It’s ALL in Our Heads ~ Studying the Consciousness to Better Understand …


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The physical brain and the conceptual mind are linked in ways that we don’t fully understand. A new collaboration is getting us closer.

How does the brain give rise to the mind? This question lies at the interface between philosophy and biology. Researchers are starting to zero in on how brain activity translates into consciousness and how we experience the world around us. The results have broad implications for cognition, brain health, human nature, and artificial intelligence.

The Azrieli Program in Brain, Mind & Consciousness is a collaboration started by the Canadian Institute for Advanced Research, bringing together a team of neuroscientists to answer these big questions.

Watch the Video

 

 

But how is it possible to probe something like consciousness? Professors Adrian Owen, Melvyn Goodale, and Lisa Saksida are all fellows of the Azrieli Program working at Western University, and they look at brain activity at the boundaries between health and dysfunction.

Owen studies patients who are losing consciousness. Communicating with patients who will soon be in a vegetative state, Owen takes functional magnetic resonance imaging (fMRI) scans to observe transitions in the brain as they lose awareness, allowing a better understanding what types of brain activity are preserved or lost.

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Along similar lines, Goodale looks at how brain damage impacts cognition, memory, sensory processing, and motor control. These insights illuminate how the brain solves problems and controls complex movement, which have implications not only in health, but also in computer science and artificial intelligence, says Goodale.

Saksida wants to understand how brain circuits are altered in Alzheimer’s Disease. Drug treatment for Alzheimer’s only treats symptoms. There is still no proven therapy that stops or reverses progression of Alzheimer’s. Saksida believes the key to effective treatments is to better understand the brain circuits involved so that they can be targeted to improve cognition.

While the mind remains a bit of a mystery, these studies are working to fill in the gaps. This understanding allows researchers to better understand how the mind emerges, how it can be damaged, and perhaps one day, how it can be imitated or repaired.

NASA & MIT Collaborate to develop space-based quantum-dot spectrometer ~ Quantum Dots in Space “simplifying instrument integration.”


A NASA technologist has teamed with the inventor of a new nanotechnology that could transform the way space scientists build spectrometers, the all-important device used by virtually all scientific disciplines to measure the properties of light emanating from astronomical objects, including Earth itself.

Mahmooda Sultana, a research engineer at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, now is collaborating with Moungi Bawendi, a chemistry professor at the Cambridge-based Massachusetts Institute of Technology, or MIT, to develop a prototype imaging spectrometer based on the emerging quantum-dot technology that Bawendi’s group pioneered. NASA’s Center Innovation Fund, which supports potentially trailblazing, high-risk technologies, is funding the effort.

Introducing Quantum Dots

Quantum dots are a type of semiconductor nanocrystal discovered in the early 1980s. Invisible to the naked eye, the dots have proven in testing to absorb different wavelengths of light depending on their size, shape, and chemical composition. The technology is promising to applications that rely on the analysis of light, including smartphone cameras, medical devices, and environmental-testing equipment.

“This is as novel as it gets,” Sultana said, referring to the technology that she believes could miniaturize and potentially revolutionize space-based spectrometers, particularly those used on uninhabited aerial vehicles and small satellites. “It really could simplify instrument integration.”

Absorption spectrometers, as their name implies, measure the absorption of light as a function of frequency or wavelength due to its interaction with a sample, such as atmospheric gases.

After passing through or interacting with the sample, the light reaches the spectrometer. Traditional spectrometers use gratings, prisms, or interference filters to split the light into its component wavelengths, which their detector pixels then detect to produce spectra. The more intense the absorption in the spectra, the greater the presence of a specific chemical.

While space-based spectrometers are getting smaller due to miniaturization, they still are relatively large, Sultana said. “Higher-spectral resolution requires long optical paths for instruments that use gratings and prisms. This often results in large instruments. Whereas here, with quantum dots that act like filters that absorb different wavelengths depending on their size and shape, we can make an ultra-compact instrument. In other words, you could eliminate optical parts, like gratings, prisms, and interference filters.”

Just as important, the technology allows the instrument developer to generate nearly an unlimited number of different dots. As their size decreases, the wavelength of the light that the quantum dots will absorb decreases. “This makes it possible to produce a continuously tunable, yet distinct, set of absorptive filters where each pixel is made of a quantum dot of a specific size, shape, or composition. We would have precise control over what each dot absorbs. We could literally customize the instrument to observe many different bands with high-spectral resolution.”

Prototype Instrument Under Development

nasa-symbolWith her NASA technology-development support, Sultana is working to develop, qualify through thermal vacuum and vibration tests, and demonstrate a 20-by-20 quantum-dot array sensitive to visible wavelengths needed to image the sun and the aurora. However, the technology easily can be expanded to cover a broader range of wavelengths, from ultraviolet to mid-infrared, which may find many potential space applications in Earth science, heliophysics, and planetary science, she said.

Under the collaboration, Sultana is developing an instrument concept particularly for a CubeSat application and MIT doctoral student Jason Yoo is investigating techniques for synthesizing different precursor chemicals to create the dots and then printing them onto a suitable substrate. “Ultimately, we would want to print the dots directly onto the detector pixels,” she said.

“This is a very innovative technology,” Sultana added, conceding that it is very early in its development. “But we’re trying to raise its technology-readiness level very quickly. Several space-science opportunities that could benefit are in the pipeline.”

NASA

MIT: New ‘Solar Skin’ Solar panels get a face-lift with custom Display Capabilities


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Startup aims for wider U.S. solar adoption with photovoltaic panels that can display any image.

