrey, said: “This incredibly exciting and ambitious piece of work illustrates the value of academic collaboration. Along with the possibility of upgrading the tools we use to monitor cells, this work has laid the foundations for machine and human interfaces that could improve lives across the world.”

Dr Yunlong Zhao and his team are currently working on novel energy storage devices, electrochemical probing, bioelectronic devices, sensors and 3D soft electronic systems. Undergraduate, graduate and postdoc students with backgrounds in energy storage, electrochemistry, nanofabrication, bioelectronics, tissue engineering are very welcome to contact Dr Zhao to explore the opportunities further.

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

Scalable ultrasmall three-dimensional nanowire transistor probes for intracellular recording by Yunlong Zhao, Siheng Sean You, Anqi Zhang, Jae-Hyun Lee, Jinlin Huang & Charles M. Lieber. Nature Nanotechnology (2019) DOI: https://doi.org/10.1038/s41565-019-0478-y Published 01 July 2019

The link I’ve provided leads to a paywall. However, I found a freely accessible version of the paper (this may not be the final published version) here.

Bacteria and graphene oxide as a basis for producing computers

A July 10, 2019 news item on ScienceDaily announces a more environmentally friendly way to produce graphene leading to more environmentally friendly devices such as computers,

In order to create new and more efficient computers, medical devices, and other advanced technologies, researchers are turning to nanomaterials: materials manipulated on the scale of atoms or molecules that exhibit unique properties.

Graphene — a flake of carbon as thin as a single later of atoms — is a revolutionary nanomaterial due to its ability to easily conduct electricity, as well as its extraordinary mechanical strength and flexibility. However, a major hurdle in adopting it for everyday applications is producing graphene at a large scale, while still retaining its amazing properties.

In a paper published in the journal ChemOpen, Anne S. Meyer, an associate professor of biology at the University of Rochester [New York state, US], and her colleagues at Delft University of Technology in the Netherlands, describe a way to overcome this barrier. The researchers outline their method to produce graphene materials using a novel technique: mixing oxidized graphite with bacteria. Their method is a more cost-efficient, time-saving, and environmentally friendly way of producing graphene materials versus those produced chemically, and could lead to the creation of innovative computer technologies and medical equipment.

A July 10, 2019 University of Rochester news release (also on EurekAlert), which originated the news item, provides details as to how this new technique for extracting graphene differs from the technique currently used,

Graphene is extracted from graphite, the material found in an ordinary pencil. At exactly one atom thick, graphene is the thinnest–yet strongest–two-dimensional material known to researchers. Scientists from the University of Manchester in the United Kingdom were awarded the 2010 Nobel Prize in Physics for their discovery of graphene; however, their method of using sticky tape to make graphene yielded only small amounts of the material.

“For real applications you need large amounts,” Meyer says. “Producing these bulk amounts is challenging and typically results in graphene that is thicker and less pure. This is where our work came in.”

In order to produce larger quantities of graphene materials, Meyer and her colleagues started with a vial of graphite. They exfoliated the graphite–shedding the layers of material–to produce graphene oxide (GO), which they then mixed with the bacteria Shewanella. They let the beaker of bacteria and precursor materials sit overnight, during which time the bacteria reduced the GO to a graphene material.

“Graphene oxide is easy to produce, but it is not very conductive due to all of the oxygen groups in it,” Meyer says. “The bacteria remove most of the oxygen groups, which turns it into a conductive material.”

While the bacterially-produced graphene material created in Meyer’s lab is conductive, it is also thinner and more stable than graphene produced chemically. It can additionally be stored for longer periods of time, making it well suited for a variety of applications, including field-effect transistor (FET) biosensors and conducting ink. FET biosensors are devices that detect biological molecules and could be used to perform, for example, real-time glucose monitoring for diabetics.

“When biological molecules bind to the device, they change the conductance of the surface, sending a signal that the molecule is present,” Meyer says. “To make a good FET biosensor you want a material that is highly conductive but can also be modified to bind to specific molecules.” Graphene oxide that has been reduced is an ideal material because it is lightweight and very conductive, but it typically retains a small number of oxygen groups that can be used to bind to the molecules of interest.

The bacterially produced graphene material could also be the basis for conductive inks, which could, in turn, be used to make faster and more efficient computer keyboards, circuit boards, or small wires such as those used to defrost car windshields. Using conductive inks is an “easier, more economical way to produce electrical circuits, compared to traditional techniques,” Meyer says. Conductive inks could also be used to produce electrical circuits on top of nontraditional materials like fabric or paper.

“Our bacterially produced graphene material will lead to far better suitability for product development,” Meyer says. “We were even able to develop a technique of ‘bacterial lithography’ to create graphene materials that were only conductive on one side, which can lead to the development of new, advanced nanocomposite materials.”

