Monthly Archives: August 2013

So, why do gold nanoparticles facilitate cell penetration without damage to cell walls?

Researchers at the Massachusetts Institute of Technology (MIT) and l’École Polytechnique Fédérale de Lausanne (EPFL) in Switerzerland have found an answer to the question about why gold nanoparticles facilitate cell penetration without damage to the cell walls. Apparently it has nothing to with the gold; it’s all in the coating according to an Aug. 23, 2013 MIT news release by David L. Chandler (also on EurekAlert),

Cells are very good at protecting their precious contents — and as a result, it’s very difficult to penetrate their membrane walls to deliver drugs, nutrients or biosensors without damaging or destroying the cell. One effective way of doing so, discovered in 2008, is to use nanoparticles of pure gold, coated with a thin layer of a special polymer. But nobody knew exactly why this combination worked so well, or how it made it through the cell wall.

Now, researchers at MIT and the Ecole Polytechnique de Lausanne in Switzerland have figured out how the process works, and the limits on the sizes of particles that can be used. …

Until now, says Van Lehn, the paper’s lead author [Reid Van Lehn], “the mechanism was unknown. … In this work, we wanted to simplify the process and understand the forces” that allow gold nanoparticles to penetrate cell walls without permanently damaging the membranes or rupturing the cells. The researchers did so through a combination of lab experiments and computer simulations.

The news release goes on to provide details about the research,

The team demonstrated that the crucial first step in the process is for coated gold nanoparticles to fuse with the lipids — a category of natural fats, waxes and vitamins — that form the cell wall. The scientists also demonstrated an upper limit on the size of such particles that can penetrate the cell wall — a limit that depends on the composition of the particle’s coating. [emphases mine]

The coating applied to the gold particles consists of a mix of hydrophobic and hydrophilic components that form a monolayer — a layer just one molecule thick — on the particle’s surface. Any of several different compounds can be used, the researchers explain. [emphases mine]

“Cells tend to engulf things on the surface,” says Alexander-Katz, an associate professor of materials science and engineering at MIT, but it’s “very unusual” for materials to cross that membrane into the cell’s interior without causing major damage. Irvine and Stellacci demonstrated in 2008 that monolayer-coated gold nanoparticles could do so; they have since been working to better understand why and how that works.

Since the nanoparticles themselves are completely coated, the fact that they are made of gold doesn’t have any direct effect, except that gold nanoparticles are an easily prepared model system, the researchers say. However, there is some evidence that the gold particles have therapeutic properties, which could be a side benefit.

Gold particles are also very good at capturing X-rays — so if they could be made to penetrate cancer cells, and were then heated by a beam of X-rays, they could destroy those cells from within. “So the fact that it’s gold may be useful,” says Irvine, a professor of materials science and engineering and biological engineering and member of the Koch Institute for Integrative Cancer Research.

Significantly, the mechanism that allows the nanoparticles to pass through the membrane seems also to seal the opening as soon as the particle has passed. “They would go through without allowing even small molecules to leak through behind them,” Van Lehn says.

Irvine says that his lab is also interested in harnessing this cell-penetrating mechanism as a way of delivering drugs to the cell’s interior, by binding them to the surface coating material. One important step in making that a useful process, he says, is finding ways to allow the nanoparticle coatings to be selective about what types of cells they attach to. “If it’s all cells, that’s not very useful,” he says, but if the coatings can be targeted to a particular cell type that is the target of a drug, that could be a significant benefit.

Another potential application of this work could be in attaching or inserting biosensing molecules on or into certain cells, Van Lehn says. In this way, scientists could detect or monitor specific biochemical markers, such as proteins that indicate the onset or decline of a disease or a metabolic process.

The research paper can be found here,

Effect of Particle Diameter and Surface Composition on the Spontaneous Fusion of Monolayer-Protected Gold Nanoparticles with Lipid Bilayers by Reid C. Van Lehn, Prabhani U. Atukorale, Randy P. Carney, Yu-Sang Yang, Francesco Stellacci, Darrell J. Irvine, and Alfredo Alexander-Katz. Nano Lett., Article ASAP DOI: 10.1021/nl401365n Publication Date (Web): August 5, 2013
Copyright © 2013 American Chemical Society

It is behind a paywall.

You say pants, I say underpants when it’s all about the scientific lingerie

I’d forgotten the Brits say pants where we Canucks say underpants, a type of linguistic confusion which can lead to crosscultural snafus, as it did for me this morning (Aug. 23, 2013) on reading Stuart Clark’s Guardian Science blog posting, Pants named after astronomer Cecilia Payne-Gaposchkin (Note: Links have been removed),

You know that science communication has reached a whole new level when someone names a pair of women’s pants after an astronomer.