Founded at the MIT Sloan School of Management, Sistine Solar creates custom solar panels designed to mimic home facades and other environments, as well as display custom designs, with aims of enticing more homeowners to install photovoltaic systems. Courtesy of Sistine Solar

Residential solar power is on a sharp rise in the United States as photovoltaic systems become cheaper and more powerful for homeowners. A 2012 study by the U.S. Department of Energy (DOE) predicts that solar could reach 1 million to 3.8 million homes by 2020, a big leap from just 30,000 homes in 2006.

But that adoption rate could still use a boost, according to MIT spinout Sistine Solar. “If you look at the landscape today, less than 1 percent of U.S. households have gone solar, so it’s nowhere near mass adoption,” says co-founder Senthil Balasubramanian MBA ’13.

Founded at the MIT Sloan School of Management, Sistine creates custom solar panels designed to mimic home facades and other environments, with aims of enticing more homeowners to install photovoltaic systems.

Sistine’s novel technology, SolarSkin, is a layer that can be imprinted with any image and embedded into a solar panel without interfering with the panel’s efficacy. Homeowners can match their rooftop or a grassy lawn. Panels can also be fitted with business logos, advertisements, or even a country’s flag. SolarSkin systems cost about 10 percent more than traditional panel installations. But over the life of the system, a homeowner can still expect to save more than $30,000, according to the startup.

A winner of a 2013 MIT Clean Energy Prize, Sistine has recently garnered significant media attention as a rising “aesthetic solar” startup. Last summer, one of its pilot projects was featured on the Lifetime television series “Designing Spaces,” where the panels blended in with the shingle roof of a log cabin in Hubbardston, Massachusetts.

In December, the startup installed its first residential SolarSkin panels, in a 10-kilowatt system that matches a cedar pattern on a house in Norwell, Massachusetts. Now, the Cambridge-based startup says it has 200 homes seeking installations, primarily in Massachusetts and California, where solar is in high demand.

“We think SolarSkin is going to catch on like wildfire,” Balasubramanian says. “There is a tremendous desire by homeowners to cut utility bills, and solar is finding reception with them — and homeowners care a lot about aesthetics.”

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Captivating people with solar – Who Said Solar Can’t Be Beautiful?

SolarSkin is the product of the co-founders’ unique vision, combined with MIT talent that helped make the product a reality.

Balasubramanian came to MIT Sloan in 2011, after several years in the solar-power industry, with hopes of starting his own solar-power startup — a passion shared by classmate and Sistine co-founder Ido Salama MBA ’13.

One day, the two were brainstorming at the Muddy Charles Pub, when a surprisingly overlooked issue popped up: Homeowners, they heard, don’t really like the look of solar panels. That began a nebulous business mission to “captivate people’s imaginations and connect people on an emotional level with solar,” Balasubramanian says.

Recruiting Jonathan Mailoa, then a PhD student in MIT’s Photovoltaic Research Laboratory, and Samantha Holmes, a mosaic artist trained in Italy who is still with the startup, the four designed solar panels that could be embedded on massive sculptures and other 3-D objects. They took the idea to 15.366 (Energy Ventures), where “it was drilled into our heads that you have to do a lot of market testing before you build a product,” Balasubramanian says.

That was a good thing, too, he adds, because they realized their product wasn’t scalable. “We didn’t want to make a few installations that people talk about. … We [wanted to] make solar so prevalent that within our lifetime we can see the entire world convert to 100 percent clean energy,” Balasubramanian says.

The team’s focus then shifted to manufacturing solar panels that could match building facades or street fixtures such as bus shelters and information kiosks. In 2013, the idea earned the team — then officially Sistine Solar — a modest DOE grant and a $20,000 prize from the MIT Clean Energy Prize competition, “which was a game-changer for us,” Balasubramanian says.

But, while trying to construct custom-designed panels, another idea struck: Why not just make a layer to embed into existing solar panels? Recruiting MIT mechanical engineering student Jody Fu, Sistine created the first SolarSkin prototype in 2015, leading to pilot projects for Microsoft, Starwood Hotels, and other companies in the region.

That summer, after earning another DOE grant for $1 million, Sistine recruited Anthony Occidentale, an MIT mechanical engineering student who has since helped further advance SolarSkin. “We benefited from the incredible talent at MIT,” Balasubramanian says. “Anthony is a shining example of someone who resonates with our vision and has all the tools to make this a reality.”

Imagination is the limit

SolarSkin is a layer that employs selective light filtration to display an image while still transmitting light to the underlying solar cells. The ad wraps displayed on bus windows offer a good analogy: The wraps reflect some light to display an image, while allowing the remaining light through so passengers inside the bus can see out. SolarSkin achieves a similar effect — “but the innovation lies in using a minute amount of light to reflect an image [and preserve] a high-efficiency solar module,” Balasubramanian says.

To achieve this, Occidentale and others at Sistine have developed undisclosed innovations in color science and human visual perception. “We’ve come up with a process where we color-correct the minimal information we have of the image on the panels to make that image appear, to the human eye, to be similar to the surrounding backdrop of roof shingles,” Occidentale says.

As for designs, Sistine has amassed a database of common rooftop patterns in the United States, such as asphalt shingles, clay tiles, and slate, in a wide variety of colors. “So if a homeowner says, for instance, ‘We have manufactured shingles in a barkwood pattern,’ we have a matching design for that,” he says. Custom designs aren’t as popular, but test projects include commercial prints for major companies, and even Occidentale’s face on a panel.

Currently, Sistine is testing SolarSkin for efficiency, durability, and longevity at the U.S. National Renewable Energy Laboratory under a DOE grant.

The field of aesthetic solar is still nascent, but it’s growing, with major companies such as Tesla designing entire solar-panel roofs. But, as far as Balasubramanian knows, Sistine is the only company that’s made a layer that can be integrated into any solar panel, and that can display any color as well as intricate patterns and actual images.

