Tag Archives: University of California at Riverside

Gecko lets go!

After all these years of writing about geckos and their adhesive properties it seems that geckos sometimes slip or let go, theoretically. (BTW, there’s a Canadian connection’ one of  the researchers is at the University of Calgary in the province of Alberta.) From a July 19, 2017 Cornell University news release (also on EurekAlert),

Geckos climb vertically up trees, walls and even windows, thanks to pads on the digits of their feet that employ a huge number of tiny bristles and hooks.

Scientists have long marveled at the gecko’s adhesive capabilities, which have been described as 100 times more than what is needed to support their body weight or run quickly up a surface.

But a new theoretical study examines for the first time the limits of geckos’ gripping ability in natural contexts. The study, recently published in the Journal of the Royal Society Interface, reports there are circumstances – such as when geckos fear for their lives, leap into the air and are forced to grab on to a leaf below – when they need every bit of that fabled adhesive ability, and sometimes it’s not enough.

“Geckos are notoriously described as having incredible ability to adhere to a surface,” said Karl Niklas, professor of plant evolution at Cornell University and a co-author of the paper. The study’s lead authors, Timothy Higham at the University of California, Riverside, and Anthony Russell at the University of Calgary, Canada, both zoologists, brought Niklas into the project for his expertise on plant biomechanics.

“The paper shows that [adhesive capability] might be exaggerated, because geckos experience falls and a necessity to grip a surface like a leaf that requires a much more tenacious adhesion force; the paper shows that in some cases the adhesive ability can be exceeded,” Niklas said.

In the theoretical study, the researchers developed computer models to understand if there are common-place instances when the geckos’ ability to hold on to surfaces might be challenged, such as when canopy-dwelling geckos are being chased by a predator and are forced to leap from a tree, hoping to land on a leaf below. The researchers incorporated ecological observations, adhesive force measurements, and body size and shape measurements of museum specimens to conduct simulations. They also considered the biomechanics of the leaves, the size of the leaves and the angles on the surface that geckos might land on to determine impact forces. Calculations were also based on worst-case scenarios, where a gecko reaches a maximum speed when it is no longer accelerating, called “terminal settling velocity.”

“Leaves are cantilevered like diving boards and they go through harmonic motion [when struck], so you have to calculate the initial deflection and orientation, and then consider how does that leaf rebound and can the gecko still stay attached,” Niklas said.

The final result showed that in some cases geckos don’t have enough adhesion to save themselves, he added.

Higham and Russell are planning to travel to French Guiana to do empirical adhesive force studies on living geckos in native forests.

The basic research helps people better understand how geckos stick to surfaces, and has the potential for future applications that mimic such biological mechanisms.

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

Leaping lizards landing on leaves: escape-induced jumps in the rainforest canopy challenge the adhesive limits of geckos by Timothy E. Higham, Anthony P. Russell, Karl J. Niklas. Journal of the Royal Society Interface June 2017 Volume 14, issue 131 DOI: 10.1098/rsif.2017.0156 Published 28 June 2017

I think the authors had some fun with that title. In any event, the paper is behind a paywall.

Nanomechanics for deciphering beetle exoskeletons

Beetles carry remarkably light yet strong armor in the form of their exoskeletons and a research team at Northwestern University (US) is looking to those beetle exoskeletons for inspiration according to a Jan. 11, 2017 news item on ScienceDaily,

What can a beetle tell us about good design principles? Quite a lot, actually.

Many insects and crustaceans possess hard, armor-like exoskeletons that, in theory, should weigh the creatures down. But, instead, the exoskeletons are surprisingly light — even allowing the armor-wearing insects, like the beetle, to fly.

Northwestern Engineering’s Horacio D. Espinosa and his group are working to understand the underlying design principles and mechanical properties that result in structures with these unique, ideal properties. This work could ultimately uncover information that could guide the design and manufacturing of new and improved artificial materials by emulating these time-tested natural patterns, a process known as bio-mimicry.

Supported by the Air Force Office of Scientific Research’s Multidisciplinary University Research Initiative (MURI), the research was featured on the cover of Advanced Functional Materials. Postdoctoral fellows Ruiguo Yang and Wei Gao and graduate student Alireza Zaheri, all members of Espinosa’s laboratory, were co-first authors of the paper. Cheryl Hayashi, professor of biology at the University of California, Riverside, was also a co-author.

A Jan. 11, 2017 Northwestern University news release, which originated the news item, expands on the theme,

Though there are more than a million species of beetles, the team is first studying the exoskeleton of the Cotinis mutabilis, a field crop pest beetle native to the western United States. Like all insects and crustaceans, its exoskeleton is composed of twisted plywood structures, known as Bouligand structures, which help protect against predators. Fibers in this Bouligand structure are bundles of chitin polymer chains wrapped with proteins. In this chain structure, each fiber has a higher density along the length than along the transverse.

“It is very challenging to characterize the properties of such fibers given that they are directionally dependent and have a small diameter of just 20 nanometers,” said Espinosa, the James N. and Nancy J. Farley Professor in Manufacturing and Entrepreneurship at Northwestern’s McCormick School of Engineering. “We had to develop a novel characterization method by taking advantage of the spatial distribution of fibers in the Bouligand structure.”

To meet this challenge, Espinosa and his team employed a creative way to identify the geometry and material properties of the fibers that comprise the exoskeleton. They cut the Bouligand structure along a plane, resulting in a surface composed of closely packed cross-sections of fibers with different orientations. They were then able to analyze the mechanics of the fibers.

“With more than a million species, which greatly vary from each other in taxomic relatedness, size, and ecology, the beetle is the largest group of insects,” Hayashi said. “What makes this research exciting is that the methods applied to the Cotinis mutabilis beetle exoskeleton can be extended to other beetle species.”

By correlating the mechanical properties with the exoskeleton geometries from diverse beetle species, Espinosa and his team plan to gain insight into natural selection and better understand structure-function-properties relationships.