Today [August 23, 2013], internet-based retailer Who Made Your Pants? launches a line of women’s pants called Cecilia, named after Cecilia Payne-Gaposchkin, the pioneering 20th century astronomer who explained the composition of the stars.

I’ve been an admirer of Payne’s achievements for a long time and couldn’t resist using her as a character in my novel The Day Without Yesterday.

She changed the face of astrophysics with her 1925 PhD thesis, in which she demonstrated that the sun was made almost exclusively from hydrogen and helium. Only 2% of its mass came from the other chemical elements, such as iron, oxygen and silicon.

Her name was chosen for the undergarment in a popular vote on the Who Made Your Pants? Facebook page. Customers were offered a choice between Cecilia, cell donor Henrietta Lacks and astronaut Sally Ride.

Becky John, who runs the company, and is also an organiser of the Winchester Science Festival says, “We will always name our pants after women who have been forgotten.”

Clark’s piece is amusing (he’s got a good punch line at the end) and informative and I recommend reading it.

As for Becky Johnson’s company,  Who Made Your Pants?, here’s a bit about the company from the About Us page,

Who Made Your Pants? is a campaigning lingerie brand based in Southampton, UK. We’re about two things – amazing pants, and amazing women.

We think that every day should be a good pants day, and that there should be a little bit of gorgeous under everyone’s clothes, something just for them. So we buy fabrics that have been sold on by big underwear companies at the end of season, stop them ending up as waste and turn them into gorgeous new pants that have a great start in life. They’re designed to sit flat under clothes, have no VPL [visible panty line], and be comfortable and all day fabulous.

We also think that it’s not really on for anyone to be made to work in bad conditions just for a cheap pair of pants. Who could feel lovely in something made in a bad place? So we make our pants in a great place. We’ve a little factory in Southampton where we create jobs for women who’ve had a hard time. The first job everyone learns is making the pants. We hope that all jobs within the business can be filled by the women as they gain skills though – if someone is interested in marketing, or finance, we’ll arrange training

When I first clicked through to the company website I was expecting to see what the Brits call trousers and found this instead,

Named for astronomer Cecilia Payne, our first side seamed shortie is made from smooth comfortable strecth fabrics and topped with reclaimed lace. A pretty lettuce edge hem finishes them off - and we can't wait to show you the next colours we have planned... [downloaded from]

Named for astronomer Cecilia Payne, our first side seamed shortie is made from smooth comfortable strecth fabrics and topped with reclaimed lace. A pretty lettuce edge hem finishes them off – and we can’t wait to show you the next colours we have planned… [downloaded from]

The company also has a ‘Rosalind’ as in a Rosalind Franklin pant,

Named for Rosalind Franklin, the higher cut shortie is based on a shape our designer saw and loved in Brazil. Smooth lycra or jersey is edged with reclaimed stretch lace for a stay put, no VPL, all day every day style. A great shape to show off gorgeous print fabrics [downloaded from]

Named for Rosalind Franklin, the higher cut shortie is based on a shape our designer saw and loved in Brazil. Smooth lycra or jersey is edged with reclaimed stretch lace for a stay put, no VPL, all day every day style. A great shape to show off gorgeous print fabrics [downloaded from]

It seems to be a ‘Rosalind Franklin’ week here as I embedded a rap created by a grade seven class for Tom McFadden’s Battle Rap Histories of Epic Science (Brahe’s Battles) about her in an Aug. 19, 2013 posting (scroll down to the end of the post for the video). For anyone not familiar with Rosalind Franklin and the controversy, here’s an essay about it and her on the San Diego Supercomputer Center website.

Reliable method for detecting silver nanoparticle in fresh food and produce

The tone of an Aug. 22, 2013 news item on ScienceDaily about detecting silver naooparticles seems a bit alarmist,

Over the last few years, the use of nanomaterials for water treatment, food packaging, pesticides, cosmetics and other industries has increased. For example, farmers have used silver nanoparticles as a pesticide because of their capability to suppress the growth of harmful organisms. However, a growing concern is that these particles could pose a potential health risk to humans and the environment. In a new study, researchers at the University of Missouri have developed a reliable method for detecting silver nanoparticles in fresh produce and other food products. [emphasis mine]

“More than 1,000 products on the market are nanotechnology-based products,” said Mengshi Lin, associate professor of food science in the MU College of Agriculture, Food and Natural Resources. “This is a concern because we do not know the toxicity of the nanoparticles. [emphasis mine] Our goal is to detect, identify and quantify these nanoparticles in food and food products and study their toxicity as soon as possible.” [emphasis mine]

