Category Archives: nanotechnology

Like a starfish shell, facetless crystals

Made by accident, these facetless crystals could prove useful in applications for cells, medications, and more according to researchers at the University of Michigan in an Oct. 20, 2014 news item on Nanowerk,

In a design that mimics a hard-to-duplicate texture of starfish shells, University of Michigan engineers have made rounded crystals that have no facets.

“We call them nanolobes. They look like little hot air balloons that are rising from the surface,” said Olga Shalev, a doctoral student in materials science and engineering who worked on the project.

There is a video with the researcher, Olga Shalev, describing the nanolobes in more detail,

An Oct. 17, 2014 University of Michigan news release (also on EurekAlert*), which originated the news item, offers text for those who prefer to read about the science rather than receive it by video,

Both the nanolobes’ shape and the way they’re made have promising applications, the researchers say. The geometry could potentially be useful to guide light in advanced LEDs, solar cells and nonreflective surfaces. A layer might help a material repel water or dirt. And the process used to manufacture them – organic vapor jet printing – might lend itself to 3D-printing medications that absorb better into the body and make personalized dosing possible.

The nanoscale shapes are made out of boron subphthalocyanine chloride, a material often used in organic solar cells. It’s in a family of small molecular compounds that tend to make either flat films or faceted crystals with sharp edges, says Max Shtein, an associate professor of materials science and engineering, macromolecular science and engineering, chemical engineering, and art and design.

“In my years of working with these kinds of materials, I’ve never seen shapes that looked like these. They’re reminiscent of what you get from biological processes,” Shtein said. “Nature can sometimes produce crystals that are smooth, but engineers haven’t been able to do it reliably.”

Echinoderm sea creatures such as brittle stars have ordered rounded structures on their bodies that work as lenses to gather light into their rudimentary eyes. But in a lab, crystals composed of the same minerals tend either to be faceted with flat faces and sharp angles, or smooth, but lacking molecular order.

The U-M researchers made the curved crystals by accident several years ago. They’ve since traced their steps and figured out how to do it on purpose.

In 2010, Shaurjo Biswas, then a doctoral student at U-M, was making solar cells with the organic vapor jet printer. He was recalibrating the machine after switching between materials. Part of the recalibration process involves taking a close look at the fresh layers of material, of films, printed on a plate. Biswas X-rayed several films of different thicknesses to observe the crystal structure. He noticed that the boron subphthalocyanine chloride, which typically does not form ordered shapes, started to do so once the film got thicker than 600 nanometers. He made some thicker films to see what would happen.

“At first, we wondered if our apparatus was functioning properly,” Shtein said.

At 800 nanometers thick, the repeating nanolobe pattern emerged every time.

For a long while, the blobs were lab curiosities. Researchers were focused on other things. Then doctoral student Shalev got involved. She was fascinated by the structures and wanted to understand the reason for the phenomenon. She repeated the experiments in a modified apparatus that gave more control over the conditions to vary them systematically. She collaborated with physics professor Roy Clarke to gain a better understanding of the crystallization, and mechanical engineering professor Wei Lu to simulate the evolution of the surface.. She’s first author of a paper on the findings published in the current edition of Nature Communications.

“As far as we know, no other technology can do this,” Shalev said.

The organic vapor jet printing process the researchers use is a technique Shtein helped to develop when he was in graduate school. He describes it as spray painting, but with a gas rather than with a liquid. It’s cheaper and easier to do for certain applications than competing approaches that involve stencils or can only be done in a vacuum, Shtein says. He’s especially hopeful about the prospects for this technique to advance emerging 3D-printed pharmaceutical concepts.

For example, Shtein and Shalev believe this method offers a precise way to control the size and shape of the medicine particles, for easier absorption into the body. It could also allow drugs to be attached directly to other materials and it doesn’t require solvents that might introduce impurities.

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

Growth and modelling of spherical crystalline morphologies of molecular materials by O. Shalev, S. Biswas, Y. Yang, T. Eddir, W. Lu, R. Clarke,  & M. Shtein. Nature Communications 5, Article number: 5204 doi:10.1038/ncomms6204 Published 16 October 2014

This paper is behind a paywall.

* EurekAlert link added on Oct. 20, 2014 at 1035 hours PDT.

Heart of stone

Researchers in Europe do not want to find out what would Europe look like without its stone castles, Stonehenge, Coliseum, cathedrals, and other monumental stone structures, and have found a possible solution to the problem of deterioration according to an Oct. 20, 2014 news item on Nanowerk,

Castles and cathedrals, statues and spires… Europe’s built environment would not be the same without these witnesses of centuries past. But, eventually, even the hardest stone will crumble. EU-funded researchers have developed innovative nanomaterials to improve the preservation of our architectural heritage.

“Our objective,” says Professor Gerald Ziegenbalg of IBZ Salzchemie, “was to find new possibilities to consolidate stone and mortar, especially in historical buildings.” The products available at the time, he adds, didn’t meet the full range of requirements, and some could actually damage the artefacts they were meant to preserve. Alternatives compatible with the original materials were needed.

A July 9, 2014 European Commission press release, which originated the news item, provides more details about this project (Note: A link has been removed),

 Ziegenbalg was the coordinator of the Stonecore project, which rose to this monumental challenge within a mere three years. It developed and commercialised a new type of material that penetrates right into the stone, protecting it without any risk of damage or harmful residues. The team also invented new ways to assess damage to stone and refined a number of existing techniques.

The concept behind the new material developed by the Stonecore partners is ingenious. It involves lime nanoparticles suspended in alcohol, a substance that evaporates completely upon exposure to air. The nanoparticles then react with carbon dioxide in the atmosphere to form limestone.