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

AFM Identification of Beetle Exocuticle: Bouligand Structure and Nanofiber Anisotropic Elastic Properties by Ruiguo Yang, Alireza Zaheri, Wei Gao, Cheryl Hayashi, and Horacio D. Espinosa. Advanced Functional Materials DOI: 10.1002/adfm.201603993 Version of Record online: 27 DEC 2016

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

The mathematics of Disney’s ‘Moana’

The hit Disney movie “Moana” features stunning visual effects, including the animation of water to such a degree that it becomes a distinct character in the film. Courtesy of Walt Disney Animation Studios

Few people think to marvel over the mathematics when watching an animated feature but without mathematicians, the artists would not be able to achieve their artistic goals as a Jan. 4, 2017 news item on phys.org makes clear (Note: A link has been removed),

UCLA [University of California at Los Angeles] mathematics professor Joseph Teran, a Walt Disney consultant on animated movies since 2007, is under no illusion that artists want lengthy mathematics lessons, but many of them realize that the success of animated movies often depends on advanced mathematics.

“In general, the animators and artists at the studios want as little to do with mathematics and physics as possible, but the demands for realism in animated movies are so high,” Teran said. “Things are going to look fake if you don’t at least start with the correct physics and mathematics for many materials, such as water and snow. If the physics and mathematics are not simulated accurately, it will be very glaring that something is wrong with the animation of the material.”

Teran and his research team have helped infuse realism into several Disney movies, including “Frozen,” where they used science to animate snow scenes. Most recently, they applied their knowledge of math, physics and computer science to enliven the new 3-D computer-animated hit, “Moana,” a tale about an adventurous teenage girl who is drawn to the ocean and is inspired to leave the safety of her island on a daring journey to save her people.

A Jan. 3, 2017 UCLA news release, which originated the news item, explains in further nontechnical detail,

Alexey Stomakhin, a former UCLA doctoral student of Teran’s and Andrea Bertozzi’s, played an important role in the making of “Moana.” After earning his Ph.D. in applied mathematics in 2013, he became a senior software engineer at Walt Disney Animation Studios. Working with Disney’s effects artists, technical directors and software developers, Stomakhin led the development of the code that was used to simulate the movement of water in “Moana,” enabling it to play a role as one of the characters in the film.

“The increased demand for realism and complexity in animated movies makes it preferable to get assistance from computers; this means we have to simulate the movement of the ocean surface and how the water splashes, for example, to make it look believable,” Stomakhin explained. “There is a lot of mathematics, physics and computer science under the hood. That’s what we do.”

“Moana” has been praised for its stunning visual effects in words the mathematicians love hearing. “Everything in the movie looks almost real, so the movement of the water has to look real too, and it does,” Teran said. “’Moana’ has the best water effects I’ve ever seen, by far.”

Stomakhin said his job is fun and “super-interesting, especially when we cheat physics and step beyond physics. It’s almost like building your own universe with your own laws of physics and trying to simulate that universe.

“Disney movies are about magic, so magical things happen which do not exist in the real world,” said the software engineer. “It’s our job to add some extra forces and other tricks to help create those effects. If you have an understanding of how the real physical laws work, you can push parameters beyond physical limits and change equations slightly; we can predict the consequences of that.”

To make animated movies these days, movie studios need to solve, or nearly solve, partial differential equations. Stomakhin, Teran and their colleagues build the code that solves the partial differential equations. More accurately, they write algorithms that closely approximate the partial differential equations because they cannot be solved perfectly. “We try to come up with new algorithms that have the highest-quality metrics in all possible categories, including preserving angular momentum perfectly and preserving energy perfectly. Many algorithms don’t have these properties,” Teran said.

Stomakhin was also involved in creating the ocean’s crashing waves that have to break at a certain place and time. That task required him to get creative with physics and use other tricks. “You don’t allow physics to completely guide it,” he said.  “You allow the wave to break only when it needs to break.”

Depicting boats on waves posed additional challenges for the scientists.

“It’s easy to simulate a boat traveling through a static lake, but a boat on waves is much more challenging to simulate,” Stomakhin said. “We simulated the fluid around the boat; the challenge was to blend that fluid with the rest of the ocean. It can’t look like the boat is splashing in a little swimming pool — the blend needs to be seamless.”

Stomakhin spent more than a year developing the code and understanding the physics that allowed him to achieve this effect.

“It’s nice to see the great visual effect, something you couldn’t have achieved if you hadn’t designed the algorithm to solve physics accurately,” said Teran, who has taught an undergraduate course on scientific computing for the visual-effects industry.

While Teran loves spectacular visual effects, he said the research has many other scientific applications as well. It could be used to simulate plasmas, simulate 3-D printing or for surgical simulation, for example. Teran is using a related algorithm to build virtual livers to substitute for the animal livers that surgeons train on. He is also using the algorithm to study traumatic leg injuries.

Teran describes the work with Disney as “bread-and-butter, high-performance computing for simulating materials, as mechanical engineers and physicists at national laboratories would. Simulating water for a movie is not so different, but there are, of course, small tweaks to make the water visually compelling. We don’t have a separate branch of research for computer graphics. We create new algorithms that work for simulating wide ranges of materials.”

Teran, Stomakhin and three other applied mathematicians — Chenfanfu Jiang, Craig Schroeder and Andrew Selle — also developed a state-of-the-art simulation method for fluids in graphics, called APIC, based on months of calculations. It allows for better realism and stunning visual results. Jiang is a UCLA postdoctoral scholar in Teran’s laboratory, who won a 2015 UCLA best dissertation prize.  Schroeder is a former UCLA postdoctoral scholar who worked with Teran and is now at UC Riverside. Selle, who worked at Walt Disney Animation Studios, is now at Google.

Their newest version of APIC has been accepted for publication by the peer-reviewed Journal of Computational Physics.

“Alexey is using ideas from high-performance computing to make movies,” Teran said, “and we are contributing to the scientific community by improving the algorithm.”

Unfortunately, the paper does not seem to have been published early online so I cannot offer a link.

Final comment, it would have been interesting to have had a comment from one of the film’s artists or animators included in the article but it may not have been possible due to time or space constraints.

Unleashing graphene electronics potential with a trio of 2D nanomaterials

Graphene has excited a great deal of interest, especially with regard to its application in the field of electronics. However, it seems that graphene may need a little help from its friends, tantalum sulfide and boron nitride, according to a July 6, 2016 news item on ScienceDaily,

Graphene has emerged as one of the most promising two-dimensional crystals, but the future of electronics may include two other nanomaterials, according to a new study by researchers at the University of California, Riverside and the University of Georgia.

