For some reason it took a lot longer than usual to find this research paper despite having the journal (Nature Communications), the title (Spontaneous formation …), and the authors’ names. Thankfully, success was wrested from the jaws of defeat (I don’t care if that is trite; it’s how I felt) and links, etc. follow at the end as usual.
An experiment that, by design, was not supposed to turn up anything of note instead produced a “bewildering” surprise, according to the Stanford scientists who made the discovery: a new way of creating gold nanoparticles and nanowires using water droplets.
The technique, detailed April 19  in the journal Nature Communications, is the latest discovery in the new field of on-droplet chemistry and could lead to more environmentally friendly ways to produce nanoparticles of gold and other metals, said study leader Richard Zare, a chemist in the School of Humanities and Sciences and a co-founder of Stanford Bio-X.
“Being able to do reactions in water means you don’t have to worry about contamination. It’s green chemistry,” said Zare, who is the Marguerite Blake Wilbur Professor in Natural Science at Stanford.
Gold is known as a noble metal because it is relatively unreactive. Unlike base metals such as nickel and copper, gold is resistant to corrosion and oxidation, which is one reason it is such a popular metal for jewelry.
Around the mid-1980s, however, scientists discovered that gold’s chemical aloofness only manifests at large, or macroscopic, scales. At the nanometer scale, gold particles are very chemically reactive and make excellent catalysts. Today, gold nanostructures have found a role in a wide variety of applications, including bio-imaging, drug delivery, toxic gas detection and biosensors.
Until now, however, the only reliable way to make gold nanoparticles was to combine the gold precursor chloroauric acid with a reducing agent such as sodium borohydride.
The reaction transfers electrons from the reducing agent to the chloroauric acid, liberating gold atoms in the process. Depending on how the gold atoms then clump together, they can form nano-size beads, wires, rods, prisms and more.
A spritz of gold
Recently, Zare and his colleagues wondered whether this gold-producing reaction would proceed any differently with tiny, micron-size droplets of chloroauric acid and sodium borohydide. How large is a microdroplet? “It is like squeezing a perfume bottle and out spritzes a mist of microdroplets,” Zare said.
From previous experiments, the scientists knew that some chemical reactions proceed much faster in microdroplets than in larger solution volumes.
Indeed, the team observed that gold nanoparticle grew over 100,000 times faster in microdroplets. However, the most striking observation came while running a control experiment in which they replaced the reducing agent – which ordinarily releases the gold particles – with microdroplets of water.
“Much to our bewilderment, we found that gold nanostructures could be made without any added reducing agents,” said study first author Jae Kyoo Lee, a research associate.
Viewed under an electron microscope, the gold nanoparticles and nanowires appear fused together like berry clusters on a branch.
The surprise finding means that pure water microdroplets can serve as microreactors for the production of gold nanostructures. “This is yet more evidence that reactions in water droplets can be fundamentally different from those in bulk water,” said study coauthor Devleena Samanta, a former graduate student in Zare’s lab and co-author on the paper.
If the process can be scaled up, it could eliminate the need for potentially toxic reducing agents that have harmful health side effects or that can pollute waterways, Zare said.
It’s still unclear why water microdroplets are able to replace a reducing agent in this reaction. One possibility is that transforming the water into microdroplets greatly increases its surface area, creating the opportunity for a strong electric field to form at the air-water interface, which may promote the formation of gold nanoparticles and nanowires.
“The surface area atop a one-liter beaker of water is less than one square meter. But if you turn the water in that beaker into microdroplets, you will get about 3,000 square meters of surface area – about the size of half a football field,” Zare said.
The team is exploring ways to utilize the nanostructures for various catalytic and biomedical applications and to refine their technique to create gold films.
“We observed a network of nanowires that may allow the formation of a thin layer of nanowires,” Samanta said.
Here’s more about the latest Café Scientifique talk from an August 22, 2018 announcement received via email,
Our next café will happen on TUESDAY, AUGUST 28TH at 7:30PM in the back
room at YAGGER'S DOWNTOWN (433 W Pender [St., Vancouver]). Our speaker for the
evening will be DR. KATIE MARSHALL from the Department of Zoology at
UBC [University of British Columbia]. Her topic will be:
GETTING THE MESSAGE: WHAT IS GENE EXPRESSION AND WHY DOES IT MATTER?
Many of us think that DNA is like a light switch; you have a particular
sequence of base pairs or a particular chromosome, and these directly
cause a large change in biological functioning. But the truth is that
any given gene can be up or downregulated through a dizzying array of
biochemical “dimmer switches” that finely control how much that
particular gene is expressed. Understanding how this works is key to
answering questions like “How does a sequence of base pairs in DNA
become a whole organism?” and “Why is it that every cell has the
same DNA sequence but different function?”. We’ll chat about the
advances in computing needed to answer these questions, the importance
of gene expression in disease, and how this science can help us
understand social issues better too.
I wasn’t able to find out too much more about Dr. Katie but there is this profile page on the UBC Zoology Department website,
The long-term goal of my research is to understand how abiotic stress filters through physiology to shape species abundance and distribution. While abiotic stressors such as temperature have been used very successfully to predict population growth, distribution, and diversity of insect species, integration of the mechanisms of how these stressors are experienced by individuals from alteration of physiology through to fitness impacts has lagged. Inclusion of these mechanisms is crucial for accurate modelling predictions of individual (and therefore population-level) responses. My research to date has focused on how the impact of frequency of stress (rather than the duration or intensity of stress) is a superior predictor of both survival and reproductive success , and used insect cold tolerance as a model system.
At UBC I’ll be focusing on the cold tolerance and cryobiology of invertebrates in the intertidal. These organisms face freezing stress through the winter, yet remarkably little is known about how they do so. I’ll also be investigating plasticity in cold tolerance by looking for interactive effects of ocean acidification and community composition on thermal tolerance.
Should you have an oil well nearby (see The Urban Oil Fields of Los Angeles in an August 28, 2014 photo essay by Alan Taylor for The Atlantic for examples of oil wells in various municipalities and cities associated with LS) , this news from Texas may interest you.
Oil and water tend to separate, but they mix well enough to form stable oil-in-water emulsions in produced water from oil reservoirs to become a problem. Rice University scientists have developed a nanoparticle-based solution that reliably removes more than 99 percent of the emulsified oil that remains after other processing is done.
The Rice lab of chemical engineer Sibani Lisa Biswal made a magnetic nanoparticle compound that efficiently separates crude oil droplets from produced water that have proven difficult to remove with current methods.
Produced water [emphasis mine] comes from production wells along with oil. It often includes chemicals and surfactants pumped into a reservoir to push oil to the surface from tiny pores or cracks, either natural or fractured, deep underground. Under pressure and the presence of soapy surfactants, some of the oil and water form stable emulsions that cling together all the way back to the surface.
While methods exist to separate most of the oil from the production flow, engineers at Shell Global Solutions, which sponsored the project, told Biswal and her team that the last 5 percent of oil tends to remain stubbornly emulsified with little chance to be recovered.
“Injected chemicals and natural surfactants in crude oil can oftentimes chemically stabilize the oil-water interface, leading to small droplets of oil in water which are challenging to break up,” said Biswal, an associate professor of chemical and biomolecular engineering and of materials science and nanoengineering.