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

Creation of Conductive Graphene Materials by Bacterial Reduction Using Shewanella Oneidensis by Benjamin A. E. Lehner, Vera A. E. C. Janssen, Dr. Ewa M. Spiesz, Dominik Benz, Dr. Stan J. J. Brouns, Dr. Anne S. Meyer, Prof. Dr. Herre S. J. van der Zant. ChemistryOpen Volume 8, Issue 7 July 2019 Pages 888-895 DOI: https://doi.org/10.1002/open.201900186
First published: 04 July 2019

As you would expect given the journal’s title, this paper is open access.

Smartphone as augmented reality system with software from Brown University

You need to see this,

Amazing, eh? The researchers are scheduled to present this work sometime this week at the ACM Symposium on User Interface Software and Technology (UIST) being held in New Orleans, US, from October 20-23, 2019.

Here’s more about ‘Portal-ble’ in an October 16, 2019 news item on ScienceDaily,

A new software system developed by Brown University [US] researchers turns cell phones into augmented reality portals, enabling users to place virtual building blocks, furniture and other objects into real-world backdrops, and use their hands to manipulate those objects as if they were really there.

The developers hope the new system, called Portal-ble, could be a tool for artists, designers, game developers and others to experiment with augmented reality (AR). The team will present the work later this month at the ACM Symposium on User Interface Software and Technology (UIST 2019) in New Orleans. The source code for Andriod is freely available for download on the researchers’ website, and iPhone code will follow soon.

“AR is going to be a great new mode of interaction,” said Jeff Huang, an assistant professor of computer science at Brown who developed the system with his students. “We wanted to make something that made AR portable so that people could use anywhere without any bulky headsets. We also wanted people to be able to interact with the virtual world in a natural way using their hands.”

An October 16, 2019 Brown University news release (also on EurekAlert), which originated the news item, provides more detail,

Huang said the idea for Portal-ble’s “hands-on” interaction grew out of some frustration with AR apps like Pokemon GO. AR apps use smartphones to place virtual objects (like Pokemon characters) into real-world scenes, but interacting with those objects requires users to swipe on the screen.

“Swiping just wasn’t a satisfying way of interacting,” Huang said. “In the real world, we interact with objects with our hands. We turn doorknobs, pick things up and throw things. So we thought manipulating virtual objects by hand would be much more powerful than swiping. That’s what’s different about Portal-ble.”

The platform makes use of a small infrared sensor mounted on the back of a phone. The sensor tracks the position of people’s hands in relation to virtual objects, enabling users to pick objects up, turn them, stack them or drop them. It also lets people use their hands to virtually “paint” onto real-world backdrops. As a demonstration, Huang and his students used the system to paint a virtual garden into a green space on Brown’s College Hill campus.

Huang says the main technical contribution of the work was developing the right accommodations and feedback tools to enable people to interact intuitively with virtual objects.

“It turns out that picking up a virtual object is really hard if you try to apply real-world physics,” Huang said. “People try to grab in the wrong place, or they put their fingers through the objects. So we had to observe how people tried to interact with these objects and then make our system able accommodate those tendencies.”

To do that, Huang enlisted students in a class he was teaching to come up with tasks they might want to do in the AR world — stacking a set of blocks, for example. The students then asked other people to try performing those tasks using Portal-ble, while recording what people were able to do and what they couldn’t. They could then adjust the system’s physics and user interface to make interactions more successful.

“It’s a little like what happens when people draw lines in Photoshop,” Huang said. “The lines people draw are never perfect, but the program can smooth them out and make them perfectly straight. Those were the kinds of accommodations we were trying to make with these virtual objects.”

The team also added sensory feedback — visual highlights on objects and phone vibrations — to make interactions easier. Huang said he was somewhat surprised that phone vibrations helped users to interact. Users feel the vibrations in the hand they’re using to hold the phone, not in the hand that’s actually grabbing for the virtual object. Still, Huang said, vibration feedback still helped users to more successfully interact with objects.

In follow-up studies, users reported that the accommodations and feedback used by the system made tasks significantly easier, less time-consuming and more satisfying.

Huang and his students plan to continue working with Portal-ble — expanding its object library, refining interactions and developing new activities. They also hope to streamline the system to make it run entirely on a phone. Currently the infrared sensor requires an infrared sensor and external compute stick for extra processing power.

Huang hopes people will download the freely available source code and try it for themselves. 
“We really just want to put this out there and see what people do with it,” he said. “The code is on our website for people to download, edit and build off of. It will be interesting to see what people do with it.

