Category Archives: nanotechnology

Rapid formation of micro- and nanoplastics in the environment

Image: Nora Meides.

A June 18, 2021 news item on phys.org announces the results of research into how materials made of plastic break down into micro- and nanoplastic particles in the environment,

Most microplastic particles in the environment originate from larger pieces of plastic. In a long-term study, an interdisciplinary research team at the University of Bayreuth has simulated how quickly plastic breaks down into fragments under natural influences. High-tech laboratory tests on polystyrene show two phases of abiotic degradation. To begin with, the stability of the plastic is weakened by photo-oxidation. Then cracks form and more and more and smaller fragments are released into the environment. The study, published in the journal Environmental Science & Technology, allows conclusions to be drawn about other plastics that are common in the environment.

A June 17, 2021 University of Bayreuth press release, which originated the news item, provides more detail,

Polystyrene is an inexpensive plastic that is often used for packaging and thermal insulation, and is therefore particularly common in plastic waste. As part of their long-term study, the Bayreuth researchers for the first time combined analytical investigations, which were also carried out on polystyrene particles at the atomic level, with measurements determining the behaviour of these particles under mechanical stress. On the basis of this, they developed a model for abiotic degradation, i.e. degradation without the influence of living organisms.

“Our study shows that a single microplastic particle with a diameter of 160 micrometres releases about 500 particles in the order of 20 micrometres – i.e. 0.02 millimetres – over the course of one and a half years of being exposed to natural weathering processes in the environment. Over time, these particles in turn break down into smaller and smaller fragments. An ecocorona can form around these tiny particles, possibly facilitating penetration into the cells of living organisms. This was discovered a few months ago by another Bayreuth research group,” says first author Nora Meides, a doctoral student in macromolecular chemistry at the University of Bayreuth.

n the water, the microplastic particles were exposed to two stress factors: intense sunlight and continuous mechanical stress produced by agitation. In the real-world environment, sunlight and mechanical stress are in fact the two main abiotic factors that contribute to the gradual fragmentation of the particles. Irradiation by sunlight triggers oxidation processes on the surface of the particles. This photo-oxidation, in combination with mechanical stress, has significant consequences. The polystyrene chains become ever shorter. Furthermore, they become increasingly polar, i.e. centres of charge are formed in the molecules. In the second phase, the microplastic particles begin to fragment. Here, the particles break down into smaller and smaller micro- and nanoplastic fragments.

“Our research results are a valuable basis for investigating the abiotic degradation of macro- and microplastics in the environment – both on land and at the surface of water – in more detail, using other types of plastic as examples. We were surprised by the speed of fragmentation ourselves, which again shows the potential risks that could emanate from the growing burden of plastics on the environment. Especially larger plastic waste objects, are – when exposed to sunlight and abrasion – a reservoir of constant microplastic input. It is precisely these tiny particles, barely visible to the naked eye, that spread to the remotest ecosystems via various transport routes,” says Teresa Menzel, PhD student in the area of Polymer Engineering.

“The polystyrene investigated in our long-term study has a carbon-chain backbone, just like polyethylene and polypropylene. It is very likely that the two-phase model we have developed on polystyrene can be transferred to these plastics,” adds lead author Prof. Dr. Jürgen Senker, Professor of Inorganic Chemistry, who coordinated the research work. 

The study that has now been published is the result of the close interdisciplinary cooperation of a working group belonging to the DFG Collaborative Research Centre “Microplastics” at the University of Bayreuth. In this team, scientists from macromolecular chemistry, inorganic chemistry, engineering science, and animal ecology are jointly researching the formation and degradation of microplastics. Numerous types of research technology are available on the Bayreuth campus for this purpose, which were used in the long-term study: among others, ¹³C-MAS-NMR spectroscopy, energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and gel permeation chromatography (GPC).

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

Reconstructing the Environmental Degradation of Polystyrene by Accelerated Weathering by Nora Meides, Teresa Menzel, Björn Poetzschner, Martin G. J. Löder, Ulrich Mansfeld, Peter Strohriegl, Volker Altstaedt, and Jürgen Senker. Environ. Sci. Technol. 2021, 55, 12, 7930–7938 DOI: https://doi.org/10.1021/acs.est.0c07718 Publication Date: May 21, 2021 Copyright © 2021 The Authors. Published by American Chemical Society

This paper is behind a paywall.

Use AI to reduce worries about nanoparticles in food

A June 16, 2021 news item on ScienceDaily announces research into the impact that engineered metallic nanoparticles used in agricultural practices have on food,

While crop yield has achieved a substantial boost from nanotechnology in recent years, alarms over the health risks posed by nanoparticles within fresh produce and grains have also increased. In particular, nanoparticles entering the soil through irrigation, fertilizers and other sources have raised concerns about whether plants absorb these minute particles enough to cause toxicity.

In a new study published online in the journal Environmental Science and Technology, researchers at Texas A&M University have used machine learning [a form of artificial intelligence {AI}] to evaluate the salient properties of metallic nanoparticles that make them more susceptible for plant uptake. The researchers said their algorithm could indicate how much plants accumulate nanoparticles in their roots and shoots.

