Water is the key component in a Rice University process to reliably create patterns of metallic and semiconducting wires less than 10 nanometers wide.
The technique by the Rice lab of chemist James Tour builds upon its discovery that the meniscus – the curvy surface of water at its edge – can be an effective mask to make nanowires.
The Rice team of Tour and graduate students Vera Abramova and Alexander Slesarev have now made nanowires between 6 and 16 nanometers wide from silicon, silicon dioxide, gold, chromium, tungsten, titanium, titanium dioxide and aluminum. They have also made crossbar structures of conducting nanowires from one or more of the materials.
The process is promising for the semiconductor industry as it seeks to make circuits ever smaller. State-of-the-art integrated circuit fabrication allows for signal wires that approach 10 nanometers, visible only with powerful microscopes. These are the paths that connect the billions of transistors in modern electronic devices.
“This could have huge ramifications for chip production since the wires are easily made to sub-10-nanometer sizes,” Tour said of the Rice process. “There’s no other way in the world to do this en masse on a surface.”
Current approaches to making such tiny wires take several paths. Lithography, the standard method for etching integrated circuits, is approaching the physical limits of its ability to shrink them further. Bulk synthesis of semiconducting and metallic nanowires is also possible, but the wires are difficult to position in integrated circuits.
Water’s tendency to adhere to surfaces went from an annoyance to an advantage when the Rice researchers found they could use it as a mask to make patterns. The water molecules gather wherever a raised pattern joins the target material and forms a curved meniscus created by the surface tension of water.
The meniscus-mask process involves adding and then removing materials in a sequence that ultimately leaves a meniscus covering the wire and climbing the sidewall of a sacrificial metal mask that, when etched away, leaves the nanowire standing alone.
Tour said the process should work with modern fabrication technology with no modifications to existing equipment and minimal changes in fabrication protocols. No new tools or materials are needed.
The researchers have provided an image,
These nanowires were created at Rice University through a process called meniscus-mask lithography. From left, they’re made of silicon, silicon dioxide, gold, chromium, tungsten, titanium, titanium dioxide and aluminum. The scale bar is 1 micron for all images. (Credit: Tour Group/Rice University)
I have two items about implants and brains and an item about being able to exert remote control of the brain, all of which hint at a cyborg future for at least a few of us.
e-Dura, the spinal column, and the brain
The first item concerns some research, at the École Polytechnique de Lausanne (EPFL) which features flexible electronics. From a March 24, 2015 article by Ben Schiller for Fast Company (Note: Links have been removed),
Researchers at the Swiss Federal Institute of Technology, in Lausanne, have developed the e-Dura—a tiny skinlike device that attaches directly to damaged spinal cords. By sending out small electrical pulses, it stimulates the cord as if it were receiving signals from the brain, thus allowing movement.
“The purpose of the neuro-prosthesis is to excite the neurons that are on the spinal cord below the site of the injury and activate them, just like if they were receiving information from the brain,” says Stéphanie Lacour, a professor at the institute.
EPFL scientists have managed to get rats walking on their own again using a combination of electrical and chemical stimulation. But applying this method to humans would require multifunctional implants that could be installed for long periods of time on the spinal cord without causing any tissue damage. This is precisely what the teams of professors Stéphanie Lacour and Grégoire Courtine have developed. Their e-Dura implant is designed specifically for implantation on the surface of the brain or spinal cord. The small device closely imitates the mechanical properties of living tissue, and can simultaneously deliver electric impulses and pharmacological substances. The risks of rejection and/or damage to the spinal cord have been drastically reduced. An article about the implant will appear in early January  in Science Magazine.
So-called “surface implants” have reached a roadblock; they cannot be applied long term to the spinal cord or brain, beneath the nervous system’s protective envelope, otherwise known as the “dura mater,” because when nerve tissues move or stretch, they rub against these rigid devices. After a while, this repeated friction causes inflammation, scar tissue buildup, and rejection.