Companies could thus use SolarSkin solar panels to double as business signs. Municipalities could install light-powering solar panels on highways that blend in with the surrounding nature. Panels with changeable advertisements could be placed on bus shelters to charge cell phones, information kiosks, and other devices. “You can start putting solar in places you typically didn’t think of before,” Balasubramanian says. “Imagination is really the only limit with this technology.”

Switched-on DNA: Sparking nano-electronic applications


DNA, the stuff of life, may very well also pack quite the jolt for engineers trying to advance the development of tiny, low-cost electronic devices. Credit: ASU

Switched-on DNA

DNA, the stuff of life, may very well also pack quite the jolt for engineers trying to advance the development of tiny, low-cost electronic devices.

Much like flipping your light switch at home—-only on a scale 1,000 times smaller than a human hair—-an ASU-led team has now developed the first controllable DNA switch to regulate the flow of electricity within a single, atomic-sized molecule. 

The new study, led by ASU Biodesign Institute researcher Nongjian Tao, was published in the advanced online journal Nature Communications.

“It has been established that charge transport is possible in DNA, but for a useful device, one wants to be able to turn the charge transport on and off. We achieved this goal by chemically modifying DNA,” said Tao, who directs the Biodesign Center for Bioelectronics and Biosensors and is a professor in the Fulton Schools of Engineering. 

“Not only that, but we can also adapt the modified DNA as a probe to measure reactions at the single-molecule level. This provides a unique way for studying important reactions implicated in disease, or photosynthesis reactions for novel renewable energy applications.”

Engineers often think of electricity like water, and the research team’s new DNA switch acts to control the flow of electrons on and off, just like water coming out of a faucet.

Previously, Tao’s research group had made several discoveries to understand and manipulate DNA to more finely tune the flow of electricity through it. They found they could make DNA behave in different ways—and could cajole electrons to flow like waves according to quantum mechanics, or “hop” like rabbits in the way electricity in a copper wire works —creating an exciting new avenue for DNA-based, nano-electronic applications.

Tao assembled a multidisciplinary team for the project, including ASU postdoctoral student Limin Xiang and Li Yueqi performing bench experiments, Julio Palma working on the theoretical framework, with further help and oversight from collaborators Vladimiro Mujica (ASU) and Mark Ratner (Northwestern University).

Tao’s group, modified just one of DNA’s iconic double helix chemical letters, abbreviated as A, C, T or G, with another chemical group, called anthraquinone (Aq). Anthraquinone is a three-ringed carbon structure that can be inserted in …more




To accomplish their engineering feat, Tao’s group, modified just one of DNA’s iconic double helix chemical letters, abbreviated as A, C, T or G, with another chemical group, called anthraquinone (Aq). Anthraquinone is a three-ringed carbon structure that can be inserted in between DNA base pairs but contains what chemists call a redox group (short for reduction, or gaining electrons or oxidation, losing electrons).
 

These chemical groups are also the foundation for how our bodies’ convert chemical energy through switches that send all of the electrical pulses in our brains, our hearts and communicate signals within every cell that may be implicated in the most prevalent diseases.

The modified Aq-DNA helix could now help it perform the switch, slipping comfortably in between the rungs that make up the ladder of the DNA helix, and bestowing it with a new found ability to reversibly gain or lose electrons.

Through their studies, when they sandwiched the DNA between a pair of electrodes, they careful controlled their electrical field and measured the ability of the modified DNA to conduct electricity. This was performed using a staple of nano-electronics, a scanning tunneling microscope, which acts like the tip of an electrode to complete a connection, being repeatedly pulled in and out of contact with the DNA molecules in the solution like a finger touching a water droplet.

“We found the electron transport mechanism in the present anthraquinone-DNA system favors electron “hopping” via anthraquinone and stacked DNA bases,” said Tao. In addition, they found they could reversibly control the conductance states to make the DNA switch on (high-conductance) or switch-off (low conductance). 

When anthraquinone has gained the most electrons (its most-reduced state), it is far more conductive, and the team finely mapped out a 3-D picture to account for how anthraquinone controlled the electrical state of the DNA.

For their next project, they hope to extend their studies to get one step closer toward making DNA nano-devices a reality.

“We are particularly excited that the engineered DNA provides a nice tool to examine redox reaction kinetics, and thermodynamics the single molecule level,” said Tao.

 Explore further: Scientists engineer tunable DNA for electronics applications

More information: Gate-controlled conductance switching in DNA, Nature Communications, DOI: 10.1038/ncomms14471 

Journal reference: Nature Communications  

Provided by: Arizona State University  

ASU and Stanford Researchers Achieve Record Breaking Efficiency with Tandem (Perovskite + Silicon) Solar Cell


ecee-perovskite-silicon-tandem-cell-pz-0035-w-1280x640Above: A perovskite/silicon tandem solar cell, created by research teams from Arizona State University and Stanford University, capable of record-breaking sunlight-to-electricity conversion efficiency. Photographer: Pete Zrioka/ASU

Some pairs are better together than their individual counterparts — peanut butter and chocolate, warm weather and ice cream, and now, in the realm of photovoltaic technology, silicon and perovskite.

As existing solar energy technologies near their theoretical efficiency limits, researchers are exploring new methods to improve performance — such as stacking two photovoltaic materials in a tandem cell. Collaboration between researchers at Arizona State University and Stanford University has birthed such a cell with record-breaking conversion efficiency — effectively finding the peanut butter to silicon’s chocolate.

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The results of their work, published February 17 in Nature Energy, outline the use of perovskite and silicon to create a tandem solar cell capable of converting sunlight to energy with an efficiency of 23.6 percent, just shy of the all-time silicon efficiency record.

“The best silicon solar cell alone has achieved 26.3 percent efficiency,” says Zachary Holman, an assistant professor of electrical engineering at the Ira A. Fulton Schools of Engineering. “Now we’re gunning for 30 percent with these tandem cells, and I think we could be there within two years.”

