Extreme water repellency achieved by combining nanostructured surfaces with Leidenfrost effect

Apparently a new twist has been added to the water repellency story. From a May 17, 2016 news item on ScienceDaily,

What do you get if you combine nanotextured ‘Cassie’ surfaces with the Leidenfrost effect? Highly water-repellent surfaces that show potential for developing future self-cleaning windows, windshields, exterior paints and more [sic]

Combining superhydrophobic surfaces with Leidenfrost levitation–picture a water droplet hovering over a hot surface rather than making physical contact with it–has been explored extensively for the past decade by researchers hoping to uncover the holy grail of water-repellent surfaces.

A May 17, 2016 American Institute of Physics news release on EurekAlert, which originated the news item, provides more detail about the work,

In a new twist, a group of South Korean researchers from Seoul National University and Dankook University report an anomalous water droplet-bouncing phenomenon generated by Leidenfrost levitation on nanotextured surfaces in Applied Physics Letters, from AIP Publishing.

“Wettability plays a key role in determining the equilibrium contact angles, contact angle hysteresis, and adhesion between a solid surface and liquid, as well as the retraction process of a liquid droplet impinged on the surface,” explained Doo Jin Lee, lead author, and a postdoctoral researcher in the Department of Materials and Engineering at Seoul National University.

Nonwetting surfaces tend to be created by one of two methods. “First, textured surfaces enable nonwettability because a liquid can’t penetrate into the micro- or nano-features, thanks to air entrapment between asperities on the textured materials,” Lee said.

Or, second, the Leidenfrost effect “can help produce a liquid droplet dancing on a hot surface by floating it on a cushion of its own vapor,” he added. “The vapor film between the droplet and heated surface allows the droplet to bounce off the surface–also known as the ‘dynamic Leidenfrost phenomenon.'”

Lee and colleagues developed a special “nonwetting, nanotextured surface” so they could delve into the dynamic Leidenfrost effect’s impact on the material.

“Our nanotextured surface was verified to be ‘nonwetting’ via thermodynamic analysis,” Lee elaborated. “This analytical approach shows that the water droplet isn’t likely to penetrate into the surface’s nanoholes, which is advantageous for designing nonwetting, water-repellant systems. And the water droplet bouncing was powered by the synergetic combination of the nonwetting surface–often called a ‘Cassie surface’–and the Leidenfrost effect.”

By comparing the hydrophobic surface and nanotextured surface, the group discovered that enhanced water droplet bouncing was created by the combined impact of the Leidenfrost levitation and the nonwetting Cassie state.

“A thermodynamic approach predicts the nonwettability on the nanotextured surface, and a scaling law between the capillary and vapor pressure of the droplet explains the mechanism of the dynamic Leidenfrost phenomenon,” said Lee.

These findings should “be of value for a wide range of research areas, such as the study of nonwetting surfaces by the Leidenfrost effect and nanotextured features, enhanced liquid droplet bouncing, and film boiling of liquid droplets on heated Cassie surfaces,” he added.

Significantly, the group’s work furthers the fundamental understanding of the dynamic Leidenfrost droplet levitation and droplet-bouncing phenomena on hydrophobic and nanoengineered surfaces. This means that it will be useful for developing highly water-repellant surfaces for industrial applications such as self-cleaning windows, windshields, exterior paints, anti-fouling coatings, roof tiles, and textiles in the future.

“Our future work will focus on developing multiscale structures with microscale and nanoscale regularities, and explore the nonwetting characteristics of their surfaces with the dynamic Leidenfrost effect,” Lee noted.

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

Anomalous water drop bouncing on a nanotextured surface by the Leidenfrost levitation by Doo Jin Lee and Young Seok Song.  Appl. Phys. Lett. 108, 201604 (2016); http://dx.doi.org/10.1063/1.4948769

This paper appears to be open access.

A Victoria & Albert Museum installation integrates of biomimicry, robotic fabrication and new materials research in architecture

The Victoria & Albert Museum (V&A) in London, UK, opened its Engineering Season show on May 18, 2016 (it runs until Nov. 6, 2016) featuring a robot installation and an exhibition putting the spotlight on Ove Arup, “the most significant engineer of the 20th century” according to the V&A’s May ??, 2016 press release,

The first major retrospective of the most influential engineer of the 20th century and a site specific installation inspired by nature and fabricated by robots will be the highlights of the V&A’s first ever Engineering Season, complemented by displays, events and digital initiatives dedicated to global engineering design. The V&A Engineering Season will highlight the importance of engineering in our daily lives and consider engineers as the ‘unsung heroes’ of design, who play a vital and creative role in the creation of our built environment.

Before launching into the robot/biomimicry part of this story, here’s a very brief description of why Ove Arup is considered so significant and influential,

Engineering the World: Ove Arup and the Philosophy of Total Design will explore the work and legacy of Ove Arup (1895-1988), … . Ove pioneered a multidisciplinary approach to design that has defined the way engineering is understood and practiced today. Spanning 100 years of engineering and architectural design, the exhibition will be guided by Ove’s writings about design and include his early projects, such as the Penguin Pool at London Zoo, as well as renowned projects by the firm including Sydney Opera House [Australia] and the Centre Pompidou in Paris. Arup’s collaborations with major architects of the 20th century pioneered new approaches to design and construction that remain influential today, with the firm’s legacy visible in many buildings across London and around the world. It will also showcase recent work by Arup, from major infrastructure projects like Crossrail and novel technologies for acoustics and crowd flow analysis, to engineering solutions for open source housing design.

Robots, biomimicry and the Elytra Filament Pavilion

A May 18, 2016 article by Tim Master for BBC (British Broadcasting Corporation) news online describes the pavilion installation,

A robot has taken up residence at the Victoria & Albert Musuem to construct a new installation at its London gardens.

The robot – which resembles something from a car assembly line – will build new sections of the Elytra Filament Pavilion over the coming months.