Co-authors on the research paper were Jing Qian, Jiaju Ma, Xiangyu Li, Benjamin Attal, Haoming Lai, James Tompkin and John Hughes. The work was supported by the National Science Foundation (IIS-1552663) and by a gift from Pixar.

You can find the conference paper here on jeffhuang.com,

Portal-ble: Intuitive Free-hand Manipulationin Unbounded Smartphone-based Augmented Reality by Jing Qian, Jiaju Ma, Xiangyu Li∗, Benjamin Attal, Haoming Lai,James Tompkin, John F. Hughes, Jeff Huang. Brown University, Providence RI, USA; Southeast University, Nanjing, China. Presented at ACM Symposium on User Interface Software and Technology (UIST) being held in New Orleans, US

This is the first time I’ve seen an augmented reality system that seems accessible, i.e., affordable. You can find out more on the Portal-ble ‘resource’ page where you’ll also find a link to the source code repository. The researchers, as noted in the news release, have an Android version available now with an iPhone version to be released in the future.

Monitoring forest soundscapes for conservation and more about whale songs

I don’t understand why anyone would publicize science work featuring soundscapes without including an audio file. However, no one from Princeton University (US) phoned and asked for my advice :).

On the plus side, my whale story does have a sample audio file. However, I’m not sure if I can figure out how to embed it here.

Princeton and monitoring forests

In addition to a professor from Princeton University, there’s the founder of an environmental news organization and someone who’s both a professor at the University of Queensland (Australia) and affiliated with the Nature Conservancy making this of the more unusual collaborations I’ve seen.

Moving on to the news, a January 4, 2019 Princeton University news release (also on EurekAlert but published on Jan. 3, 2019) by B. Rose Kelly announces research into monitoring forests,

Recordings of the sounds in tropical forests could unlock secrets about biodiversity and aid conservation efforts around the world, according to a perspective paper published in Science.

Compared to on-the-ground fieldwork, bioacoustics –recording entire soundscapes, including animal and human activity — is relatively inexpensive and produces powerful conservation insights. The result is troves of ecological data in a short amount of time.

Because these enormous datasets require robust computational power, the researchers argue that a global organization should be created to host an acoustic platform that produces on-the-fly analysis. Not only could the data be used for academic research, but it could also monitor conservation policies and strategies employed by companies around the world.

“Nongovernmental organizations and the conservation community need to be able to truly evaluate the effectiveness of conservation interventions. It’s in the interest of certification bodies to harness the developments in bioacoustics for better enforcement and effective measurements,” said Zuzana Burivalova, a postdoctoral research fellow in Professor David Wilcove’s lab at Princeton University’s Woodrow Wilson School of Public and International Affairs.

“Beyond measuring the effectiveness of conservation projects and monitoring compliance with forest protection commitments, networked bioacoustic monitoring systems could also generate a wealth of data for the scientific community,” said co-author Rhett Butler of the environmental news outlet Mongabay.

Burivalova and Butler co-authored the paper with Edward Game, who is based at the Nature Conservancy and the University of Queensland.

The researchers explain that while satellite imagery can be used to measure deforestation, it often fails to detect other subtle ecological degradations like overhunting, fires, or invasion by exotic species. Another common measure of biodiversity is field surveys, but those are often expensive, time consuming and cover limited ground.

Depending on the vegetation of the area and the animals living there, bioacoustics can record animal sounds and songs from several hundred meters away. Devices can be programmed to record at specific times or continuously if there is solar polar or a cellular network signal. They can also record a range of taxonomic groups including birds, mammals, insects, and amphibians. To date, several multiyear recordings have already been completed.

Bioacoustics can help effectively enforce policy efforts as well. Many companies are engaged in zero-deforestation efforts, which means they are legally obligated to produce goods without clearing large forests. Bioacoustics can quickly and cheaply determine how much forest has been left standing.

“Companies are adopting zero deforestation commitments, but these policies do not always translate to protecting biodiversity due to hunting, habitat degradation, and sub-canopy fires. Bioacoustic monitoring could be used to augment satellites and other systems to monitor compliance with these commitments, support real-time action against prohibited activities like illegal logging and poaching, and potentially document habitat and species recovery,” Butler said.

Further, these recordings can be used to measure climate change effects. While the sounds might not be able to assess slow, gradual changes, they could help determine the influence of abrupt, quick differences to land caused by manufacturing or hunting, for example.

Burivalova and Game have worked together previously as you can see in a July 24, 2017 article by Justine E. Hausheer for a nature.org blog ‘Cool Green Science’ (Note: Links have been removed),

Morning in Musiamunat village. Across the river and up a steep mountainside, birds-of-paradise call raucously through the rainforest canopy, adding their calls to the nearly deafening insect chorus. Less than a kilometer away, small birds flit through a grove of banana trees, taro and pumpkin vines winding across the rough clearing. Here too, the cicadas howl.