We leap from “could pose a potential health risk” to “we do not know the toxicity” to “study their toxicity as soon as possible” within the space of a few sentences. It’s a bit dizzying for those of us who prefer a more measured approach. The Aug. 22, 2013 University of Missouri news release on EurekAlert, which originated the news item, continues in this vein,

Lin and his colleagues, including MU scientists Azlin Mustapha and Bongkosh Vardhanabhuti, studied the residue and penetration of silver nanoparticles on pear skin. First, the scientists immersed the pears in a silver nanoparticle solution similar to pesticide application. The pears were then washed and rinsed repeatedly. Results showed that four days after the treatment and rinsing, silver nanoparticles were still attached to the skin, and the smaller particles were able to penetrate the skin and reach the pear pulp.

“The penetration of silver nanoparticles is dangerous to consumers because they have the ability to relocate in the human body after digestion,” Lin said. “Therefore, smaller nanoparticles may be more harmful to consumers than larger counterparts.”

When ingested, nanoparticles pass into the blood and lymph system, circulate through the body and reach potentially sensitive sites such as the spleen, brain, liver and heart.

The growing trend to use other types of nanoparticles has revolutionized the food industry by enhancing flavors, improving supplement delivery, keeping food fresh longer and brightening the colors of food. However, researchers worry that the use of silver nanoparticles could harm the human body.

Before I point out one of the other problems I have with this news release, here’s an image that seemingly shows how the silver nanoparticles were applied to the pears,

Caption: Graduate student Zhong Zhang applies silver nanoparticles to a piece of fruit. In a recent study, University of Missouri researchers found that these particles could pose a potential health risk to humans and the environment. Credit: University of Missouri

Caption: Graduate student Zhong Zhang applies silver nanoparticles to a piece of fruit. In a recent study, University of Missouri researchers found that these particles could pose a potential health risk to humans and the environment.
Credit: University of Missouri

Using a syringe to apply silver nanoparticles to a portion of a pear is not the same thing as applying a pesticide in an orchard.  I think it’s problematic to draw conclusions from a testing procedure that does not begin to emulate real life conditions where wind, rain, soil conditions and biological processes come into play.

I have written elsewhere about the difficulties of deciding if silver nanoparticles are good or bad notably in my April 16, 2013 posting, Silver nanoparticles: we love you/we hate you, which features links to various research pieces arguing both pro and con. The Duke University mesocosm project is mentioned in the April 16 posting and is featured in the Feb. 28, 2013 posting, Silver nanoparticles, water, the environment, and toxicity, because it that testing emulated real life conditions.

Reservations about the tone of the news release aside, here’s a link to and a citation for the published paper from the University of Missouri researchers,

Detection of Engineered Silver Nanoparticle Contamination in Pears by Zhong Zhang, Fanbin Kong, Bongkosh Vardhanabhuti, Azlin Mustapha, and Mengshi Lin. J. Agric. Food Chem., 2012, 60 (43), pp 10762–10767 DOI: 10.1021/jf303423q Publication Date (Web): October 19, 2012
Copyright © 2012 American Chemical Society

This article is behind a paywall.

Assembly-line 3-D tissue engineering

It looks as if the researchers at Singapore’s Institute of Bioengineering and Nanotechnology (IBN), have developed a template for producing complex tissues such as those in liver and in fat, from an Aug. 20, 2013 news item on ScienceDaily,

Researchers at the Institute of Bioengineering and Nanotechnology (IBN) have developed a simple method of organizing cells and their microenvironments in hydrogel fibers. Their unique technology provides a feasible template for assembling complex structures, such as liver and fat tissues, as described in their recent publication in Nature Communications.

According to IBN Executive Director Professor Jackie Y. Ying, “Our tissue engineering approach gives researchers great control and flexibility over the arrangement of individual cell types, making it possible to engineer prevascularized tissue constructs easily. This innovation brings us a step closer toward developing viable tissue or organ replacements.”

The Aug. 19, 2013 A*STAR’s (Singapore’s Agency for Science and Technology Research) IBN  press release, which originated the news item, offers a detailed explanation of how this discovery could make tissue and organ replacements much easier,

IBN Team Leader and Principal Research Scientist, Dr Andrew Wan, elaborated, “Critical to the success of an implant is its ability to rapidly integrate with the patient’s circulatory system. This is essential for the survival of cells within the implant, as it would ensure timely access to oxygen and essential nutrients, as well as the removal of metabolic waste products. Integration would also facilitate signaling between the cells and blood vessels, which is important for tissue development.”