In research published Monday (July 4 [2016]) in the journal Nature Nanotechnology, the researchers described the integration of three very different two-dimensional (2D) materials to yield a simple, compact, and fast voltage-controlled oscillator (VCO) device. A VCO is an electronic oscillator whose oscillation frequency is controlled by a voltage input.

Titled “An integrated Tantalum Sulfide–Boron Nitride–Graphene Oscillator: A Charge-Density-Wave Device Operating at Room Temperature,” the paper describes the development of the first useful device that exploits the potential of charge-density waves to modulate an electrical current through a 2D material. The new technology could become an ultralow power alternative to conventional silicon-based devices, which are used in thousands of applications from computers to clocks to radios. The thin, flexible nature of the device would make it ideal for use in wearable technologies.

A July 5, 2016 University of California at Riverside (UCR) news release (also on EurekAlert) by Sarah Nightingale, which originated the news item, expands on the theme,

Graphene, a single layer of carbon atoms that exhibits exceptional electrical and thermal conductivities, shows promise as a successor to silicon-based transistors. However, its application has been limited by its inability to function as a semiconductor, which is critical for the ‘on-off’ switching operations performed by electronic components.

To overcome this shortfall, the researchers turned to another 2D nanomaterial, Tantalum Sulfide (TaS2). They showed that voltage-induced changes in the atomic structure of the ‘1T prototype’ of TaS2 enable it to function as an electrical switch at room temperature–a requirement for practical applications.

“There are many charge-density wave materials that have interesting electrical switching properties. However, most of them reveal these properties at very low temperature only. The particular polytype of TaS2 that we used can have abrupt changes in resistance above room temperature. That made a crucial difference,” said Alexander Balandin, UC presidential chair professor of electrical and computer engineering in UCR’s Bourns College of Engineering, who led the research team.

To protect the TaS2 from environmental damage, the researchers coated it with another 2D material, hexagonal boron nitrate, to prevent oxidation. By pairing the boron nitride-capped TaS2 with graphene, the team constructed a three-layer VCO that could pave the way for post-silicon electronics. In the proposed design, graphene functions as an integrated tunable load resistor, which enables precise voltage control of the current and VCO frequency. The prototype UCR devices operated at MHz frequency used in radios, and the extremely fast physical processes that define the device functionality allow for the operation frequency to increase all the way to THz.

Balandin said the integrated system is the first example of a functional voltage-controlled oscillator device comprising 2D materials that operates at room temperature.

“It is difficult to compete with silicon, which has been used and improved for the past 50 years. However, we believe our device shows a unique integration of three very different 2D materials, which utilizes the intrinsic properties of each of these materials. The device can potentially become a low-power alternative to conventional silicon technologies in many different applications,” Balandin said.

The electronic function of graphene envisioned in the proposed 2D device overcomes the problem associated with the absence of the energy band gap, which so far prevented graphene’s use as the transistor channel material. The extremely high thermal conductivity of graphene comes as an additional benefit in the device structure, by facilitating heat removal. The unique heat conduction properties of graphene were experimentally discovered and theoretically explained in 2008 by Balandin’s group at UCR. The Materials Research Society recognized this groundbreaking achievement by awarding Balandin the MRS Medal in 2013.

The Balandin group also demonstrated the first integrated graphene heat spreaders for high-power transistors and light-emitting diodes. “In those applications, graphene was used exclusively as heat conducting material. Its thermal conductivity was the main property. In the present device, we utilize both electrical and thermal conductivity of graphene,” Balandin added.

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

A charge-density-wave oscillator based on an integrated tantalum disulfide–boron nitride–graphene device operating at room temperature by Guanxiong Liu, Bishwajit Debnath, Timothy R. Pope, Tina T. Salguero, Roger K. Lake, & Alexander A. Balandin. Nature Nanotechnology (2016) doi:10.1038/nnano.2016.108 Published online 04 July 2016

This paper is behind a paywall.

Boosting chip speeds with graphene

There’s a certain hysteria associated with chip speeds as engineers and computer scientists try to achieve the ever improved speed times that consumers have enjoyed for some decades. The question looms, is there some point at which we can no longer improve the speed? Well, we haven’t reached that point yet according to a June 18, 2015 news item on Nanotechnology Now,

Stanford engineers find a simple yet clever way to boost chip speeds: Inside each chip are millions of tiny wires to transport data; wrapping them in a protective layer of graphene could boost speeds by up to 30 percent. [emphasis mine]

A June 16, 2015 Stanford University news release by Tom Abate (also on EurekAlert but dated June 17, 2015), which originated the news item, describes how computer chips are currently designed and the redesign which yields more speed,

A typical computer chip includes millions of transistors connected with an extensive network of copper wires. Although chip wires are unimaginably short and thin compared to household wires both have one thing in common: in each case the copper is wrapped within a protective sheath.

For years a material called tantalum nitride has formed protective layer in chip wires.

Now Stanford-led experiments demonstrate that a different sheathing material, graphene, can help electrons scoot through tiny copper wires in chips more quickly.

Graphene is a single layer of carbon atoms arranged in a strong yet thin lattice. Stanford electrical engineer H.-S. Philip Wong says this modest fix, using graphene to wrap wires, could allow transistors to exchange data faster than is currently possible. And the advantages of using graphene would become greater in the future as transistors continue to shrink.

Wong led a team of six researchers, including two from the University of Wisconsin-Madison, who will present their findings at the Symposia of VLSI Technology and Circuits in Kyoto, a leading venue for the electronics industry.

Ling Li, a graduate student in electrical engineering at Stanford and first author of the research paper, explained why changing the exterior wrapper on connecting wires can have such a big impact on chip performance.

It begins with understanding the dual role of this protective layer: it isolates the copper from the silicon on the chip and also serve to conduct electricity.

On silicon chips, the transistors act like tiny gates to switch electrons on or off. That switching function is how transistors process data.

The copper wires between the transistors transport this data once it is processed.