To the ear, both garden and forest are awash with noise. But hidden within this dawn chorus are clues to the forest’s health.

New acoustic research from Nature Conservancy scientists indicates that forest fragmentation drives distinct changes in the dawn and dusk choruses of forests in Papua New Guinea. And this innovative method can help evaluate the conservation benefits of land-use planning efforts with local communities, reducing the cost of biodiversity monitoring in the rugged tropics.

“It’s one thing for a community to say that they cut fewer trees, or restricted hunting, or set aside a protected area, but it’s very difficult for small groups to demonstrate the effectiveness of those efforts,” says Eddie Game, The Nature Conservancy’s lead scientist for the Asia-Pacific region.

Aside from the ever-present logging and oil palm, another threat to PNG’s forests is subsistence agriculture, which feeds a majority of the population. In the late 1990s, The Nature Conservancy worked with 11 communities in the Adelbert Mountains to create land-use plans, dividing each community’s lands into different zones for hunting, gardening, extracting forest products, village development, and conservation. The goal was to limit degradation to specific areas of the forest, while keeping the rest intact.

But both communities and conservationists needed a way to evaluate their efforts, before the national government considered expanding the program beyond Madang province. So in July 2015, Game and two other scientists, Zuzana Burivalova and Timothy Boucher, spent two weeks gathering data in the Adelbert Mountains, a rugged lowland mountain range in Papua New Guinea’s Madang province.

Working with conservation rangers from Musiamunat, Yavera, and Iwarame communities, the research team tested an innovative method — acoustic sampling — to measure biodiversity across the community forests. Game and his team used small acoustic recorders placed throughout the forest to record 24-hours of sound from locations in each of the different land zones.

Soundscapes from healthy, biodiverse forests are more complex, so the scientists hoped that these recordings would show if parts of the community forests, like the conservation zones, were more biodiverse than others. “Acoustic recordings won’t pick up every species, but we don’t need that level of detail to know if a forest is healthy,” explains Boucher, a conservation geographer with the Conservancy.

Here’s a link to and a citation for the latest work from Burivalova and Game,

The sound of a tropical forest by Zuzana Burivalova, Edward T. Game, Rhett A. Butler. Science 04 Jan 2019: Vol. 363, Issue 6422, pp. 28-29 DOI: 10.1126/science.aav1902

This paper is behind a paywall. You can find out more about Mongabay and Rhett Butler in its Wikipedia entry.

***ETA July 18, 2019: Cara Cannon Byington, Associate Director, Science Communications for the Nature Conservancy emailed to say that a January 3, 2019 posting on the conservancy’s Cool Green Science Blog features audio files from the research published in ‘The sound of a tropical forest. Scroll down about 75% of the way for the audio.***

Whale songs

Whales share songs when they meet and a January 8, 2019 Wildlife Conservation Society news release (also on EurekAlert) describes how that sharing takes place,

Singing humpback whales from different ocean basins seem to be picking up musical ideas from afar, and incorporating these new phrases and themes into the latest song, according to a newly published study in Royal Society Open Science that’s helping scientists better understand how whales learn and change their musical compositions.

The new research shows that two humpback whale populations in different ocean basins (the South Atlantic and Indian Oceans) in the Southern Hemisphere sing similar song types, but the amount of similarity differs across years. This suggests that males from these two populations come into contact at some point in the year to hear and learn songs from each other.

The study titled “Culturally transmitted song exchange between humpback whales (Megaptera novaeangliae) in the southeast Atlantic and southwest Indian Ocean basins” appears in the latest edition of the Royal Society Open Science journal. The authors are: Melinda L. Rekdahl, Carissa D. King, Tim Collins, and Howard Rosenbaum of WCS (Wildlife Conservation Society); Ellen C. Garland of the University of St. Andrews; Gabriella A. Carvajal of WCS and Stony Brook University; and Yvette Razafindrakoto of COSAP [ (Committee for the Management of the Protected Area of Bezà Mahafaly ] and Madagascar National Parks.

“Song sharing between populations tends to happen more in the Northern Hemisphere where there are fewer physical barriers to movement of individuals between populations on the breeding grounds, where they do the majority of their singing. In some populations in the Southern Hemisphere song sharing appears to be more complex, with little song similarity within years but entire songs can spread to neighboring populations leading to song similarity across years,” said Dr. Melinda Rekdahl, marine conservation scientist for WCS’s Ocean Giants Program and lead author of the study. “Our study shows that this is not always the case in Southern Hemisphere populations, with similarities between both ocean basin songs occurring within years to different degrees over a 5-year period.”