A June 16, 2021 Texas A&M University news release (also on EurekAlert), which originated the news item, describes the research, which employed two different machine learning algorithms, in more detail,

Nanoparticles are a burgeoning trend in several fields, including medicine, consumer products and agriculture. Depending on the type of nanoparticle, some have favorable surface properties, charge and magnetism, among other features. These qualities make them ideal for a number of applications. For example, in agriculture, nanoparticles may be used as antimicrobials to protect plants from pathogens. Alternatively, they can be used to bind to fertilizers or insecticides and then programmed for slow release to increase plant absorption.

These agricultural practices and others, like irrigation, can cause nanoparticles to accumulate in the soil. However, with the different types of nanoparticles that could exist in the ground and a staggeringly large number of terrestrial plant species, including food crops, it is not clearly known if certain properties of nanoparticles make them more likely to be absorbed by some plant species than others.

“As you can imagine, if we have to test the presence of each nanoparticle for every plant species, it is a huge number of experiments, which is very time-consuming and expensive,” said Xingmao “Samuel” Ma, associate professor in the Zachry Department of Civil and Environmental Engineering. “To give you an idea, silver nanoparticles alone can have hundreds of different sizes, shapes and surface coatings, and so, experimentally testing each one, even for a single plant species, is impractical.”

Instead, for their study, the researchers chose two different machine learning algorithms, an artificial neural network and gene-expression programming. They first trained these algorithms on a database created from past research on different metallic nanoparticles and the specific plants in which they accumulated. In particular, their database contained the size, shape and other characteristics of different nanoparticles, along with information on how much of these particles were absorbed from soil or nutrient-enriched water into the plant body.

Once trained, their machine learning algorithms could correctly predict the likelihood of a given metallic nanoparticle to accumulate in a plant species. Also, their algorithms revealed that when plants are in a nutrient-enriched or hydroponic solution, the chemical makeup of the metallic nanoparticle determines the propensity of accumulation in the roots and shoots. But if plants are grown in soil, the contents of organic matter and the clay in soil are key to nanoparticle uptake.

Ma said that while the machine learning algorithms could make predictions for most food crops and terrestrial plants, they might not yet be ready for aquatic plants. He also noted that the next step in his research would be to investigate if the machine learning algorithms could predict nanoparticle uptake from leaves rather than through the roots.

“It is quite understandable that people are concerned about the presence of nanoparticles in their fruits, vegetables and grains,” said Ma. “But instead of not using nanotechnology altogether, we would like farmers to reap the many benefits provided by this technology but avoid the potential food safety concerns.”

This image accompanies the paper’s research abstract,

[downloaded frm https://pubs.acs.org/doi/full/10.1021/acs.est.1c01603]

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

Prediction of Plant Uptake and Translocation of Engineered Metallic Nanoparticles by Machine Learning by Xiaoxuan Wang, Liwei Liu, Weilan Zhang, and Xingmao Ma. Environ. Sci. Technol. 2021, 55, 11, 7491–7500 DOI: https://doi.org/10.1021/acs.est.1c01603 Publication Date:May 17, 2021 Copyright © 2021 American Chemical Society

This paper is behind a paywall.

Walrus from Space project (citizen science)

Image:: Norwegian Atlantic Walrus. Photo: Tor Lund / WWF [Downloaded from: https://eminetra.co.uk/climate-change-the-walrus-from-space-project-is-calling-on-the-general-public-to-help-search-for-animals-on-satellite-imagery-climate-news/755984/]

Yesterday (October 14, 2021), the World Wildlife Federation (WWF) announced their Walrus from Space project in a press release,

WWF and British Antarctic Survey (BAS) are seeking the public’s help to search for walrus in thousands of satellite images taken from space, with the aim of learning more about how walrus will be impacted by the climate crisis. It’s hoped half a million people worldwide will join the new ‘Walrus from Space’ research project, a census of Atlantic walrus and walrus from the Laptev Sea, using satellite images provided by space and intelligence company Maxar Technologies’ DigitalGlobe.

Walrus are facing the reality of the climate crisis: their Arctic home is warming almost three times faster than the rest of the world and roughly 13% of summer sea ice is disappearing per decade.

From the comfort of their own homes, aspiring conservationists around the world can study the satellite pictures online, spot areas where walrus haul out onto land, and then count them. The data collected in this census of Atlantic and Laptev walrus will give scientists a clearer picture of how each population is doing—without disturbing the animals. The data will also help inform management decisions aimed at conservation efforts for the species.

Walrus use sea ice for resting and to give birth to their young. As sea ice diminishes, more walrus are forced to seek refuge on land, congregating for the chance to rest. Overcrowded beaches can have fatal consequences; walrus are easily frightened, and when spooked they stampede towards the water, trampling one another in their panic. Resting on land (as opposed to sea ice) may also force walrus to swim further and expand more energy to reach their food—food which in turn is being negatively impacted by the warming and acidification of the ocean.

In addition walrus can also be disturbed by shipping traffic and industrial development as the loss of sea ice makes the Arctic more accessible. Walrus are almost certainly going to be impacted by the climate crisis, which could result in significant population declines.