Assistant Professor Zachary Holman, holds one of the many solar cells his research group has created. Photographer: Jessica Hochreiter/ASU

Silicon solar cells are the backbone of a $30 billion a year industry, and this breakthrough shows that there’s room for significant improvement within such devices by finding partner materials to boost efficiency.

The high-performance tandem cell’s layers are each specially tuned to capture different wavelengths of light. The top layer, composed of a perovskite compound, was designed to excel at absorbing visible light. The cell’s silicon base is tuned to capture infrared light.

Perovskite, a cheap, easily manufacturable photovoltaic material, has emerged as a challenger to silicon’s dominance in the solar market. Since its introduction to solar technology in 2009, the efficiency of perovskite solar cells has increased from 3.8 percent to 22.1 percent in early 2016, according to the National Renewable Energy Laboratory.

The perovskite used in the tandem cell came courtesy of Stanford researchers Professor Michael McGehee and doctoral student Kevin Bush, who fabricated the compound and tested the materials.

The research team at ASU provided the silicon base and modeling to determine other material candidates for use in the tandem cell’s supporting layers.

OVERCOMING CHALLENGES WITH PEROVSKITES

 Zhengshan (Jason) Yu, an electrical engineering doctoral student at ASU, holds up a tiny black solar cell which is flanked by two conductors. The small cell has yielded big improvements, resulting in a record-breaking 23.6 percent efficiency rate.

Though low-cost and highly efficient, perovskites have been limited by poor stability, degrading at a much faster rate than silicon in hot and humid environments. Additionally, perovskite solar cells have suffered from parasitic absorption, in which light is absorbed by supporting layers in the cell that don’t generate electricity.

“We have improved the stability of the perovskite solar cells in two ways,” says McGehee, a materials science and engineering professor at Stanford’s School of Engineering. “First, we replaced an organic cation with cesium. Second, we protected the perovskite with an impermeable indium tin oxide layer that also functions as an electrode.”

Though McGehee’s compound achieves record stability, perovskites remain delicate materials, making it difficult to employ in tandem solar technology.

“In many solar cells, we put a layer on top that is both transparent and conductive,” says Holman, a faculty member in the School of Electrical, Computer and Energy Engineering. “It’s transparent so light can go through and conductive so we can take electrical charges off it.”

This top conductive layer is applied using a process called sputtering deposition, which historically has led to damaged perovskite cells. However, McGehee was able to apply a tin oxide layer with help from chemical engineering Professor Stacey Bent and doctoral student Axel Palmstrom of Stanford. The pair developed a thin layer that protects the delicate perovskite from the deposition of the final conductive layer without contributing to parasitic absorption, further boosting the cell’s efficiency.

The deposition of the final conductive layer wasn’t the only engineering challenge posed by integrating perovskites and silicon.

“It was difficult to apply the perovskite itself without compromising the performance of the silicon cell,” says Zhengshan (Jason) Yu, an electrical engineering doctoral student at ASU.

Silicon wafers are placed in a potassium hydroxide solution during fabrication, which creates a rough, jagged surface. This texture, ideal for trapping light and generating more energy, works well for silicon, but perovskite prefers a smooth — and unfortunately reflective — surface for deposition.

Additionally, the perovskite layer of the tandem cell is less than a micron thick, opposed to the 250-micron thick silicon layer. This means when the thin perovskite layer was deposited, it was applied unevenly, pooling in the rough silicon’s low points and failing to adhere to its peaks.

Yu developed a method to create a planar surface only on the front of the silicon solar cell using a removable, protective layer. This resulted in a smooth surface on one side of the cell, ideal for applying the perovskite, while leaving the backside rough, to trap the weakly-absorbed near-infrared light in the silicon.

“With the incorporation of a silicon nanoparticle rear reflector, this infrared-tuned silicon cell becomes an excellent bottom cell for tandems,” says Yu.

BUILDING ON PREVIOUS SUCCESSES

The success of the tandem cell is built on existing achievements from both teams of researchers. In October 2016, McGehee and post-doctoral scholar Tomas Leijtens fabricated an all-perovskite cell capable of 20.3 percent efficiency. The high-performance cell was achieved in part by creating a perovskite with record stability, marking McGehee’s group as one of the first teams to devote research efforts to fabricating stable perovskite compounds.

Likewise, Holman has considerable experience working with silicon and tandem cells.

“We’ve tried to position our research group as the go-to group in the U.S. for silicon bottom cells for tandems,” says Holman, who’s been pursuing additional avenues to create high-efficiency tandem solar cells.

In fact, Holman and Yu published a comment in Nature Energy in September 2016 outlining the projected efficiencies of different cell combinations in tandems.

“People often ask, ‘given the fundamental laws of physics, what’s the best you can do?’” says Holman. “We’ve asked and answered a different, more useful question: Given two existing materials, if you could put them together, ideally, what would you get?”’

The publication is a sensible guide to designing a tandem solar cell, specifically with silicon as the bottom solar cell, according to Holman.

It calculates what the maximum efficiency would be if you could pair two existing solar cells in a tandem without any performance loss. The guide has proven useful in directing research efforts to pursue the best partner materials for silicon.

“We have eight projects with different universities and organizations, looking at different types of top cells that go on top of silicon,” says Holman. “So far out of all our projects, our perovskite/silicon tandem cell with Stanford is the leader.”

Oregon St. University: New hydronium-ion battery show promise for sustainable energy storage


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February 20, 2017

 
A new type of battery developed by scientists at Oregon State University shows promise for sustainable, high-power energy storage.

It’s the world’s first battery to use only hydronium ions as the charge carrier.
The new battery provides an additional option for researchers, particularly in the area of stationary storage.