The study authors examined humpback whale song recordings from both sides of the African continent–from animals off the coasts of Gabon and Madagascar respectively–and transcribed more than 1,500 individual sounds that were recorded between 2001-2005. Song similarity was quantified using statistical methods.

Male humpback whales are one of the animal kingdom’s most noteworthy singers, and individual animals sing complex compositions consisting of moans, cries, and other vocalizations called “song units.” Song units are composed into larger phrases, which are repeated to form “themes.” Different themes are produced in a sequence to form a song cycle that are then repeated for hours, or even days. For the most part, all males within the same population sing the same song type, and this population-wide song similarity is maintained despite continual evolution or change to the song leading to seasonal “hit songs.” Some song learning can occur between populations that are in close proximity and may be able to hear the other population’s song.

Over time, the researchers detected shared phrases and themes in both populations, with some years exhibiting more similarities than others. In the beginning of the study, whale populations in both locations shared five “themes.” One of the shared themes, however, had differences. Gabon’s version of Theme 1, the researchers found, consisted of a descending “cry-woop”, whereas the Madagascar singers split Theme 1 into two parts: a descending cry followed by a separate woop or “trumpet.”

Other differences soon emerged over time. By 2003, the song sung by whales in Gabon became more elaborate than their counterparts in Madagascar. In 2004, both population song types shared the same themes, with the whales in Gabon’s waters singing three additional themes. Interestingly, both whale groups had dropped the same two themes from the previous year’s song types. By 2005, songs being sung on both sides of Africa were largely similar, with individuals in both locations singing songs with the same themes and order. However, there were exceptions, including one whale that revived two discontinued themes from the previous year.

The study’s results stands in contrast to other research in which a song in one part of an ocean basin replaces or “revolutionizes” another population’s song preference. In this instance, the gradual changes and degrees of similarity shared by humpbacks on both sides of Africa was more gradual and subtle.

“Studies such as this one are an important means of understanding connectivity between different whale populations and how they move between different seascapes,” said Dr. Howard Rosenbaum, Director of WCS’s Ocean Giants Program and one of the co-authors of the new paper. “Insights on how different populations interact with one another and the factors that drive the movements of these animals can lead to more effective plans for conservation.”

The humpback whale is one of the world’s best-studied marine mammal species, well known for its boisterous surface behavior and migrations stretching thousands of miles. The animal grows up to 50 feet in length and has been globally protected from commercial whaling since the 1960s. WCS has studied humpback whales since that time and–as the New York Zoological Society–played a key role in the discovery that humpback whales sing songs. The organization continues to study humpback whale populations around the world and right here in the waters of New York; research efforts on humpback and other whales in New York Bight are currently coordinated through the New York Aquarium’s New York Seascape program.

I’m not able to embed the audio file here but, for the curious, there is a portion of a humpback whale song from Gabon here at EurekAlert.

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

Culturally transmitted song exchange between humpback whales (Megaptera novaeangliae) in the southeast Atlantic and southwest Indian Ocean basins by Melinda L. Rekdahl, Ellen C. Garland, Gabriella A. Carvajal, Carissa D. King, Tim Collins, Yvette Razafindrakoto and Howard Rosenbaum. Royal Society Open Science 21 November 2018 Volume 5 Issue 11 https://doi.org/10.1098/rsos.172305 Published:28 November 2018

This is an open access paper.

Ouchies no more! Not from bandages, anyway.

An adhesive that US and Chinese scientists have developed shows great promise not just for bandages but wearable robotics too. From a December 14, 2018 news item on Nanowerk,

Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and Xi’an Jiaotong University in China have developed a new type of adhesive that can strongly adhere wet materials — such as hydrogel and living tissue — and be easily detached with a specific frequency of light.

The adhesives could be used to attach and painlessly detach wound dressings, transdermal drug delivery devices, and wearable robotics.

A December 18, 2018 SEAS news release by Leah Burrows (also on EurekAlert but published Dec. 14, 2018), which originated the news item, delves further,

“Strong adhesion usually requires covalent bonds, physical interactions, or a combination of both,” said Yang Gao, first author of the paper and researcher at Xi’an Jiaotong University. “Adhesion through covalent bonds is hard to remove and adhesion through physical interactions usually requires solvents, which can be time-consuming and environmentally harmful. Our method of using light to trigger detachment is non-invasive and painless.”

The adhesive uses an aqueous solution of polymer chains spread between two, non-sticky materials — like jam between two slices of bread. On their own, the two materials adhere poorly together but the polymer chains act as a molecular suture, stitching the two materials together by forming a network with the two preexisting polymer networks. This process is known as topological entanglement.

When exposed to ultra-violet light, the network of stitches dissolves, separating the two materials.