The futuristic structure will grow and change shape using data based on how visitors interact with it.

Elytra’s canopy is made up of 40 hexagonal cells – made from strips of carbon and glass fibre – which have been tightly wound into shape by the computer-controlled Kuka robot.

Each cell takes about three hours to build. On certain days, visitors to the V&A will be able to watch the robot create new cells that will be added to the canopy.

Here are some images made available by V&A,

Elytra Filament Pavilion arriving at the V&A, 2016. © Victoria and Albert Museum, London

Elytra Filament Pavilion arriving at the V&A, 2016. © Victoria and Albert Museum, London

Kuka robot weaving Elytra Filament Pavilion cell fibres, 2016. © Victoria and Albert Museum, London

Kuka robot weaving Elytra Filament Pavilion cell fibres, 2016. © Victoria and Albert Museum, London

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Elytra Filament Pavilion at the V&A, 2016. © Victoria and Albert Museum, London

Elytra Filament Pavilion at the V&A, 2016. © Victoria and Albert Museum, London

Here’s more detail from the V&A’s Elytra Filament Pavilion installation description,

Elytra Filament Pavilion has been created by experimental German architect Achim Menges with Moritz Dörstelmann, structural engineer Jan Knippers and climate engineer Thomas Auer.

Menges and Knippers are leaders of research institutes at the University of Stuttgart that are pioneering the integration of biomimicry, robotic fabrication and new materials research in architecture. This installation emerges from their ongoing research projects and is their first-ever major commission in the UK.

The pavilion explores the impact of emerging robotic technologies on architectural design, engineering and making.

Its design is inspired by lightweight construction principles found in nature, the filament structures of the forewing shells of flying beetles known as elytra. Made of glass and carbon fibre, each component of the undulating canopy is produced using an innovative robotic winding technique developed by the designers. Like beetle elytra, the pavilion’s filament structure is both very strong and very light – spanning over 200m2 it weighs less than 2,5 tonnes.

Elytra is a responsive shelter that will grow over the course of the V&A Engineering Season. Sensors in the canopy fibres will collect data on how visitors inhabit the pavilion and monitor the structure’s behaviour, ultimately informing how and where the canopy grows. During a series of special events as part of the Engineering Season, visitors will have the opportunity to witness the pavilion’s construction live, as new components are fabricated on-site by a Kuka robot.

Unfortunately, I haven’t been able to find more technical detail, particularly about the materials being used in the construction of the pavilion, on the V&A website.

One observation, I’m a little uncomfortable with how they’re gathering data “Sensors in the canopy fibres will collect data on how visitors inhabit the pavilion … .” It sounds like surveillance to me.

Nonetheless, the Engineering Season offers the promise of a very intriguing approach to fulfilling the V&A’s mandate as a museum dedicated to decorative arts and design.

Nanoparticles in baby formula

Needle-like particles of hydroxyapatite found in infant formula by ASU researchers. Westerhoff and Schoepf/ASU, CC BY-ND

Needle-like particles of hydroxyapatite found in infant formula by ASU [Arizona State University] researchers. Westerhoff and Schoepf/ASU, CC BY-ND

Nanowerk is featuring an essay about hydroxyapatite nanoparticles in baby formula written by Dr. Andrew Maynard in a May 17, 2016 news item (Note: A link has been removed),

There’s a lot of stuff you’d expect to find in baby formula: proteins, carbs, vitamins, essential minerals. But parents probably wouldn’t anticipate finding extremely small, needle-like particles. Yet this is exactly what a team of scientists here at Arizona State University [ASU] recently discovered.

The research, commissioned and published by Friends of the Earth (FoE) – an environmental advocacy group – analyzed six commonly available off-the-shelf baby formulas (liquid and powder) and found nanometer-scale needle-like particles in three of them. The particles were made of hydroxyapatite – a poorly soluble calcium-rich mineral. Manufacturers use it to regulate acidity in some foods, and it’s also available as a dietary supplement.

Andrew’s May 17, 2016 essay first appeared on The Conversation website,

Looking at these particles at super-high magnification, it’s hard not to feel a little anxious about feeding them to a baby. They appear sharp and dangerous – not the sort of thing that has any place around infants. …

… questions like “should infants be ingesting them?” make a lot of sense. However, as is so often the case, the answers are not quite so straightforward.

Andrew begins by explaining about calcium and hydroxyapatite (from The Conversation),

Calcium is an essential part of a growing infant’s diet, and is a legally required component in formula. But not necessarily in the form of hydroxyapatite nanoparticles.

Hydroxyapatite is a tough, durable mineral. It’s naturally made in our bodies as an essential part of bones and teeth – it’s what makes them so strong. So it’s tempting to assume the substance is safe to eat. But just because our bones and teeth are made of the mineral doesn’t automatically make it safe to ingest outright.

The issue here is what the hydroxyapatite in formula might do before it’s digested, dissolved and reconstituted inside babies’ bodies. The size and shape of the particles ingested has a lot to do with how they behave within a living system.

He then discusses size and shape, which are important at the nanoscale,

Size and shape can make a difference between safe and unsafe when it comes to particles in our food. Small particles aren’t necessarily bad. But they can potentially get to parts of our body that larger ones can’t reach. Think through the gut wall, into the bloodstream, and into organs and cells. Ingested nanoscale particles may be able to interfere with cells – even beneficial gut microbes – in ways that larger particles don’t.

These possibilities don’t necessarily make nanoparticles harmful. Our bodies are pretty well adapted to handling naturally occurring nanoscale particles – you probably ate some last time you had burnt toast (carbon nanoparticles), or poorly washed vegetables (clay nanoparticles from the soil). And of course, how much of a material we’re exposed to is at least as important as how potentially hazardous it is.