The Rice lab’s experience with magnetic particles and expertise in amines, courtesy of former postdoctoral researcher and lead author Qing Wang, led it to combine techniques. The researchers added amines to magnetic iron nanoparticles. Amines carry a positive charge that helps the nanoparticles find negatively charged oil droplets. Once they do, the nanoparticles bind the oil. Magnets are then able to pull the droplets and nanoparticles out of the solution.
“It’s often hard to design nanoparticles that don’t simply aggregate in the high salinities that are typically found in reservoir fluids, but these are quite stable in the produced water,” Biswal said.
The enhanced nanoparticles were tested on emulsions made in the lab with model oil as well as crude oil.
In both cases, researchers inserted nanoparticles into the emulsions, which they simply shook by hand and machine to break the oil-water bonds and create oil-nanoparticle bonds within minutes. Some of the oil floated to the top, while placing the test tube on a magnet pulled the infused nanotubes to the bottom, leaving clear water in between.
Best of all, Biswal said, the nanoparticles can be washed with a solvent and reused while the oil can be recovered. The researchers detailed six successful charge-discharge cycles of their compound and suspect it will remain effective for many more.
She said her lab is designing a flow-through reactor to process produced water in bulk and automatically recycle the nanoparticles. That would be valuable for industry and for sites like offshore oil rigs, where treated water could be returned to the ocean.
It seems to me that ‘produced water’ is another term for polluted water.I guess it’s the reverse to Shakespeare’s “a rose by any other name would smell as sweet” with polluted water by any other name seeming more palatable.
Rice has included this image amongst others in their news release,
Rice University engineers have developed magnetic nanoparticles that separate the last droplets of oil from produced water at wells. The particles draw in the bulk of the oil and are then attracted to the magnet, as demonstrated here. Photo by Jeff Fitlow
There’s also this video, which, in my book, borders on magical,
Beauty products aren’t usually the first applications that come to mind when discussing graphene or any other research and development (R&D) as I learned when teaching a course a few years ago. But research and development in that field are imperative as every company is scrambling for a short-lived competitive advantage for a truly new products or a perceived competitive advantage in a field where a lot of products are pretty much the same.
Graphene, a naturally black material, could provide a new strategy for dyeing hair in difficult-to-create dark shades. And because it’s a conductive material, hair dyed with graphene might also be less prone to staticky flyaways. Now, researchers have put it to the test. In an article published March 15  in the journal Chem, they used sheets of graphene to make a dye that adheres to the surface of hair, forming a coating that is resistant to at least 30 washes without the need for chemicals that open up and damage the hair cuticle.
Most permanent hair dyes used today are harmful to hair. “Your hair is covered in these cuticle scales like the scales of a fish, and people have to use ammonia or organic amines to lift the scales and allow dye molecules to get inside a lot quicker,” says senior author Jiaxing Huang, a materials scientist at Northwestern University. But lifting the cuticle makes the strands of the hair more brittle, and the damage is only exacerbated by the hydrogen peroxide that is used to trigger the reaction that synthesizes the dye once the pigment molecules are inside the hair.
These problems could theoretically be solved by a dye that coats rather than penetrates the hair. “However, the obvious problem of coating-based dyes is that they tend to wash out very easily,” says Huang. But when he and his team coated samples of human hair with a solution of graphene sheets, they were able to turn platinum blond hair black and keep it that way for at least 30 washes–the number necessary for a hair dye to be considered “permanent.”
This effectiveness has to do with the structure of graphene: it’s made of up thin, flexible sheets that can adapt to uneven surfaces. “Imagine a piece of paper. A business card is very rigid and doesn’t flex by itself. But if you take a much bigger sheet of newspaper–if you still can find one nowadays–it can bend easily. This makes graphene sheets a good coating material,” he says. And once the coating is formed, the graphene sheets are particularly good at keeping out water during washes, which keeps the water from eroding both the graphene and the polymer binder that the team also added to the dye solution to help with adhesion.
The graphene dye has additional advantages. Each coated hair is like a little wire in that it is able to conduct heat and electricity. This means that it’s easy for graphene-dyed hair to dissipate static electricity, eliminating the problem of flyaways on dry winter days. The graphene flakes are large enough that they won’t absorb through the skin like other dye molecules. And although graphene is typically black, its precursor, graphene oxide, is light brown. But the color of graphene oxide can be gradually darkened with heat or chemical reactions, meaning that this dye could be used for a variety of shades or even for an ombre effect.
What Huang thinks is particularly striking about this application of graphene is that it takes advantage of graphene’s most obvious property. “In many potential graphene applications, the black color of graphene is somewhat undesirable and something of a sore point,” he says. Here, though, it’s applied to a field where creating dark colors has historically been a problem.
The graphene used for hair dye also doesn’t need to be of the same high quality as it does for other applications. “For hair dye, the most important property is graphene being black. You can have graphene that is too lousy for higher-end electronic applications, but it’s perfectly okay for this. So I think this application can leverage the current graphene product as is, and that’s why I think that this could happen a lot sooner than many of the other proposed applications,” he says.
Making it happen is his next goal. He hopes to get funding to continue the research and make these dyes a reality for the people whose lives they would improve. “This is an idea that was inspired by curiosity. It was very fun to do, but it didn’t sound very big and noble when we started working on it,” he says. “But after we deep-dived into studying hair dyes, we realized that, wow, this is actually not at all a small problem. And it’s one that graphene could really help to solve.”
Northwestern University’s Amanda Morris also wrote a March 15, 2018 news release (it’s repetitive but there are some interesting new details; Note: Links have been removed),
It’s an issue that has plagued the beauty industry for more than a century: Dying hair too often can irreparably damage your silky strands.
Now a Northwestern University team has used materials science to solve this age-old problem. The team has leveraged super material graphene to develop a new hair dye that is less harmful [emphasis mine], non-damaging and lasts through many washes without fading. Graphene’s conductive nature also opens up new opportunities for hair, such as turning it into in situ electrodes or integrating it with wearable electronic devices.
Dying hair might seem simple and ordinary, but it’s actually a sophisticated chemical process. Called the cuticle, the outermost layer of a hair is made of cells that overlap in a scale-like pattern. Commercial dyes work by using harsh chemicals, such as ammonia and bleach, to first pry open the cuticle scales to allow colorant molecules inside and then trigger a reaction inside the hair to produce more color. Not only does this process cause hair to become more fragile, some of the small molecules are also quite toxic.
Huang and his team bypassed harmful chemicals altogether by leveraging the natural geometry of graphene sheets. While current hair dyes use a cocktail of small molecules that work by chemically altering the hair, graphene sheets are soft and flexible, so they wrap around each hair for an even coat. Huang’s ink formula also incorporates edible, non-toxic polymer binders to ensure that the graphene sticks — and lasts through at least 30 washes, which is the commercial requirement for permanent hair dye. An added bonus: graphene is anti-static, so it keeps winter-weather flyaways to a minimum.
“It’s similar to the difference between a wet paper towel and a tennis ball,” Huang explained, comparing the geometry of graphene to that of other black pigment particles, such as carbon black or iron oxide, which can only be used in temporary hair dyes. “The paper towel is going to wrap and stick much better. The ball-like particles are much more easily removed with shampoo.”