Rod Downie, chief polar adviser at WWF, said:

“Walrus are an iconic species of great cultural significance to the people of the Arctic, but climate change is melting their icy home. It’s easy to feel powerless in the face of the climate and nature emergency, but this project enables individuals to take action to understand a species threatened by the climate crisis, and to help to safeguard their future. “What happens in the Arctic doesn’t stay there; the climate crisis is a global problem, bigger than any person, species or region. Ahead of hosting this year’s global climate summit, the UK must raise its ambition and keep all of its climate promises—for the sake of the walrus, and the world.”

Previous population estimates are based upon the best data and knowledge available, but there are challenges associated with working with marine mammals in such a vast, remote and largely inaccessible place. This project will build upon the knowledge of Indigenous communities, using satellite technology to provide an up-to-date count of Atlantic and Laptev walrus populations.

Hannah Cubaynes, wildlife from space research associate at British Antarctic Survey, said:

“Assessing walrus populations by traditional methods is very difficult as they live in extremely remote areas, spend much of their time on the sea ice and move around a lot, Satellite images can solve this problem as they can survey huge tracts of coastline to assess where walrus are and help us count the ones that we find. “However, doing that for all the Atlantic and Laptev walrus will take huge amounts of imagery, too much for a single scientist or small team, so we need help from thousands of citizen scientists to help us learn more about this iconic animal.”

Earlier this year Cub Scouts from across the UK became walrus spotters to test the platform ahead of its public release. The Scouts have been a partner of WWF since the early 1970s, and over 57 million scouts globally are engaged in environmental projects.

Cub Scout Imogen Scullard, age 9, said:

“I love learning about the planet and how it works. We need to protect it from climate change. We are helping the planet by doing the walrus count with space satellites, which is really cool. It was a hard thing to do but we stuck at it”

The ‘Walrus From Space’ project, which is supported by players of the People’s Postcode Lottery, as well as RBC Tech For Nature and WWF supporters, aims to recruit more than 500,000 citizen scientists over the next five years. Over the course of the project counting methods will be continually refined and improved as data is gathered.

Laura Chow, head of charities at People’s Postcode Lottery, said:

“We’re delighted that players’ support is bringing this fantastic project to life. We encourage everyone to get involved in finding walrus so they can play a part in helping us better understand the effects of climate change on this species and their ecosystem. “Players of People’s Postcode Lottery are supporting this project as part of our Postcode Climate Challenge initiative, which is providing 12 charities with an additional £24 million for projects tackling climate change this year.”

Aspiring conservationists can help protect the species by going to wwf.org.uk/walrusfromspace where they can register to participate, and then be guided through a training module before joining the walrus census.

Download our FAQ

The WWF has released a charming video invitation”Become A Walrus Detective,” (Note: It may be a little over the top for some),

The WWF has a Learn about Walrus from Space webpage, which features the video above and includes a registration button.

Is the United Kingdom an Arctic nation?

No. They are not. (You can check here on the Arctic Countries webpage of The Arctic Institute website.)

Nonetheless and leaving aside that the Arctic and the Antarctic are literally polar opposites, I gather that the British Government in the form of the British Antarctic Survey (BAS), is quite interested in the Arctic, viz.: the Walrus from Space project.

If you keep digging you’ll find a chain of UK government agencies, from the BAS About page (at the bottom), Note: Links have been removed,,

British Antarctic Survey (BAS) is a component of the Natural Environment Research Council (NERC).

NERC is part of UK Research and Innovation

Keep digging (from the UK Research and Innovation entry on Wikipedia), Note: Links have been removed,

UK Research and Innovation (UKRI) is a non-departmental public body of the Government of the United Kingdom that directs research and innovation funding, funded through the science budget of the Department for Business, Energy and Industrial Strategy [emphases mine].

Interesting, non?

There doesn’t have to be a sinister connection between a government agency devoted to supporting business and industry and a climate change project. If we are to grapple with climate change in a significant way, we will need cooperation from many groups and coutnries (some of which may have been adversaries in the past).

Of course, the problem with the business community is that efforts aimed at the public good are often publicity stunts.

For anyone curious about the businesses mentioned in the press release, Maxar Technologies can be found here, Maxar’s DigitalGlobe here, and RBC (Royal of Bank of Canada) Tech for Nature here.

BTW, I love that walrus picture at the beginning of this posting.

A gas, gas, gas for creating semiconducting nanomaterials?

A June 14, 2021 news item on phys.org highlights some new research from Rice University (Texas, US),

Scientific studies describing the most basic processes often have the greatest impact in the long run. A new work by Rice University engineers could be one such, and it’s a gas, gas, gas for nanomaterials.

Yes, I ‘stole’ the phrase from the news item/release for my headline. For anyone unfamiliar with the word gas’ used as slang, it mean something is good or wonderful (See Urban Dictionary).

Getting back to science, gas, and nanomaterials, a June 11, 2021 Rice University news release (also on EurekAlert), which originated the news item, answers some questions about how manufacturing nanomaterial used in electronics could be more easily manufactured,

Rice materials theorist Boris Yakobson, graduate student Jincheng Lei and alumnus Yu Xie of Rice’s Brown School of Engineering have unveiled how a popular 2D material, molybdenum disulfide (MoS2), flashes into existence during chemical vapor deposition (CVD).