Yet there’s a lot we still don’t know about the safety of intentionally engineered nanoparticles in food. Toxicologists have started paying close attention to such particles, just in case their tiny size makes them more harmful than otherwise expected.

Currently, hydroxyapatite is considered safe at the macroscale by the US Food and Drug Administration (FDA). However, the agency has indicated that nanoscale versions of safe materials such as hydroxyapatite may not be safe food additives. From Andrew’s May 17, 2016 essay,

Hydroxyapatite is a tough, durable mineral. It’s naturally made in our bodies as an essential part of bones and teeth – it’s what makes them so strong. So it’s tempting to assume the substance is safe to eat. But just because our bones and teeth are made of the mineral doesn’t automatically make it safe to ingest outright.

The issue here is what the hydroxyapatite in formula might do before it’s digested, dissolved and reconstituted inside babies’ bodies. The size and shape of the particles ingested has a lot to do with how they behave within a living system. Size and shape can make a difference between safe and unsafe when it comes to particles in our food. Small particles aren’t necessarily bad. But they can potentially get to parts of our body that larger ones can’t reach. Think through the gut wall, into the bloodstream, and into organs and cells. Ingested nanoscale particles may be able to interfere with cells – even beneficial gut microbes – in ways that larger particles don’t.These possibilities don’t necessarily make nanoparticles harmful. Our bodies are pretty well adapted to handling naturally occurring nanoscale particles – you probably ate some last time you had burnt toast (carbon nanoparticles), or poorly washed vegetables (clay nanoparticles from the soil). And of course, how much of a material we’re exposed to is at least as important as how potentially hazardous it is.Yet there’s a lot we still don’t know about the safety of intentionally engineered nanoparticles in food. Toxicologists have started paying close attention to such particles, just in case their tiny size makes them more harmful than otherwise expected.

Putting particle size to one side for a moment, hydroxyapatite is classified by the US Food and Drug Administration (FDA) as “Generally Regarded As Safe.” That means it considers the material safe for use in food products – at least in a non-nano form. However, the agency has raised concerns that nanoscale versions of food ingredients may not be as safe as their larger counterparts.Some manufacturers may be interested in the potential benefits of “nanosizing” – such as increasing the uptake of vitamins and minerals, or altering the physical, textural and sensory properties of foods. But because decreasing particle size may also affect product safety, the FDA indicates that intentionally nanosizing already regulated food ingredients could require regulatory reevaluation.In other words, even though non-nanoscale hydroxyapatite is “Generally Regarded As Safe,” according to the FDA, the safety of any nanoscale form of the substance would need to be reevaluated before being added to food products.Despite this size-safety relationship, the FDA confirmed to me that the agency is unaware of any food substance intentionally engineered at the nanoscale that has enough generally available safety data to determine it should be “Generally Regarded As Safe.”Casting further uncertainty on the use of nanoscale hydroxyapatite in food, a 2015 report from the European Scientific Committee on Consumer Safety (SCCS) suggests there may be some cause for concern when it comes to this particular nanomaterial.Prompted by the use of nanoscale hydroxyapatite in dental products to strengthen teeth (which they consider “cosmetic products”), the SCCS reviewed published research on the material’s potential to cause harm. Their conclusion?

The available information indicates that nano-hydroxyapatite in needle-shaped form is of concern in relation to potential toxicity. Therefore, needle-shaped nano-hydroxyapatite should not be used in cosmetic products.

This recommendation was based on a handful of studies, none of which involved exposing people to the substance. Researchers injected hydroxyapatite needles directly into the bloodstream of rats. Others exposed cells outside the body to the material and observed the effects. In each case, there were tantalizing hints that the small particles interfered in some way with normal biological functions. But the results were insufficient to indicate whether the effects were meaningful in people.

As Andrew also notes in his essay, none of the studies examined by the SCCS OEuropean Scientific Committee on Consumer Safety) looked at what happens to nano-hydroxyapatite once it enters your gut and that is what the researchers at Arizona State University were considering (from the May 17, 2016 essay),

The good news is that, according to preliminary studies from ASU researchers, hydroxyapatite needles don’t last long in the digestive system.

This research is still being reviewed for publication. But early indications are that as soon as the needle-like nanoparticles hit the highly acidic fluid in the stomach, they begin to dissolve. So fast in fact, that by the time they leave the stomach – an exceedingly hostile environment – they are no longer the nanoparticles they started out as.

These findings make sense since we know hydroxyapatite dissolves in acids, and small particles typically dissolve faster than larger ones. So maybe nanoscale hydroxyapatite needles in food are safer than they sound.

This doesn’t mean that the nano-needles are completely off the hook, as some of them may get past the stomach intact and reach more vulnerable parts of the gut. But the findings do suggest these ultra-small needle-like particles could be an effective source of dietary calcium – possibly more so than larger or less needle-like particles that may not dissolve as quickly.

Intriguingly, recent research has indicated that calcium phosphate nanoparticles form naturally in our stomachs and go on to be an important part of our immune system. It’s possible that rapidly dissolving hydroxyapatite nano-needles are actually a boon, providing raw material for these natural and essential nanoparticles.

While it’s comforting to know that preliminary research suggests that the hydroxyapatite nanoparticles are likely safe for use in food products, Andrew points out that more needs to be done to insure safety (from the May 17, 2016 essay),

And yet, even if these needle-like hydroxyapatite nanoparticles in infant formula are ultimately a good thing, the FoE report raises a number of unresolved questions. Did the manufacturers knowingly add the nanoparticles to their products? How are they and the FDA ensuring the products’ safety? Do consumers have a right to know when they’re feeding their babies nanoparticles?

Whether the manufacturers knowingly added these particles to their formula is not clear. At this point, it’s not even clear why they might have been added, as hydroxyapatite does not appear to be a substantial source of calcium in most formula. …

And regardless of the benefits and risks of nanoparticles in infant formula, parents have a right to know what’s in the products they’re feeding their children. In Europe, food ingredients must be legally labeled if they are nanoscale. In the U.S., there is no such requirement, leaving American parents to feel somewhat left in the dark by producers, the FDA and policy makers.