This geometry also contributes to why graphene is a safer alternative. Whereas small molecules can easily be inhaled or pass through the skin barrier, graphene is too big to enter the body. “Compared to those small molecules used in current hair dyes, graphene flakes are humongous,” said Huang, who is a member of Northwestern’s International Institute of Nanotechnology.
Ever since graphene — the two-dimensional network of carbon atoms — burst onto the science scene in 2004, the possibilities for the promising material have seemed nearly endless. With its ultra-strong and lightweight structure, graphene has potential for many applications in high-performance electronics, high-strength materials and energy devices. But development of those applications often require graphene materials to be as structurally perfect as possible in order to achieve extraordinary electrical, mechanical or thermal properties.
The most important graphene property for Huang’s hair dye, however, is simply its color: black. So Huang’s team used graphene oxide, an imperfect version of graphene that is a cheaper, more available oxidized derivative.
“Our hair dye solves a real-world problem without relying on very high-quality graphene, which is not easy to make,” Huang said. “Obviously more work needs to be done, but I feel optimistic about this application.”
Still, future versions of the dye could someday potentially leverage graphene’s notable properties, including its highly conductive nature.
“People could apply this dye to make hair conductive on the surface,” Huang said. “It could then be integrated with wearable electronics or become a conductive probe. We are only limited by our imagination.”
So far, Huang has developed graphene-based hair dyes in multiple shades of brown and black. Next, he plans to experiment with more colors.
Interestingly, the tiny note of caution”less harmful” doesn’t appear in the Cell Press news release. Never fear, Dr. Andrew Maynard (Director Risk Innovation Lab at Arizona State University) has written a March 20, 2018 essay on The Conversation suggesting a little further investigation (Note: Links have been removed),
Northwestern University’s press release proudly announced, “Graphene finds new application as nontoxic, anti-static hair dye.” The announcement spawned headlines like “Enough with the toxic hair dyes. We could use graphene instead,” and “’Miracle material’ graphene used to create the ultimate hair dye.”
From these headlines, you might be forgiven for getting the idea that the safety of graphene-based hair dyes is a done deal. Yet having studied the potential health and environmental impacts of engineered nanomaterials for more years than I care to remember, I find such overly optimistic pronouncements worrying – especially when they’re not backed up by clear evidence.
Tiny materials, potentially bigger problems
Engineered nanomaterials like graphene and graphene oxide (the particular form used in the dye experiments) aren’t necessarily harmful. But nanomaterials can behave in unusual ways that depend on particle size, shape, chemistry and application. Because of this, researchers have long been cautious about giving them a clean bill of health without first testing them extensively. And while a large body of research to date doesn’t indicate graphene is particularly dangerous, neither does it suggest it’s completely safe.
A quick search of scientific papers over the past few years shows that, since 2004, over 2,000 studies have been published that mention graphene toxicity; nearly 500 were published in 2017 alone.
This growing body of research suggests that if graphene gets into your body or the environment in sufficient quantities, it could cause harm. A 2016 review, for instance, indicated that graphene oxide particles could result in lung damage at high doses (equivalent to around 0.7 grams of inhaled material). Another review published in 2017 suggested that these materials could affect the biology of some plants and algae, as well as invertebrates and vertebrates toward the lower end of the ecological pyramid. The authors of the 2017 study concluded that research “unequivocally confirms that graphene in any of its numerous forms and derivatives must be approached as a potentially hazardous material.”
These studies need to be approached with care, as the precise risks of graphene exposure will depend on how the material is used, how exposure occurs and how much of it is encountered. Yet there’s sufficient evidence to suggest that this substance should be used with caution – especially where there’s a high chance of exposure or that it could be released into the environment.
Unfortunately, graphene-based hair dyes tick both of these boxes. Used in this way, the substance is potentially inhalable (especially with spray-on products) and ingestible through careless use. It’s also almost guaranteed that excess graphene-containing dye will wash down the drain and into the environment.
Undermining other efforts?
I was alerted to just how counterproductive such headlines can be by my colleague Tim Harper, founder of G2O Water Technologies – a company that uses graphene oxide-coated membranes to treat wastewater. Like many companies in this area, G2O has been working to use graphene responsibly by minimizing the amount of graphene that ends up released to the environment.
Yet as Tim pointed out to me, if people are led to believe “that bunging a few grams of graphene down the drain every time you dye your hair is OK, this invalidates all the work we are doing making sure the few nanograms of graphene on our membranes stay put.” Many companies that use nanomaterials are trying to do the right thing, but it’s hard to justify the time and expense of being responsible when someone else’s more cavalier actions undercut your efforts.
Overpromising results and overlooking risk
This is where researchers and their institutions need to move beyond an “economy of promises” that spurs on hyperbole and discourages caution, and think more critically about how their statements may ultimately undermine responsible and beneficial development of a technology. They may even want to consider using guidelines, such as the Principles for Responsible Innovation developed by the organization Society Inside, for instance, to guide what they do and say.
If you have time, I encourage you to read Andrew’s piece in its entirety.
Here’s a link to and a citation for the paper,
Multifunctional Graphene Hair Dye by Chong Luo, Lingye Zhou, Kevin Chiou, and Jiaxing Huang. Chem DOI: https://doi.org/10.1016/j.chempr.2018.02.02 Publication stage: In Press Corrected Proof
This paper appears to be open access.
*Two paragraphs (repetitions) were deleted from the excerpt of Dr. Andrew Maynard’s essay on August 14, 2018
Libraries, archives, records management, oral history, etc. there are many institutions and names for how we manage collective and personal memory. You might call it a peculiarly human obsession stretching back into antiquity. For example, there’s the Library of Alexandria (Wikipedia entry) founded in the third, or possibly 2nd, century BCE (before the common era) and reputed to store all the knowledge in the world. It was destroyed although accounts differ as to when and how but its loss remains a potent reminder of memory’s fragility.
These days, the technology community is terribly concerned with storing ever more bits of data on materials that are reaching their limits for storage.I have news of a possible solution, an interview of sorts with the researchers working on this new technology, and some very recent research into policies for cryptocurrency mining and development. That bit about cryptocurrency makes more sense when you read what the response to one of the interview questions.
It seems University of Alberta researchers may have found a way to increase memory exponentially, from a July 23, 2018 news item on ScienceDaily,
The most dense solid-state memory ever created could soon exceed the capabilities of current computer storage devices by 1,000 times, thanks to a new technique scientists at the University of Alberta have perfected.
“Essentially, you can take all 45 million songs on iTunes and store them on the surface of one quarter,” said Roshan Achal, PhD student in Department of Physics and lead author on the new research. “Five years ago, this wasn’t even something we thought possible.”
Previous discoveries were stable only at cryogenic conditions, meaning this new finding puts society light years closer to meeting the need for more storage for the current and continued deluge of data. One of the most exciting features of this memory is that it’s road-ready for real-world temperatures, as it can withstand normal use and transportation beyond the lab.
“What is often overlooked in the nanofabrication business is actual transportation to an end user, that simply was not possible until now given temperature restrictions,” continued Achal. “Our memory is stable well above room temperature and precise down to the atom.”
Achal explained that immediate applications will be data archival. Next steps will be increasing readout and writing speeds, meaning even more flexible applications.
“With this last piece of the puzzle now in-hand, atom-scale fabrication will become a commercial reality in the very near future,” said Wolkow. Wolkow’s Spin-off [sic] company, Quantum Silicon Inc., is hard at work on commercializing atom-scale fabrication for use in all areas of the technology sector.