This innovation is on the market under the brand name CaLoSil. It is available in various consistencies – liquids and pastes – and in a number of formulations based on different types of alcohol, as well as with added filler materials such as marble. The product is applied by dipping, spraying or injection into the stone.

Beyond its use as a consolidant, CaLoSil can also be used to clean stone and mortar, as it helps to treat fungus and algae. The dehydrating effect of the alcohol and the acidity of the lime destroy the cells, and the growth can then be washed off. This method, says Ziegenbalg, is more effective than conventional chemical or mechanical approaches, and it does not damage the stone.

Limestone face-lifts

The partners tested their new product in a number of locations across Europe, on a wide variety of materials exposed to very different conditions. Together, they rejuvenated statues and sculptures, saved features in cathedrals and citadels, and treated materials as diverse as sandstone, marble and tuff.

The opportunity to access such a wide variety of sites, says Ziegenbalg, was one of the many advantages of working with partners from several countries. It pre-empted the risk of developing a product that was too narrowly focused on a specific application.

Inside the heart of stone

A number of techniques enable conservation teams to assess the state of the objects in their care. To obtain a clearer picture of deeper damage, Stonecore improved existing approaches involving ultrasound, developing a new device. The project also pioneered a new technique based on ground-penetrating radar, which one partner is now offering as a commercial service.

The team also developed an innovative micro-drilling tool and refined an existing technique for measuring the water uptake of stone.

A further innovation is a new technique to measure surface degradation. For this so-called “peeling test”, a length of adhesive tape is affixed to the object. The weight of the particles that come off with the tape when it is removed indicate how likely the stone is to degrade.

Carving out solutions

The partners’ achievements have not gone unnoticed. In 2013, Stonecore was shortlisted along with 10 other projects for the annual EuroNanoForum’s Best Project Award.

Ziegenbalg attributes the team’s success mainly to the partners’ wide range of complementary expertise, and to their dedication. “The participating small and medium-sized enterprises were extremely active,” he says. “They were highly motivated to handle the more practical work, while the universities supported them with the necessary research input.”

While it’s not clear from this press release or the Stonecore website, it appears this project has run its course as part of European Union’s Framework Programme 7.

University of Calgary (Alberta, Canada) welcomes ‘oil sands’ researcher with two news releases

I gather the boffins at the University of Calgary are beside themselves with joy as they welcome Steven Bryant from Texas, a nanoscience researcher with long ties to oil industry research. From an Oct. 17, 2014 University of Calgary news release by Stéphane Massinon,

The greatest energy challenge of the 21st century is to meet energy demand from available fuels while drastically reducing society’s environmental footprint.

The challenge is massive. The solution, according to Steven Bryant, may be miniscule.

Bryant will lead and co-ordinate nanotechnology and materials science research at the University of Calgary, and the integrated team of researchers from across campus who will aim to drastically change how the oilsands are developed.

Bryant says Alberta’s oilsands are a key resource for meeting the world’s energy demands and the status quo is not acceptable.

“There is a huge desire to extract this energy resource with less environmental impact and, we think, conceivably even zero-impact, because of some of the cool things that are becoming possible with nanotechnology,” says Bryant.

“That’s kind of blue-sky but that’s one of the things we will be trying to sow the seeds for — alternative ways to get the energy out of this resource altogether. It’s a chance to do things better than we are currently doing them because of rapid advances in mesoscience.”

The mention of mesoscience called to mind the mesocosm project featured in an Aug. 15, 2011 posting (Mesocosms and nanoparticles at Duke University) although it seems that mesoscience is a somewhat different beast according to Massinon’s news release,

Mesoscience — technology developed at smaller than 100 nanometres — offers many tantalizing options to increase the efficiency of in-situ oilsands development, or Steam-Assisted Gravity drainage (SAGD). SAGD is the extraction process in which producers drill horizontal wells beneath the surface to pump steam into the underground oilsands reservoirs to loosen the oil and pump it to the surface.

SAGD is the method currently used to pump nearly one million barrels per day in Alberta and the output is forecast to double by 2022. SAGD uses considerable volumes of water and requires energy to heat the water to produce the steam that softens the underground oil that is caked in sand.

By using nanotechnology, Bryant and his team are working on reducing the amount of energy needed to heat water to create steam while also making the underground heat source more efficient at gathering more oil.

“The holy grail for the last 30 years has been trying to get CO2 to be less viscous. If you can do that, then you can get it to contact a lot more of the oil and for the same amount of CO2, you get a lot more oil produced. That turned out to be hard to do because there aren’t many chemical ways to make CO2 more viscous,” says Bryant.

By employing innovative approaches now, industry, environment and consumers can benefit greatly in the not-too-distant future.

“These alternative ways to get the energy out are at least 10 years away. So it’s not going to happen tomorrow, but it’s worth thinking about now to try to see what might be possible,” says Bryant.

Apparently, Bryant (no mention of family members) is terribly excited about moving to Calgary, from the news release,

Bryant is looking forward to working in Canada’s energy hub and says he will also work with industry to tackle oil production issues.

Industry wants to be more efficient at extracting oil because it saves them money. Efficiency also means reducing the environmental footprint. He believes oil companies will welcome the research produced from the university and said Calgary is the ideal place to be world leaders in energy production and energy research.

“The university is close to where the action is. All the major operators are in town and there’s a chance to take things from the lab to the field. The University of Calgary is very well situated in that regard.”

Bryant is joining the Department of Chemical and Petroleum Engineering in the Schulich School of Engineering. Before accepting this position, he was at the University of Texas at Austin, as Bank of America Centennial Professor in the Department of Petroleum and Geosystems Engineering, and directed the Geological CO2 Storage Joint Industry Project and the Nanoparticles for Subsurface Engineering Industrial Affiliates Program.