As far as I’m aware, the Canadian situation is much the same as the US. If the material is considered safe at the macroscale, there is no requirement to indicate that a nanoscale version of the material is in the product.

I encourage you to read Andrew’s essay in its entirety. As for the FoE report (Nanoparticles in baby formula: Tiny new ingredients are a big concern), that is here.

Spider webs inspire liquid wire

Courtesy University of Oxford

Courtesy University of Oxford

Usually, when science talk runs to spider webs the focus is on strength but this research from the UK and France is all about resilience. From a May 16, 2016 news item on phys.org,

Why doesn’t a spider’s web sag in the wind or catapult flies back out like a trampoline? The answer, according to new research by an international team of scientists, lies in the physics behind a ‘hybrid’ material produced by spiders for their webs.

Pulling on a sticky thread in a garden spider’s orb web and letting it snap back reveals that the thread never sags but always stays taut—even when stretched to many times its original length. This is because any loose thread is immediately spooled inside the tiny droplets of watery glue that coat and surround the core gossamer fibres of the web’s capture spiral.

This phenomenon is described in the journal PNAS by scientists from the University of Oxford, UK and the Université Pierre et Marie Curie, Paris, France.

The researchers studied the details of this ‘liquid wire’ technique in spiders’ webs and used it to create composite fibres in the laboratory which, just like the spider’s capture silk, extend like a solid and compress like a liquid. These novel insights may lead to new bio-inspired technology.

A May 16, 2016 University of Oxford press release (also on EurekAlert), which originated the news item, provides more detail,

Professor Fritz Vollrath of the Oxford Silk Group in the Department of Zoology at Oxford University said: ‘The thousands of tiny droplets of glue that cover the capture spiral of the spider’s orb web do much more than make the silk sticky and catch the fly. Surprisingly, each drop packs enough punch in its watery skins to reel in loose bits of thread. And this winching behaviour is used to excellent effect to keep the threads tight at all times, as we can all observe and test in the webs in our gardens.’

The novel properties observed and analysed by the scientists rely on a subtle balance between fibre elasticity and droplet surface tension. Importantly, the team was also able to recreate this technique in the laboratory using oil droplets on a plastic filament. And this artificial system behaved just like the spider’s natural winch silk, with spools of filament reeling and unreeling inside the oil droplets as the thread extended and contracted.

Dr Hervé Elettro, the first author and a doctoral researcher at Institut Jean Le Rond D’Alembert, Université Pierre et Marie Curie, Paris, said: ‘Spider silk has been known to be an extraordinary material for around 40 years, but it continues to amaze us. While the web is simply a high-tech trap from the spider’s point of view, its properties have a huge amount to offer the worlds of materials, engineering and medicine.

‘Our bio-inspired hybrid threads could be manufactured from virtually any components. These new insights could lead to a wide range of applications, such as microfabrication of complex structures, reversible micro-motors, or self-tensioned stretchable systems.’

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

In-drop capillary spooling of spider capture thread inspires hybrid fibers with mixed solid–liquid mechanical properties by Hervé Elettro, Sébastien Neukirch, Fritz Vollrath, and Arnaud Antkowiak. PNAS doi: 10.1073/pnas.1602451113

This paper appears to be open access.

Two May 31, 2016 talks (Why nuclear power is necessary and DNA is not destiny) in Vancouver, Canada

Both the upcoming science talks in Vancouver are scheduled for May 31, 2016. Isn’t that always the way?

Why nuclear power is necessary

This talk is being held by ARPICO (Society of Italian Researchers & Professionals in Western Canada). From the ARPICO event page,

Why Nuclear Power is Necessary

Presenter

Patrick Walden graduated with a B.Sc. in Physics from UBC and a Ph.D in Particle Physics from Caltech. His Post Doctoral research was done at the Stanford University Linear Accelerator (SLAC), and since 1974 he has been at TRIUMF here in Vancouver. Patrick has been active in the fields of pion photo-production, meson spectroscopy, the dynamics of pion production from nuclei, and nuclear astrophysics.

Abstract

Nuclear power is the second largest source of greenhouse gas emissions-free energy in the world. It supplies approximately 5% of the world’s total energy demand. Presently, human activity is on the brink of initiating a global greenhouse climate catastrophe unless we can limit our greenhouse gas emissions.

In this talk, Dr. Patrick Walden will examine the concerns about nuclear power and the reasons why, contrary to public perception, nuclear power is one of the safest, most economical, plentiful, and greenest sources of energy available.

Logistics

  • May 31, 2016 – 7:00pm
  • Roundhouse Community Centre – Room B – (181 Roundhouse Mews, Vancouver BC V6Z2W3)
  • Underground pay parking is available, access off Drake St. south of Pacific Blvd.
    Admission by donation. Q&A and complimentary refreshments follow. Registration is highly recommended as seating is limited. RSVP at info@arpico.ca or at EventBrite by May 28th, 2016.

A map for the location can be found here.

There is a Skytrain station nearbyYaletown-Roundhouse Canada Line Station

DNA is not destiny

This month’s Café Scientifique talk is being held in downtown Vancouver at Yaggers (433 W. Pender St.). Details of the talk are (from the May 13, 2016 email announcement,

… Our speaker for the evening will be Dr. Steven Heine, a Professor in the Department of Psychology at UBC [University of British Columbia]. The title of his talk is:

DNA is Not Destiny: How Essences Distort how we Think about Genes

People the world over are essentialist thinkers – they are attracted to the idea that hidden essences make things as they are. And because genetic concepts remind people of essences, they tend to think of genes in ways similar to essences. That is, people tend to think about genetic causes as immutable, deterministic, homogenous, discrete, and natural.  Dr. Heine will discuss how our essentialist biases lead people to think differently about sex, race, crime, eugenics, and disease whenever these are described in genetic terms. Moreover, Dr. Heine will discuss how our essentialistic biases make people vulnerable to the sensationalist hype that has emerged with the genomic revolution and access to direct-to-consumer genotyping services.