To demonstrate the new discovery, Achal, Wolkow, and their fellow scientists not only fabricated the world’s smallest maple leaf, they also encoded the entire alphabet at a density of 138 terabytes, roughly equivalent to writing 350,000 letters across a grain of rice. For a playful twist, Achal also encoded music as an atom-sized song, the first 24 notes of which will make any video-game player of the 80s and 90s nostalgic for yesteryear but excited for the future of technology and society.
As noted in the news release, there is an atom-sized song, which is available in this video,
For interested parties, you can find Quantum Silicon (QSI) here. My Edmonton geography is all but nonexistent, still, it seems to me the company address on Saskatchewan Drive is a University of Alberta address. It’s also the address for the National Research Council of Canada. Perhaps this is a university/government spin-off company?
I sent some questions to the researchers at the University of Alberta who very kindly provided me with the following answers. Roshan Achal passed on one of the questions to his colleague Taleana Huff for her response. Both Achal and Huff are associated with QSI.
Unfortunately I could not find any pictures of all three researchers (Achal, Huff, and Wolkow) together.
Roshan Achal (left) used nanotechnology perfected by his PhD supervisor, Robert Wolkow (right) to create atomic-scale computer memory that could exceed the capacity of today’s solid-state storage drives by 1,000 times. (Photo: Faculty of Science)
(1) SHRINKING THE MANUFACTURING PROCESS TO THE ATOMIC SCALE HAS
ATTRACTED A LOT OF ATTENTION OVER THE YEARS STARTING WITH SCIENCE
FICTION OR RICHARD FEYNMAN OR K. ERIC DREXLER, ETC. IN ANY EVENT, THE
ORIGINS ARE CONTESTED SO I WON’T PUT YOU ON THE SPOT BY ASKING WHO
STARTED IT ALL INSTEAD ASKING HOW DID YOU GET STARTED?
I got started in this field about 6 years ago, when I undertook a MSc
with Dr. Wolkow here at the University of Alberta. Before that point, I
had only ever heard of a scanning tunneling microscope from what was
taught in my classes. I was aware of the famous IBM logo made up from
just a handful of atoms using this machine, but I didn’t know what
else could be done. Here, Dr. Wolkow introduced me to his line of
research, and I saw the immense potential for growth in this area and
decided to pursue it further. I had the chance to interact with and
learn from nanofabrication experts and gain the skills necessary to
begin playing around with my own techniques and ideas during my PhD.
(2) AS I UNDERSTAND IT, THESE ARE THE PIECES YOU’VE BEEN
WORKING ON: (1) THE TUNGSTEN MICROSCOPE TIP, WHICH MAKE[s] (2) THE SMALLEST
QUANTUM DOTS (SINGLE ATOMS OF SILICON), (3) THE AUTOMATION OF THE
QUANTUM DOT PRODUCTION PROCESS, AND (4) THE “MOST DENSE SOLID-STATE
MEMORY EVER CREATED.” WHAT’S MISSING FROM THE LIST AND IS THAT WHAT
YOU’RE WORKING ON NOW?
One of the things missing from the list, that we are currently working
on, is the ability to easily communicate (electrically) from the
macroscale (our world) to the nanoscale, without the use of a scanning
tunneling microscope. With this, we would be able to then construct
devices using the other pieces we’ve developed up to this point, and
then integrate them with more conventional electronics. This would bring
us yet another step closer to the realization of atomic-scale
(3) PERHAPS YOU COULD CLARIFY SOMETHING FOR ME. USUALLY WHEN SOLID STATE
MEMORY IS MENTIONED, THERE’S GREAT CONCERN ABOUT MOORE’S LAW. IS
THIS WORK GOING TO CREATE A NEW LAW? AND, WHAT IF ANYTHING DOES
;YOUR MEMORY DEVICE HAVE TO DO WITH QUANTUM COMPUTING?
That is an interesting question. With the density we’ve achieved,
there are not too many surfaces where atomic sites are more closely
spaced to allow for another factor of two improvement. In that sense, it
would be difficult to improve memory densities further using these
techniques alone. In order to continue Moore’s law, new techniques, or
storage methods would have to be developed to move beyond atomic-scale
The memory design itself does not have anything to do with quantum
computing, however, the lithographic techniques developed through our
work, may enable the development of certain quantum-dot-based quantum
(4) THIS MAY BE A LITTLE OUT OF LEFT FIELD (OR FURTHER OUT THAN THE
OTHERS), COULD;YOUR MEMORY DEVICE HAVE AN IMPACT ON THE
DEVELOPMENT OF CRYPTOCURRENCY AND BLOCKCHAIN? IF SO, WHAT MIGHT THAT
I am not very familiar with these topics, however, co-author Taleana
Huff has provided some thoughts:
Taleana Huff (downloaded from https://ca.linkedin.com/in/taleana-huff]
“The memory, as we’ve designed it, might not have too much of an
impact in and of itself. Cryptocurrencies fall into two categories.
Proof of Work and Proof of Stake. Proof of Work relies on raw
computational power to solve a difficult math problem. If you solve it,
you get rewarded with a small amount of that coin. The problem is that
it can take a lot of power and energy for your computer to crunch
through that problem. Faster access to memory alone could perhaps
streamline small parts of this slightly, but it would be very slight.
Proof of Stake is already quite power efficient and wouldn’t really
have a drastic advantage from better faster computers.
Now, atomic-scale circuitry built using these new lithographic
techniques that we’ve developed, which could perform computations at
significantly lower energy costs, would be huge for Proof of Work coins.
One of the things holding bitcoin back, for example, is that mining it
is now consuming power on the order of the annual energy consumption
required by small countries. A more efficient way to mine while still
taking the same amount of time to solve the problem would make bitcoin
much more attractive as a currency.”
Thank you to Roshan Achal and Taleana Huff for helping me to further explore the implications of their work with Dr. Wolkow.
As usual, after receiving the replies I have more questions but these people have other things to do so I’ll content myself with noting that there is something extraordinary in the fact that we can imagine a near future where atomic scale manufacturing is possible and where as Achal says, ” … storage methods would have to be developed to move beyond atomic-scale [emphasis mine] storage”. In decades past it was the stuff of science fiction or of theorists who didn’t have the tools to turn the idea into a reality. With Wolkow’s, Achal’s, Hauff’s, and their colleagues’ work, atomic scale manufacturing is attainable in the foreseeable future.
Hopefully we’ll be wiser than we have been in the past in how we deploy these new manufacturing techniques. Of course, before we need the wisdom, scientists, as Achal notes, need to find a new way to communicate between the macroscale and the nanoscale.
A study [behind a paywall] published in Energy Research & Social Science warns that failure to lower the energy use by Bitcoin and similar Blockchain designs may prevent nations from reaching their climate change mitigation obligations under the Paris Agreement.
The study, authored by Jon Truby, PhD, Assistant Professor, Director of the Centre for Law & Development, College of Law, Qatar University, Doha, Qatar, evaluates the financial and legal options available to lawmakers to moderate blockchain-related energy consumption and foster a sustainable and innovative technology sector. Based on this rigorous review and analysis of the technologies, ownership models, and jurisdictional case law and practices, the article recommends an approach that imposes new taxes, charges, or restrictions to reduce demand by users, miners, and miner manufacturers who employ polluting technologies, and offers incentives that encourage developers to create less energy-intensive/carbon-neutral Blockchain.