Knowing how the process works will give scientists and engineers a way to optimize the bulk manufacture of MoS2 and other valuable materials classed as transition metal dichalcogenides (TMDs), semiconducting crystals that are good bets to find a home in next-generation electronics.

Their study in the American Chemical Society journal ACS Nano focuses on MoS2’s “pre-history,” specifically what happens in a CVD furnace once all the solid ingredients are in place. CVD, often associated with graphene and carbon nanotubes, has been exploited to make a variety of 2D materials by providing solid precursors and catalysts that sublimate into gas and react. The chemistry dictates which molecules fall out of the gas and settle on a substrate, like copper or silicone, and assemble into a 2D crystal.

The problem has been that once the furnace cranks up, it’s impossible to see or measure the complicated chain of reactions in the chemical stew in real time.

“Hundreds of labs are cooking these TMDs, quite oblivious to the intricate transformations occurring in the dark oven,” said Yakobson, the Karl F. Hasselmann Professor of Materials Science and NanoEngineering and a professor of chemistry. “Here, we’re using quantum-chemical simulations and analysis to reveal what’s there, in the dark, that leads to synthesis.”

Yakobson’s theories often lead experimentalists to make his predictions come true. (For example, boron buckyballs.) This time, the Rice lab determined the path molybdenum oxide (MoO3) and sulfur powder take to deposit an atomically thin lattice onto a surface.

The short answer is that it takes three steps. First, the solids are sublimated through heating to change them from solid to gas, including what Yakobson called a “beautiful” ring-molecule, trimolybdenum nonaoxide (Mo3O9). Second, the molybdenum-containing gases react with sulfur atoms under high heat, up to 4,040 degrees Fahrenheit. Third, molybdenum and sulfur molecules fall to the surface, where they crystallize into the jacks-like lattice that is characteristic of TMDs.

What happens in the middle step was of the most interest to the researchers. The lab’s simulations showed a trio of main gas phase reactants are the prime suspects in making MoS2: sulfur, the ring-like Mo3O9 molecules that form in sulfur’s presence and the subsequent hybrid of MoS6 that forms the crystal, releasing excess sulfur atoms in the process.

Lei said the molecular dynamics simulations showed the activation barriers that must be overcome to move the process along, usually in picoseconds.

“In our molecular dynamics simulation, we find that this ring is opened by its interaction with sulfur, which attacks oxygen connected to the molybdenum atoms,” he said. “The ring becomes a chain, and further interactions with the sulfur molecules separate this chain into molybdenum sulfide monomers. The most important part is the chain breaking, which overcomes the highest energy barrier.”

That realization could help labs streamline the process, Lei said. “If we can find precursor molecules with only one molybdenum atom, we would not need to overcome the high barrier of breaking the chain,” he said.

Yakobson said the study could apply to other TMDs.

“The findings raise oftentimes empirical nanoengineering to become a basic science-guided endeavor, where processes can be predicted and optimized,” he said, noting that while the chemistry has been generally known since the discovery of TMD fullerenes in the early ’90s, understanding the specifics will further the development of 2D synthesis.

“Only now can we ‘sequence’ the step-by-step chemistry involved,” Yakobson said. “That will allow us to improve the quality of 2D material, and also see which gas side-products might be useful and captured on the way, opening opportunities for chemical engineering.”

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

Gas-Phase “Prehistory” and Molecular Precursors in Monolayer Metal Dichalcogenides Synthesis: The Case of MoS2 by Jincheng Lei, Yu Xie, and Boris I. Yakobson. ACS Nano 2021, 15, 6, 10525–10531 DOI: https://doi.org/10.1021/acsnano.1c03103 Publication Date: June 9, 2021 Copyright © 2021 American Chemical Society

This paper is behind a paywall.

Autonopia will pilot automated window cleaning in Vancouver (Canada) in 2022

Construction worker working outdoors with the project. Courtesy: Autonopia

Kenneth Chan in a June 10, 2021 article for the Daily Hive describes a startup company in Vancouver (Canada), which hopes to run a pilot project in 2022 for its “HŌMĀN, a highly capable, fast and efficient autonomous machine, designed specifically for cleaning the glasses [windows] perfectly and quickly.” (The description is from Autonopia’s homepage.)

Chan’s June 10, 2021 article describe the new automated window washer as a roomba-like robot,

The business of washing windows on a tower with human labour is a dangerous, inefficient, and costly practice, but a Vancouver innovator’s robotic solution could potentially disrupt this service globally.

Researchers with robotic systems startup Autonopia have come up with a robot that can mimic the behaviour of human window washers, including getting into the nooks and crannies of all types of complicated building facades — any surface structure.

It is also far more efficient than humans, cleaning windows three to four times faster, and can withstand wind and cold temperatures. According to a [news?] release, the robot is described as a modular device with a plug-and-play design [emphasis mine] that allows it to work on any building without requiring any additional infrastructure to be installed.

While artificial intelligence and the robotic device replaces manual work, it still requires a skilled operator to oversee the cleaning.

“It’s intimidating, hard work that most workers don’t want to do, [emphasis mine]” said Autonopia co-founder Mohammad Dabiri, who came up with the idea after witnessing an accident in Southeast Asia [emphasis mine].