 
Stationary storage refers to batteries in a permanent location that store grid power – including power generated from alternative energy sources such as wind turbines or solar cells – for use on a standby or emergency basis.

 
Hydronium, also known as H3O+, is a positively charged ion produced when a proton is added to a water molecule. Researchers in the OSU College of Science have demonstrated that hydronium ions can be reversibly stored in an electrode material consisting of perylenetetracarboxylic dianhydridem, or PTCDA.

 
This material is an organic, crystalline, molecular solid. The battery, created in the Department of Chemistry at Oregon State, uses dilute sulfuric acid as the electrolyte.
Graduate student Xingfeng Wang was the first author on the study, which has been published in the journal Angewandte Chemie International Edition, a publication of the German Chemical Society.

 
“This may provide a paradigm-shifting opportunity for more sustainable batteries,” said Xiulei Ji, assistant professor of chemistry at OSU and the corresponding author on the research. “It doesn’t use lithium or sodium or potassium to carry the charge, and just uses acid as the electrolyte. There’s a huge natural abundance of acid so it’s highly renewable and sustainable.” Ji points out that until now, cations – ions with a positive charge – that have been used in batteries have been alkali metal, alkaline earth metals or aluminum.
“No nonmetal cations were being considered seriously for batteries,” he said.
The study observed a big dilation of the PTCDA lattice structure during intercalation – the process of its receiving ions between the layers of its structure. That meant the electrode was being charged, and the PTCDA structure expanded, by hydronium ions, rather than extremely tiny protons, which are already used in some batteries.

 
“Organic solids are not typically contemplated as crystalline electrode materials, but many are very crystalline, arranged in a very ordered structure,” Ji said. “This PTCDA material has a lot of internal space between its molecule constituents so it provides an opportunity for storing big ions and good capacity.” The hydronium ions also migrate through the electrode structure with comparatively low “friction,” which translates to high power.
“It’s not going to power electric cars,” Ji said. “But it does provide an opportunity for battery researchers to go in a new direction as they look for new alternatives for energy storage, particularly for stationary grid storage.”

More information: Xingfeng Wang et al, Hydronium-Ion Batteries with Perylenetetracarboxylic Dianhydride Crystals as an Electrode, Angewandte Chemie International Edition (2017). DOI: 10.1002/anie.201700148
Provided by: Oregon State University

Energy-collecting Windows Dream One-Step Closer


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Silicon-based luminescent solar concentrator. While most of the light concentrated to the edge of the silicon-based luminescent solar concentrator is actually invisible, we can better see the concentration effect by the naked eye when the slab is illuminated by a “black light” which is composed of mostly ultraviolet wavelengths. (image: Uwe Kortshagen, University of Minnesota)

February 20, 2017

Researchers at the University of Minnesota and University of Milano-Bicocca are bringing the dream of windows that can efficiently collect solar energy one step closer to reality thanks to high tech silicon nanoparticles.

The researchers developed technology to embed the silicon nanoparticles into what they call efficient luminescent solar concentrators (LSCs). These LSCs are the key element of windows that can efficiently collect solar energy. When light shines through the surface, the useful frequencies of light are trapped inside and concentrated to the edges where small solar cells can be put in place to capture the energy.

The research is published today in Nature Photonics (“Highly efficient luminescent solar concentrators based on Earth-abundant indirect-bandgap silicon quantum dots”).

Windows that can collect solar energy, called photovoltaic windows, are the next frontier in renewable energy technologies, as they have the potential to largely increase the surface of buildings suitable for energy generation without impacting their aesthetics—a crucial aspect, especially in metropolitan areas. LSC-based photovoltaic windows do not require any bulky structure to be applied onto their surface and since the photovoltaic cells are hidden in the window frame, they blend invisibly into the built environment.

The idea of solar concentrators and solar cells integrated into building design has been around for decades, but this study included one key difference—silicon nanoparticles. Until recently, the best results had been achieved using relatively complex nanostructures based either on potentially toxic elements, such as cadmium or lead, or on rare substances like indium, which is already massively utilized for other technologies. Silicon is abundant in the environment and non-toxic. It also works more efficiently by absorbing light at different wavelengths than it emits. However, silicon in its conventional bulk form, does not emit light or luminesce.

“In our lab, we ‘trick’ nature by shrinking the dimension of silicon crystals to a few nanometers, that is about one ten-thousandths of the diameter of human hair,” said University of Minnesota mechanical engineering professor Uwe Kortshagen, inventor of the process for creating silicon nanoparticles and one of the senior authors of the study. “At this size, silicon’s properties change and it becomes an efficient light emitter, with the important property not to re-absorb its own luminescence. This is the key feature that makes silicon nanoparticles ideally suited for LSC applications.”

Using the silicon nanoparticles opened up many new possibilities for the research team.

“Over the last few years, the LSC technology has experienced rapid acceleration, thanks also to pioneering studies conducted in Italy, but finding suitable materials for harvesting and concentrating solar light was still an open challenge,” said Sergio Brovelli, physics professor at the University of Milano-Bicocca, co-author of the study, and co-founder of the spin-off company Glass to Power that is industrializing LSCs for photovoltaic windows “Now, it is possible to replace these elements with silicon nanoparticles.”

Researchers say the optical features of silicon nanoparticles and their nearly perfect compatibility with the industrial process for producing the polymer LSCs create a clear path to creating efficient photovoltaic windows that can capture more than 5 percent of the sun’s energy at unprecedented low costs.

“This will make LSC-based photovoltaic windows a real technology for the building-integrated photovoltaic market without the potential limitations of other classes of nanoparticles based on relatively rare materials,” said Francesco Meinardi, physics professor at the University of Milano-Bicocca and one of the first authors of the paper.

The silicon nanoparticles are produced in a high-tech process using a plasma reactor and formed into a powder.