Here’s what the implant looks like,
The press release describes how the implant is placed (Note: A link has been removed),
Flexible and stretchy, the implant developed at EPFL is placed beneath the dura mater, directly onto the spinal cord. Its elasticity and its potential for deformation are almost identical to the living tissue surrounding it. This reduces friction and inflammation to a minimum. When implanted into rats, the e-Dura prototype caused neither damage nor rejection, even after two months. More rigid traditional implants would have caused significant nerve tissue damage during this period of time.
The researchers tested the device prototype by applying their rehabilitation protocol — which combines electrical and chemical stimulation – to paralyzed rats. Not only did the implant prove its biocompatibility, but it also did its job perfectly, allowing the rats to regain the ability to walk on their own again after a few weeks of training.
“Our e-Dura implant can remain for a long period of time on the spinal cord or the cortex, precisely because it has the same mechanical properties as the dura mater itself. This opens up new therapeutic possibilities for patients suffering from neurological trauma or disorders, particularly individuals who have become paralyzed following spinal cord injury,” explains Lacour, co-author of the paper, and holder of EPFL’s Bertarelli Chair in Neuroprosthetic Technology.
The press release goes on to describe the engineering achievements,
Developing the e-Dura implant was quite a feat of engineering. As flexible and stretchable as living tissue, it nonetheless includes electronic elements that stimulate the spinal cord at the point of injury. The silicon substrate is covered with cracked gold electric conducting tracks that can be pulled and stretched. The electrodes are made of an innovative composite of silicon and platinum microbeads. They can be deformed in any direction, while still ensuring optimal electrical conductivity. Finally, a fluidic microchannel enables the delivery of pharmacological substances – neurotransmitters in this case – that will reanimate the nerve cells beneath the injured tissue.
The implant can also be used to monitor electrical impulses from the brain in real time. When they did this, the scientists were able to extract with precision the animal’s motor intention before it was translated into movement.
“It’s the first neuronal surface implant designed from the start for long-term application. In order to build it, we had to combine expertise from a considerable number of areas,” explains Courtine, co-author and holder of EPFL’s IRP Chair in Spinal Cord Repair. “These include materials science, electronics, neuroscience, medicine, and algorithm programming. I don’t think there are many places in the world where one finds the level of interdisciplinary cooperation that exists in our Center for Neuroprosthetics.”
For the time being, the e-Dura implant has been primarily tested in cases of spinal cord injury in paralyzed rats. But the potential for applying these surface implants is huge – for example in epilepsy, Parkinson’s disease and pain management. The scientists are planning to move towards clinical trials in humans, and to develop their prototype in preparation for commercialization.
EPFL has provided a video of researcher Stéphanie Lacour describing e-Dura and expressing hopes for its commercialization,
Here’s a link to and a citation for the paper,
Electronic dura mater for long-term multimodal neural interfaces by Ivan R. Minev, Pavel Musienko, Arthur Hirsch, Quentin Barraud, Nikolaus Wenger, Eduardo Martin Moraud, Jérôme Gandar, Marco Capogrosso, Tomislav Milekovic, Léonie Asboth, Rafael Fajardo Torres, Nicolas Vachicouras, Qihan Liu, Natalia Pavlova, Simone Duis, Alexandre Larmagnac, Janos Vörös, Silvestro Micera, Zhigang Suo, Grégoire Courtine, Stéphanie P. Lacour. Science 9 January 2015: Vol. 347 no. 6218 pp. 159-163 DOI: 10.1126/science.1260318
This paper is behind a paywall.
Carbon nanotube fibres could connect to the brain
Researchers at Rice University (Texas, US) are excited about the possibilities that carbon nanotube fibres offer in the field of implantable electronics for the brain. From a March 25, 2015 news item on Nanowerk,
Carbon nanotube fibers invented at Rice University may provide the best way to communicate directly with the brain.