The isolating material–currently tantalum nitride–keeps the copper from migrating into the silicon transistors and rendering them non-functional.

Why switch to graphene?

Two reasons, starting with the ceaseless desire to keep making electronic components smaller.

When the Stanford team used the thinnest possible layer of tantalum nitride needed to perform this isolating function, they found that the industry-standard was eight times thicker than the graphene layer that did the same work.

Graphene had a second advantage as a protective sheathing and here it’s important to differentiate how this outer layer functions in chip wires versus a household wires.

In house wires the outer layer insulates the copper to prevent electrocution or fires.

In a chip the layer around the wires is a barrier to prevent copper atoms from infiltrating the silicon. Were that to happen the transistors would cease to function. So the protective layer isolates the copper from the silicon

The Stanford experiment showed that graphene could perform this isolating role while also serving as an auxiliary conductor of electrons. Its lattice structure allows electrons to leap from carbon atom to carbon atom straight down the wire, while effectively containing the copper atoms within the copper wire.

These benefits–the thinness of the graphene layer and its dual role as isolator and auxiliary conductor–allow this new wire technology to carry more data between transistors, speeding up overall chip performance in the process.

In today’s chips the benefits are modest; a graphene isolator would boost wire speeds from four percent to 17 percent, depending on the length of the wire. [emphasis mine]

But as transistors and wires continue to shrink in size, the benefits of the ultrathin yet conductive graphene isolator become greater. [emphasis mine] The Stanford engineers estimate that their technology could increase wire speeds by 30 percent in the next two generations

The Stanford researchers think the promise of faster computing will induce other researchers to get interested in wires, and help to overcome some of the hurdles needed to take this proof of principle into common practice.

This would include techniques to grow graphene, especially growing it directly onto wires while chips are being mass-produced. In addition to his University of Wisconsin collaborator Professor Michael Arnold, Wong cited Purdue University Professor Zhihong Chen. Wong noted that the idea of using graphene as an isolator was inspired by Cornell University Professor Paul McEuen and his pioneering research on the basic properties of this marvelous material. Alexander Balandin of the University of California-Riverside has also made contributions to using graphene in chips.

“Graphene has been promised to benefit the electronics industry for a long time, and using it as a copper barrier is perhaps the first realization of this promise,” Wong said.

I gather they’ve decided to highlight the most optimistic outcomes.

Earthquakes, deep and shallow, and their nanocrystals

Those of us who live in this region are warned on a regular basis that a ‘big’ one is overdue somewhere along the West Coast of Canada and the US. It gives me an interest in the geological side of things  While the May 19, 2015 news items on Azonano featuring the research story as told by the University of Oklahoma and the University of California at Riverside doesn’t fall directly under my purview, it’s close enough.

Here’s the lead researcher, Harry W. Green II, from the University of California at Riverside explaining, the work,

The May 18, 2015 University of Oklahoma news release on EurekAlert offers a succinct summary,

A University of Oklahoma structural geologist and collaborators are studying earthquake instability and the mechanisms associated with fault weakening during slip. The mechanism of this weakening is central to understanding earthquake sliding.

Ze’ev Reches, professor in the OU School of Geology and Geophysics, is using electron microscopy to examine velocity and temperature in two key observations: (1) a high-speed friction experiment on carbonate at conditions of shallow earthquakes, and (2) a high-pressure/high-temperature faulting experiment at conditions of very deep earthquakes.

Reches and his collaborators have shown phase transformation and the formation of nano-size (millionth of a millimeter) grains are associated with profound weakening and that fluid is not necessary for such weakening. If this mechanism operates in major earthquakes, it resolves two major conflicts between laboratory results and natural faulting–lack of a thermal zone around major faults and the rarity of glassy rocks along faults.

The May 18, 2015 University of California at Riverside (UCR) news release provides more detail about earthquakes,

Earthquakes are labeled “shallow” if they occur at less than 50 kilometers depth.  They are labeled “deep” if they occur at 300-700 kilometers depth.  When slippage occurs during these earthquakes, the faults weaken.  How this fault weakening takes place is central to understanding earthquake sliding.

A new study published online in Nature Geoscience today by a research team led by University of California, Riverside geologists now reports that a universal sliding mechanism operates for earthquakes of all depths – from the deep ones all the way up to the crustal ones.

“Although shallow earthquakes – the kind that threaten California – must initiate differently from the very deep ones, our new work shows that, once started, they both slide by the same physics,” said deep-earthquake expert Harry W. Green II, a distinguished professor of the Graduate Division in UC Riverside’s Department of Earth Sciences, who led the research project. “Our research paper presents a new, unifying model of how earthquakes work. Our results provide a more accurate understanding of what happens during earthquake sliding that can lead to better computer models and could lead to better predictions of seismic shaking danger.”

The UCR news release goes on to describe the physics of sliding and a controversy concerning shallow and deep earthquakes,

The physics of the sliding is the self-lubrication of the earthquake fault by flow of a new material consisting of tiny new crystals, the study reports. Both shallow earthquakes and deep ones involve phase transformations of rocks that produce tiny crystals of new phases on which sliding occurs.

“Other researchers have suggested that fluids are present in the fault zones or generated there,” Green said. “Our study shows fluids are not necessary for fault weakening. As earthquakes get started, local extreme heating takes place in the fault zone. The result of that heating in shallow earthquakes is to initiate reactions like the ones that take place in deep earthquakes so they both end up lubricated in the same way.”

Green explained that at 300-700 kilometers depth, the pressure and temperature are so high that rocks in this deep interior of the planet cannot break by the brittle processes seen on Earth’s surface. In the case of shallow earthquakes, stresses on the fault increase slowly in response to slow movement of tectonic plates, with sliding beginning when these stresses exceed static friction. While deep earthquakes also get started in response to increasing stresses, the rocks there flow rather than break, except under special conditions.

“Those special conditions of temperature and pressure induce minerals in the rock to break down to other minerals, and in the process of this phase transformation a fault can form and suddenly move, radiating the shaking – just like at shallow depths,” Green said.

The research explains why large faults like the San Andreas Fault in California do not have a heat-flow anomaly around them. Were shallow earthquakes to slide by the grinding and crunching of rock, as geologists once imagined, the process would generate enough heat so that major faults like the San Andreas would be a little warmer along their length than they would be otherwise.