“Each particle is made up of less than two thousand silicon atoms,” said Samantha Ehrenberg, a University of Minnesota mechanical Ph.D. student and another first author of the study. “The powder is turned into an ink-like solution and then embedded into a polymer, either forming a sheet of flexible plastic material or coating a surface with a thin film.”

The University of Minnesota invented the process for creating silicon nanoparticles about a dozen years ago and holds a number of patents on this technology. In 2015, Kortshagen met Brovelli, who is an expert in LSC fabrication and had already demonstrated various successful approaches to efficient LSCs based on other nanoparticle systems. The potential of silicon nanoparticles for this technology was immediately clear and the partnership was born. The University of Minnesota produced the particles and researchers in Italy fabricated the LSCs by embedding them in polymers through an industrial based method, and it worked.

“This was truly a partnership where we gathered the best researchers in their fields to make an old idea truly successful,” Kortshagen said. “We had the expertise in making the silicon nanoparticles and our partners in Milano had expertise in fabricating the luminescent concentrators. When it all came together, we knew we had something special.”

Source: University of Minnesota

 

Materials for (ALL) the Ages ~ Nanomaterials and the (coming) Fourth Industrial Revolution


nano-vacince-28432767823_7110f5293b_oThis nano-vaccine can stimulate an anti-tumour response in patients with cancer. Brenda Melendez and Rita Serda, NIH Image Gallery/Flickr (CC BY-NC 2.0)

HUMAN PROGRESS HAS LONG BEEN DENOTED BY THE DOMINANT MATERIAL OF THE PERIOD. WILL WE SOON BE LIVING IN THE NANOMATERIAL AGE?  

The kind of material used by a society has often served as a yardstick for how developed that society is. From the stone wheel to the iPhone, a bronze axe to a Boeing 747, materials technology has been our constant companion throughout the millennia, and a driving force for continued progress and societal change. Now it is believed that we may be on the cusp of another great materials revolution, this time powered by nanotechnology. With implications for fields ranging from clean energy to medicine, nanotechnology has the potential to have far-reaching impacts on many aspects of our lives, and may earn itself naming rights to the next age in the process.

Sticks and stones and metals

During the Stone Age, our ancestors used natural materials such as animal skins, plant fibres and, of course, stones. These materials were our bread and butter before bread or butter, until humans began to experiment with metalwork. Copper, alloyed with a bit of tin, had such superior properties to stone implements that if a society failed to use the new material, they found themselves in danger of being conquered. Thus, the Bronze Age was born. Bronze had its heyday for millennia, until bronze itself was surpassed by another stronger, more versatile metal.

 

Further advancement in metalwork allowed the production of iron tools and weapons, followed by ones crafted from steel. These implements were stronger and sharper than their bronze counterparts, without a significant increase in weight. There is actually some contention among historians about what constitutes the end of the Iron Age. A common demarcation uses an increase in the survival of written histories, which reduced the burden previously placed on archaeology. However, some believe the Iron Age may have never really ended as iron and steel still play a substantial role in contemporary society.

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 Tools from the Stone age (left) gave way to those required for metal work in the Bronze and Iron ages (above). Patrick Gray/Flickr (CC BY 2.0) and Wikimedia Commons (public domain)

While naming time periods after their defining material has fallen somewhat out of vogue, the progression of society is still driven by advances in materials science and technology.

The industrial revolution, globalization and the Information Age

Coal and the steam engine literally and figuratively fueled the industrial revolution, moulding us into our modern consumer culture. Before the industrial revolution, a high percentage of the population had to farm the land to provide enough food for everyone to survive.

Mechanized farming practices reduced the burden on manpower, while also producing higher yields. As a result, few farmers were required to feed the growing urban populace. This freed up large sections of the population to pursue work in other fields, such as manufacturing, commerce and research. The importance of this transition is still evident today, including our tendency to group countries based on how industrialized they are.

Advances in lightweight materials, such as composites and light metals, facilitated the development of aircraft that fly us around an ever-shrinking globe, and allowed us to be propelled beyond our planet’s life-supporting atmosphere. In the final decades of the 20th century, the world got even smaller following the rapid development of silicon processing chips and personal electronics. The revolutionary impact these silicon products have had on modern society can’t be overstated. Indeed, this article was written, and is likely being read, on devices powered by what is effectively processed sand.

Much to the chagrin of silicon atoms everywhere, we are not currently in the silicon age, but the information or digital age. However, we are likely on the verge of another significant advance in materials technology.

The promises of the nanotechnology age

Scientists have been heralding the Nano Age, proclaiming “nanotechnology will become the most powerful tool the human species has ever used”. This is engineering on an atomic scale, the stuff of science fiction only decades ago. Now, some experts believe nanotechnology will prove to be the foundation of our wildest dreams (or darkest nightmares).
While such claims may seem sensational or outlandish, the inherent potential of nanotechnology is apparent in current research. The University of Queensland (UQ) boasts a nanomaterials research centre with a multidisciplinary team that is working to implement nanomaterials in three key research areas: energy, environment and health. If there can be consensus about issues that are integral to the survival of humanity, the shortlist must surely include these three.

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Read About: Why Everyone Must Get Ready for the Fourth Industrial Revolution

 
Professor Lianzhou Wang is the director of the UQ Nanomaterials Centre, and his work is focused on the first two areas: energy and environment. Prof Wang’s group aims to use nanomaterials to improve the efficiency of solar cells. Due to Australia’s abundant sunshine, the country has a vested interest and solid track record in solar cell research. However, much of that research focuses on improving the efficiency of solar cells, and usually involves increasingly expensive materials and manufacturing techniques. Prof Wang has a more egalitarian approach and is focused on developing renewable energy technology that will be more accessible to the population at large. In his lab, nanomaterials such as metal oxides and quantum dots are used to create cheap, efficient solar cells with the hope of encouraging more widespread utilization of this green power source.