The researchers, led by Zhigang Suo, the Allen E. and Marilyn M. Puckett Professor of Mechanics and Materials at SEAS, tested adhesion and detachment on a range of materials, sticking together hydrogels; hydrogels and organic tissue; elastomers; hydrogels and elastomers; and hydrogels and inorganic solids.

“Our strategy works across a range of materials and may enable broad applications,” said Kangling Wu, co-lead author and researcher at Xi’an Jiaotong University in China.
While the researchers focused on using UV light to trigger detachment, their work suggests the possibility that the stitching polymer could detach with near-infrared light, a feature which could be applied to a range of new medical procedures.

“In nature, wet materials don’t like to adhere together,” said Suo. “We have discovered a general approach to overcome this challenge. Our molecular sutures can strongly adhere wet materials together. Furthermore, the strong adhesion can be made permanent, transient, or detachable on demand, in response to a cue. So, as we see it, nature is full of loopholes, waiting to be stitched.”

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

Photodetachable Adhesion by Yang Gao, Kangling Wu, Zhigang Suo. https://doi.org/10.1002/adma.201806948 First published: 14 December 2018

This paper is behind a paywall.

Two-dimensional material stacks into multiple layers to build a memory cell for longer lasting batteries

This research comes from Purdue University (US) and the December announcement seemed particularly timely since battery-powered gifts are popular at Christmas but since it could be many years before this work is commercialized, you may want to tuck it away for future reference.  Also, readers familiar with memristors might see a resemblance to the memory cells mentioned in the following excerpt. From a December 13, 2018 news item on Nanowerk,

The more objects we make “smart,” from watches to entire buildings, the greater the need for these devices to store and retrieve massive amounts of data quickly without consuming too much power.

Millions of new memory cells could be part of a computer chip and provide that speed and energy savings, thanks to the discovery of a previously unobserved functionality in a material called molybdenum ditelluride.

The two-dimensional material stacks into multiple layers to build a memory cell. Researchers at Purdue University engineered this device in collaboration with the National Institute of Standards and Technology (NIST) and Theiss Research Inc.

A December 13, 2018 Purdue University news release by Kayla Wiles, which originated the news item,  describes the work in more detail,

Chip-maker companies have long called for better memory technologies to enable a growing network of smart devices. One of these next-generation possibilities is resistive random access memory, or RRAM for short.

In RRAM, an electrical current is typically driven through a memory cell made up of stacked materials, creating a change in resistance that records data as 0s and 1s in memory. The sequence of 0s and 1s among memory cells identifies pieces of information that a computer reads to perform a function and then store into memory again.

A material would need to be robust enough for storing and retrieving data at least trillions of times, but materials currently used have been too unreliable. So RRAM hasn’t been available yet for widescale use on computer chips.

Molybdenum ditelluride could potentially last through all those cycles.
“We haven’t yet explored system fatigue using this new material, but our hope is that it is both faster and more reliable than other approaches due to the unique switching mechanism we’ve observed,” Joerg Appenzeller, Purdue University’s Barry M. and Patricia L. Epstein Professor of Electrical and Computer Engineering and the scientific director of nanoelectronics at the Birck Nanotechnology Center.

Molybdenum ditelluride allows a system to switch more quickly between 0 and 1, potentially increasing the rate of storing and retrieving information. This is because when an electric field is applied to the cell, atoms are displaced by a tiny distance, resulting in a state of high resistance, noted as 0, or a state of low resistance, noted as 1, which can occur much faster than switching in conventional RRAM devices.

“Because less power is needed for these resistive states to change, a battery could last longer,” Appenzeller said.

In a computer chip, each memory cell would be located at the intersection of wires, forming a memory array called cross-point RRAM.

Appenzeller’s lab wants to explore building a stacked memory cell that also incorporates the other main components of a computer chip: “logic,” which processes data, and “interconnects,” wires that transfer electrical signals, by utilizing a library of novel electronic materials fabricated at NIST.

“Logic and interconnects drain battery too, so the advantage of an entirely two-dimensional architecture is more functionality within a small space and better communication between memory and logic,” Appenzeller said.

Two U.S. patent applications have been filed for this technology through the Purdue Office of Technology Commercialization.

The work received financial support from the Semiconductor Research Corporation through the NEW LIMITS Center (led by Purdue University), NIST, the U.S. Department of Commerce and the Material Genome Initiative.

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

Electric-field induced structural transition in vertical MoTe2- and Mo1–xWxTe2-based resistive memories by Feng Zhang, Huairuo Zhang, Sergiy Krylyuk, Cory A. Milligan, Yuqi Zhu, Dmitry Y. Zemlyanov, Leonid A. Bendersky, Benjamin P. Burton, Albert V. Davydov, & Joerg Appenzeller. Nature Materials volume 18, pages 55–61 (2019) Published: 10 December 2018 DOI: https://doi.org/10.1038/s41563-018-0234-y

This paper is behind a paywall.