“But such a predicted warm region along such faults has never been found,” Green said.  “The logical conclusion is that the fault must move more easily than we thought.  Extreme heating in a very thin zone along the fault produces the very weak lubricant.  The volume of material that is heated is very small and survives for a very short time – seconds, perhaps – followed by very little heat generation during sliding because the lubricant is very weak.”

The new research also explains why faults with glass on them (reflecting the fact that during the earthquake the fault zone melted) are rare. As shallow earthquakes start, the temperature rises locally until it is hot enough to start a chemical reaction – usually the breakdown of clays or carbonates or other hydrous phases in the fault zone.  The reactions that break down the clays or carbonates stop the temperature from climbing higher, with heat being used up in the reactions that produce the nanocrystalline lubricant.

If the fault zone does not have hydrous phases or carbonates, the sudden heating that begins when sliding starts raises the local temperature on the fault all the way to the melting temperature of the rock.  In such cases, the melt behaves like a lubricant and the sliding surface ends up covered with melt (that would quench to a glass) instead of the nanocrystalline lubricant.

“The reason this does not happen often, that is, the reason we do not see lots of faults with glass on them, is that the Earth’s crust is made up to a large degree of hydrous and carbonate phases, and even the rocks that don’t have such phases usually have feldspars that get crushed up in the fault zone,” Green explained. “The feldspars will ‘rot’ to clays during the hundred years or so between earthquakes as water moves along the fault zone. In that case, when the next earthquake comes, the fault zone is ready with clays and other phases that can break down, and the process repeats itself.”

The research involved the study of laboratory earthquakes – high-pressure earthquakes as well as high-speed ones – using electron microscopy in friction and faulting experiments. It was Green’s laboratory that first conducted a serendipitous series of experiments, in 1989, on the right kind of mantle rocks that give geologists insight into how deep earthquakes work. In the new work, Green and his team also investigated the Punchbowl Fault, an ancestral branch of the San Andreas Fault that has been exhumed by erosion from several kilometers depth, and found nanometric materials within the fault – as predicted by their model.

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

Phase transformation and nanometric flow cause extreme weakening during fault slip by H. W. Green II, F. Shi, K. Bozhilov, G. Xia, & Z. Reches. Nature Geoscience (2015) doi:10.1038/ngeo2436 Published online 18 May 2015

This paper is behind a paywall.

Metal nanoparticles and gut microbiomes

What happens when you eat or drink nanoparticles, metallic or otherwise? No one really knows. Part of the problem with doing research now is there are no benchmarks for the quantity we’ve been ingesting over the centuries. Nanoparticles do occur naturally, as well, people who’ve eaten with utensils made of or coated with silver or gold have ingested silver or gold nanoparticles that were shed by those very utensils. In short, we’ve been ingesting any number of nanoparticles through our food, drink, and utensils in addition to the engineered nanoparticles that are found in consumer products. So, part of what researchers need to determine is the point at which we need to be concerned about nanoparticles. That’s trickier than it might seem since we ingest our nanoparticles and recycle them into the environment (air, water, soil) to reingest (inhale, drink, eat, etc.) them at a later date. The endeavour to understand what impact engineered nanoparticles in particular will have on us as more are used in our products is akin to assembling a puzzle.

There’s a May 5, 2015 news item on Azonano which describes research into the effects that metallic nanoparticles have on the micriobiome (bacteria) in our guts,

Exposure of a model human colon to metal oxide nanoparticles, at levels that could be present in foods, consumer goods, or treated drinking water, led to multiple, measurable differences in the normal microbial community that inhabits the human gut. The changes observed in microbial metabolism and the gut microenvironment with exposure to nanoparticles could have implications for overall human health, as discussed in an article published in Environmental Engineering Science, a peer-reviewed journal from Mary Ann Liebert, Inc., publishers. The article is available free on the Environmental Engineering Science website until June 1, 2015.

A May 4, 2015 Mary Ann Liebert publisher news release on EurekAlert, which originated the news item, describes the research in more detail (Note: A link has been removed),

Alicia Taylor, Ian Marcus, Risa Guysi, and Sharon Walker, University of California, Riverside, individually introduced three different nanoparticles–zinc oxide, cerium dioxide, and titanium dioxide–commonly used in products such as toothpastes, cosmetics, sunscreens, coatings, and paints, into a model of the human colon. The model colon mimics the normal gut environment and contains the microorganisms typically present in the human microbiome.

In the article “Metal Oxide Nanoparticles Induce Minimal Phenotypic Changes in a Model Colon Gut Microbiota” the researchers described changes in both specific characteristics of the microbial community and of the gut microenvironment after exposure to the nanoparticles.

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

Metal Oxide Nanoparticles Induce Minimal Phenotypic Changes in a Model Colon Gut Microbiota by Alicia A. Taylor, Ian M. Marcus Ian, Risa L., Guysi, and Sharon L. Walker. Environmental Engineering Science. DOI:10.1089/ees.2014.0518 Online Ahead of Print: April 24, 2015

I’ve taken a quick look at the research while it’s still open access (till June 1, 2015) to highlight the bits I consider interesting. There’s this about the nanoparticle (NP) quantities used in the study (Note: Links have been removed),

Environmentally relevant NP concentrations were chosen to emulate human exposures to NPs through ingestion of both food and drinking water at 0.01 μg/L ZnO NP, 0.01 μg/L CeO2 NP, and 3 mg/L TiO2 NP (Gottschalk et al., 2009; Kiser et al., 2009, 2013; Weir et al., 2012; Keller and Lazareva, 2013). Recent work has also indicated that adults in the USA ingest 5 mg TiO2 per day, half of which is in the nano-size range (Lomer et al., 2000; Powell et al., 2010). Exposure routes and reliable dosing information of NPs that are embedded in solid matrices are difficult to predict, and this is often a limitation of analytical techniques (Nowack et al., 2012; Yang and Westerhoff, 2014). The exposure levels used in this study were predominately selected from literature values that give predictions on amount of NPs in water and food sources (Gottschalk et al., 2009; Kiser et al., 2009; Weir et al., 2012; Keller and Lazareva, 2013; Keller et al., 2013).