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 Solar panels on rooftops allow residents to take advantage of the Australian sun. Wikimedia Commons (public domain)

 
Using nanotechnology, Prof Wang’s group can make solar cells that are cheaper than currently available commercial silicon and thin film solar cells. They are able to do this because nanomaterials have a much lower processing temperature than conventional materials, which corresponds to a decrease in manufacturing costs. Nanomaterials also impart flexibility during processing and design, as they can be printed on both flexible and rigid substrates.

 
“This is where nanomaterials can play a role: performance, of course, but also cost,” said Prof Wang. By reducing the cost of the solar cells, he hopes to lower the barrier to entry of the market and thereby introduce the technology to a greater proportion of the population. In the case of nanotechnology, it turns out that less really is more.

Solar Shades

 Flexible solar panels have greater utility than their rigid counterparts, and can be used in a wider variety of scenarios, such as on tents. Wikimedia Commons (public domain)

Flexible solar panels have greater utility than their rigid counterparts, and can be used in a wider variety of scenarios, such as on tents. Wikimedia Commons (public domain)
However, not content to call that a good day’s work, Prof Wang is also working toward a solution for another issue plaguing the green energy sector: power storage. Although not particularly nuanced, a common argument against green energies asks what happens when the sun isn’t shining or the wind isn’t blowing. As frustratingly reductive as this may seem, it still presents a serious challenge. The uptake of green energy sources, including solar, is severely limited by inadequate or expensive batteries. The inability to easily and effectively store unused power for a rainy day (pardon the pun) is a limiting factor for many renewable energy technologies.

 
In an effort to address this issue many research groups, including Prof Wang’s, intend to improve batteries with nanotechnology. As with solar cells, the advantage stems from their increased surface area. Nanoparticles, particularly nanocrystallites, have a higher surface area ratio than conventional battery materials, which allows shorter ion diffusion length and faster charge transfer. This not only increases the storage capacity of the battery, but also reduces charging time. Using this technique, Prof Wang’s group believe they have developed new cathode materials for lithium ion batteries that would potentially improve the mileage of electric cars from 450km/charge to 600-700km. “This is an increase of almost a third, and will make these cars competitive with most petrol-powered cars,” said Prof Wang.

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 Electric cars such as the Tesla model S are only as good as their battery life, and nanomaterials have the potential to extend driving time on one charge. Wikimedia Commons (public domain)

 

Exploring how to harness nanomaterials for the betterment of the environment is another key research area for the UQ nanomaterials group. There are a variety of ways nanomaterials can assist in environmental management, but artificial photosynthesis is arguably one of the most innovative. Using nanoparticles as a photoactive catalyst, carbon dioxide in the atmosphere reacts with water to produce by-products including carbon monoxide, methane and hydrogen gas. Prof Wang sums up how remarkable this is: “We can not only remove the CO2 from the atmosphere, we [also] get something useful in the process.” All of the by-products mentioned (carbon monoxide, methane and hydrogen) are potential fuel or power sources. Consequently, artificial photosynthesis not only provides a useful tool for combating climate change, it also generates alternative fuel sources in the process.

Finally, nanotecnology may prove useful for health applications in fields as diverse as targeted drug delivery, gene therapy, diagnostics and tissue engineering, demonstrating its broad potential in medicine. It is thought by some that nanotechnology may hold the key to curing cancer at the genetic level, while also providing insights about immortality.

 

Whether the next great age of humanity is officially labelled the Nano Age or not, nanotechnology will almost certainly play an instrumental role in future innovations and will shape societies for decades to come. Whether it be tackling cancer or climate change, it appears that anything is possible, if we just think small enough.

Breakthrough in ‘wonder’ materials paves way for flexible tech


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Credit: University of Warwick

 

Gadgets are set to become flexible, highly efficient and much smaller, following a breakthrough in measuring two-dimensional ‘wonder’ materials by the University of Warwick.

Dr Neil Wilson in the Department of Physics has developed a new technique to measure the electronic structures of stacks of two-dimensional materials – flat, atomically thin, highly conductive, and extremely strong materials – for the first time.

Multiple stacked layers of 2-D materials – known as heterostructures – create highly efficient optoelectronic devices with ultrafast electrical charge, which can be used in nano-circuits, and are stronger than materials used in traditional circuits.

Various heterostructures have been created using different 2-D materials – and stacking different combinations of 2-D materials creates new with new properties.

Dr Wilson’s technique measures the electronic properties of each layer in a stack, allowing researchers to establish the optimal structure for the fastest, most efficient transfer of electrical energy.

The technique uses the photoelectric effect to directly measure the momentum of electrons within each layer and shows how this changes when the layers are combined.

The ability to understand and quantify how 2-D material heterostructures work – and to create optimal semiconductor structures – paves the way for the development of highly efficient nano-circuitry, and smaller, flexible, more wearable gadgets.

Solar power could also be revolutionised with heterostructures, as the atomically thin layers allow for strong absorption and efficient power conversion with a minimal amount of photovoltaic material.

Dr Wilson comments on the work: “It is extremely exciting to be able to see, for the first time, how interactions between atomically thin layers change their electronic structure. This work also demonstrates the importance of an international approach to research; we would not have been able to achieve this outcome without our colleagues in the USA and Italy.”

Dr Wilson worked formulated the technique in collaboration with colleagues in the theory groups at the University of Warwick and University of Cambridge, at the University of Washington in Seattle, and the Elettra Light Source, near Trieste in Italy.

Understanding how interactions between the atomic layers change their required the help of computational models developed by Dr Nick Hine, also from Warwick’s Department of Physics.