“Digital currency mining is the first major industry developed from Blockchain, because its transactions alone consume more electricity than entire nations,” said Dr. Truby. “It needs to be directed towards sustainability if it is to realize its potential advantages.
“Many developers have taken no account of the environmental impact of their designs, so we must encourage them to adopt consensus protocols that do not result in high emissions. Taking no action means we are subsidizing high energy-consuming technology and causing future Blockchain developers to follow the same harmful path. We need to de-socialize the environmental costs involved while continuing to encourage progress of this important technology to unlock its potential economic, environmental, and social benefits,” explained Dr. Truby.
As a digital ledger that is accessible to, and trusted by all participants, Blockchain technology decentralizes and transforms the exchange of assets through peer-to-peer verification and payments. Blockchain technology has been advocated as being capable of delivering environmental and social benefits under the UN’s Sustainable Development Goals. However, Bitcoin’s system has been built in a way that is reminiscent of physical mining of natural resources – costs and efforts rise as the system reaches the ultimate resource limit and the mining of new resources requires increasing hardware resources, which consume huge amounts of electricity.
Putting this into perspective, Dr. Truby said, “the processes involved in a single Bitcoin transaction could provide electricity to a British home for a month – with the environmental costs socialized for private benefit.
“Bitcoin is here to stay, and so, future models must be designed without reliance on energy consumption so disproportionate on their economic or social benefits.”
The study evaluates various Blockchain technologies by their carbon footprints and recommends how to tax or restrict Blockchain types at different phases of production and use to discourage polluting versions and encourage cleaner alternatives. It also analyzes the legal measures that can be introduced to encourage technology innovators to develop low-emissions Blockchain designs. The specific recommendations include imposing levies to prevent path-dependent inertia from constraining innovation:
Registration fees collected by brokers from digital coin buyers.
“Bitcoin Sin Tax” surcharge on digital currency ownership.
Green taxes and restrictions on machinery purchases/imports (e.g. Bitcoin mining machines).
Smart contract transaction charges.
According to Dr. Truby, these findings may lead to new taxes, charges or restrictions, but could also lead to financial rewards for innovators developing carbon-neutral Blockchain.
The press release doesn’t fully reflect Dr. Truby’s thoughtfulness or the incentives he has suggested. it’s not all surcharges, taxes, and fees constitute encouragement. Here’s a sample from the conclusion,
The possibilities of Blockchain are endless and incentivisation can help solve various climate change issues, such as through the development of digital currencies to fund climate finance programmes. This type of public-private finance initiative is envisioned in the Paris Agreement, and fiscal tools can incentivize innovators to design financially rewarding Blockchain technology that also achieves environmental goals. Bitcoin, for example, has various utilitarian intentions in its White Paper, which may or may not turn out to be as envisioned, but it would not have been such a success without investors seeking remarkable returns. Embracing such technology, and promoting a shift in behaviour with such fiscal tools, can turn the industry itself towards achieving innovative solutions for environmental goals.
I realize Wolkow, et. al, are not focused on cryptocurrency and blockchain technology per se but as Huff notes in her reply, “… new lithographic techniques that we’ve developed, which could perform computations at significantly lower energy costs, would be huge for Proof of Work coins.”
Whether or not there are implications for cryptocurrencies, energy needs, climate change, etc., it’s the kind of innovative work being done by scientists at the University of Alberta which may have implications in fields far beyond the researchers’ original intentions such as more efficient computation and data storage.
ETA Aug. 6, 2018: Dexter Johnson weighed in with an August 3, 2018 posting on his Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers] website),
Researchers at the University of Alberta in Canada have developed a new approach to rewritable data storage technology by using a scanning tunneling microscope (STM) to remove and replace hydrogen atoms from the surface of a silicon wafer. If this approach realizes its potential, it could lead to a data storage technology capable of storing 1,000 times more data than today’s hard drives, up to 138 terabytes per square inch.
As a bit of background, Gerd Binnig and Heinrich Rohrer developed the first STM in 1986 for which they later received the Nobel Prize in physics. In the over 30 years since an STM first imaged an atom by exploiting a phenomenon known as tunneling—which causes electrons to jump from the surface atoms of a material to the tip of an ultrasharp electrode suspended a few angstroms above—the technology has become the backbone of so-called nanotechnology.
In addition to imaging the world on the atomic scale for the last thirty years, STMs have been experimented with as a potential data storage device. Last year, we reported on how IBM (where Binnig and Rohrer first developed the STM) used an STM in combination with an iron atom to serve as an electron-spin resonance sensor to read the magnetic pole of holmium atoms. The north and south poles of the holmium atoms served as the 0 and 1 of digital logic.
The Canadian researchers have taken a somewhat different approach to making an STM into a data storage device by automating a known technique that uses the ultrasharp tip of the STM to apply a voltage pulse above an atom to remove individual hydrogen atoms from the surface of a silicon wafer. Once the atom has been removed, there is a vacancy on the surface. These vacancies can be patterned on the surface to create devices and memories.
If you have the time, I recommend reading Dexter’s posting as he provides clear explanations, additional insight into the work, and more historical detail.
(Matias Careaga) [downloaded from https://www.smithsonianmag.com/smart-news/scientists-made-matchcom-profile-bolivias-loneliest-frog-180968140/]
That is a very soulful look. How could any female Sehuencas water frog resist it? Sadly, that’s the problem. They havn’t found any female Sehuencas water frogs yet.
It’s not for want of trying. Back in February 2018 worldwide interest was raised when scientists as the Cochabamba Natural History Museum (Bolivia) started a campaign to find a mate and raise funds for a search. ( I don’t know how I missed this story the first time. For long time readers, this is my frog story for this year.) From a February 14, 2018 article by Anoop Menon for India.com,
Scientists are scouring for a mate for Romeo, who has been calling forth for mates for the last nine years now. But alas, a mate hasn’t been found in the rivers and streams of the Sehuencas water frog’s natural habitat so far. So scientists have decided to make a Match.com profile for the lovelorn frog, according to the BBC [British Broadcasting Corporation]. The effort hopes to raise awareness of the condition of the Sehuencas water frog and raise money to fund searches for the Sehuencas water frog in areas where they once thrived.
Romeo’s dating profile reads, “I’m a pretty simple guy. I tend to keep to myself and have the best nights just chilling at home, maybe binge-watching the waters around me. I do love food, though, and will throw a pair of pants on and get out of the house if there’s a worm or snail to be eaten!” His preference is for females between two to three inches tall and is okay with drinkers but not smokers. But honestly, at this point, he should be fine with just about anything.
All jokes aside, Romeo’s plight is an important one. The profile links to the campaign donation page that it is part of, with an aim of raising USD 15,000 to search for more Sehuencas water frogs. And Match.com is doing its part by matching all donations made from February 9 to today, Valentine’s Day.
Zoe Schlanger’s February 10, 2018 article for Quartz, in the context of Romeo’s (and the scientists’) quest, offers information about the ‘current state of amphibia’, Note: Links have been removed)
As the Earth faces what some experts call its “sixth mass extinction,” amphibians, like frogs, are among the most imperiled. Around half of amphibian species (which includes toads, salamanders, frogs, and newts) are reported to be in decline. A third are considered to be threatened with extinction.