Logistics

Tuesday May 31st, 7:30pm at Yagger’s Downtown (433 W Pender).

I have found a little more information about Dr. Steven Heine and his work (from his University of British Columbia webpage),

Our lab is currently working on three distinct research programs, which we refer to as Cultural Psychology, Meaning Maintenance, and Genetic Essentialism.

Our third research program on genetic esssentialism considers how people understand essences and genetic foundations for human behavior. We propose that encounters with genetic explanations for human outcomes prompts people to think of those outcomes in essentiialized ways, by viewing those outcomes as more deterministic, immutable, and fatalistic. For example, we find that women are more vulnerable to stereotype threat when they hear of genetic reasons for why men outperform women in math than when they hear of environmental reasons for this difference. We also find that men are more tolerant of sex crimes when they learn of genetic basis for sexual motivations than when they hear of social-constructivist accounts. We are conducting several studies to explore the ways that people respond to genetic accounts for human conditions.

Have fun whichever one you choose to attend.

Hologram with nanostructures could improve fraud protection

This research on holograms comes from Harvard University according to a May 13, 2016 news item on ScienceDaily,

Holograms are a ubiquitous part of our lives. They are in our wallets — protecting credit cards, cash and driver’s licenses from fraud — in grocery store scanners and biomedical devices.

Even though holographic technology has been around for decades, researchers still struggle to make compact holograms more efficient, complex and secure.

Researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences have programmed polarization into compact holograms. These holograms use nanostructures that are sensitive to polarization (the direction in which light vibrates) to produce different images depending on the polarization of incident light. This advancement, which works across the spectrum of light, improves anti-fraud holograms as well as those used in entertainment displays.

A May 13, 2016 Harvard University press release (also on EurekAlert) by Leah Burrows, which originated the news item, provides more detail,

“The novelty in this research is that by using nanotechnology, we’ve made holograms that are highly efficient, meaning that very little light is lost to create the image,” said Federico Capasso, the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering and senior author of the paper. “By using incident polarized light, you can see far a crisper image and can store and retrieve more images. Polarization adds another dimension to holograms that can be used to protect against counterfeiting and in applications like displays.”

Harvard’s Office of Technology Development has filed patents on this and related technologies and is actively pursuing commercial opportunities.

Holograms, like digital photographs, capture a field of light around an object and encode it on a chip. However, photographs only record the intensity of light while holograms also capture the phase of light, which is why holograms appear three-dimensional.

“Our holograms work like any other but the image produced depends on the polarization state of the illuminating light, providing an extra degree of freedom in design for versatile applications,” said Mohammadreza Khorasaninejad, postdoctoral fellow in the Capasso Lab and first author of the paper.

There are several states of polarization. In linearly polarized light the direction of vibration remains constant while in circularly polarized light it rotates clockwise or counterclockwise. The direction of rotation is the chirality.

The team built silicon nanostructured patterns on a glass substrate, which act as superpixels. Each superpixel responds to a certain polarization state of the incident light. Even more information can be encoded in the hologram by designing and arranging the nanofins to respond differently to the chirality of the polarized incident light.

“Being able to encode chirality can have important applications in information security such as anti-counterfeiting,” said Antonio Ambrosio, a research scientist in the Capasso Lab and co-first author. “For example, chiral holograms can be made to display a sequence of certain images only when illuminated with light of specific polarization not known to the forger.”

“By using different nanofin designs in the future, one could store and retrieve far more images by employing light with many states of polarization,” said Capasso.

Because this system is compact, it has application in portable projectors, 3D movies and wearable optics.

“Modern polarization imaging systems require cascading several optical components such as beam splitters, polarizers and wave plates,” said Ambrosio. “Our metasurface can distinguish between incident polarization using a single layer dielectric surface.”

“We have also incorporated in some of the holograms a lens function that has allowed us to produce images at large angles,” said Khorasaninejad. “This functionality combined with the small footprint and lightweight, has significant potential for wearable optics applications.”

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

Broadband and chiral binary dielectric meta-holograms by Mohammadreza Khorasaninejad, Antonio Ambrosio, Pritpal Kanhaiya, and Federico Capasso. Science Advances  13 May 2016: Vol. 2, no. 5, e1501258 DOI: 10.1126/sciadv.1501258

This paper is open access.

Light-captured energetics (harvesting light for optoelectronics)

Comparing graphene to a tiger is unusual but that’s what researcher Sanfeng Wu does—eventually—in a May 13, 2016 University of Washington news release (also on EurekAlert) about his work,

In the quest to harvest light for electronics, the focal point is the moment when photons — light particles — encounter electrons, those negatively-charged subatomic particles that form the basis of our modern electronic lives. If conditions are right when electrons and photons meet, an exchange of energy can occur. Maximizing that transfer of energy is the key to making efficient light-captured energetics possible.

“This is the ideal, but finding high efficiency is very difficult,” said University of Washington physics doctoral student Sanfeng Wu. “Researchers have been looking for materials that will let them do this — one way is to make each absorbed photon transfer all of its energy to many electrons, instead of just one electron in traditional devices.”

In traditional light-harvesting methods, energy from one photon only excites one electron or none depending on the absorber’s energy gap, transferring just a small portion of light energy into electricity. The remaining energy is lost as heat. But in a paper released May 13 in Science Advances, Wu, UW associate professor Xiaodong Xu and colleagues at four other institutions describe one promising approach to coax photons into stimulating multiple electrons. Their method exploits some surprising quantum-level interactions to give one photon multiple potential electron partners. Wu and Xu, who has appointments in the UW’s Department of Materials Science & Engineering and the Department of Physics, made this surprising discovery using graphene.