The fibers have proven superior to metal electrodes for deep brain stimulation and to read signals from a neuronal network. Because they provide a two-way connection, they show promise for treating patients with neurological disorders while monitoring the real-time response of neural circuits in areas that control movement, mood and bodily functions.
New experiments at Rice demonstrated the biocompatible fibers are ideal candidates for small, safe electrodes that interact with the brain’s neuronal system, according to the researchers. They could replace much larger electrodes currently used in devices for deep brain stimulation therapies in Parkinson’s disease patients.
They may also advance technologies to restore sensory or motor functions and brain-machine interfaces as well as deep brain stimulation therapies for other neurological disorders, including dystonia and depression, the researchers wrote.
The fibers created by the Rice lab of chemist and chemical engineer Matteo Pasquali consist of bundles of long nanotubes originally intended for aerospace applications where strength, weight and conductivity are paramount.
The individual nanotubes measure only a few nanometers across, but when millions are bundled in a process called wet spinning, they become thread-like fibers about a quarter the width of a human hair.
“We developed these fibers as high-strength, high-conductivity materials,” Pasquali said. “Yet, once we had them in our hand, we realized that they had an unexpected property: They are really soft, much like a thread of silk. Their unique combination of strength, conductivity and softness makes them ideal for interfacing with the electrical function of the human body.”
The simultaneous arrival in 2012 of Caleb Kemere, a Rice assistant professor who brought expertise in animal models of Parkinson’s disease, and lead author Flavia Vitale, a research scientist in Pasquali’s lab with degrees in chemical and biomedical engineering, prompted the investigation.
“The brain is basically the consistency of pudding and doesn’t interact well with stiff metal electrodes,” Kemere said. “The dream is to have electrodes with the same consistency, and that’s why we’re really excited about these flexible carbon nanotube fibers and their long-term biocompatibility.”
Weeks-long tests on cells and then in rats with Parkinson’s symptoms proved the fibers are stable and as efficient as commercial platinum electrodes at only a fraction of the size. The soft fibers caused little inflammation, which helped maintain strong electrical connections to neurons by preventing the body’s defenses from scarring and encapsulating the site of the injury.
The highly conductive carbon nanotube fibers also show much more favorable impedance – the quality of the electrical connection — than state-of-the-art metal electrodes, making for better contact at lower voltages over long periods, Kemere said.
The working end of the fiber is the exposed tip, which is about the width of a neuron. The rest is encased with a three-micron layer of a flexible, biocompatible polymer with excellent insulating properties.
The challenge is in placing the tips. “That’s really just a matter of having a brain atlas, and during the experiment adjusting the electrodes very delicately and putting them into the right place,” said Kemere, whose lab studies ways to connect signal-processing systems and the brain’s memory and cognitive centers.
Doctors who implant deep brain stimulation devices start with a recording probe able to “listen” to neurons that emit characteristic signals depending on their functions, Kemere said. Once a surgeon finds the right spot, the probe is removed and the stimulating electrode gently inserted. Rice carbon nanotube fibers that send and receive signals would simplify implantation, Vitale said.
The fibers could lead to self-regulating therapeutic devices for Parkinson’s and other patients. Current devices include an implant that sends electrical signals to the brain to calm the tremors that afflict Parkinson’s patients.
“But our technology enables the ability to record while stimulating,” Vitale said. “Current electrodes can only stimulate tissue. They’re too big to detect any spiking activity, so basically the clinical devices send continuous pulses regardless of the response of the brain.”
Kemere foresees a closed-loop system that can read neuronal signals and adapt stimulation therapy in real time. He anticipates building a device with many electrodes that can be addressed individually to gain fine control over stimulation and monitoring from a small, implantable device.
“Interestingly, conductivity is not the most important electrical property of the nanotube fibers,” Pasquali said. “These fibers are intrinsically porous and extremely stable, which are both great advantages over metal electrodes for sensing electrochemical signals and maintaining performance over long periods of time.”
The paper is open access provided you register on the website.