Tissues designed with pre-formed vascular networks are known to promote rapid vascular integration with the host. Generally, prevascularization has been achieved by seeding or encapsulating endothelial cells, which line the interior surfaces of blood vessels, with other cell types. In many of these approaches, the eventual distribution of vessels within a thick structure is reliant on in vitro cellular infiltration and self-organization of the cell mixture. These are slow processes, often leading to a non-uniform network of vessels within the tissue. As vascular self-assembly requires a large concentration of endothelial cells, this method also severely restricts the number of other cells that may be co-cultured.

Alternatively, scientists have attempted to direct the distribution of newly formed vessels via three-dimensional (3D) co-patterning of endothelial cells with other cell types in a hydrogel. This approach allows large concentrations of endothelial cells to be positioned in specific regions within the tissue, leaving the rest of the construct available for other cell types. The hydrogel also acts as a reservoir of nutrients for the encapsulated cells. However, co-patterning multiple cell types within a hydrogel is not easy. Conventional techniques, such as micromolding and organ printing, are limited by slow cell assembly, large volumes of cell suspension, complicated multi-step processes and expensive instruments. These factors also make it difficult to scale up the production of implantable 3D cell-patterned constructs. To date, these approaches have been unsuccessful in achieving vascularization and mass transport through thick engineered tissues.

To overcome these limitations, IBN researchers have used interfacial polyelectrolyte complexation (IPC) fiber assembly, a unique cell patterning technology patented by IBN, to produce cell-laden hydrogel fibers under aqueous conditions at room temperature. Unlike other methods, IBN’s novel technique allows researchers to incorporate different cell types separately into different fibers, and these cell-laden fibers may then be assembled into more complex constructs with hierarchical tissue structures. In addition, IBN researchers are able to tailor the microenvironment for each cell type for optimal functionality by incorporating the appropriate factors, e.g. proteins, into the fibers. Using IPC fiber assembly, the researchers have engineered an endothelial vessel network, as well as cell-patterned fat and liver tissue constructs, which have successfully integrated with the host circulatory system in a mouse model and produced vascularized tissues.

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

Patterned prevascularised tissue constructs by assembly of polyelectrolyte hydrogel fibres by Meng Fatt Leong,    Jerry K. C. Toh, Chan Du, Karthikeyan Narayanan, Hong Fang Lu, Tze Chiun Lim, Andrew C. A. Wan, & Jackie Y. Ying. Nature Communications 4, Article number: 2353 doi:10.1038/ncomms3353 Published 19 August 2013

This article is behind a paywall although you can preview it with ReadingCube access.

Nanomaterials, toxicology, and alternatives to animal testing

It seems that alternatives to animal testing may offer some additional capabilities for nanotoxicology studies according to an Aug. 21, 2013 news item on Nanowerk,

A group of international experts from government, industry and academia have concluded that alternative testing strategies (ATSs) that don’t rely on animals will be needed to cope with the wave of new nanomaterials emerging from the boom in nanoscience and nanotechnology. …

… Tests on laboratory mice, rats and other animals have been the standard way of checking new materials for health and environmental effects. Since those tests are costly, labor-intensive and time-consuming, workshop participants considered whether ATSs could have a larger role in checking the safety of ENMs [engineered nanomaterials].

They concluded that rapid cellular screening, computer modeling and other ATSs could serve as quick, cost-effective and reliable approaches for gathering certain types of information about the health and environmental effects of ENMs. “After lively discussions, a short list of generally shared viewpoints on this topic was generated, including a general view that ATS approaches for ENMs can significantly benefit chemical safety analysis,” they say.

The experts have had their consensus statement from the workshop published and before offering a citation for and a link to the statement, here’s the Abstract,

There has been a conceptual shift in toxicological studies from describing what happens to explaining how the adverse outcome occurs, thereby enabling a deeper and improved understanding of how biomolecular and mechanistic profiling can inform hazard identification and improve risk assessment. Compared to traditional toxicology methods, which have a heavy reliance on animals, new approaches to generate toxicological data are becoming available for the safety assessment of chemicals, including high-throughput and high-content screening (HTS, HCS). With the emergence of nanotechnology, the exponential increase in the total number of engineered nanomaterials (ENMs) in research, development, and commercialization requires a robust scientific approach to screen ENM safety in humans and the environment rapidly and efficiently. Spurred by the developments in chemical testing, a promising new toxicological paradigm for ENMs is to use alternative test strategies (ATS), which reduce reliance on animal testing through the use of in vitro and in silico methods such as HTS, HCS, and computational modeling. Furthermore, this allows for the comparative analysis of large numbers of ENMs simultaneously and for hazard assessment at various stages of the product development process and overall life cycle. [emphasis mine] Using carbon nanotubes as a case study, a workshop bringing together national and international leaders from government, industry, and academia was convened at the University of California, Los Angeles, to discuss the utility of ATS for decision-making analyses of ENMs. …

It seems that ATS has opened the door to more comprehensive testing (as per life cycles) than has previously been possible.