There has been intense research on graphene’s electrical properties but the researchers’ discovery adds a new property to be investigated (from the news release),

“Graphene is a substance with many exciting properties,” said Wu, the paper’s lead author. “For our purposes, it shows a very efficient interaction with light.”

Graphene is a two-dimensional hexagonal lattice of carbon atoms bonded to one another, and electrons are able to move easily within graphene. The researchers took a single layer of graphene — just one sheet of carbon atoms thick — and sandwiched it between two thin layers of a material called boron-nitride.

Boron-nitride is a material that has excited a great deal of interest in the last 12 to 18 months (from the news release),

“Boron-nitride has a lattice structure that is very similar to graphene, but has very different chemical properties,” said Wu. “Electrons do not flow easily within boron-nitride; it essentially acts as an insulator.”

Xu and Wu discovered that when the graphene layer’s lattice is aligned with the layers of boron-nitride, a type of “superlattice” is created with properties allowing efficient optoelectronics that researchers had sought. These properties rely on quantum mechanics, the occasionally baffling rules that govern interactions between all known particles of matter. Wu and Xu detected unique quantum regions within the superlattice known as Van Hove singularities.

Here’s an animated .gif illustrating the superlattice in action,

The Moire superlattice they created by aligning graphene and boron-nitride. Credit: Sanfeng Wu.

The Moire superlattice they created by aligning graphene and boron-nitride. Credit: Sanfeng Wu.

The news release goes on to describe the Van Hove singularities within the superlattice and to mention the ‘tiger’,

“These are regions of huge electron density of states, and they were not accessed in either the graphene or boron-nitride alone,” said Wu. “We only created these high electron density regions in an accessible way when both layers were aligned together.”

When Xu and Wu directed energetic photons toward the superlattice, they discovered that those Van Hove singularities were sites where one energized photon could transfer its energy to multiple electrons that are subsequently collected by electrodes— not just one electron or none with the remaining energy lost as heat. By a conservative estimate, Xu and Wu report that within this superlattice one photon could “kick” as many as five electrons to flow as current.

With the discovery of collecting multiple electrons upon the absorption of one photon, researchers may be able to create highly efficient devices that could harvest light with a large energy profit. Future work would need to uncover how to organize the excited electrons into electrical current for optimizing the energy-converting efficiency and remove some of the more cumbersome properties of their superlattice, such as the need for a magnetic field. But they believe this efficient process between photons and electrons represents major progress.

“Graphene is a tiger with great potential for optoelectronics, but locked in a cage,” said Wu. “The singularities in this superlattice are a key to unlocking that cage and releasing graphene’s potential for light harvesting application.”

H/t to a May 13, 2016 news item on phys.org.

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

Multiple hot-carrier collection in photo-excited graphene Moiré superlattices by Sanfeng Wu, Lei Wang, You Lai, Wen-Yu Shan, Grant Aivazian, Xian Zhang, Takashi Taniguchi, Kenji Watanabe, Di Xiao, Cory Dean, James Hone, Zhiqiang Li, and Xiaodong Xu. Science Advances 13 May 2016: Vol. 2, no. 5, e1600002 DOI: 10.1126/sciadv.1600002

This paper is open access.

AquAdvantage salmon (genetically modified) approved for consumption in Canada

This is an update of the AquAdvantage salmon story covered in my Dec. 4, 2015 post (scroll down about 40% of the way). At the time, the US Food and Drug Administration (FDA) had just given approval for consumption of the fish. There was speculation there would be a long hard fight over approval in Canada. This does not seem to have been the case, according to a May 10, 2016 news item announcing Health Canada’s on phys.org,

Canada’s health ministry on Thursday [May 19, 2016] approved a type of genetically modified salmon as safe to eat, making it the first transgenic animal destined for Canadian dinner tables.

This comes six months after US authorities gave the green light to sell the fish in American grocery stores.

The decisions by Health Canada and the US Food and Drug Administration follow two decades of controversy over the fish, which is an Atlantic salmon injected with genes from Pacific Chinook salmon and a fish known as the ocean pout to make it grow faster.

The resulting fish, called AquAdvantage Salmon, is made by AquaBounty Technologies in Massachusetts, and can reach adult size in 16 to 18 months instead of 30 months for normal Atlantic salmon.

A May 19, 2016 BIOTECanada news release on businesswire provides more detail about one of the salmon’s Canadian connections,

Canadian technology emanating from Memorial University developed the AquAdvantage salmon by introducing a growth hormone gene from Chinook salmon into the genome of Atlantic salmon. This results in a salmon which grows faster and reaches market size quicker and AquAdvantage salmon is identical to other farmed salmon. The AquAdvantage salmon also received US FDA approval in November 2015. With the growing world population, AquaBounty is one of many biotechnology companies offering safe and sustainable means to enhance the security and supply of food in the world. AquaBounty has improved the productivity of aquaculture through its use of biotechnology and modern breeding technics that have led to the development of AquAdvantage salmon.

“Importantly, today’s approval is a result of a four year science-based regulatory approval process which involved four federal government departments including Agriculture and AgriFood, Canada Food Inspection Agency, Environment and Climate Change, Fisheries and Oceans and Health which demonstrates the rigour and scope of science based regulatory approvals in Canada. Coupled with the report from the [US] National Academy of Sciences today’s [May 19, 2016] approval clearly demonstrates that genetic engineering of food is not only necessary but also extremely safe,” concluded Casey [Andrew Casey, President and CEO BIOTECanada].

There’s another connection, the salmon hatcheries are based in Prince Edward Island.