Remote control for stimulation of the brain
Mo Costandi, neuroscientist and freelance science writer, has written a March 24, 2015 post for the Guardian science blog network focusing on neuronal remote control,
Two teams of scientists have developed new ways of stimulating neurons with nanoparticles, allowing them to activate brain cells remotely using light or magnetic fields. The new methods are quicker and far less invasive than other hi-tech methods available, so could be more suitable for potential new treatments for human diseases.
Researchers have various methods for manipulating brain cell activity, arguably the most powerful being optogenetics, which enables them to switch specific brain cells on or off with unprecedented precision, and simultaneously record their behaviour, using pulses of light.
This is very useful for probing neural circuits and behaviour, but involves first creating genetically engineered mice with light-sensitive neurons, and then inserting the optical fibres that deliver light into the brain, so there are major technical and ethical barriers to its use in humans.
Nanomedicine could get around this. Francisco Bezanilla of the University of Chicago and his colleagues knew that gold nanoparticles can absorb light and convert it into heat, and several years ago they discovered that infrared light can make neurons fire nervous impulses by heating up their cell membranes.
Polina Anikeeva’s team at the Massachusetts Institute of Technology adopted a slightly different approach, using spherical iron oxide particles that give off heat when exposed to an alternating magnetic field.
Although still in the experimental stages, research like this may eventually allow for wireless and minimally invasive deep brain stimulation of the human brain. Bezanilla’s group aim to apply their method to develop treatments for macular degeneration and other conditions that kill off light-sensitive cells in the retina. This would involve injecting nanoparticles into the eye so that they bind to other retinal cells, allowing natural light to excite them into firing impulses to the optic nerve.
Costandi’s article is intended for an audience that either understands the science or can deal with the uncertainty of not understanding absolutely everything. Provided you fall into either of those categories, the article is well written and it provides links and citations to the papers for both research teams being featured.
Taken together, the research at EPFL, Rice University, University of Chicago, and Massachusetts Institute of Technology provides a clue as to how much money and intellectual power is being directed at the brain.
A Feb. 10, 2015 news item on Azonano features injectable nanoparticles that act as antioxidants useful in case of injury, in particular, brain injury,
Injectable nanoparticles that could protect an injured person from further damage due to oxidative stress have proven to be astoundingly effective in tests to study their mechanism.
Scientists at Rice University, Baylor College of Medicine and the University of Texas Health Science Center at Houston (UTHealth) Medical School designed methods to validate their 2012 discovery that combined polyethylene glycol-hydrophilic carbon clusters — known as PEG-HCCs — could quickly stem the process of overoxidation that can cause damage in the minutes and hours after an injury.
The tests revealed a single nanoparticle can quickly catalyze the neutralization of thousands of damaging reactive oxygen species molecules that are overexpressed by the body’s cells in response to an injury and turn the molecules into oxygen. These reactive species can damage cells and cause mutations, but PEG-HCCs appear to have an enormous capacity to turn them into less-reactive substances.
The researchers hope an injection of PEG-HCCs as soon as possible after an injury, such as traumatic brain injury or stroke, can mitigate further brain damage by restoring normal oxygen levels to the brain’s sensitive circulatory system.
“Effectively, they bring the level of reactive oxygen species back to normal almost instantly,” said Rice chemist James Tour. “This could be a useful tool for emergency responders who need to quickly stabilize an accident or heart attack victim or to treat soldiers in the field of battle.” Tour led the new study with neurologist Thomas Kent of Baylor College of Medicine and biochemist Ah-Lim Tsai of UTHealth.
The news release goes on to describe the antioxidant particles and previous research,
PEG-HCCs are about 3 nanometers wide and 30 to 40 nanometers long and contain from 2,000 to 5,000 carbon atoms. In tests, an individual PEG-HCC nanoparticle can catalyze the conversion of 20,000 to a million reactive oxygen species molecules per second into molecular oxygen, which damaged tissues need, and hydrogen peroxide while quenching reactive intermediates.