For the curious, here’s the citation for and the link to the published paper,

A Multi-Stakeholder Perspective on the Use of Alternative Test Strategies for Nanomaterial Safety Assessment by Andre E. Nel, Elina Nasser, Hilary Godwin, David Avery, Tina Bahadori, Lynn Bergeson #, Elizabeth Beryt, James C. Bonner, Darrell Boverhof, Janet Carter, Vince Castranova, J. R. DeShazo, Saber M. Hussain ●, Agnes B. Kane, Frederick Klaessig, Eileen Kuempel, Mark Lafranconi, Robert Landsiedel, Timothy Malloy, Mary Beth Miller, Jeffery Morris, Kenneth Moss, Gunter Oberdorster, Kent Pinkerton, Richard C. Pleus, Jo Anne Shatkin, Russell Thomas, Thabet Tolaymat, Amy Wang, and Jeffrey Wong. ACS Nano, Article ASAP DOI: 10.1021/nn4037927 Publication Date (Web): August 7, 2013

Copyright © 2013 American Chemical Society

This article is behind a paywall.

Light-harvesting antennas from laboratory constructs that are like ‘sun sponges’

As we know, plants are the best at harvesting energy from the sun but there are some scientists at Washington University in Saint Louis (Missouri, US) who claim they’ve developed a complex that’s better. From an Aug. 21, 2013 news item on Nanowerk,

In diagrams it looks like a confection of self-curling ribbon with bits of bling hung off the ribbon here and there. In fact it is a carefully designed ring of proteins with attached pigments that self-assembles into a structure that soaks up sunlight.

The scientists who made it call it a testbed, or platform for rapid prototyping of light-harvesting antennas–structures found in plants and photosynthesizing bacteria–that take the first step in converting sunlight into usable energy. The antennas consist of protein scaffolding that holds pigment molecules in ideal positions to capture and transfer the sun’s energy. The number and variety of the pigment molecules determines how much of the sun’s energy the antennas can grab and dump into an energy trap.

The Aug. 21, 2013 Washington University in Saint Louis news release by Diana Lutz, which originated the news item, provides more detail,

In the August 6, 2013 online edition of Chemical Science, a new publication of the Royal Society of Chemistry, the scientists describe two prototype antennas they’ve built on their testbed. One incorporated synthetic dyes called Oregon Green and Rhodamine Red and the other combined Oregon Green and a synthetic version of the bacterial pigment bacteriochlorophyll that absorbs light in the near-infrared region of the spectrum.

Both designs soak up more of the sun’s spectrum than native antennas in purple bacteria that provided the inspiration and some components for the testbed. The prototypes were also far easier to assemble than synthetic antennas made entirely from scratch. In this sense they offer the best of both worlds, combining human synthetic ingenuity with the repertoire of robust chemical machinery selected by evolution.

One day a two-part system (consisting of an antenna and a second unit called a reaction center) might serve as a miniature power outlet into which photochemical modules could be plugged. The sun’s energy could then be used directly to split water, generate electricity, or build molecular-scale devices.

The news release goes on to discuss the pigments used in the project and the complex’s self-assembly.

For those who want all the detail, here’s a link to and a citation for the published paper,

Integration of multiple chromophores with native photosynthetic antennas to enhance solar energy capture and delivery by Michelle A. Harris, Pamela S. Parkes-Loach, Joseph W. Springer, Jianbing Jiang, Elizabeth C. Martin, Pu Qian, Jieying Jiao, Dariusz M. Niedzwiedzki, Christine Kirmaier, John D. Olsen, David F. Bocian, Dewey Holten, C. Neil Hunter, Jonathan S. Lindsey and Paul A. Loach.  Chem. Sci., 2013, Advance Article DOI: 10.1039/C3SC51518D First published online 06 Aug 2013

I believe this is behind a paywall.

Another day, another solar cell improvement: replacing platinum with 3D graphene

On the plus side, this may replace platinum but it does seem to be one of a plethora of solar cell improvements that don’t make much difference in the current marketplace as this and other improvements are still at the laboratory stage.  Still, it’s encouraging to remember that scientific and technical progress in an area can be agonizingly slow in the early stages only to gain speed at an exponential rate in later stages of development. Fingers crossed this is the case with solar cells.