While BIOTECanada’s Andrew Casey is crowing about this approval, it should be noted that there was a losing court battle with British Columbia’s Living Oceans Society and Nova Scotia’s Ecology Action Centre both challenging the federal government’s approval. They may have lost battle but, as the cliché goes, ‘the war is not over yet’. There’s an Issue about the lack of labeling and there’s always the  possibility that retailers and/or consumers may decide to boycott the fish.

As for BIOTECanada, there’s this description from the news release,

BIOTECanada is the national industry association with more than 230 members reflecting the diverse nature of Canada’s health, industrial and agricultural biotechnology sectors. In addition to providing significant health benefits for Canadians, the biotechnology industry has quickly become an essential part of the transformation of many traditional cornerstones of the Canadian economy including manufacturing, automotive, energy, aerospace and forestry industries. Biotechnology in all of its applications from health, agriculture and industrial is offering solutions for the collective population.

You can find the BIOTECanada website here.

Personally, I’m a bit ambivalent about it all. I understand the necessity for changing our food production processes but I do think more attention should be paid to consumers’ concerns and that organizations such as BIOTECanada could do a better job of communicating.

Chief science adviser/advisor for Canada (we’re still waiting)

I half-thought we might get an announcement about Canada’s new science adviser/advisor/officer during the 2016 Science Odyssey  (formerly Canada’s National Science and Technology Week) being held from May 6–15, 2016. Especially in light of Science Minister Kirsty Duncan’s May 6, 2016 article “Duncan: New federal science adviser will be key to evidence-based policy” for the Ottawa Citizen,

The creation of a permanent Chief Science Officer demonstrates our government’s commitment to making sure science finds its rightful place at the federal table. In the six months since arriving in office, I have consulted extensively – both domestically and internationally – on this position. I have examined how similar positions, often called a chief science adviser, work in other countries such as the United Kingdom, New Zealand, the United States and Israel. My survey of international models will help create a position that is modern and yet tailor-made to suit Canada.

To-date, I have received valuable input from more than 80 experts, stakeholders and parliamentary colleagues from across the political spectrum. They have provided views such as the importance of recruiting someone who can provide independent, transparent and non-partisan scientific advice to the prime minister and our government. Our consultations have also underscored the importance of building relationships between a Chief Science Officer and the research community that allow for the best scientific expertise to be part of decision-making at the highest levels of government.

Our stakeholders also emphasized the importance of appointing someone who would have access to and an open dialogue with federal scientists, along with other scientists across Canada and abroad.

And when I speak of scientists here, I mean all scientists. As Stephen J. Toope, president of the Federation for the Humanities and Social Sciences, wrote in the Citizen Friday [May 6, 2016], our lead scientist would be welcome to gather the best evidence from all scientific disciplines: the natural and applied sciences, engineering, health sciences and the social sciences and humanities. The officer would do so without the influence of political agendas. And with ease in both official languages.

I have learned from my consultations that in order for Canada to enhance its science advisory system and give this new position permanence, it is important to properly define and take the time necessary to recruit someone who has a deep respect for Canada’s scientists and the role of science in society. So far, I am encouraged that members of our stakeholder community and parliamentarians understand the need for a credible process to appoint a worthy individual who will serve our prime minister, our government, our citizens and scientists.

Tim Lougheed in a Feb. 29, 2016 article for the Canadian Science Policy Centre passed on a few thoughts from Sir Peter Gluckman, Chief Science Advisor (CSO; either advisor or adviser seems to be correct) to New Zealand’s Prime Minister,

So, the Canadian science adviser is supposed to have an impact on policy,

“There can be expectations that when you’re fighting for a science advisor you’re fighting for an in-house lobbyist for the science community,” he cautions. “But of course you’re not: you’re fighting for an in-house lobbyist for the use of science by government. There’s a really important difference.”

Gluckman was honoured this February [2016] in Washington [DC] at the annual meeting of the American Association for the Advancement of Science, which gave him its 2015 Award for Science Diplomacy. He understands the need for diplomacy in any kind of CSO undertaking, especially whenever he has found himself wedged in between a political leadership seeking objective consultation and a research community disappointed with their share of government funding.

“When the roles of science advisors get conflated, they tend to get more politicized,” he explains. “What we try to do is to show that science can be an apolitical powerful input into better decision-making by governments.”

Canada [has] already long taken advantage of this powerful input through the Science Technology and Innovation Council, created in 2007, and before that the Council of Science and Technology Advisors, which dates back to 1996. However, the deliberations of these bodies largely took place behind closed doors and neither was ever intended to maintain the public accountability and profile of a CSO, who could easily become a lightning rod in exceptional circumstances such as those that highlighted Koop’s career.

“They’re going to have to earn the trust of the Prime Minister and the Cabinet,” says University of Ottawa Biology Professor Rees Kassen. “They have to show value and at the same time they have to show value to the country.”

Kassen, a longtime advocate of bridge-building between government and the research community, underscores that “country” refers to everyone, not just those two parties. In order to succeed, the CSO must be seen to benefit Canada as a whole.

“I would like to see the role of science advisor not rely solely on the heroic capabilities of one person,” he adds. “We have a very rich ecosystem of scientific knowledge creation, of scientific activity, of scientific translation — and potentially, of scientific advice.”

Kassen, a longtime advocate of bridge-building between government and the research community, underscores that “country” refers to everyone, not just those two parties. In order to succeed, the CSO must be seen to benefit Canada as a whole.

“I would like to see the role of science advisor not rely solely on the heroic capabilities of one person,” he adds. “We have a very rich ecosystem of scientific knowledge creation, of scientific activity, of scientific translation — and potentially, of scientific advice.”

Gluckman — who himself coordinates the work of a variety of other science advisors located in other parts of the New Zealand government, and collaborates closely with the Royal Society of New Zealand (the National Academy)— absolutely agrees. Moreover, he concludes that the effectiveness of any CSO will depend on how far and wide their influence extends.

“That really determines how this role works,” he says. “Ultimately if this person doesn’t report across the whole of government, they can’t do the role I’m talking about.”