An artificial synapse tuned by light, a ferromagnetic memristor, and a transparent, flexible artificial synapse

Down the memristor rabbit hole one more time.* I started out with news about two new papers and inadvertently found two more. In a bid to keep this posting to a manageable size, I’m stopping at four.

UK

In a June 19, 2019 Nanowerk Spotlight article, Dr. Neil Kemp discusses memristors and some of his latest work (Note: A link has been removed),

Memristor (or memory resistors) devices are non-volatile electronic memory devices that were first theorized by Leon Chua in the 1970’s. However, it was some thirty years later that the first practical device was fabricated. This was in 2008 when a group led by Stanley Williams at HP Research Labs realized that switching of the resistance between a conducting and less conducting state in metal-oxide thin-film devices was showing Leon Chua’s memristor behaviour.

The high interest in memristor devices also stems from the fact that these devices emulate the memory and learning properties of biological synapses. i.e. the electrical resistance value of the device is dependent on the history of the current flowing through it.

There is a huge effort underway to use memristor devices in neuromorphic computing applications and it is now reasonable to imagine the development of a new generation of artificial intelligent devices with very low power consumption (non-volatile), ultra-fast performance and high-density integration.

These discoveries come at an important juncture in microelectronics, since there is increasing disparity between computational needs of Big Data, Artificial Intelligence (A.I.) and the Internet of Things (IoT), and the capabilities of existing computers. The increases in speed, efficiency and performance of computer technology cannot continue in the same manner as it has done since the 1960s.

To date, most memristor research has focussed on the electronic switching properties of the device. However, for many applications it is useful to have an additional handle (or degree of freedom) on the device to control its resistive state. For example memory and processing in the brain also involves numerous chemical and bio-chemical reactions that control the brain structure and its evolution through development.

To emulate this in a simple solid-state system composed of just switches alone is not possible. In our research, we are interested in using light to mediate this essential control.

We have demonstrated that light can be used to make short and long-term memory and we have shown how light can modulate a special type of learning, called spike timing dependent plasticity (STDP). STDP involves two neuronal spikes incident across a synapse at the same time. Depending on the relative timing of the spikes and their overlap across the synaptic cleft, the connection strength is other strengthened or weakened.

In our earlier work, we were only able to achieve to small switching effects in memristors using light. In our latest work (Advanced Electronic Materials, “Percolation Threshold Enables Optical Resistive-Memory Switching and Light-Tuneable Synaptic Learning in Segregated Nanocomposites”), we take advantage of a percolating-like nanoparticle morphology to vastly increase the magnitude of the switching between electronic resistance states when light is incident on the device.

We have used an inhomogeneous percolating network consisting of metallic nanoparticles distributed in filamentary-like conduction paths. Electronic conduction and the resistance of the device is very sensitive to any disruption of the conduction path(s).

By embedding the nanoparticles in a polymer that can expand or contract with light the conduction pathways are broken or re-connected causing very large changes in the electrical resistance and memristance of the device.

Our devices could lead to the development of new memristor-based artificial intelligence systems that are adaptive and reconfigurable using a combination of optical and electronic signalling. Furthermore, they have the potential for the development of very fast optical cameras for artificial intelligence recognition systems.

Our work provides a nice proof-of-concept but the materials used means the optical switching is slow. The materials are also not well suited to industry fabrication. In our on-going work we are addressing these switching speed issues whilst also focussing on industry compatible materials.

Currently we are working on a new type of optical memristor device that should give us orders of magnitude improvement in the optical switching speeds whilst also retaining a large difference between the resistance on and off states. We hope to be able to achieve nanosecond switching speeds. The materials used are also compatible with industry standard methods of fabrication.

The new devices should also have applications in optical communications, interfacing and photonic computing. We are currently looking for commercial investors to help fund the research on these devices so that we can bring the device specifications to a level of commercial interest.

If you’re interested in memristors, Kemp’s article is well written and quite informative for nonexperts, assuming of course you can tolerate not understanding everything perfectly.

Here are links and citations for two papers. The first is the latest referred to in the article, a May 2019 paper and the second is a paper appearing in July 2019.

Percolation Threshold Enables Optical Resistive‐Memory Switching and Light‐Tuneable Synaptic Learning in Segregated Nanocomposites by Ayoub H. Jaafar, Mary O’Neill, Stephen M. Kelly, Emanuele Verrelli, Neil T. Kemp. Advanced Electronic Materials DOI: https://doi.org/10.1002/aelm.201900197 First published: 28 May 2019

Wavelength dependent light tunable resistive switching graphene oxide nonvolatile memory devices by Ayoub H.Jaafar, N.T.Kemp. DOI: https://doi.org/10.1016/j.carbon.2019.07.007 Carbon Available online 3 July 2019

The first paper (May 2019) is definitely behind a paywall and the second paper (July 2019) appears to be behind a paywall.