Bryant pioneered the fields of digital petrophysics and nanoparticles for engineering applications, and has made some of the most significant advances in the past 20 years in porous media modeling, reactive transport theory and CO2 sequestration. Bryant has been published more than 280 times in books, book chapters, peer-reviewed journals and conference proceedings on applications in production engineering, reservoir engineering and formation evaluation. Over his career, Bryant has led major research initiatives involving industry partnerships and trained over 90 graduate students and postdoctoral fellows who found positions in several of the largest energy companies and national laboratories.

He looks forward to what happens next.

“There’s still a lot of cool, basic science to be done, but we’ll be doing it with an eye to making a difference in terms of how you get energy out of the oilsands. This won’t be business as usual.”

Meanwhile, there’s an Oct. 17, 2014 news item on Azonano that focuses on the University of Calgary’s response to receiving its first Canada Excellence Research Chair (a programme where the federal Canadian government throws a lot of money for salaries and research at universities which then try to recruit ‘world class’ researchers),

A world-leading nanotechnology researcher has come to Canada’s energy capital to become the first Canada Excellence Research Chair (CERC) at the University of Calgary.

Minister of State (Western Economic Diversification) Michelle Rempel announced today $10 million in federal funding to the university over seven years to create the CERC for Materials Engineering for Unconventional Oil Reservoirs. These funds will be matched by the University of Calgary.

The CERC has been awarded to renowned researcher Steven Bryant, who has joined the Schulich School of Engineering and will integrate a team of researchers from several departments of the Schulich School of Engineering and Faculty of Science.

An Oct. 17, 2014 University of Calgary news release (no byline is given but this is presumably from the university’s ‘corporate’ communications team), which originated the news item on Azonano,

Rempel said the federal government is focused on developing, attracting, and retaining world-leading researchers through record investment in science, technology and innovation. She added that Bryant’s application of new nanomaterials and technology will seek to develop new efficiencies within the oilsands industry while training the next generation of highly talented Canadian researchers.

“Our government is committed to ensuring advancement in sustainable energy resource technology. Dr. Bryant’s arrival at the University of Calgary will help consolidate Canada’s position as a global leader in this area. The research being conducted at the university is good for Calgary, good for the economy and good for Canada,” said Rempel.

President Elizabeth Cannon thanked the federal government for its financial support and said Bryant’s arrival vaults the university’s existing energy research to the next level.

“The University of Calgary is thrilled to have Dr. Steven Bryant join our energy research team, where he will play a key role exploring new and sustainable ways of developing unconventional resources,” said Cannon.

“We are confident that Dr. Bryant and his colleagues, working here at Canada’s energy university, will offer innovative solutions to the pressing challenges faced by our society: meeting ever-growing energy demands and drastically reducing our environmental footprint.”

In addition to the matching funds, the University of Calgary is planning additional support for major infrastructure and equipment for the CERC.

In 2008, the federal government launched the CERC program to encourage some of the most accomplished researchers around the world to work at Canadian universities.

The Canada Excellence Research Chair plays a significant role in the university’s energy strategy, which aims to make the University of Calgary a global leader in energy research. It is also critical to our Eyes High goal to becoming a top five Canadian research university.

Attracting world-class researchers to campus helps attract more students and post-docs to the university and exposes students and faculty to some of the world’s cutting-edge research.

Oddly, there’s no message of congratulations or recognition of this addition to Alberta’s nanotechnology community from Canada’s National Institute for Nanotechnology (NINT) located at the University of Alberta in Edmonton.

Bendable, stretchable, light-weight, and transparent: a new competitor in the competition for ‘thinnest electric generator’

An Oct. 15, 2014 Columbia University (New York, US) press release (also on EurekAlert), describes another contender for the title of the world’s thinnest electric generator,

Researchers from Columbia Engineering and the Georgia Institute of Technology [US] report today [Oct. 15, 2014] that they have made the first experimental observation of piezoelectricity and the piezotronic effect in an atomically thin material, molybdenum disulfide (MoS2), resulting in a unique electric generator and mechanosensation devices that are optically transparent, extremely light, and very bendable and stretchable.

In a paper published online October 15, 2014, in Nature, research groups from the two institutions demonstrate the mechanical generation of electricity from the two-dimensional (2D) MoS2 material. The piezoelectric effect in this material had previously been predicted theoretically.

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

Piezoelectricity of single-atomic-layer MoS2 for energy conversion and piezotronics by Wenzhuo Wu, Lei Wang, Yilei Li, Fan Zhang, Long Lin, Simiao Niu, Daniel Chenet, Xian Zhang, Yufeng Hao, Tony F. Heinz, James Hone, & Zhong Lin Wang. Nature (2014) doi:10.1038/nature13792 Published online 15 October 2014

This paper is behind a paywall. There is a free preview available with ReadCube Access.

Getting back to the Columbia University press release, it offers a general description of piezoelectricity and some insight into this new research on molybdenum disulfide,

Piezoelectricity is a well-known effect in which stretching or compressing a material causes it to generate an electrical voltage (or the reverse, in which an applied voltage causes it to expand or contract). But for materials of only a few atomic thicknesses, no experimental observation of piezoelectricity has been made, until now. The observation reported today provides a new property for two-dimensional materials such as molybdenum disulfide, opening the potential for new types of mechanically controlled electronic devices.

“This material—just a single layer of atoms—could be made as a wearable device, perhaps integrated into clothing, to convert energy from your body movement to electricity and power wearable sensors or medical devices, or perhaps supply enough energy to charge your cell phone in your pocket,” says James Hone, professor of mechanical engineering at Columbia and co-leader of the research.

“Proof of the piezoelectric effect and piezotronic effect adds new functionalities to these two-dimensional materials,” says Zhong Lin Wang, Regents’ Professor in Georgia Tech’s School of Materials Science and Engineering and a co-leader of the research. “The materials community is excited about molybdenum disulfide, and demonstrating the piezoelectric effect in it adds a new facet to the material.”