“There’s high overhead to manage the hiring, allocation and training of workers, and sometimes they quit as soon as it comes time to go on a high rise.”

“We realized this problem has existed for a while, and yet none of the available solutions has managed to scale,” said Kamali Hossein, the co-founder and CTO of Autonopia, and a Mitacs postdoctoral research [sic] in mechatronic systems engineering at Simon Fraser University.

To clarify, the company is Autonopia and the product the company is promoting is HŌMĀN, an automated or robotic window washer for tall buildings (towers).

HŌMĀN (as it’s written in the Encyclopedia Iranica) or Houmān, as it’s written in Wikipedia, seems to be a literary hero or, perhaps, superhero,

… is one of the most famous Turanian heroes in Shahnameh, the national epic of Greater Iran. Houmān is famous for his bravery, loyalty, and chivalry, such that even Iranians who are longtime enemies of Turanians admire his personality. He is a descendant of Tur, a son of Viseh and brother of Piran. Houmān is the highest ranking Turanian commander and after Piran, he is the second leading member of Viseh clan. Houman first appears in the story of Rostam and Sohrab, …

Autonopia’s website is very attractive and weirdly uninformative. I looked for a more in depth description of ‘plug and play’ and found this,

Modular and Maintainable

The design of simple, but highly capable and modular components, along with the overall simplicity of the robot structure allows for a shorter build time and maintenance turnover. …

Cleans any tower

The flexible and capable design of the robot allows it to adjust to the complexities of the structures and it can maneuver uneven surfaces of different buildings very quickly and safely. No tower is off-limits for HŌMĀN. It is designed to cater to the specific requirements of each high-rise

I wish there were more details about the hardware and the software, e.g., there’s no mention of artificial intelligence as mentioned in Chan’s article.

As for whether or not this is “intimidating, hard work that most workers don’t want to do,” I wonder how Mohammad Dabiri can be so certain. If this product is successful, it will have an impact on people who rely on this work for their livelihoods. Possibly adding some insult to injury, Dabiri and Hossein claim their product is better at the job than humans are.

Nobody can argue about making work safer but it would be nice if some of these eager, entrepreneurial types put some thought into the impact both positive and negative that their bright ideas can have on other people.

As for whether HŌMĀN can work on any tower, photographs like the one at the beginning of this posting, feature modern office buildings which look like glass sheets held together with steel and concrete. So, it doesn’t look likely to work (and it’s probably not feasible from a business perspective) on older buildings with fewer stories, stone ornamentation, and even more nooks and crannies. As for some of the newer buildings which feature odd shapes and are reintroducing ornamentation, I’d imagine that will be problematic. But perhaps the market is overseas where tall buildings can range from 65 stories to over 100 stories (Wikipedia ‘List of tallest buildings‘). After all the genesis for this project was an incident in Southeast Asia. Vancouver doesn’t have 65 story buildings—yet. But, I’m sure there’s a developer or two out there with some plans.

A graphene ‘camera’ and your beating heart: say cheese

Comparing it to a ‘camera’, even with the quotes, is a bit of a stretch for my taste but I can’t come up with a better comparison. Here’s a video so you can judge for yourself,

Caption: This video repeats three times the graphene camera images of a single beat of an embryonic chicken heart. The images, separated by 5 milliseconds, were measured by a laser bouncing off a graphene sheet lying beneath the heart. The images are about 2 millimeters on a side. Credit: UC Berkeley images by Halleh Balch, Alister McGuire and Jason Horng

A June 16, 2021 news item on ScienceDaily announces the research,

Bay Area [San Francisco, California] scientists have captured the real-time electrical activity of a beating heart, using a sheet of graphene to record an optical image — almost like a video camera — of the faint electric fields generated by the rhythmic firing of the heart’s muscle cells.

A University of California at Berkeley (UC Berkeley) June 16, 2021 news release (also on EurekAlert) by Robert Sanders, which originated the news item, provides more detail,

The graphene camera represents a new type of sensor useful for studying cells and tissues that generate electrical voltages, including groups of neurons or cardiac muscle cells. To date, electrodes or chemical dyes have been used to measure electrical firing in these cells. But electrodes and dyes measure the voltage at one point only; a graphene sheet measures the voltage continuously over all the tissue it touches.

The development, published online last week in the journal Nano Letters, comes from a collaboration between two teams of quantum physicists at the University of California, Berkeley, and physical chemists at Stanford University.

“Because we are imaging all cells simultaneously onto a camera, we don’t have to scan, and we don’t have just a point measurement. We can image the entire network of cells at the same time,” said Halleh Balch, one of three first authors of the paper and a recent Ph.D. recipient in UC Berkeley’s Department of Physics.

While the graphene sensor works without having to label cells with dyes or tracers, it can easily be combined with standard microscopy to image fluorescently labeled nerve or muscle tissue while simultaneously recording the electrical signals the cells use to communicate.

“The ease with which you can image an entire region of a sample could be especially useful in the study of neural networks that have all sorts of cell types involved,” said another first author of the study, Allister McGuire, who recently received a Ph.D. from Stanford and. “If you have a fluorescently labeled cell system, you might only be targeting a certain type of neuron. Our system would allow you to capture electrical activity in all neurons and their support cells with very high integrity, which could really impact the way that people do these network level studies.”