Of course, there are some assumptions being made as Paul Cairney *notes* in his March 10, 2016 article for the Guardian about science advice and its impact on policy and policymakers,

… these efforts will fail if scientists and other experts fail to understand how the policy process works. To do so requires us to reject two romantic notions: first, that policymakers will ever think like scientists; and second, that there is a clearly identifiable point of decision at which scientists can contribute evidence to make a demonstrable impact.

To better understand how policymakers think, we need a full account of “bounded rationality.” This phrase describes the fact that policymakers can only gather limited information before they make decisions quickly. They will have made a choice before you have a chance to say “more research is needed”! To do so, they use two short cuts: rational ways to gather quickly the best evidence on solutions to meet their goals; and irrational ways – including drawing on emotions and gut feeling – to identify problems even more quickly.

This highlights a potential flaw in academic strategies. The most common response to bounded rationality in scientific articles is to focus on the supply of evidence: to develop a hierarchy of evidence, which often privileges randomised control trials; to generate knowledge; and to present it in a form that is understandable to policymakers.

We need to pay more attention to the demand for evidence, taking more account of lurches of policymaker attention, often driven by quick and emotional decisions. For example, there is no point in taking the time to make evidence-based solutions easier to understand if policymakers are no longer interested. Successful advocates recognise the value of emotional appeals and simple stories to draw attention to a problem.

To identify when and how to contribute evidence, we need to understand the complicated environment in which policymaking takes place. There is no “policy cycle” in which to inject scientific evidence at the point of decision. Rather, the policy process is messy and often unpredictable. It is a complex system in which the same injection of evidence can have no effect, or a major effect.

The article offers more insight into the issues with science advice, evidence, and policymaking. Coincidentally Cairney was promoting a new book at the time (from Cairney’s article),

… his new book The Politics of Evidence Based Policymaking, which was launched this week by the Alliance for Useful Evidence. More details are available on his website.

All this speculation has been quite interesting and I look forward to an announcement at some point. For those who’d like more opinions about the matter, there’s the Canadian Science Policy Centre’s Chief Science Officer: Insights and Recommendations webpage, which, as of May 19, 2016, hosts seven opinion pieces including one from Ted Hsu, former Liberal Member of Parliament, one of the few to hold a science degree (in his case, physics).

*’notes’ added on May 19,2016 at 1412 PDT.

First Canadian Governor-General’s innovation award goes to professor Robert Burrell (nanoscientist) at the University of Alberta

The first innovation award ever given by the Canadian Governor General* has gone to a nanomedicine pioneer at the University of Alberta. From a May 12, 2016 news article by Marc Montgomery for Radio Canada International*, Note: A link has been removed,

Professor Robert Burrell of the University of Alberta has won a prestigious Governor-General’s Innovation Award for the world’s first therapeutic use of nanotechnology.

Professor Burrell used nano-technology on a wound bandage that has already begun transforming treatment of wounds in situations around the world.

Robert Burrell,  Professor in the Faculty of Chemical and Mechanical Engineering at the University of Alberta, is also Canada Research Chair in Nanostructured Biomaterials, and Chair, Biomedical Engineering at the university.

Burrell’s development called Acticoat came from research into nano-forms of silver.  When silver is reduced to nano scale it’s properties and chemical activity change.

In his research prior to joining the University in 2002, Burrell created a coating of nano-crystals of silver which not only kills bacteria but also has anti-inflammatory properties.

A May 9, 2016 University of Alberta news release has a bit more information,

… The chair of the U of A Department of Biomedical Engineering has been awarded a new national innovation prize in recognition of an invention that transformed wound care around the world.

Rob Burrell PhD, FCAHS, who holds the Canada Research Chair in Nanostructure Biomaterials and leads the Department of Biomedical Engineering, is one of six Canadians to win the inaugural round of the Governor General’s Innovation Awards. The awards recognize “exceptional and transformative work” that has helped “shape our future and positively impact our quality of life.”

“It was a nice surprise,” Burrell says of receiving the award. “I got an email in April—and was wondering why the Secretary to the Governor General of Canada [David Johnston is the current Governor General] wanted to talk to me. When we had our phone call he congratulated me on winning the award.”

Burrell invented Acticoat, a new wound dressing that uses nanocrystalline silver to fight bacteria and inflammation in wounds, while working for Westaim Biomedical, later Nucryst Pharmaceuticals. He joined the Faculty of Engineering in 2002.

The dressing was the world’s first therapeutic use of nanotechnology and has saved thousands of lives and limbs, transforming the treatment of burns and wounds.

“We have three projects on the go now. We’ve developed a new dressing and applied for a patent on it for scar control and we’re looking at commercializing that,” he said. “I have two of my grad students—and this summer we will have three summer students—working on a diagnostic tool that will allow a surgeon in an operating room to assess a tumour in 10 to 15 minutes. The analysis of the tumour can determine the type of surgery and post-surgical care the patient receives.”

You can find out more about the Governor General awards, which include, in addition to the new innovation category, the arts,  the sciences and humanities, and more here.

* I have a couple of explanatory notes for those unfamiliar with the concept of a Governor General and/or those who may be curious about Radio Canada International.

The Governor General is the Queen’s or the British monarch’s representative in Canada. Here’s another more general definition from a Wikipedia entry,

Governor-general or governor general, in modern usage, is the title of an office-holder appointed to represent the monarch of a sovereign state in the governing of an independent realm. Governors-general have also previously been appointed in respect of major colonial states or other territories held by either a monarchy or republic, such as French Indochina.

Radio Canada International is a little complicated. Radio Canada is the French language arm of the Canadian Broadcasting Corporation (CBC) and the name ‘Radio Canada’ refers to its radio, television, and internet services.

Interestingly Radio Canada International is the global outreach for both Radio Canada and CBC, presumably, uniting the English and French language services under one banner.