Hone and his research group demonstrated in 2008 that graphene, a 2D form of carbon, is the strongest material. He and Lei Wang, a postdoctoral fellow in Hone’s group, have been actively exploring the novel properties of 2D materials like graphene and MoS2 as they are stretched and compressed.

Zhong Lin Wang and his research group pioneered the field of piezoelectric nanogenerators for converting mechanical energy into electricity. He and postdoctoral fellow Wenzhuo Wu are also developing piezotronic devices, which use piezoelectric charges to control the flow of current through the material just as gate voltages do in conventional three-terminal transistors.

There are two keys to using molybdenum disulfide for generating current: using an odd number of layers and flexing it in the proper direction. The material is highly polar, but, Zhong Lin Wang notes, so an even number of layers cancels out the piezoelectric effect. The material’s crystalline structure also is piezoelectric in only certain crystalline orientations.

For the Nature study, Hone’s team placed thin flakes of MoS2 on flexible plastic substrates and determined how their crystal lattices were oriented using optical techniques. They then patterned metal electrodes onto the flakes. In research done at Georgia Tech, Wang’s group installed measurement electrodes on samples provided by Hone’s group, then measured current flows as the samples were mechanically deformed. They monitored the conversion of mechanical to electrical energy, and observed voltage and current outputs.

The researchers also noted that the output voltage reversed sign when they changed the direction of applied strain, and that it disappeared in samples with an even number of atomic layers, confirming theoretical predictions published last year. The presence of piezotronic effect in odd layer MoS2 was also observed for the first time.

“What’s really interesting is we’ve now found that a material like MoS2, which is not piezoelectric in bulk form, can become piezoelectric when it is thinned down to a single atomic layer,” says Lei Wang.

To be piezoelectric, a material must break central symmetry. A single atomic layer of MoS2 has such a structure, and should be piezoelectric. However, in bulk MoS2, successive layers are oriented in opposite directions, and generate positive and negative voltages that cancel each other out and give zero net piezoelectric effect.

“This adds another member to the family of piezoelectric materials for functional devices,” says Wenzhuo Wu.

In fact, MoS2 is just one of a group of 2D semiconducting materials known as transition metal dichalcogenides, all of which are predicted to have similar piezoelectric properties. These are part of an even larger family of 2D materials whose piezoelectric materials remain unexplored. Importantly, as has been shown by Hone and his colleagues, 2D materials can be stretched much farther than conventional materials, particularly traditional ceramic piezoelectrics, which are quite brittle.

The research could open the door to development of new applications for the material and its unique properties.

“This is the first experimental work in this area and is an elegant example of how the world becomes different when the size of material shrinks to the scale of a single atom,” Hone adds. “With what we’re learning, we’re eager to build useful devices for all kinds of applications.”

Ultimately, Zhong Lin Wang notes, the research could lead to complete atomic-thick nanosystems that are self-powered by harvesting mechanical energy from the environment. This study also reveals the piezotronic effect in two-dimensional materials for the first time, which greatly expands the application of layered materials for human-machine interfacing, robotics, MEMS, and active flexible electronics.

I see there’s a reference in that last paragraph to “harvesting mechanical energy from  the environment.” I’m not sure what they mean by that but I have written a few times about harvesting biomechanical energy. One of my earliest pieces is a July 12, 2010 post which features work by Zhong Lin Wang on harvesting energy from heart beats, blood flow, muscle stretching, or even irregular vibrations. One of my latest pieces is a Sept. 17, 2014 post about some work in Canada on harvesting energy from the jaw as you chew.

A final note, Dexter Johnson discusses this work in an Oct. 16, 2014 post on the Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers] website).

Replacing copper wire in motors?

Finnish researchers at Lappeenranta University of Technology (LUT) believe it may be possible to replace copper wire used in motors with spun carbon nanotubes. From an Oct. 15, 2014 news item on Azonano,

Lappeenranta University of Technology (LUT) introduces the first electrical motor applying carbon nanotube yarn. The material replaces copper wires in windings. The motor is a step towards lightweight, efficient electric drives. Its output power is 40 W and rotation speed 15000 rpm.

Aiming at upgrading the performance and energy efficiency of electrical machines, higher-conductivity wires are searched for windings. Here, the new technology may revolutionize the industry. The best carbon nanotubes (CNTs) demonstrate conductivities far beyond the best metals; CNT windings may have double the conductivity of copper windings.

”If we keep the design parameters unchanged only replacing copper with carbon nanotube yarns, the Joule losses in windings can be reduced to half of present machine losses. By lighter and more ecological CNT yarn, we can reduce machine dimensions and CO2 emissions in manufacturing and operation. Machines could also be run in higher temperatures,” says Professor Pyrhönen [Juha Pyrhönen], leading the prototype design at LUT.

An Oct. ??, 2014 (?) LUT press release, which originated the news item, further describes the work,

Traditionally, the windings in electrical machines are made of copper, which has the second best conductivity of metals at room temperature. Despite the high conductivity of copper, a large proportion of the electrical machine losses occur in the copper windings. For this reason, the Joule losses are often referred to as copper losses. The carbon nanotube yarn does not have a definite upper limit for conductivity (e.g. values of 100 MS/m have already been measured).

According to Pyrhönen, the electrical machines are so ubiquitous in everyday life that we often forget about their presence. In a single-family house alone there can be tens of electrical machines in various household appliances such as refrigerators, washing machines, hair dryers, and ventilators.

“In the industry, the number of electrical motors is enormous: there can be up to tens of thousands of motors in a single process industry unit. All these use copper in the windings. Consequently, finding a more efficient material to replace the copper conductors would lead to major changes in the industry,” tells Professor Pyrhönen.