For anyone unfamiliar with chemical notations, ZnO NP is zinc oxide nanoparticle, 0.01 μg/L is one/one hundredth of a microgram per litre,  CeO2 is cesisum dioxide NP, and TiO2 is titanium dioxide NP while 3 mg/L, is 3 milligrams per litre.

After assuring the quantities used in the study are the same as they expect humans to be ingesting on a regular basis, the researchers describe some of the factors which may affect the interaction between the tested nanoparticles and the bacteria (Note: Links have been removed),

It is essential to note that interactions between NPs and bacteria in the intestines may be dependent on numerous factors: the surface charge of the NPs and bacteria, the chemical composition and surface charge of the digested food, and variability in diet. These factors may ultimately correlate to effects seen in humans on an individual basis. In fact, similar work has demonstrated that exposing common NPs found in food to stomach-like conditions will change their surface chemistry from negative to neutral or positive, causing the NPs to interact with negatively charged mucus proteins in the gastrointestinal tract and, in turn, affecting the transport of NPs within the intestine (McCracken et al., 2013). The purpose of this work was to measure responses of the microbial community during the NP exposures. Based on previous research, it is anticipated that the NPs altered by stomach-like conditions would also cause changes in the gut environment (McCracken et al., 2013).

Here’s some of what they discovered,

Our initial hypothesis, that NPs induce phenotypic changes in a gut microbial community, was affirmed through significant measurable effects seen in the data. Tests that supported that NPs caused changes in the phenotype included hydrophobicity, EPM, sugar content of the EPS, cell size, conductivity, and SFCA (specifically butyric acid) production. Data for cell concentration and the protein content of the EPS demonstrated no significant results. Data were inconclusive for pH. With such a complex biological system, it is very likely that the phenotypic and biochemical changes observed are combinations of responses happening in parallel. The effects seen may be attributed to both changes induced by the NPs and natural phenomena associated with microbial community activity and other metabolic processes in a multifaceted environment such as the gut. Some examples of natural processes that could also influence the phenotypic and biochemical parameters are osmolarity, active metabolites, and electrolyte concentrations (Miller and Wood, 1996; Record et al., 1998).

Here’s the concluding sentence from the abstract,

Overall, the NPs caused nonlethal, significant changes to the microbial community’s phenotype, which may be related to overall health effects. [emphasis mine]

This research like the work I featured in a June 27, 2013 posting points to some issues with researching the impact that nanoparticles may have on our bodies. There was no cause for immediate alarm in 2013 and it appears that is still the case in 2015. However, that assumes quantities being ingested don’t increase significantly.

Copper nanoparticles, toxicity research, colons, zebrafish, and septic tanks

Alicia Taylor, a graduate student at UC Riverside, surrounded by buckets of effluent from the septic tank system she used for her research. Courtesy: University of California at Riverside

Alicia Taylor, a graduate student at UC Riverside, surrounded by buckets of effluent from the septic tank system she used for her research. Courtesy: University of California at Riverside

Those buckets of efflluent are strangely compelling. I think it’s the abundance of orange. More seriously, a March 2, 2015 news item on Nanowerk poses a question about copper nanoparticles,

What do a human colon, septic tank, copper nanoparticles and zebrafish have in common?

They were the key components used by researchers at the University of California, Riverside and UCLA [University of California at Los Angeles] to study the impact copper nanoparticles, which are found in everything from paint to cosmetics, have on organisms inadvertently exposed to them.

The researchers found that the copper nanoparticles, when studied outside the septic tank, impacted zebrafish embryo hatching rates at concentrations as low as 0.5 parts per million. However, when the copper nanoparticles were released into the replica septic tank, which included liquids that simulated human digested food and household wastewater, they were not bioavailable and didn’t impact hatching rates.

A March 2, 2015 University of California at Riverside (UCR) news release (also on EurekAlert), which originated the news item, provides more detail about the research,

“The results are encouraging because they show with a properly functioning septic tank we can eliminate the toxicity of these nanoparticles,” said Alicia Taylor, a graduate student working in the lab of Sharon Walker, a professor of chemical and environmental engineering at the University of California, Riverside’s Bourns College of Engineering.

The research comes at a time when products with nanoparticles are increasingly entering the marketplace. While the safety of workers and consumers exposed to nanoparticles has been studied, much less is known about the environmental implications of nanoparticles. The Environmental Protection Agency is currently accessing the possible effects of nanomaterials, including those made of copper, have on human health and ecosystem health.

The UC Riverside and UCLA [University of California at Los Angeles] researchers dosed the septic tank with micro copper and nano copper, which are elemental forms of copper but encompass different sizes and uses in products, and CuPRO, a nano copper-based material used as an antifungal agent to spray agricultural crops and lawns.

While these copper-based materials have beneficial purposes, inadvertent exposure to organisms such as fish or fish embryos has not received sufficient attention because it is difficult to model complicated exposure environments.

The UC Riverside researchers solved that problem by creating a unique experimental system that consists of the replica human colon and a replica two-compartment septic tank, which was originally an acyclic septic tank. The model colon is made of a custom-built 20-inch-long glass tube with a 2-inch diameter with a rubber stopper at both ends and a tube-shaped membrane typically used for dialysis treatments within the glass tube.

To simulate human feeding, 100 milliliters of a 20-ingredient mixture that replicated digested food was pumped into the dialysis tube at 9 a.m., 3 p.m. and 9 p.m. for five-day-long experiments over nine months.

The septic tank was filled with waste from the colon along with synthetic greywater, which is meant to simulate wastewater from sources such as sinks and bathtubs, and the copper nanoparticles. The researchers built a septic tank because 20 to 30 percent of American households rely on them for sewage treatment. Moreover, research has shown up to 40 percent of septic tanks don’t function properly. This is a concern if the copper materials are disrupting the function of the septic system, which would lead to untreated waste entering the soil and groundwater.

Once the primary chamber of the septic system was full, liquid began to enter the second chamber. Once a week, the effluent was drained from the secondary chamber and it was placed into sealed five-gallon containers. The effluent was then used in combination with zebrafish embryos in a high content screening process using multiwall plates to access hatching rates.