From the Aug. 20, 2013 Michigan Technological University news release by Marcia Goodrich (also on EurekAlert),

One of the most promising types of solar cells has a few drawbacks. …

Dye-sensitized solar cells are thin, flexible, easy to make and very good at turning sunshine into electricity. However, a key ingredient is one of the most expensive metals on the planet: platinum. While only small amounts are needed, at $1,500 an ounce, the cost of the silvery metal is still significant.

Yun Hang Hu, the Charles and Caroll McArthur Professor of Materials Science and Engineering [Michigan Technological University], has developed a new, inexpensive material that could replace the platinum in solar cells without degrading their efficiency: 3D graphene.

Regular graphene is a famously two-dimensional form of carbon just a molecule or so thick. Hu and his team invented a novel approach to synthesize a unique 3D version with a honeycomb-like structure. To do so, they combined lithium oxide with carbon monoxide in a chemical reaction that forms lithium carbonate (Li2CO3) and the honeycomb graphene. The Li2CO3 helps shape the graphene sheets and isolates them from each other, preventing the formation of garden-variety graphite.  Furthermore, the Li2CO3 particles can be easily removed from 3D honeycomb-structured graphene by an acid.

The researchers determined that the 3D honeycomb graphene had excellent conductivity and high catalytic activity, raising the possibility that it could be used for energy storage and conversion. So they replaced the platinum counter electrode in a dye-sensitized solar cell with one made of the 3D honeycomb graphene. Then they put the solar cell in the sunshine and measured its output.

The cell with the 3D graphene counter electrode converted 7.8 percent of the sun’s energy into electricity, nearly as much as the conventional solar cell using costly platinum (8 percent).

Synthesizing the 3D honeycomb graphene is neither expensive nor difficult, said Hu, and making it into a counter electrode posed no special challenges.

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

3D Honeycomb-Like Structured Graphene and Its High Efficiency as a Counter-Electrode Catalyst for Dye-Sensitized Solar Cells by Yun Hang Hu, Hui Wang, Franklin Tao, Dario J. Stacchiola, and Kai Sun. Angewandte Chemie, International Edition, Article first published online: 29 JUL 2013 DOI: 10.1002/anie.201303497

The article is behind a paywall.

A strange state of light

Apparently combining a hologram with subwavelength structures at a scale of just tens of nanometers can lead to ‘strange’ light. From the Aug. 20, 2013 news item on Nanowerk,

Applied physicists at the Harvard School of Engineering and Applied Sciences (SEAS) have demonstrated that they can change the intensity, phase, and polarization of light rays using a hologram-like design decorated with nanoscale structures.

As a proof of principle, the researchers have used it to create an unusual state of light called a radially polarized beam, which—because it can be focused very tightly—is important for applications like high-resolution lithography and for trapping and manipulating tiny particles like viruses.

The Aug. 20, 2013 Harvard University news release by Manny Marone, which originated the news item, further describes the device and the effect (Note: A link has been removed),

This is the first time a single, simple device has been designed to control these three major properties of light at once. (Phase describes how two waves interfere to either strengthen or cancel each other, depending on how their crests and troughs overlap; polarization describes the direction of light vibrations; and the intensity is the brightness.)

“Our lab works on using nanotechnology to play with light,” says Patrice Genevet, a research associate at Harvard SEAS and co-lead author of a paper published this month in Nano Letters. “In this research, we’ve used holography in a novel way, incorporating cutting-edge nanotechnology in the form of subwavelength structures at a scale of just tens of nanometers.” One nanometer equals one billionth of a meter.

Using these novel nanostructured holograms, the Harvard researchers have converted conventional, circularly polarized laser light into radially polarized beams at wavelengths spanning the technologically important visible and near-infrared light spectrum.

“When light is radially polarized, its electromagnetic vibrations oscillate inward and outward from the center of the beam like the spokes of a wheel,” explains Capasso [Federico Capasso, professor of applied physics]. “This unusual beam manifests itself as a very intense ring of light with a dark spot in the center.”

“It is noteworthy,” Capasso points out, “that the same nanostructured holographic plate can be used to create radially polarized light at so many different wavelengths. Radially polarized light can be focused much more tightly than conventionally polarized light, thus enabling many potential applications in microscopy and nanoparticle manipulation.”

The new device resembles a normal hologram grating with an additional, nanostructured pattern carved into it. Visible light, which has a wavelength in the hundreds of nanometers, interacts differently with apertures textured on the ‘nano’ scale than with those on the scale of micrometers or larger. By exploiting these behaviors, the modular interface can bend incoming light to adjust its intensity, phase, and polarization.