There are big plans for this work according to the press release,

The prototype motor uses carbon nanotube yarns spun and converted into an isolated tape by a Japanese-Dutch company Teijin Aramid, which has developed the spinning technology in collaboration with Rice University, the USA. The industrial applications of the new material are still in their infancy; scaling up the production capacity together with improving the yarn performance will facilitate major steps in the future, believes Business Development Manager Dr. Marcin Otto from Teijin Aramid, agreeing with Professor Pyrhönen.

“There is a significant improvement potential in the electrical machines, but we are now facing the limits of material physics set by traditional winding materials. Superconductivity appears not to develop to such a level that it could, in general, be applied to electrical machines. Carbonic materials, however, seem to have a pole position: We expect that in the future, the conductivity of carbon nanotube yarns could be even three times the practical conductivity of copper in electrical machines. In addition, carbon is abundant while copper needs to be mined or recycled by heavy industrial processes.”

The researchers have produced this video about their research,

There’s a reference to some work done at Rice University (Texas, US) with Teijin Armid (Japanese-Dutch company) and Technion Institute (Israel) with spinning carbon nanotubes into threads that look like black cotton (you’ll see the threads in the video). It’s this work that has made the latest research in Finland possible. I have more about the the Rice/Teijin Armid/Technion CNT project in my Jan. 11, 2013 posting, Prima donna of nanomaterials (carbon nanotubes) tamed by scientists at Rice University (Texas, US), Teijin Armid (Dutch/Japanese company), and Technion Institute (based in Israel).

Single layer graphene as a solid lubricant

Graphite (from which graphene springs) has been used as a solid lubricant for many years but it has limitations which researchers at the US Dept. of Energy’s Argonne National Laboratory are attempting to overcome by possibly replacing it with graphene. An Oct. 14, 2014 news item on phys.org describes the research (Note: A link has been removed),

Nanoscientist Anirudha Sumant and his colleagues at Argonne’s Center for Nanoscale Materials and Argonne’s Energy Systems division applied a one-atom-thick layer of graphene, a two-dimensional form of carbon, in between a steel ball and a steel disk. They found that just the single layer of graphene lasted for more than 6,500 “wear cycles,” a dramatic improvement over conventional lubricants like graphite or molybdenum disulfide.

An Oct. 13, 2014 Argonne National Laboratory news release by Jared Sagoff, which originated the news item, provides more information about this research (Note: A link has been removed),

“For comparison,” Sumant said, “conventional lubricants would need about 1,000 layers to last for 1,000 wear cycles. That’s a huge advantage in terms of cost savings with much better performance.”

Graphite has been used as an industrial lubricant for more than 40 years, but not without certain drawbacks, Sumant explained.  “Graphite is limited by the fact that it really works only in humid environments. If you have a dry setting, it’s not going to be nearly as effective,” he said.

This limitation arises from the fact that graphite – unlike graphene – has a three-dimensional structure.  The water molecules in the moist air create slipperiness by weaving themselves in between graphite’s carbon sheets. When there are not enough water molecules in the air, the material loses its slickness.

Molybdenum disulfide, another common lubricant, has the reverse problem, Sumant said. It works in dry environments but not well in wet ones. “Essentially the challenge is to find a single all-purpose lubricant that works well for mechanical systems, no matter where they are,” he said.

Graphene’s two-dimensional structure gives it a significant advantage. “The material is able to bond directly to the surface of the stainless steel ball, making it so perfectly even that even hydrogen atoms are not able to penetrate it,” said Argonne materials scientist Ali Erdemir, a collaborator on the study who tested graphene-coated steel surfaces in his lab.

In a previous study in Materials Today, Sumant and his colleagues showed that a few layers of graphene works equally well in humid and dry environments as a solid lubricant, solving the 40-year-old puzzle of finding a flawless solid lubricant. However, the team wanted to go further and test just a single graphene layer.

While doing so in an environment containing molecules of pure hydrogen, they observed a dramatic improvement in graphene’s operational lifetime. When the graphene monolayer eventually starts to wear away, hydrogen atoms leap in to repair the lattice, like stitching a quilt back together. “Hydrogen can only get into the fabric where there is already an opening,” said Subramanian Sankaranarayanan, an Argonne computational scientist and co-author in this study. This means the graphene layer stays intact longer.

Researchers had previously done experiments to understand the mechanical strength of a single sheet of graphene, but the Argonne study is the first to explain the extraordinary wear resistance of one-atom-thick graphene.

Here’s a link to and a citation for the August 2014 study,

Extraordinary Macroscale Wear Resistance of One Atom Thick Graphene Layer by Diana Berman, Sanket A. Deshmukh, Subramanian K. R. S. Sankaranarayanan, Ali Erdemir, and Anirudha V. Sumant. Advanced Funtional Materials DOI: 10.1002/adfm.201401755 Article first published online: 26 AUG 2014

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This article is behind a paywall.

Silver nanoparticles: liquid on the outside, crystal on the inside

Research from the Massachusetts Institute of Technology (MIT) has revealed a new property of metal nanoparticles, in this case, silver. From an Oct. 12, 2014 news item on ScienceDaily,

A surprising phenomenon has been found in metal nanoparticles: They appear, from the outside, to be liquid droplets, wobbling and readily changing shape, while their interiors retain a perfectly stable crystal configuration.

The research team behind the finding, led by MIT professor Ju Li, says the work could have important implications for the design of components in nanotechnology, such as metal contacts for molecular electronic circuits.

The results, published in the journal Nature Materials, come from a combination of laboratory analysis and computer modeling, by an international team that included researchers in China, Japan, and Pittsburgh, as well as at MIT.