The remaining effluent has been saved and sits in 30 five-gallon buckets in a closet at UC Riverside because some collaborators have requested samples of the liquid for their experiments.

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

Understanding the Transformation, Speciation, and Hazard Potential of Copper Particles in a Model Septic Tank System Using Zebrafish to Monitor the Effluent* by Sijie Lin, Alicia A. Taylor, Zhaoxia Ji, Chong Hyun Chang, Nichola M. Kinsinger, William Ueng, Sharon L. Walker, and André E. Nel. ACS Nano, 2015, 9 (2), pp 2038–2048 DOI: 10.1021/nn507216f
Publication Date (Web): January 27, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.

* Link added March 10, 2015.

Sand and nanotechnology

There’s some good news coming out of the University of California, Riverside regarding sand and lithium-ion (li-ion) batteries, which I will temper with some additional information later in this posting.

First, the good news is that researchers have a new non-toxic, low cost way to produce a component in lithium-ion (li-ion) batteries according to a July 8, 2014 news item on ScienceDaily,

Researchers at the University of California, Riverside’s Bourns College of Engineering have created a lithium ion battery that outperforms the current industry standard by three times. The key material: sand. Yes, sand.

“This is the holy grail — a low cost, non-toxic, environmentally friendly way to produce high performance lithium ion battery anodes,” said Zachary Favors, a graduate student working with Cengiz and Mihri Ozkan, both engineering professors at UC Riverside.

The idea came to Favors six months ago. He was relaxing on the beach after surfing in San Clemente, Calif. when he picked up some sand, took a close look at it and saw it was made up primarily of quartz, or silicon dioxide.

His research is centered on building better lithium ion batteries, primarily for personal electronics and electric vehicles. He is focused on the anode, or negative side of the battery. Graphite is the current standard material for the anode, but as electronics have become more powerful graphite’s ability to be improved has been virtually tapped out.

A July 8, 2014 University of California at Riverside news release by Sean Nealon, which originated the news item, describes some of the problems with silicon as a replacement for graphite and how the researchers approached those problems,

Researchers are now focused on using silicon at the nanoscale, or billionths of a meter, level as a replacement for graphite. The problem with nanoscale silicon is that it degrades quickly and is hard to produce in large quantities.

Favors set out to solve both these problems. He researched sand to find a spot in the United States where it is found with a high percentage of quartz. That took him to the Cedar Creek Reservoir, east of Dallas, where he grew up.

Sand in hand, he came back to the lab at UC Riverside and milled it down to the nanometer scale, followed by a series of purification steps changing its color from brown to bright white, similar in color and texture to powdered sugar.

After that, he ground salt and magnesium, both very common elements found dissolved in sea water into the purified quartz. The resulting powder was then heated. With the salt acting as a heat absorber, the magnesium worked to remove the oxygen from the quartz, resulting in pure silicon.

The Ozkan team was pleased with how the process went. And they also encountered an added positive surprise. The pure nano-silicon formed in a very porous 3-D silicon sponge like consistency. That porosity has proved to be the key to improving the performance of the batteries built with the nano-silicon.

Now, the Ozkan team is trying to produce larger quantities of the nano-silicon beach sand and is planning to move from coin-size batteries to pouch-size batteries that are used in cell phones.

The research is supported by Temiz Energy Technologies. The UCR Office of Technology Commercialization has filed patents for inventions reported in the research paper.

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

Scalable Synthesis of Nano-Silicon from Beach Sand for Long Cycle Life Li-ion Batteries by Zachary Favors, Wei Wang, Hamed Hosseini Bay, Zafer Mutlu, Kazi Ahmed, Chueh Liu, Mihrimah Ozkan, & Cengiz S. Ozkan. Scientific Reports 4, Article number: 5623 doi:10.1038/srep05623 Published 08 July 2014

While this is good news, it does pose a conundrum of sorts. It seems that supplies of sand are currently under siege. A documentary, Sand Wars (2013) lays out the issues (from the Sand Wars website’s Synopsis page),

Most of us think of it as a complimentary ingredient of any beach vacation. Yet those seemingly insignificant grains of silica surround our daily lives. Every house, skyscraper and glass building, every bridge, airport and sidewalk in our modern society depends on sand. We use it to manufacture optical fiber, cell phone components and computer chips. We find it in our toothpaste, powdered foods and even in our glass of wine (both the glass and the wine, as a fining agent)!

Is sand an infinite resource? Can the existing supply satisfy a gigantic demand fueled by construction booms?  What are the consequences of intensive beach sand mining for the environment and the neighboring populations?

Based on encounters with sand smugglers, barefoot millionaires, corrupt politicians, unscrupulous real estate developers and environmentalists, this investigation takes us around the globe to unveil a new gold rush and a disturbing fact: the “SAND WARS” have begun.

Dr. Muditha D Senarath Yapa of John Keells Research at John Keells Holdings comments on the situation in Sri Lanka in his June 22, 2014 article (Nanotechnology – Depleting the most precious minerals for a few dollars) for The Nation,

Many have written for many years about the mineral sands of Pulmoddai. It is a national tragedy that for more than 50 years, we have been depleting the most precious minerals of our land for a few dollars. There are articles that appeared in various newspapers on how the mineral sands industry has boomed over the years. I hope the readers understand that it only means that we are depleting our resources faster than ever. According to the Lanka Mineral Sands Limited website, 90,000 tonnes of ilmenite, 9,000 tonnes of rutile, 5,500 tonnes of zircon, 100 tonnes of monazite and 4,000 tonnes of high titanium ilmenite are produced annually and shipped away to other countries.

… It is time for Sri Lanka to look at our own resources with this new light and capture the future nano materials market to create value added materials.

It’s interesting that he starts with the depletion of the sands as a national tragedy and ends with a plea to shift from a resource-based economy to a manufacturing-based economy. (This plea resonates strongly here in Canada where we too are a resource-based economy.)