Graphene is a one-atom thick sheet of carbon atoms arranged in a two-dimensional hexagonal pattern reminiscent of honeycomb. The 2D structure has captured the interest of physicists for several decades because of its unique electrical properties and robustness and its interesting optical and optoelectronic properties.

“This is maybe the first example where you can use an optical readout of 2D materials to measure biological electrical fields,” said senior author Feng Wang, UC Berkeley professor of physics. “People have used 2D materials to do some sensing with pure electrical readout before, but this is unique in that it works with microscopy so that you can do parallel detection.”

The team calls the tool a critically coupled waveguide-amplified graphene electric field sensor, or CAGE sensor.

“This study is just a preliminary one; we want to showcase to biologists that there is such a tool you can use, and you can do great imaging. It has fast time resolution and great electric field sensitivity,” said the third first author, Jason Horng, a UC Berkeley Ph.D. recipient who is now a postdoctoral fellow at the National Institute of Standards and Technology. “Right now, it is just a prototype, but in the future, I think we can improve the device.”

Graphene is sensitive to electric fields

Ten years ago, Wang discovered that an electric field affects how graphene reflects or absorbs light. Balch and Horng exploited this discovery in designing the graphene camera. They obtained a sheet of graphene about 1 centimeter on a side produced by chemical vapor deposition in the lab of UC Berkeley physics professor Michael Crommie and placed on it a live heart from a chicken embryo, freshly extracted from a fertilized egg. These experiments were performed in the Stanford lab of Bianxiao Cui, who develops nanoscale tools to study electrical signaling in neurons and cardiac cells.

The team showed that when the graphene was tuned properly, the electrical signals that flowed along the surface of the heart during a beat were sufficient to change the reflectance of the graphene sheet.

“When cells contract, they fire action potentials that generate a small electric field outside of the cell,” Balch said. “The absorption of graphene right under that cell is modified, so we will see a change in the amount of light that comes back from that position on the large area of graphene.”

In initial studies, however, Horng found that the change in reflectance was too small to detect easily. An electric field reduces the reflectance of graphene by at most 2%; the effect was much less from changes in the electric field when the heart muscle cells fired an action potential.

Together, Balch, Horng and Wang found a way to amplify this signal by adding a thin waveguide below graphene, forcing the reflected laser light to bounce internally about 100 times before escaping. This made the change in reflectance detectable by a normal optical video camera.

“One way of thinking about it is that the more times that light bounces off of graphene as it propagates through this little cavity, the more effects that light feels from graphene’s response, and that allows us to obtain very, very high sensitivity to electric fields and voltages down to microvolts,” Balch said.

The increased amplification necessarily lowers the resolution of the image, but at 10 microns, it is more than enough to study cardiac cells that are several tens of microns across, she said.

Another application, McGuire said, is to test the effect of drug candidates on heart muscle before these drugs go into clinical trials to see whether, for example, they induce an unwanted arrhythmia. To demonstrate this, he and his colleagues observed the beating chicken heart with CAGE and an optical microscope while infusing it with a drug, blebbistatin, that inhibits the muscle protein myosin. They observed the heart stop beating, but CAGE showed that the electrical signals were unaffected.

Because graphene sheets are mechanically tough, they could also be placed directly on the surface of the brain to get a continuous measure of electrical activity — for example, to monitor neuron firing in the brains of those with epilepsy or to study fundamental brain activity. Today’s electrode arrays measure activity at a few hundred points, not continuously over the brain surface.

“One of the things that is amazing to me about this project is that electric fields mediate chemical interactions, mediate biophysical interactions — they mediate all sorts of processes in the natural world — but we never measure them. We measure current, and we measure voltage,” Balch said. “The ability to actually image electric fields gives you a look at a modality that you previously had little insight into.”

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

Graphene Electric Field Sensor Enables Single Shot Label-Free Imaging of Bioelectric Potentials by Halleh B. Balch, Allister F. McGuire, Jason Horng, Hsin-Zon Tsai, Kevin K. Qi, Yi-Shiou Duh, Patrick R. Forrester, Michael F. Crommie, Bianxiao Cui, and Feng Wang. Nano Lett. 2021, XXXX, XXX, XXX-XXX OI: https://doi.org/10.1021/acs.nanolett.1c00543 Publication Date: June 8, 2021 © 2021 American Chemical Society

This paper is behind a paywall.

A library of properties for nanomaterials

Researchers at the University of Birmingham (UK) announced the development of a library of nanomaterial properties according to a June 8, 2021 news item on Nanowerk (Note: Links have been removed),

Researchers have developed a ‘library of properties’ to help identify the environmental impact of nanomaterials faster and more cost effectively.

Whilst nanomaterials have benefited a wide range of industries and revolutionized everyday life, there are concerns over potential adverse effects—including toxic effects following accumulation in different organs and indirect effects from transport of co-pollutants.

The European Union H2020-funded NanoSolveIT project is developing a ground-breaking computer-based Integrated Approach to Testing and Assessment (IATA) for the environmental health and safety of nanomaterials.

A June 8, 2021 University of Birmingham press release (also on EurekAlert) spells out the details,

Over the last two years, researchers from the University of Birmingham have worked with experts at NovaMechanics, in Nicosia, Cyprus to develop a decision support system in the form of both stand-alone open software and a Cloud platform.