Dr. Kemp’s work has been featured here previously in a January 3, 2018 posting in the subsection titled, Shining a light on the memristor.

China

This work from China was announced in a June 20, 2019 news item on Nanowerk,

Memristors, demonstrated by solid-state devices with continuously tunable resistance, have emerged as a new paradigm for self-adaptive networks that require synapse-like functions. Spin-based memristors offer advantages over other types of memristors because of their significant endurance and high energy effciency.

However, it remains a challenge to build dense and functional spintronic memristors with structures and materials that are compatible with existing ferromagnetic devices. Ta/CoFeB/MgO heterostructures are commonly used in interfacial PMA-based [perpendicular magnetic anisotropy] magnetic tunnel junctions, which exhibit large tunnel magnetoresistance and are implemented in commercial MRAM [magnetic random access memory] products.

“To achieve the memristive function, DW is driven back and forth in a continuous manner in the CoFeB layer by applying in-plane positive or negative current pulses along the Ta layer, utilizing SOT that the current exerts on the CoFeB magnetization,” said Shuai Zhang, a coauthor in the paper. “Slowly propagating domain wall generates a creep in the detection area of the device, which yields a broad range of intermediate resistive states in the AHE [anomalous Hall effect] measurements. Consequently, AHE resistance is modulated in an analog manner, being controlled by the pulsed current characteristics including amplitude, duration, and repetition number.”

“For a follow-up study, we are working on more neuromorphic operations, such as spike-timing-dependent plasticity and paired pulsed facilitation,” concludes You. …

Here’s are links to and citations for the paper (Note: It’s a little confusing but I believe that one of the links will take you to the online version, as for the ‘open access’ link, keep reading),

A Spin–Orbit‐Torque Memristive Device by Shuai Zhang, Shijiang Luo, Nuo Xu, Qiming Zou, Min Song, Jijun Yun, Qiang Luo, Zhe Guo, Ruofan Li, Weicheng Tian, Xin Li, Hengan Zhou, Huiming Chen, Yue Zhang, Xiaofei Yang, Wanjun Jiang, Ka Shen, Jeongmin Hong, Zhe Yuan, Li Xi, Ke Xia, Sayeef Salahuddin, Bernard Dieny, Long You. Advanced Electronic Materials Volume 5, Issue 4 April 2019 (print version) 1800782 DOI: https://doi.org/10.1002/aelm.201800782 First published [online]: 30 January 2019 Note: there is another DOI, https://doi.org/10.1002/aelm.201970022 where you can have open access to Memristors: A Spin–Orbit‐Torque Memristive Device (Adv. Electron. Mater. 4/2019)

The paper published online in January 2019 is behind a paywall and the paper (almost the same title) published in April 2019 has a new DOI and is open access. Final note: I tried accessing the ‘free’ paper and opened up a free file for the artwork featuring the work from China on the back cover of the April 2019 of Advanced Electronic Materials.

Korea

Usually when I see the words transparency and flexibility, I expect to see graphene is one of the materials. That’s not the case for this paper (link to and citation for),

Transparent and flexible photonic artificial synapse with piezo-phototronic modulator: Versatile memory capability and higher order learning algorithm by Mohit Kumar, Joondong Kim, Ching-Ping Wong. Nano Energy Volume 63, September 2019, 103843 DOI: https://doi.org/10.1016/j.nanoen.2019.06.039 Available online 22 June 2019

Here’s the abstract for the paper where you’ll see that the material is made up of zinc oxide silver nanowires,

An artificial photonic synapse having tunable manifold synaptic response can be an essential step forward for the advancement of novel neuromorphic computing. In this work, we reported the development of highly transparent and flexible two-terminal ZnO/Ag-nanowires/PET photonic artificial synapse [emphasis mine]. The device shows purely photo-triggered all essential synaptic functions such as transition from short-to long-term plasticity, paired-pulse facilitation, and spike-timing-dependent plasticity, including in the versatile memory capability. Importantly, strain-induced piezo-phototronic effect within ZnO provides an additional degree of regulation to modulate all of the synaptic functions in multi-levels. The observed effect is quantitatively explained as a dynamic of photo-induced electron-hole trapping/detraining via the defect states such as oxygen vacancies. We revealed that the synaptic functions can be consolidated and converted by applied strain, which is not previously applied any of the reported synaptic devices. This study will open a new avenue to the scientific community to control and design highly transparent wearable neuromorphic computing.

This paper is behind a paywall.