An Oct. 12, 2014 MIT news release (also on EurekAlert), which originated the news item, offers both more information about the research and a surprising comparison of nanometers to the width of a human hair,

The experiments were conducted at room temperature, with particles of pure silver less than 10 nanometers across — less than one-thousandth of the width of a human hair. [emphasis mine] But the results should apply to many different metals, says Li, senior author of the paper and the BEA Professor of Nuclear Science and Engineering.

Silver has a relatively high melting point — 962 degrees Celsius, or 1763 degrees Fahrenheit — so observation of any liquidlike behavior in its nanoparticles was “quite unexpected,” Li says. Hints of the new phenomenon had been seen in earlier work with tin, which has a much lower melting point, he says.

The use of nanoparticles in applications ranging from electronics to pharmaceuticals is a lively area of research; generally, Li says, these researchers “want to form shapes, and they want these shapes to be stable, in many cases over a period of years.” So the discovery of these deformations reveals a potentially serious barrier to many such applications: For example, if gold or silver nanoligaments are used in electronic circuits, these deformations could quickly cause electrical connections to fail.

It was a bit surprising to see the reference to 10 nanometers as being less than 1/1,000th (one/one thousandth) of the width of a human hair in a news release from MIT. Generally, a nanometer has been described as being anywhere from less than 1/50,000th to 1/120,000th of the width of a human hair with less than 1/100,000th being one of the most common descriptions. While it’s true that 10 nanometers is less than 1/1,000th of the width of a human hair, it seems a bit misleading when it could be described, in keeping with the more common description, as less than 1/10,000th.

Getting back to the research, the news release offers more details as to how it was conducted,

The researchers’ detailed imaging with a transmission electron microscope and atomistic modeling revealed that while the exterior of the metal nanoparticles appears to move like a liquid, only the outermost layers — one or two atoms thick — actually move at any given time. As these outer layers of atoms move across the surface and redeposit elsewhere, they give the impression of much greater movement — but inside each particle, the atoms stay perfectly lined up, like bricks in a wall.

“The interior is crystalline, so the only mobile atoms are the first one or two monolayers,” Li says. “Everywhere except the first two layers is crystalline.”

By contrast, if the droplets were to melt to a liquid state, the orderliness of the crystal structure would be eliminated entirely — like a wall tumbling into a heap of bricks.

Technically, the particles’ deformation is pseudoelastic, meaning that the material returns to its original shape after the stresses are removed — like a squeezed rubber ball — as opposed to plasticity, as in a deformable lump of clay that retains a new shape.

The phenomenon of plasticity by interfacial diffusion was first proposed by Robert L. Coble, a professor of ceramic engineering at MIT, and is known as “Coble creep.” “What we saw is aptly called Coble pseudoelasticity,” Li says.

Now that the phenomenon has been understood, researchers working on nanocircuits or other nanodevices can quite easily compensate for it, Li says. If the nanoparticles are protected by even a vanishingly thin layer of oxide, the liquidlike behavior is almost completely eliminated, making stable circuits possible.

There are some benefits to this insight (from the news release),

On the other hand, for some applications this phenomenon might be useful: For example, in circuits where electrical contacts need to withstand rotational reconfiguration, particles designed to maximize this effect might prove useful, using noble metals or a reducing atmosphere, where the formation of an oxide layer is destabilized, Li says.

The new finding flies in the face of expectations — in part, because of a well-understood relationship, in most materials, in which mechanical strength increases as size is reduced.

“In general, the smaller the size, the higher the strength,” Li says, but “at very small sizes, a material component can get very much weaker. The transition from ‘smaller is stronger’ to ‘smaller is much weaker’ can be very sharp.”

That crossover, he says, takes place at about 10 nanometers at room temperature — a size that microchip manufacturers are approaching as circuits shrink. When this threshold is reached, Li says, it causes “a very precipitous drop” in a nanocomponent’s strength.

The findings could also help explain a number of anomalous results seen in other research on small particles, Li says.

For more details about the various attempts to create smaller computer chips, you can read my July 11, 2014 posting about IBM and its proposed 7 nanometer chip where you will also find links to announcements and posts about Intel’s smaller chips and HP Labs’ attempt to recreate computers.

As for the research into liquid-like metallic (silver) nanoparticles, here’s a link to and a citation for the paper,

Liquid-like pseudoelasticity of sub-10-nm crystalline ​silver particle by Jun Sun, Longbing He, Yu-Chieh Lo, Tao Xu, Hengchang Bi, Litao Sun, Ze Zhang, Scott X. Mao, & Ju Li. Nature Materials (2014) doi:10.1038/nmat4105 Published online 12 October 2014

This paper is behind a paywall. There is a free preview via ReadCube Access.

SLIPS (Slippery Liquid-Infused Porous Surfaces) technology repels blood and bacteria from medical devices

Researchers at Harvard University’s Wyss Institute for Biologically Inspired Engineering have developed a coating for medical devices that helps to address some of these devices’ most  troublesome aspects. From an Oct. 12, 2014 news item on ScienceDaily,

From joint replacements to cardiac implants and dialysis machines, medical devices enhance or save lives on a daily basis. However, any device implanted in the body or in contact with flowing blood faces two critical challenges that can threaten the life of the patient the device is meant to help: blood clotting and bacterial infection.

A team of Harvard scientists and engineers may have a solution. They developed a new surface coating for medical devices using materials already approved by the Food and Drug Administration (FDA). The coating repelled blood from more than 20 medically relevant substrates the team tested — made of plastic to glass and metal — and also suppressed biofilm formation in a study reported in Nature Biotechnology. But that’s not all.

The team implanted medical-grade tubing and catheters coated with the material in large blood vessels in pigs, and it prevented blood from clotting for at least eight hours without the use of blood thinners such as heparin. Heparin is notorious for causing potentially lethal side-effects like excessive bleeding but is often a necessary evil in medical treatments where clotting is a risk.