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

Nanostructured Holograms for Broadband Manipulation of Vector Beams by Jiao Lin, Patrice Genevet, Mikhail A. Kats, Nicholas Antoniou, and Federico Capasso. Nano Lett., Article ASAP DOI: 10.1021/nl402039y Publication Date (Web): August 5, 2013
Copyright © 2013 American Chemical Society

This article is behind a paywall.

I last wrote about Federico Carpasso’s work in an Oct. 16, 2013 posting, Harvard researchers look deeply into oily puddles as they rethink thin films and optical loss.

Free Global STEMx (science, technology, engineering, mathematics) Education Conference online in September 2013

A notice for this conference slipped into my mailbox on Aug. 19, 2013,

We hope you will consider joining us for the Global 2013 STEMx Education Conference, the world’s first massively open online conference for educators focusing on Science, Technology, Engineering, Math, and more. The conference will be held over the course of three days, September 19-21, 2013, and will be free to attend! STEMxCon will be a highly inclusive event that will engage students and educators around the globe and will encourage primary, secondary, and tertiary (K-16) educators around the world to share and learn about innovative approaches to STEMx learning and teaching. …

Please register at to attend and to be kept informed.

Usually, I’d jump to a description of the keynote speakers but I think this explanation for why they’ve added an x to STEM bears some attention (from the notice),

The Science, Technology, Engineering, and Mathematics acronym is no longer adequate, as it is missing well over 20 letters that represent key skills & disciplines. As such, x = Computer Science (CS), Computational Thinking (CT), Inquiry (I), Creativity & Innovation (CI), Global Fluency (GF), Collaboration ( C ), …and other emerging disciplines & 21st century skills.

The Council of Canadian Academies (CCA) assessment Strengthening Canada’s Research Capacity: The Gender Dimension; The Expert Panel on Women in University Research also noted that the STEM designation leaves something to be desired (my Feb. 22, 2013 posting).

Now onto the keynote speakers (from the notice),

We have a terrific set of keynote speakers for STEMxCon, including

  • Tim Bell on computer science in New Zealand,
  • Al Byers on STEM teacher learning communities at the NSTA [National Science Teachers Association],
  • Jeanne Century on STEM schools,
  • Cristin Frodella on the Google Science Fair,
  • Paloma Garcia-Lopez on the Maker Education Initiative,
  • Iris Lapinski on Apps for Good,
  • Ramsey Musallar on an inquiry-based learning cycle,
  • Ramji Raghavan on sparking curiosity and nurturing creativity, and
  • Avis Yates Rivers on inspiring the next generation in IT.

More information at

It’s still possible to respond to the call for presentation proposals, from the  ‘Call’ page,

Proposals can be submitted from May 30th – September 1st, 2013, and we will begin accepting proposals starting June 30th, 2013. We encourage you to submit your proposal as early as possible because as soon as a proposal is accepted, you are given the ability to select from the available presentation times (the time choices become increasingly limited closer to the event). You may submit more than one proposal, but we will give priority to providing as many presenters the chance to present as possible.

Your presentation proposal, once submitted, will be listed on the STEMx Conference website, with the opportunity for members of this network to view, comment on, and/or “like” your presentation proposal. This will give you and the other members of this site the chance to share ideas and to make connections before, during, and after the conference. …

Presentations should be at least 20 minutes in length, and all sessions must be completed (including Q&A) within one hour. All sessions will be held in the Blackboard Collaborate online platform (previously Elluminate/Wimba). You will be responsible for familiarizing yourself with the web conferencing platform. We will send you recorded training material, as well as provide live training sessions where you can ask questions. To practice, you can also sign up for the Collaborate trial room at

All presentations will be recorded and released under a Creative Commons Attribution-NonCommercial-NoDerivs License. For more information, please visit: By submitting to present, you are agreeing to these terms.

Presentations must be non-commercial. Interest in commercial sponsorship or presentations should be directed to Steve Hargadon at

The guidelines for submissions and other pertinent details are on the Call for proposals page.

I did find some information about the organization and the entities supporting its conference efforts on the 2013 STEMx Conference Welcome! webpage (Note: Links have been removed),

STEMxCon’s founding sponsor is HP [Hewlett Packard]. As one of the world’s largest technology companies with operations in more than 170 countries, HP is helping to solve environmental and social challenges by uniting the power of people and technology. The HP Sustainability & Social Innovation team focuses on improving lives and businesses every day by focusing on the environment, health, education, and community. By bringing together the expertise of their more than 300,000 HP employees in collaboration with our partners, HP makes technology work for people in powerful ways that create a positive impact on the world.