Tour and Kent led the earlier research that determined an infusion of nontoxic PEG-HCCs may quickly stabilize blood flow in the brain and protect against reactive oxygen species molecules overexpressed by cells during a medical trauma, especially when accompanied by massive blood loss.
Their research targeted traumatic brain injuries, after which cells release an excessive amount of the reactive oxygen species known as a superoxide into the blood. These toxic free radicals are molecules with one unpaired electron that the immune system uses to kill invading microorganisms. In small concentrations, they contribute to a cell’s normal energy regulation. Generally, they are kept in check by superoxide dismutase, an enzyme that neutralizes superoxides.
But even mild traumas can release enough superoxides to overwhelm the brain’s natural defenses. In turn, superoxides can form such other reactive oxygen species as peroxynitrite that cause further damage.
“The current research shows PEG-HCCs work catalytically, extremely rapidly and with an enormous capacity to neutralize thousands upon thousands of the deleterious molecules, particularly superoxide and hydroxyl radicals that destroy normal tissue when left unregulated,” Tour said.
“This will be important not only in traumatic brain injury and stroke treatment, but for many acute injuries of any organ or tissue and in medical procedures such as organ transplantation,” he said. “Anytime tissue is stressed and thereby oxygen-starved, superoxide can form to further attack the surrounding good tissue.”
These details about the research are also noted in the news release,
The researchers used an electron paramagnetic resonance spectroscopy technique that gets direct structure and rate information for superoxide radicals by counting unpaired electrons in the presence or absence of PEG-HCC antioxidants. Another test with an oxygen-sensing electrode, peroxidase and a red dye confirmed the particles’ ability to catalyze superoxide conversion.
“In sharp contrast to the well-known superoxide dismutase, PEG-HCC is not a protein and does not have metal to serve the catalytic role,” Tsai said. “The efficient catalytic turnover could be due to its more ‘planar,’ highly conjugated carbon core.”
The tests showed the number of superoxides consumed far surpassed the number of possible PEG-HCC bonding sites. The researchers found the particles have no effect on important nitric oxides that keep blood vessels dilated and aid neurotransmission and cell protection, nor was the efficiency sensitive to pH changes.
“PEG-HCCs have enormous capacity to convert superoxide to oxygen and the ability to quench reactive intermediates while not affecting nitric oxide molecules that are beneficial in normal amounts,” Kent said. “So they hold a unique place in our potential armamentarium against a range of diseases that involve loss of oxygen and damaging levels of free radicals.”
The study also determined PEG-HCCs remain stable, as batches up to 3 months old performed as good as new.
They’re not billing this as a joint US-China project but with Rice University being in Texas, US and Shandong University being in Shandong (province) in China, I think it’s reasonable to describe it that way. Here’s more about the project from a Feb. 4, 2015 news item on Azonano,
Scientists from Rice University and Shandong University, China, celebrated the opening of the Joint Center for Carbon Nanomaterials, a collaborative facility to study nanotechnology, on Feb. 1 .
Rice faculty members Pulickel Ajayan and Jun Lou, the chair and associate chair, respectively, of the university’s Department of Materials Science and NanoEngineering, took part in the ceremony along with Rice alumnus Lijie Ci, director of the new center and a professor of materials science and engineering at Shandong. The center’s dedication was part of the first International Workshop on Engineering and Applications of Nanocarbon, held Jan. 31-Feb. 2 .
“We at Rice University are excited and honored to collaborate with Shandong University on this important endeavor,” Rice President David Leebron said in a message recorded for the ceremony. [emphasis mine] “The center represents and combines two very important initiatives for Rice: research excellence and applications in nanosciences and long-term partnerships with the best institutions worldwide.”
“A lot of people are working on carbon nanoscience on both campuses, and we expect they will be interested in taking part,” Ajayan said. “Nanotubes and graphene are essentially the building blocks for the center, but Lijie wants to build ecologically relevant, applied research that can be commercialized. That’s the long-term goal. All of the experience we have had in the area will be beneficial.”