“Devising a way to prevent blood clotting without using anticoagulants is one of the holy grails in medicine,” said Don Ingber, M.D., Ph.D., Founding Director of Harvard’s Wyss Institute for Biologically Inspired Engineering and senior author of the study. Ingber is also the Judah Folkman Professor of Vascular Biology at Harvard Medical School and Boston Children’s Hospital, as well as professor of bioengineering at Harvard School of Engineering and Applied Sciences (SEAS).

An Oct. 12, 2014 Wyss Institute news release (also on EurekAlert), which originated the news item, describes the inspiration for this work,

The idea for the coating evolved from SLIPS, a pioneering surface technology developed by coauthor Joanna Aizenberg, Ph.D., who is a Wyss Institute Core Faculty member and the Amy Smith Berylson Professor of Materials Science at Harvard SEAS. SLIPS stands for Slippery Liquid-Infused Porous Surfaces. Inspired by the slippery surface of the carnivorous pitcher plant, which enables the plant to capture insects, SLIPS repels nearly any material it contacts. The liquid layer on the surface provides a barrier to everything from ice to crude oil and blood.

“Traditional SLIPS uses porous, textured surface substrates to immobilize the liquid layer whereas medical surfaces are mostly flat and smooth – so we further adapted our approach by capitalizing on the natural roughness of chemically modified surfaces of medical devices,” said Aizenberg, who leads the Wyss Institute’s Adaptive Materials platform. “This is yet another incarnation of the highly customizable SLIPS platform that can be designed to create slippery, non-adhesive surfaces on any material.”

The Wyss team developed a super-repellent coating that can be adhered to existing, approved medical devices. In a two-step surface-coating process, they chemically attached a monolayer of perfluorocarbon, which is similar to Teflon. Then they added a layer of liquid perfluorocarbon, which is widely used in medicine for applications such as liquid ventilation for infants with breathing challenges, blood substitution, eye surgery, and more. The team calls the tethered perfluorocarbon plus the liquid layer a Tethered-Liquid Perfluorocarbon surface, or TLP for short.

In addition to working seamlessly when coated on more than 20 different medical surfaces and lasting for more than eight hours to prevent clots in a pig under relatively high blood flow rates without the use of heparin, the TLP coating achieved the following results:

  • TLP-treated medical tubing was stored for more than a year under normal temperature and humidity conditions and still prevented clot formation
  • The TLP surface remained stable under the full range of clinically relevant physiological shear stresses, or rates of blood flow seen in catheters and central lines, all the way up to dialysis machines
  • It repelled the components of blood that cause clotting (fibrin and platelets)
  • When bacteria called Pseudomonas aeruginosa were grown in TLP-coated medical tubing for more than six weeks, less than one in a billion bacteria were able to adhere. Central lines coated with TLP significantly reduce sepsis from Central-Line Mediated Bloodstream Infections (CLABSI). (Sepsis is a life-threatening blood infection caused by bacteria, and a significant risk for patients with implanted medical devices.)

Out of sheer curiosity, the researchers even tested a TLP-coated surface with a gecko – the superstar of sticking whose footpads contain many thousands of hairlike structures with tremendous adhesive strength. The gecko was unable to hold on.

“We were wonderfully surprised by how well the TLP coating worked, particularly in vivo without heparin,” said one of the co-lead authors, Anna Waterhouse, Ph.D., a Wyss Institute Postdoctoral Fellow. “Usually the blood will start to clot within an hour in the extracorporeal circuit, so our experiments really demonstrate the clinical relevance of this new coating.”

While most of the team’s demonstrations were performed on medical devices such as catheters and perfusion tubing using relatively simple setups, they say there is a lot more on the horizon.

“We feel this is just the beginning of how we might test this for use in the clinic,” said co-lead author Daniel Leslie, Ph.D., a Wyss Institute Staff Scientist, who aims to test it on more complex systems such as dialysis machines and ECMO, a machine used in the intensive care unit to help critically ill patients breathe.

I first featured SLIPS technology in a Jan. 15, 2014 post about its possible use for stain-free, self-cleaning clothing. This Wyss Institute video about the latest work featuring the use of  SLIPS technology in medical devices also describes its possible use in pipelines and airplanes,

You can find research paper with this link,

A bioinspired omniphobic surface coating on medical devices prevents thrombosis and biofouling by Daniel C Leslie, Anna Waterhouse, Julia B Berthet, Thomas M Valentin, Alexander L Watters, Abhishek Jain, Philseok Kim, Benjamin D Hatton, Arthur Nedder, Kathryn Donovan, Elana H Super, Caitlin Howell, Christopher P Johnson, Thy L Vu, Dana E Bolgen, Sami Rifai, Anne R Hansen, Michael Aizenberg, Michael Super, Joanna Aizenberg, & Donald E Ingber. Nature Biotechnology (2014) doi:10.1038/nbt.3020 Published online 12 October 2014

This paper is behind a paywall but there is a free preview available via ReadCube Access.

Gold nanorods and mucus

Mucus can kill. Most of us are lucky enough to produce mucus appropriate for our bodies’ needs but people who have cystic fibrosis and other kinds of lung disease suffer greatly from mucus that is too thick to pass easily through the body. An Oct. 9, 2014 Optical Society of America (OSA) news release (also on EurekAlert) ‘shines’ a light on the topic of mucus and viscosity,

Some people might consider mucus an icky bodily secretion best left wrapped in a tissue, but to a group of researchers from the University of North Carolina at Chapel Hill, snot is an endlessly fascinating subject. The team has developed a way to use gold nanoparticles and light to measure the stickiness of the slimy substance that lines our airways.  The new method could help doctors better monitor and treat lung diseases such as cystic fibrosis and chronic obstructive pulmonary disease.