Last year, 10,000 critically endangered “scrotum frogs” that lived in Lake Titicaca on the border between Bolivia and Peru died en masse. In the US, federal scientists say the overall amphibian population is shrinking in size by 3.8% every year. That trend has continued since the 1960s, due to a mix of climate change, pesticide applications, and diseases like infectious fungi which can quickly decimate populations.
Frogs seem to be especially vulnerable. Roughly 74% of frog species globally are in decline, and 80% of the frog species that live in India are threatened, a researcher recently told the Hindustan Times.
Arturo Munoz [Arturo Muñoz Saravia] , founder of the Bolivian Amphibian Initiative and GWC [Global Wildlife Conservaation] associate conservation scientist, said, “When biologists collected Romeo 10 years ago, we knew the Sehuencas water frog, like other amphibians in Bolivia, was in trouble, but we had no idea we wouldn’t be able to find a single other individual in all this time.”
Romeo started to call for a mate about a year after he was brought into captivity and Munoz pointed out that those calls have slowed in the last few years.
“We don’t want him to lose hope, and we continue to remain hopeful that others are out there, so we can establish a conservation breeding program to save this species,” Munoz said.
They raised almost $25,000 in funds to search for a female but there’s been no luck yet. Sehuencas water frogs live for about 15 years and Romeo has lived in the Cochabamba Natural History Museum for the last nine or 10 years. You do the arithmetic.
Apparently, Sehuencas water frogs were once found in both Ecuador and Bolivia. Today, there are only two regions of Bolivia (Cochabamba and Santa Cruz) where they are reputed to live. (There is more about the current search for a mate in a July 26, 2018 news item on phys.org.)The Sehuencas water frog Wikipedia entry has this to say (Note: Links have been removed),
While it is currently listed as vulnerable by the IUCN [International Union for Conservation of Nature], this is based on an assessment that has not been updated since 2004. No individuals have been encountered in the wild since 2008.
One possibility occurred to me (and I imagine others), if there’s someone out there who has a female Sehuencas water frog in their aquarium at home, please consider saving the species. I’m certain a deal can be made.
I don’t usually concern myself with SPF numbers on sunscreens as my primary focus has been on the inclusion of nanoscale metal particles (these are still considered safe). However, a recent conversation with a dental hygienist and coincidentally tripping across a June 19, 2018 posting on the Schrodinger’s Cat blog shortly after the convo. has me reassessing my take on SPF numbers (Note: Links have been removed),
So, what’s the deal with SPF? A recent interview of Dr Steven Q Wang, M.D., chair of The Skin Cancer Foundation Photobiology Committee, finally will give us some clarity. Apparently, the SPF number, be it 15, 30, or 50, refers to the amount of UVB protection that that sunscreen provides. Rather than comparing the SPFs to each other, like we all do at the store, SPF is a reflection of the length of time it would take for the Sun’s UVB radiation to redden your skin (used exactly as directed), versus if you didn’t apply any sunscreen at all. In ideal situations (in lab settings), if you wore SPF 30, it would take 30 times longer for you to get a sunburn than if you didn’t wear any sunscreen.
What’s more, SPF 30 is not nearly half the strength of SPF 50. Rather, SPF 30 allows 3% of UVB rays to hit your skin, and SPF 50 allows about 2% of UVB rays to hit your skin. Now before you say that that is just one measly percent, it actually is much more. According to Dr Steven Q. Wang, SPF 30 allows around 1.5 times more UV radiation onto your skin than SPF 50. That’s an actual 150% difference [according to Wang’s article “… SPF 30 is allowing 50 percent more UV radiation onto your skin.”] in protection.
Schrodinger’s Cat (author of the ‘eponymous’ blog) offers a good overview of the topic in a friendly, informative fashion albeit I found the ‘percentage’ to be a bit confusing. (S)he also provides a link to a previous posting about the ingredients in sunscreens (I do have one point of disagreement with Schrodinger’s Cat regarding oxybenzone) as well as links to Dr. Steven Q. Wang’s May 24, 2018 Ask the Expert article about sunscreens and SPF numbers on skincancer.org. You can find the percentage under the ‘What Does the SPF Number Mean?’ subsection, in the second paragraph.
Ingredients: metallic nanoparticles and oxybenzone
The use of metallic nanoparticles (usually zinc oxide and/or (titanium dioxide) in sunscreens was loathed by civil society groups, in particular Friends of the Earth (FOE) who campaigned relentlessly against their use in sunscreens. The nadir for FOE was in February 2012 when the Australian government published a survey showing that 13% of the respondents were not using any sunscreens due to their fear of nanoparticles. For those who don’t know, Australia has the highest rate of skin cancer in the world. (You can read about the debacle in my Feb. 9, 2012 posting.)
At the time, the only civil society group which supported the use of metallic nanoparticles in sunscreens was the Environmental Working Group (EWG). After an examination of the research they, to their own surprise, came out in favour (grudgingly) of metallic nanoparticles. (The EWG were more concerned about the use of oxybenzone in sunscreens.)
Over time, the EWG’s perspective has been adopted by other groups to the point where sunscreens with metallic nanoparticles are commonplace in ‘natural’ or ‘organic’ sunscreens.
As for oxybenzones, Schrodinger’s Cat in a May 23, 2018 posting about sunscreen ingredients notes this (Note: Links have been removed),
Oxybenzone – Chemical sunscreen, protects from UV damage. Oxybenzone belongs to the chemical family Benzophenone, which are persistent (difficult to get rid of), bioaccumulative (builds up in your body over time), and toxic, or PBT [or: Persistent, bioaccumulative and toxic substances (PBTs)]. They are a possible carcinogen (cancer-causing agent), endocrine disrupter; however, this is debatable. Also could cause developmental and reproductive toxicity, could cause organ system toxicity, as well as could cause irritation and potentially toxic to the environment.
It seems that the tide is turning against the use of oxybenzones (from a July 3, 2018 article by Adam Bluestein for Fast Company; Note: Links have been removed),
On July 3 , Hawaii’s Governor, David Ig, will sign into law the first statewide ban on the sale of sunscreens containing chemicals that scientists say are damaging the Earth’s coral reefs. Passed by state legislators on May 1 , the bill targets two chemicals, oxybenzone and octinoxate, which are found in thousands of sunscreens and other skincare products. Studies published over the past 10 years have found that these UV-filtering chemicals–called benzophenones–are highly toxic to juvenile corals and other marine life and contribute to the fatal bleaching of coral reefs (along with global warming and runoff pollutants from land). (A 2008 study by European researchers estimated that 4,000 to 6,000 tons of sunblock accumulates in coral reefs every year.) Also, though both substances are FDA-approved for use in sunscreens, the nonprofit Environmental Working Group notes numerous studies linking oxybenzone to hormone disruption and cell damage that may lead to skin cancer. In its 2018 annual sunscreen guide, the EWG found oxybenzone in two-thirds of the 650 products it reviewed.
The Hawaii ban won’t take effect until January 2021, but it’s already causing a wave of disruption that’s affecting sunscreen manufacturers, retailers, and the medical community.