Explore further: Model accurately predicts the electronic properties of a combination of 2-D semiconductors

More information: Neil R. Wilson et al. Determination of band offsets, hybridization, and exciton binding in 2D semiconductor heterostructures, Science Advances (2017). DOI: 10.1126/sciadv.1601832

 

Photonic Optical Fiber with ‘Einstein’s Theory’ effect


opticalfibreCoreless optical fibre: If a photonic crystal fibre is twisted, it does not require a core with a different refractive index to trap light at its centre. Credit: Science 2016/MPI for the Science of Light

Researchers at the Max Planck Institute for the Science of Light in Erlangen have discovered a new mechanism for guiding light in photonic crystal fibre (PCF). PCF is a hair-thin glass fibre with a regular array of hollow channels running along its length. When helically twisted, this spiralling array of hollow channels acts on light rays in an analogous manner to the bending of light rays when they travel through the gravitationally curved space around a star, as described by the general theory of relativity.

Optical fibres act as pipes for . And just as the inside of a pipe is enclosed by a wall, optical fibres normally have a light-guiding core, whose glass has a higher refractive index than the glass of the enclosing outer cladding. The difference in the refractive index causes the light to be reflected at the cladding interface and trapped in the core like water in a pipe. A team headed by Philip Russell, Director at the Max Planck Institute for the Science of Light, is the first to succeed in guiding light in a PCF with no core.

Photonic crystals give butterflies their colour and can also guide light

A typical photonic crystal consists of a piece of glass with holes arranged in regular periodic pattern throughout its volume. Since glass and the air have different refractive indices, the refractive index has a periodic structure. This is the reason these materials are called crystals—their atoms form an ordered, three-dimensional lattice as found in crystalline salt or silicon, for example. In a conventional crystal, the precise design of the 3-D structure determines the behaviour of electrons, resulting for example in electrical insulators, conductors and semiconductors.

In a similar manner, the optical properties of a photonic crystal depend on the periodic 3-D microstructure, which is responsible for the shimmering colours of some butterfly wings, for example. Being able to control the optical properties of materials is useful in a wide variety of applications. The photonic crystal fibres developed by Philip Russell and his team at the Erlangen-based Max Planck Institute can be used to filter specific wavelengths out of the visible spectrum or to produce very white light, for example.

As is the case with all optical fibres used in telecommunications, all conventional photonic crystal fibres have a core and cladding each with different refractive indices or optical properties. In PCF, the air-filled channels already give the glass a different from the one it would have if completely solid.

The holes define the space in a photonic crystal fibre

“We are the first to succeed in guiding light through a coreless fibre,” says Gordon Wong from the Max Planck Institute for the Science of Light in Erlangen. The researchers working in Philip Russell’s team have fabricated a photonic crystal fibre whose complete cross-section is closely packed with a large number of air-filled channels, each around one thousandth of a millimetre in diameter, which extend along its whole length.

While the core of a conventional PCF is solid glass, the cross-sectional view of the new optical fibre resembles a sieve. The holes have regular separations and are arranged so that every hole is surrounded by a regular hexagon of neighbouring holes. “This structure defines the space in the fibre,” explains Ramin Beravat, lead author of the publication. The holes can be thought of as distance markers. The interior of the fibre then has a kind of artificial spatial structure which is formed by the regular lattice of holes.

“We have now fabricated the fibre in a twisted form,” continues Beravat. The twisting causes the hollow channels to wind around the length of the fibre in helical lines. The researchers then transmitted laser light through the fibre. In the case of the regular, coreless cross-section, one would actually expect the light to distribute itself between the holes of the sieve as evenly as their pattern determines, i.e. at the edge just as much as in the centre. Instead, the physicists discovered something surprising: the light was concentrated in the central region, where the core of a conventional optical fibre is located.

In a twisted PCF, the light follows the shortest path in the interior of the fibre

“The effect is analogous to the curvature of space in Einstein’s general theory of relativity,” explains Wong. This predicts that a heavy mass such as the Sun will distort the space surrounding it – or more precisely, distort spacetime, i.e. the combination of the three spatial dimensions with the fourth dimension, time – like a sheet of rubber into which a lead sphere is placed. Light follows this curvature. The shortest path between two points is then no longer a straight line, but a curve. During a solar eclipse, stars which should really be hidden behind the Sun thus become visible. Physicists call these shortest connecting paths “geodesics”.

“By twisting the fibre, the ‘space’ in our photonic crystal fibre becomes twisted as well,” says Wong. This leads to helical geodesic lines along which light travels. This can be intuitively understood by taking into account the fact that light always takes the shortest route through a medium. The glass strands between the air-filled channels describe spirals, which define possible paths for the . The path through the wide spirals at the edge of the fibre is longer than that through the more closely wound spirals in its centre, however, resulting in curved ray paths that at a certain radius are reflected by a effect back towards the fibre axis.

A twisted PCF as a large-scale environmental sensor

The more the fibre is twisted, the narrower is the space within which the light concentrated. In analogy to Einstein’s theory, this corresponds to a stronger gravitational force and thus a greater deflection of the light. The Erlangen-based researchers write that they have created a “topological channel” for the light (topology is concerned with the properties of space which are conserved under continuous distortion).

The researchers emphasize that their work is basic research. They are one of the very few research groups working in this field anywhere in the world. Nevertheless, they can think of several applications for their discovery. A twisted fibre which is less twisted at certain intervals, for example, will allow a portion of the light to escape to the outside. Light could then interact with the environment at these defined locations. “This could be used for sensors which measure the absorption of a medium, for instance.” A network of these fibres could collect data over large areas as an environmental sensor.

Explore further: A photonic crystal fibre generates light from the ultraviolet to the mid-infrared

More information: R. Beravat et al. Twist-induced guidance in coreless photonic crystal fiber: A helical channel for light, Science Advances (2016). DOI: 10.1126/sciadv.1601421