The International Society for Technology in Education (ISTE®) is also a core conference supporter, and is the premier membership association for educators and education leaders engaged in improving learning and teaching by advancing the effective use of technology in PK–12 and teacher education. ISTE represents more than 100,000 education leaders and emerging leaders throughout the world and informs its members regarding educational issues of national and global scope.

I like the openness of their approach and the note somewhere in the submission guidelines that the language in which the presentation is being offered be mentioned suggests they’re making a big effort to attract an international audience. I wish them the best of luck.

Keeping it together—new glue for lithium-ion batteries

Glue isn’t the first component that comes to my mind when discussing ways to make lithium-ion (Li-ion) batteries more efficient but researchers at SLAC National Accelerator Laboratory at Stanford University have proved that the glue used to bind a Li-ion battery together can make a difference to its efficiency (from the Aug. 20, 2013 news item on,

When it comes to improving the performance of lithium-ion batteries, no part should be overlooked – not even the glue that binds materials together in the cathode, researchers at SLAC and Stanford have found.

Tweaking that material, which binds lithium sulfide and carbon particles together, created a cathode that lasted five times longer than earlier designs, according to a report published last month in Chemical Science. The research results are some of the earliest supported by the Department of Energy’s Joint Center for Energy Storage Research.

“We were very impressed with how important this binder was in improving the lifetime of our experimental battery,” said Yi Cui, an associate professor at SLAC and Stanford who led the research.

The Aug. 19, 2013 SLAC news release by Mike Ross, which originated the news item, provides context for this accidental finding about glue and Li-ion batteries,

Researchers worldwide have been racing to improve lithium-ion batteries, which are one of the most promising technologies for powering increasingly popular devices such as mobile electronics and electric vehicles. In theory, using silicon and sulfur as the active elements in the batteries’ terminals, called the anode and cathode, could allow lithium-ion batteries to store up to five times more energy than today’s best versions. But finding specific forms and formulations of silicon and sulfur that will last for several thousand charge-discharge cycles during real-life use has been difficult.

Cui’s group was exploring how to create a better cathode by using lithium sulfide rather than sulfur. The lithium atoms it contains can provide the ions that shuttle between anode and cathode during the battery’s charge/discharge cycle; this in turn means the battery’s other electrode can be made from a non-lithium material, such as silicon. Unfortunately, lithium sulfide is also electrically insulating, which greatly reduces any battery’s performance. To overcome this, electrically conducting carbon particles can be mixed with the sulfide; a glue-like material – the binder – holds it all together.

Scientists in Cui’s [Yi Cui, an associate professor at SLAC and Stanford who led the research] group devised a new binder that is particularly well-suited for use with a lithium sulfide cathode ­– and that also binds strongly with intermediate polysulfide molecules that dissolve out of the cathode and diminish the battery’s storage capacity and useful lifetime.

The experimental battery using the new binder, known by the initials PVP, retained 94 percent of its original energy-storage capacity after 100 charge/discharge cycles, compared with 72 percent for cells using a conventionally-used binder, known as PVDF. After 500 cycles, the PVP battery still had 69 percent of its initial capacity.

Cui said the improvement was due to PVP’s much stronger affinity for lithium sulfide; together they formed a fine-grained lithium sulfide/carbon composite that made it easier for lithium ions to penetrate and reach all of the active material within the cathode. In contrast, the previous binder, PVDF, caused the composite to grow into large clumps, which hindered the lithium ions’ penetration and ruined the battery within 100 cycles

Even the best batteries lose some energy-storage capacity with each charge/discharge cycle. Researchers aim to reduce such losses as much as possible. Further enhancements to the PVP/lithium sulfide cathode combination will be needed to extend its lifetime to more than 1,000 cycles, but Cui said he finds it encouraging that improving the usually overlooked binder material produced such dramatic benefits.

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

Stable cycling of lithium sulfide cathodes through strong affinity with a bifunctional binder by Zhi Wei Seh, Qianfan Zhang, Weiyang Li, Guangyuan Zheng, Hongbin Yaoa, and Yi Cui. Chem. Sci., 2013,4, 3673-3677 DOI: 10.1039/C3SC51476E First published online 11 Jul 2013

There’s a note on the website stating the article is free but the instructions for accessing the article are confusing seeming to suggest you need a subscription of some sort or you need to register for the site.

I have written about Yi Cui’s work with lithium-ion batteries before including this Jan. 9, 2013 posting, How is an eggshell like a lithium-ion battery?, which also features a news release by Mike Ross.