“People who are suffering from certain lung diseases have thickened mucus,” explained Amy Oldenburg, a physicist at the University of North Carolina at Chapel Hill whose research focuses on biomedical imaging systems. “In healthy adults, hair-like cell appendages called cilia line the airways and pull mucus out of the lungs and into the throat. But if the mucus is too viscous it can become trapped in the lungs, making breathing more difficult and also failing to remove pathogens that can cause chronic infections.”

Doctors can prescribe mucus-thinning drugs, but have no good way to monitor how the drugs affect the viscosity of mucus at various spots inside the body. This is where Oldenburg and her colleagues’ work may help.

The researchers placed coated gold nanorods on the surface of mucus samples and then tracked the rods’ diffusion into the mucus by illuminating the samples with laser light and analyzing the way the light bounced off the nanoparticles. The slower the nanorods diffused, the thicker the mucus. The team found this imaging method worked even when the mucus was sliding over a layer of cells—an important finding since mucus inside the human body is usually in motion.

“The ability to monitor how well mucus-thinning treatments are working in real-time may allow us to determine better treatments and tailor them for the individual,” said Oldenburg.

It will likely take five to 10 more years before the team’s mucus measuring method is tested on human patients, Oldenburg said. Gold is non-toxic, but for safety reasons the researchers would want to ensure that the gold nanorods would eventually be cleared from a patient’s system.

“This is a great example of interdisciplinary work in which optical scientists can meet a specific need in the clinic,” said Nozomi Nishimura, of Cornell University … . “As these types of optical technologies continue to make their way into medical practice, it will both expand the market for the technology as well as improve patient care.”

The team is also working on several lines of ongoing study that will some day help bring their monitoring device to the clinic. They are developing delivery methods for the gold nanorods, studying how their imaging system might be adapted to enter a patient’s airways, and further investigating how mucus flow properties differ throughout the body.

This work is being presented at:

The research team will present their work at The Optical Society’s (OSA) 98th Annual Meeting, Frontiers in Optics, being held Oct. 19-23 [2014] in Tucson, Arizona, USA.

Presentation FTu5F.2, “Imaging Gold Nanorod Diffusion in Mucus Using Polarization Sensitive OCT,” takes place Tuesday, Oct. 21 at 4:15 p.m. MST [Mountain Standard Time] in the Tucson Ballroom, Salon A at the JW Marriott Tucson Starr Pass Resort.

People with cystic fibrosis tend to have short lives (from the US National Library of Medicine MedLine Plus webpage on cystic fibrosis),

Most children with cystic fibrosis stay in good health until they reach adulthood. They are able to take part in most activities and attend school. Many young adults with cystic fibrosis finish college or find jobs.

Lung disease eventually worsens to the point where the person is disabled. Today, the average life span for people with CF who live to adulthood is about 37 years.

Death is most often caused by lung complications.

I hope this work proves helpful.

Nanoparticle-based radiogenetics to control brain cells

While the title for this post sounds like an opening for a zombie-themed story, this Oct. 8, 2014 news item on Nanowerk actually concerns brain research at Rockefeller University (US), Note: A link has been removed,

A proposal to develop a new way to remotely control brain cells from Sarah Stanley, a Research Associate in Rockefeller University’s Laboratory of Molecular Genetics, headed by Jeffrey M. Friedman, is among the first to receive funding from the BRAIN initiative. The project will make use of a technique called radiogenetics that combines the use of radio waves or magnetic fields with nanoparticles to turn neurons on or off.

An Oct. 7, 2014 Rockefeller University news release, which originated the news item, further describes the BRAIN initiative and the research (Note: Links have been removed),

The NIH [National Institutes of Health]  is one of four federal agencies involved in the BRAIN (Brain Research through Advancing Innovative Neurotechnologies) initiative. Following in the ambitious footsteps of the Human Genome Project, the BRAIN initiative seeks to create a dynamic map of the brain in action, a goal that requires the development of new technologies. The BRAIN initiative working group, which outlined the broad scope of the ambitious project, was co-chaired by Rockefeller’s Cori Bargmann, head of the Laboratory of Neural Circuits and Behavior.

Stanley’s grant, for $1.26 million over three years, is one of 58 projects to get BRAIN grants, the NIH announced. The NIH’s plan for its part of this national project, which has been pitched as “America’s next moonshot,” calls for $4.5 billion in federal funds over 12 years.

The technology Stanley is developing would enable researchers to manipulate the activity of neurons, as well as other cell types, in freely moving animals in order to better understand what these cells do. Other techniques for controlling selected groups of neurons exist, but her new nanoparticle-based technique has a unique combination of features that may enable new types of experimentation. For instance, it would allow researchers to rapidly activate or silence neurons within a small area of the brain or dispersed across a larger region, including those in difficult-to-access locations. Stanley also plans to explore the potential this method has for use treating patients.

“Francis Collins, director of the NIH, has discussed the need for studying the circuitry of the brain, which is formed by interconnected neurons. Our remote-control technology may provide a tool with which researchers can ask new questions about the roles of complex circuits in regulating behavior,” Stanley says.

Here’s an image that Rockefeller University has used to illustrate the concept of radio-controlled brain cells,

 

BRAIN control: The new technology uses radio waves to activate or silence cells remotely. The bright spots above represent cells with increased calcium after treatment with radio waves, a change that would allow neurons to fire. [downloaded from: http://newswire.rockefeller.edu/2014/10/07/rockefeller-neurobiology-lab-is-awarded-first-round-brain-initiative-grant/]

BRAIN control: The new technology uses radio waves to activate or silence cells remotely. The bright spots above represent cells with increased calcium after treatment with radio waves, a change that would allow neurons to fire. [downloaded from: http://newswire.rockefeller.edu/2014/10/07/rockefeller-neurobiology-lab-is-awarded-first-round-brain-initiative-grant/]

You can find out more about the US BRAIN initiative here.