For starters, several other municipalities have already or could soon join Hawaii’s effort. In May , the Caribbean island of Bonaire announced a ban on chemicals sunscreens, and nonprofits such as the Sierra Club and Surfrider Foundation, along with dive industry and certain resort groups, are urging legislation to stop sunscreen pollution in California, Colorado, Florida, and the U.S. Virgin Islands. Marine nature reserves in Mexico already prohibit oxybenzone-containing sunscreens, and the U.S. National Park Service website for South Florida, Hawaii, U.S. Virgin Islands, and American Samoa recommends the use of “reef safe” sunscreens, which use natural mineral ingredients–zinc oxide or titanium oxide–to protect skin.
Makers of “eco,” “organic,” and “natural” sunscreens that already meet the new standards are seizing on the news from Hawaii to boost their visibility among the islands’ tourists–and to expand their footprint on the shelves of mainland retailers. This past spring, for example, Miami-based Raw Elements partnered with Hawaiian Airlines, Honolulu’s Waikiki Aquarium, the Aqua-Aston hotel group (Hawaii’s largest), and the Sheraton Maui Resort & Spa to get samples of its reef-safe zinc-oxide-based sunscreens to their guests. “These partnerships have had a tremendous impact raising awareness about this issue,” says founder and CEO Brian Guadagno, who notes that inquiries and sales have increased this year.
As Bluestein notes there are some concerns about this and other potential bans,
“Eliminating the use of sunscreen ingredients considered to be safe and effective by the FDA with a long history of use not only restricts consumer choice, but is also at odds with skin cancer prevention efforts […],” says Bayer, owner of the Coppertone brand, in a statement to Fast Company. Bayer disputes the validity of studies used to support the ban, which were published by scientists from U.S. National Oceanic & Atmospheric Administration, the nonprofit Haereticus Environmental Laboratory, Tel Aviv University, the University of Hawaii, and elsewhere. “Oxybenzone in sunscreen has not been scientifically proven to have an effect on the environment. We take this issue seriously and, along with the industry, have supported additional research to confirm that there is no effect.”
Johnson & Johnson, which markets Neutrogena sunscreens, is taking a similar stance, worrying that “the recent efforts in Hawaii to ban sunscreens that contain oxybenzone may actually adversely affect public health,” according to a company spokesperson. “Science shows that sunscreens are a key factor in preventing skin cancer, and our scientific assessment of the lab studies done to date in Hawaii show the methods were questionable and the data insufficient to draw factual conclusions about any impact on coral reefs.”
Terrified (and rightly so) about anything scaring people away from using sunblock, The American Academy of Dermatology, also opposes Hawaii’s ban. Suzanne M. Olbricht, president of the AADA, has issued a statement that the organization “is concerned that the public’s risk of developing skin cancer could increase due to potential new restrictions in Hawaii that impact access to sunscreens with ingredients necessary for broad-spectrum protection, as well as the potential stigma around sunscreen use that could develop as a result of these restrictions.”
The fact is that there are currently a large number of widely available reef-safe products on the market that provide “full spectrum” protection up to SPF50–meaning they protect against both UVB rays that cause sunburns as well as UVA radiation, which causes deeper skin damage. SPFs higher than 50 are largely a marketing gimmick, say advocates of chemical-free products: According to the Environmental Working Group, properly applied SPF 50 sunscreen blocks 98% of UVB rays; SPF 100 blocks 99%. And a sunscreen lotion’s SPF rating has little to do with its ability to shield skin from UVA rays.
I notice neither Bayer nor Johnson & Johnson nor the American Academy of Dermatology make mention of oxybenzone’s possible role as a hormone disruptor.
Given the importance that coral reefs have to the environment we all share, I’m inclined to support the oxybenzone ban based on that alone. Of course, it’s conceivable that metallic nanoparticles may also have a deleterious effect on coral reefs as their use increases. It’s to be hoped that’s not the case but if it is, then I’ll make my decisions accordingly and hope we have a viable alternative.
As for your sunscreen questions and needs, the Environment Working Group (EWG) has extensive information including a product guide on this page (scroll down to EWG’s Sunscreen Guide) and a discussion of ‘high’ SPF numbers I found useful for my decision-making.
I received this Café Scientifique April 30, 2018 notice (received via email),
Our next café will happen on TUESDAY, MAY 29TH at 7:30PM in the back
room at YAGGER'S DOWNTOWN (433 W Pender). Our speaker for the
evening will be DR. MICHELLE TSENG, Assistant Professor in the Zoology
department at UBC. Her topic will be:
INSECTS IN THE CITY: SHRINKING BEETLES AND DISAPPEARING BEES. HOW BUGS
HELP US LEARN ABOUT THE ECOLOGICAL EFFECTS OF URBANIZATION AND CLIMATE
Living in the city, we don’t always see the good bugs amongst the
pesky ones. In this presentation, I’ll take you on a trip down insect
lane and share with you the incredible diversity of insects that have
lived in Vancouver over the last 100 years. Many of these bugs have been
collected and preserved in museums and these collections provide us with
a historical snapshot of insect communities from the past. My students
and I have made some remarkable discoveries using museum insect
collections, and these findings help us understand how these fascinating
creatures are changing in response to warming climates and increased
Michelle Tseng is a professor of insect ecology at the UBC Biodiversity
Research Centre. She and her students study the impacts of habitat and
climate change on plankton and insects. Her group’s work has been
featured in national and international media, and on CBC’s Quirks and
Quarks. Michelle is also the zoologist on the award-winning CBC kids
show Scout and the Gumboot Kids.
The Tseng lab investigates ecological and evolutionary responses of populations and communities to novel environments. We test and refine theory related to predator-prey dynamics, body size variation, intra- and interspecific competition, and the maintenance of genetic variation, using laboratory and field experiments with freshwater plant and animal communities. We also use museum collections to investigate long term patterns in organism phenotype.
This new technique seems promising but there’ve been a lot of ‘cloaking’ devices announced in the years I’ve been blogging and, in all likelihood, I was late to the party so I’m exercising a little caution before getting too excited. For the latest development in cloaking devices, there’s a January 18, 2018 news item on Nanowerk,
Northwestern University researchers have developed a first-of-its-kind technique for creating entirely new classes of optical materials and devices that could lead to light bending and cloaking devices — news to make the ears of Star Trek’s Spock perk up.
Using DNA [deoxyribonucleic acid] as a key tool, the interdisciplinary team took gold nanoparticles of different sizes and shapes and arranged them in two and three dimensions to form optically active superlattices. Structures with specific configurations could be programmed through choice of particle type and both DNA-pattern and sequence to exhibit almost any color across the visible spectrum, the scientists report.
“Architecture is everything when designing new materials, and we now have a new way to precisely control particle architectures over large areas,” said Chad A. Mirkin, the George B. Rathmann Professor of Chemistry in the Weinberg College of Arts and Sciences at Northwestern. “Chemists and physicists will be able to build an almost infinite number of new structures with all sorts of interesting properties. These structures cannot be made by any known technique.”
The technique combines an old fabrication method — top-down lithography, the same method used to make computer chips — with a new one — programmable self-assembly driven by DNA. The Northwestern team is the first to combine the two to achieve individual particle control in three dimensions.
The study was published online by the journal Science today (Jan. 18). Mirkin and Vinayak P. Dravid and Koray Aydin, both professors in Northwestern’s McCormick School of Engineering, are co-corresponding authors.