Sidebar: John Keells Holdings is a most unusual company, from the About Us page,

In terms of market capitalisation, John Keells Holdings PLC is one of the largest listed conglomerate on the Colombo Stock Exchange. Other measures tell a similar tale; our group companies manage the largest number of hotel rooms in Sri Lanka, own the country’s largest privately-owned transportation business and hold leading positions in Sri Lanka’s key industries: tea, food and beverage manufacture and distribution, logistics, real estate, banking and information technology. Our investment in Sri Lanka is so deep and widely diversified that our stock price is sometimes used by international financial analysts as a benchmark of the country’s economy.

Yapa heads the companies research effort, which recently celebrated a synthetic biology agreement (from a May 2014 John Keells news release by Nuwan),

John Keells Research Signs an Historic Agreement with the Human Genetics Unit, Faculty of Medicine, University of Colombo to establish Sri Lanka’s first Synthetic Biology Research Programme.

Getting back to sand, these three pieces, ‘sand is good for li-ion batteries’, ‘sand is a diminishing resource’, and ‘let’s stop being a source of sand for other countries’ lay bare some difficult questions about our collective future on this planet.

Environmental impacts and graphene

Researchers at the University of California at Riverside (UCR) have published the results of what they claim is the first study featuring the environmental impact from graphene use. From the April 29, 2014 news item on ScienceDaily,

In a first-of-its-kind study of how a material some think could transform the electronics industry moves in water, researchers at the University of California, Riverside Bourns College of Engineering found graphene oxide nanoparticles are very mobile in lakes or streams and therefore may well cause negative environmental impacts if released.

Graphene oxide nanoparticles are an oxidized form of graphene, a single layer of carbon atoms prized for its strength, conductivity and flexibility. Applications for graphene include everything from cell phones and tablet computers to biomedical devices and solar panels.

The use of graphene and other carbon-based nanomaterials, such as carbon nanotubes, are growing rapidly. At the same time, recent studies have suggested graphene oxide may be toxic to humans. [emphasis mine]

As production of these nanomaterials increase, it is important for regulators, such as the Environmental Protection Agency, to understand their potential environmental impacts, said Jacob D. Lanphere, a UC Riverside graduate student who co-authored a just-published paper about graphene oxide nanoparticles transport in ground and surface water environments.

I wish they had cited the studies suggesting graphene oxide (GO) may be toxic. After a quick search I found: Internalization and cytotoxicity of graphene oxide and carboxyl graphene nanoplatelets in the human hepatocellular carcinoma cell line Hep G2 by Tobias Lammel, Paul Boisseaux, Maria-Luisa Fernández-Cruz, and José M Navas (free access paper in Particle and Fibre Toxicology 2013, 10:27 http://www.particleandfibretoxicology.com/content/10/1/27). From what I can tell, this was a highly specialized investigation conducted in a laboratory. While the results seem concerning it’s difficult to draw conclusions from this study or others that may have been conducted.

Dexter Johnson in a May 1, 2014 post on his Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers] website) provides more relevant citations and some answers (Note: Links have been removed),

While the UC Riverside  did not look at the toxicity of GO in their study, researchers at the Hersam group from Northwestern University did report in a paper published in the journal Nano Letters (“Minimizing Oxidation and Stable Nanoscale Dispersion Improves the Biocompatibility of Graphene in the Lung”) that GO was the most toxic form of graphene-based materials that were tested in mice lungs. In other research published in the Journal of Hazardous Materials (“Investigation of acute effects of graphene oxide on wastewater microbial community: A case study”), investigators determined that the toxicity of GO was dose dependent and was toxic in the range of 50 to 300 mg/L. So, below 50 mg/L there appear to be no toxic effects to GO. To give you some context, arsenic is considered toxic at 0.01 mg/L.

Dexter also contrasts graphene oxide with graphene (from his May 1, 2014 post; Note: A link has been removed),

While GO is quite different from graphene in terms of its properties (GO is an insulator while graphene is a conductor), there are many applications that are similar for both GO and graphene. This is the result of GO’s functional groups allowing for different derivatives to be made on the surface of GO, which in turn allows for additional chemical modification. Some have suggested that GO would make a great material to be deposited on additional substrates for thin conductive films where the surface could be tuned for use in optical data storage, sensors, or even biomedical applications.

Getting back to the UCR research, an April 28, 2014 UCR news release (also on EurekAlert but dated April 29, 2014) describes it  in more detail,

Walker’s [Sharon L. Walker, an associate professor and the John Babbage Chair in Environmental Engineering at UC Riverside] lab is one of only a few in the country studying the environmental impact of graphene oxide. The research that led to the Environmental Engineering Science paper focused on understanding graphene oxide nanoparticles’ stability, or how well they hold together, and movement in groundwater versus surface water.

The researchers found significant differences.

In groundwater, which typically has a higher degree of hardness and a lower concentration of natural organic matter, the graphene oxide nanoparticles tended to become less stable and eventually settle out or be removed in subsurface environments.

In surface waters, where there is more organic material and less hardness, the nanoparticles remained stable and moved farther, especially in the subsurface layers of the water bodies.

The researchers also found that graphene oxide nanoparticles, despite being nearly flat, as opposed to spherical, like many other engineered nanoparticles, follow the same theories of stability and transport.

I don’t know what conclusions to draw from the information that the graphene nanoparticles remain stable and moved further in the water. Is a potential buildup of graphene nanoparticles considered a problem because it could end up in our water supply and we would be poisoned by these particles? Dexter provides an answer (from his May 1, 2014 post),

Ultimately, the question of danger of any material or chemical comes down to the simple equation: Hazard x Exposure=Risk. To determine what the real risk is of GO reaching concentrations equal to those that have been found to be toxic (50-300 mg/L) is the key question.

The results of this latest study don’t really answer that question, but only offer a tool by which to measure the level of exposure to groundwater if there was a sudden spill of GO at a manufacturing facility.

While I was focused on ingestion by humans, it seems this research was more focused on the natural environment and possible future poisoning by graphene oxide.

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

Stability and Transport of Graphene Oxide Nanoparticles in Groundwater and Surface Water by Jacob D. Lanphere, Brandon Rogers, Corey Luth, Carl H. Bolster, and Sharon L. Walker. Environmental Engineering Science. -Not available-, ahead of print. doi:10.1089/ees.2013.0392.

Online Ahead of Print: March 17, 2014

If available online, this is behind a paywall.