The team has developed a freely available cloud library containing full physicochemical characterisation of 69 nanomaterials, plus calculated molecular descriptors to increase the value of the available information, details of which are published in NanoImpact. [link and citation follow]

Professor Iseult Lynch, from the University of Birmingham commented: “One of the limitations to widespread application of computer-based approaches is the lack of large well-organised high-quality datasets, or of data with adequate metadata that will allow dataset interoperability and their combination to create larger datasets.”

“Making the library of calculated and experimental descriptors available to the community, along with the detailed description of how they were calculated is a key first step towards filling this datagap.”

Development of the cloud-based nanomaterials library is the fifth freely available web-based application that the project has delivered.

Antreas Afantitis, from NovaMechanics, commented: “Over the last two years, this project has already presented some very impressive results with more than 30 publications, making NanoSolveIT one of the most active projects in the nanomaterials safety and informatics space.”

Concerns about nanomaterials are also arising as risk assessment is lagging behind product development, mainly because current approaches to assessing exposure, hazard and risk are expensive and time-consuming, and frequently involve testing in animal models. The NanoSolveIT project aspires to address these challenges.

The latest development aims to enrich our knowledge of nanomaterials properties and the link from property to (cytotoxic) effect. The enriched dataset contains over 70 descriptors per nanomaterial.

The dataset was used to develop a computer-based workflow to predict nanomaterials’ effective surface charge (zeta-potential) based on a set of descriptors that can be used to help design and produce safer and more functional nanomaterials.

The resulting predictive read-across model has been made publicly and freely available as a web service through the Horizon 2020 (H2020) NanoCommons project (http://enaloscloud.novamechanics.com/nanocommons/mszeta/ ) and via the H2020 NanoSolveIT Cloud Platform (https://mszeta.cloud.nanosolveit.eu/ ) to ensure accessibility to the community and interested stakeholders.

In addition, the full data set, ready for further computational modeling, is available through the NanoPharos database, as the project consortium supports the FAIR data principles – committing to making its data Findable, Accessible, Interoperable and Re-usable.

I quite like this image of how the scales are illustrated (BTW, you can find NanoSolveIT here the NanoCommons project [closing date May 15, 2021] here, and NovaMechanics here)

Scales of descriptors – from whole nanoparticle to unit cell to individual atoms Courtesy University of Birmingham and NanoSolveIT

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

Computational enrichment of physicochemical data for the development of a ζ-potential read-across predictive model with Isalos Analytics Platform by Anastasios G. Papadiamantis, Antreas Afantitis, Andreas Tsoumanis, Eugenia Valsami-Jones, Iseult Lynch, Georgia Melagraki. NanoImpact Volume 22, April 2021, 100308 DOI: https://doi.org/10.1016/j.impact.2021.100308 Available online 18 March 2021

This paper is open access.

The coolest paint

It’s the ‘est’ of it all. The coolest, the whitest, the blackest … Scientists and artists are both pursuing the ‘est’. (More about the pursuit later in this posting.)

In this case, scientists have developed the coolest, whitest paint yet. From an April 16, 2021 news item on Nanowerk,

In an effort to curb global warming, Purdue University engineers have created the whitest paint yet. Coating buildings with this paint may one day cool them off enough to reduce the need for air conditioning, the researchers say.

In October [2020], the team created an ultra-white paint that pushed limits on how white paint can be. Now they’ve outdone that. The newer paint not only is whiter but also can keep surfaces cooler than the formulation that the researchers had previously demonstrated.

“If you were to use this paint to cover a roof area of about 1,000 square feet, we estimate that you could get a cooling power of 10 kilowatts. That’s more powerful than the central air conditioners used by most houses,” said Xiulin Ruan, a Purdue professor of mechanical engineering.

Caption: Xiulin Ruan, a Purdue University professor of mechanical engineering, holds up his lab’s sample of the whitest paint on record. Credit: Purdue University/Jared Pike

This is nicely done. Researcher Xiulin Ruan is standing close to a structure that could be said to resemble the sun while in shirtsleeves and sunglasses and holding up a sample of his whitest paint in April (not usually a warm month in Indiana).

An April 15, 2021 Purdue University news release (also on EurkeAlert), which originated the news item, provides more detail about the work and hints about its commercial applications both civilian and military,

The researchers believe that this white may be the closest equivalent of the blackest black, “Vantablack,” [emphasis mine; see comments later in this post] which absorbs up to 99.9% of visible light. The new whitest paint formulation reflects up to 98.1% of sunlight – compared with the 95.5% of sunlight reflected by the researchers’ previous ultra-white paint – and sends infrared heat away from a surface at the same time.

Typical commercial white paint gets warmer rather than cooler. Paints on the market that are designed to reject heat reflect only 80%-90% of sunlight and can’t make surfaces cooler than their surroundings.

The team’s research paper showing how the paint works publishes Thursday (April 15 [2021]) as the cover of the journal ACS Applied Materials & Interfaces.

What makes the whitest paint so white

Two features give the paint its extreme whiteness. One is the paint’s very high concentration of a chemical compound called barium sulfate [emphasis mine] which is also used to make photo paper and cosmetics white.