Scientists will be able to use the powerful and flexible technique to build metamaterials — materials not found in nature — for a range of applications including sensors for medical and environmental uses.
The researchers used a combination of numerical simulations and optical spectroscopy techniques to identify particular nanoparticle superlattices that absorb specific wavelengths of visible light. The DNA-modified nanoparticles — gold in this case — are positioned on a pre-patterned template made of complementary DNA. Stacks of structures can be made by introducing a second and then a third DNA-modified particle with DNA that is complementary to the subsequent layers.
In addition to being unusual architectures, these materials are stimuli-responsive: the DNA strands that hold them together change in length when exposed to new environments, such as solutions of ethanol that vary in concentration. The change in DNA length, the researchers found, resulted in a change of color from black to red to green, providing extreme tunability of optical properties.
“Tuning the optical properties of metamaterials is a significant challenge, and our study achieves one of the highest tunability ranges achieved to date in optical metamaterials,” said Aydin, assistant professor of electrical engineering and computer science at McCormick.
“Our novel metamaterial platform — enabled by precise and extreme control of gold nanoparticle shape, size and spacing — holds significant promise for next-generation optical metamaterials and metasurfaces,” Aydin said.
The study describes a new way to organize nanoparticles in two and three dimensions. The researchers used lithography methods to drill tiny holes — only one nanoparticle wide — in a polymer resist, creating “landing pads” for nanoparticle components modified with strands of DNA. The landing pads are essential, Mirkin said, since they keep the structures that are grown vertical.
The nanoscopic landing pads are modified with one sequence of DNA, and the gold nanoparticles are modified with complementary DNA. By alternating nanoparticles with complementary DNA, the researchers built nanoparticle stacks with tremendous positional control and over a large area. The particles can be different sizes and shapes (spheres, cubes and disks, for example).
“This approach can be used to build periodic lattices from optically active particles, such as gold, silver and any other material that can be modified with DNA, with extraordinary nanoscale precision,” said Mirkin, director of Northwestern’s International Institute for Nanotechnology.
Mirkin also is a professor of medicine at Northwestern University Feinberg School of Medicine and professor of chemical and biological engineering, biomedical engineering and materials science and engineering in the McCormick School.
The success of the reported DNA programmable assembly required expertise with hybrid (soft-hard) materials and exquisite nanopatterning and lithographic capabilities to achieve the requisite spatial resolution, definition and fidelity across large substrate areas. The project team turned to Dravid, a longtime collaborator of Mirkin’s who specializes in nanopatterning, advanced microscopy and characterization of soft, hard and hybrid nanostructures.
Dravid contributed his expertise and assisted in designing the nanopatterning and lithography strategy and the associated characterization of the new exotic structures. He is the Abraham Harris Professor of Materials Science and Engineering in McCormick and the founding director of the NUANCE center, which houses the advanced patterning, lithography and characterization used in the DNA-programmed structures.
As noted earlier, it could be a while before cloaking devices are made available. In the meantime, you may find this image inspiring,
Caption: Northwestern University researchers have developed a new method to precisely arrange nanoparticles of different sizes and shapes in two and three dimensions, resulting in optically active superlattices. Credit: Northwestern University
The Great Wave off Kanagawa (Under a wave off Kanagawa”), also known as The Great Wave or simply The Wave, by Katsushika Hokusai – Metropolitan Museum of Art, online database: entry 45434, Public Domain, https://commons.wikimedia.org/w/index.php?curid=2798407
I thought it might be a good idea to embed a copy of Hokusai’s Great Wave and the blue these scientists in Japan have used as their inspiration. (By the way, it seems these scientists collaborated with Mildred Dresselhaus who died at the age of 86, a few months after their paper was published. In honour of he and before the latest, here’s my Feb. 23, 2017 posting about the ‘Queen of Carbon’.)
By combining the same Prussian blue pigment used in the works of popular Edo-period artist Hokusai and cellulose nanofiber, a raw material of paper, a University of Tokyo research team succeeded in synthesizing compound nanoparticles, comprising organic and inorganic substances (Scientific Reports, “Cellulose nanofiber backboned Prussian blue nanoparticles as powerful adsorbents for the selective elimination of radioactive cesium”). This new class of organic/inorganic composite nanoparticles is able to selectively adsorb, or collect on the surface, radioactive cesium.
The team subsequently developed sponges from these nanoparticles that proved highly effective in decontaminating the water and soil in Fukushima Prefecture exposed to radioactivity following the nuclear accident there in March 2011.
I think these are the actual sponges not an artist’s impression,
Removing radioactive materials such as cesium-134 and -137 from contaminated seawater or soil is not an easy job. First of all, a huge amount of similar substances with competing functions has to be removed from the area, an extremely difficult task. Prussian blue (ferric hexacyanoferrate) has a jungle gym-like colloidal structure, and the size of its single cubic orifice, or opening, is a near-perfect match to the size of cesium ions; therefore, it is prescribed as medication for patients exposed to radiation for selectively adsorbing cesium. However, as Prussian blue is highly attracted to water, recovering it becomes highly difficult once it is dissolved into the environment; for this reason, its use in the field for decontamination has been limited.
Taking a hint from the Prussian blue in Hokusai’s woodblock prints not losing their color even when getting wet from rain, the team led by Professor Ichiro Sakata and Project Professor Bunshi Fugetsu at the University of Tokyo’s Nanotechnology Innovation Research Unit at the Policy Alternatives Research Institute, and Project Researcher Adavan Kiliyankil Vipin at the Graduate School of Engineering developed an insoluble nanoparticle obtained from combining cellulose and Prussian blue—Hokusai had in fact formed a chemical bond in his handling of Prussian blue and paper (cellulose).
The scientists created this cellulose-Prussian blue combined nanoparticle by first preparing cellulose nanofibers using a process called TEMPO oxidization and securing ferric ions (III) onto them, then introduced a certain amount of hexacyanoferrate, which adhered to Prussian blue nanoparticles with a diameter ranging from 5–10 nanometers. The nanoparticles obtained in this way were highly resistant to water, and moreover, were capable of adsorbing 139 mg of radioactive cesium ion per gram.
Field studies on soil decontamination in Fukushima have been underway since last year. A highly effective approach has been to sow and allow plant seeds to germinate inside the sponge made from the nanoparticles, then getting the plants’ roots to take up cesium ions from the soil to the sponge. Water can significantly shorten decontamination times compared to soil, which usually requires extracting cesium from it with a solvent.
It has been more than six years since the radioactive fallout from a series of accidents at the Fukushima Daiichi nuclear power plant following the giant earthquake and tsunami in northeastern Japan. Decontamination with the cellulose nanofiber-Prussian blue compound can lead to new solutions for contamination in disaster-stricken areas.
“I was pondering about how Prussian blue immediately gets dissolved in water when I happened upon a Hokusai woodblock print, and how the indigo color remained firmly set in the paper, without bleeding, even after all these years,” reflects Fugetsu. He continues, “That revelation provided a clue for a solution.”
“The amount of research on cesium decontamination increased after the Chernobyl nuclear power plant accident, but a lot of the studies were limited to being academic and insufficient for practical application in Fukushima,” says Vipin. He adds, “Our research offers practical applications and has high potential for decontamination on an industrial scale not only in Fukushima but also in other cesium-contaminated areas.”