“We looked at various commercial products, basically anything that’s white,” said Xiangyu Li, a postdoctoral researcher at the Massachusetts Institute of Technology who worked on this project as a Purdue Ph.D. student in Ruan’s lab. “We found that using barium sulfate, you can theoretically make things really, really reflective, which means that they’re really, really white.”

The second feature is that the barium sulfate particles are all different sizes in the paint. How much each particle scatters light depends on its size, so a wider range of particle sizes allows the paint to scatter more of the light spectrum from the sun.

“A high concentration of particles that are also different sizes gives the paint the broadest spectral scattering, which contributes to the highest reflectance,” said Joseph Peoples, a Purdue Ph.D. student in mechanical engineering.

There is a little bit of room to make the paint whiter, but not much without compromising the paint.”Although a higher particle concentration is better for making something white, you can’t increase the concentration too much. The higher the concentration, the easier it is for the paint to break or peel off,” Li said.

How the whitest paint is also the coolest

The paint’s whiteness also means that the paint is the coolest on record. Using high-accuracy temperature reading equipment called thermocouples, the researchers demonstrated outdoors that the paint can keep surfaces 19 degrees Fahrenheit cooler than their ambient surroundings at night. It can also cool surfaces 8 degrees Fahrenheit below their surroundings under strong sunlight during noon hours.

The paint’s solar reflectance is so effective, it even worked in the middle of winter. During an outdoor test with an ambient temperature of 43 degrees Fahrenheit, the paint still managed to lower the sample temperature by 18 degrees Fahrenheit.

This white paint is the result of six years of research building on attempts going back to the 1970s to develop radiative cooling paint as a feasible alternative to traditional air conditioners.

Ruan’s lab had considered over 100 different materials, narrowed them down to 10 and tested about 50 different formulations for each material. Their previous whitest paint was a formulation made of calcium carbonate, an earth-abundant compound commonly found in rocks and seashells.

The researchers showed in their study that like commercial paint, their barium sulfate-based paint can potentially handle outdoor conditions. The technique that the researchers used to create the paint also is compatible with the commercial paint fabrication process.

Patent applications for this paint formulation have been filed through the Purdue Research Foundation Office of Technology Commercialization. This research was supported by the Cooling Technologies Research Center at Purdue University and the Air Force Office of Scientific Research [emphasis mine] through the Defense University Research Instrumentation Program (Grant No.427 FA9550-17-1-0368). The research was performed at Purdue’s FLEX Lab and Ray W. Herrick Laboratories and the Birck Nanotechnology Center of Purdue’s Discovery Park.

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

Ultrawhite BaSO4 Paints and Films for Remarkable Daytime Subambient Radiative Cooling by Xiangyu Li, Joseph Peoples, Peiyan Yao, and Xiulin Ruan. ACS Appl. Mater. Interfaces 2021, XXXX, XXX, XXX-XXX DOI: https://doi.org/10.1021/acsami.1c02368 Publication Date:April 15, 2021 © 2021 American Chemical Society

This paper is behind a paywall.

Vantablack and the ongoing ‘est’ of blackest

Vantablack’s 99.9% light absorption no longer qualifies it for the ‘blackest black’. A newer standard for the ‘blackest black’ was set by the US National Institute of Standards and Technology at 99.99% light absorption with its N.I.S.T. ultra-black in 2019, although that too seems to have been bested.

I have three postings covering the Vantablack and blackest black story,

The third posting (December 2019) provides a brief summary of the story along with what was the latest from the US National Institute of Standards and Technology. There’s also a little bit about the ‘The Redemption of Vanity’ an art piece demonstrating the blackest black material from the Massachusetts Institute of Technology, which they state has 99.995% (at least) absorption of light.

From a science perspective, the blackest black would be useful for space exploration.

I am surprised there doesn’t seem to have been an artistic rush to work with the whitest white. That impression may be due to the fact that the feuds get more attention than quiet work.

Dark side to the whitest white?

Andrew Parnell, research fellow in physics and astronomy at the University of Sheffield (UK), mentions a downside to obtaining the material needed to produce this cooling white paint in a June 10, 2021 essay on The Conversation (h/t Fast Company), Note: Links have been removed,

… this whiter-than-white paint has a darker side. The energy required to dig up raw barite ore to produce and process the barium sulphite that makes up nearly 60% of the paint means it has a huge carbon footprint. And using the paint widely would mean a dramatic increase in the mining of barium.

Parnell ends his essay with this (Note: Links have been removed),

Barium sulphite-based paint is just one way to improve the reflectivity of buildings. I’ve spent the last few years researching the colour white in the natural world, from white surfaces to white animals. Animal hairs, feathers and butterfly wings provide different examples of how nature regulates temperature within a structure. Mimicking these natural techniques could help to keep our cities cooler with less cost to the environment.

The wings of one intensely white beetle species called Lepidiota stigma appear a strikingly bright white thanks to nanostructures in their scales, which are very good at scattering incoming light. This natural light-scattering property can be used to design even better paints: for example, by using recycled plastic to create white paint containing similar nanostructures with a far lower carbon footprint. When it comes to taking inspiration from nature, the sky’s the limit.