Ajayan expects students from both universities will travel. “People from Rice will be engaged in some of the activities of this joint center, including advising students there. And we hope Shandong students will have the opportunity to come to Rice for a short time,” he said. “The center also contributes to Rice’s goal to build closer connections with China.” [emphases mine]
Ajayan and Ci came to Rice together in 2007 from Rensselaer Polytechnic Institute; Ajayan was a faculty member and Ci was a postdoctoral researcher. At Rice, they introduced the darkest material ever measured at the time of its invention in 2008, an accomplishment that landed them in the Guinness Book of World Records.
Caption: Low-cost experiments to test the toxicity of nanomaterials focused on populations of roundworms. Rice University scientists were able to test 20 nanomaterials in a short time, and see their method as a way to determine which nanomaterials should undergo more extensive testing. Credit: Zhong Lab/Rice University
Until now, ‘cute’ and ‘adorable’ are not words I would have associated with worms of any kind or with Rice University, for that matter. It’s amazing what a single image can do, eh?
A Feb. 3, 2015 news item on Azonano describes how roundworms have been used in research investigating the toxicity of various kinds of nanoparticles,
The lowly roundworm is the star of an ambitious Rice University project to measure the toxicity of nanoparticles.
The low-cost, high-throughput study by Rice scientists Weiwei Zhong and Qilin Li measures the effects of many types of nanoparticles not only on individual organisms but also on entire populations.
The Rice researchers tested 20 types of nanoparticles and determined that five, including the carbon-60 molecules (“buckyballs”) discovered at Rice in 1985, showed little to no toxicity.
Others were moderately or highly toxic to Caenorhabditis elegans, several generations of which the researchers observed to see the particles’ effects on their health.
The results were published by the American Chemical Society journal Environmental Sciences and Technology. They are also available on the researchers’ open-source website.
“Nanoparticles are basically new materials, and we don’t know much about what they will do to human health and the health of the ecosystem,” said Li, an associate professor of civil and environmental engineering and of materials science and nanoengineering. “There have been a lot of publications showing certain nanomaterials are more toxic than others. So before we make more products that incorporate these nanomaterials, it’s important that we understand we’re not putting anything toxic into the environment or into consumer products.
“The question is, How much cost can we bear?” she said. “It’s a long and expensive process to do a thorough toxicological study of any chemical, not just nanomaterials.” She said that due to the large variety of nanomaterials being produced at high speed and at such a large scale, there is “an urgent need for high-throughput screening techniques to prioritize which to study more extensively.”
Rice’s pilot study proves it is possible to gather a lot of toxicity data at low cost, said Zhong, an assistant professor of biosciences, who has performed extensive studies on C. elegans, particularly on their gene networks. Materials alone for each assay, including the worms and the bacteria they consumed and the culture media, cost about 50 cents, she said.
The researchers used four assays to see how worms react to nanoparticles: fitness, movement, growth and lifespan. The most sensitive assay of toxicity was fitness. In this test, the researchers mixed the nanoparticles in solutions with the bacteria that worms consume. Measuring how much bacteria they ate over time served as a measure of the worms’ “fitness.”
“If the worms’ health is affected by the nanoparticles, they reproduce less and eat less,” Zhong said. “In the fitness assay, we monitor the worms for a week. That is long enough for us to monitor toxicity effects accumulated through three generations of worms.” C. elegans has a life cycle of about three days, and since each can produce many offspring, a population that started at 50 would number more than 10,000 after a week. Such a large number of tested animals also enabled the fitness assay to be highly sensitive.
The researchers’ “QuantWorm” system allowed fast monitoring of worm fitness, movement, growth and lifespan. In fact, monitoring the worms was probably the least time-intensive part of the project. Each nanomaterial required specific preparation to make sure it was soluble and could be delivered to the worms along with the bacteria. The chemical properties of each nanomaterial also needed to be characterized in detail.
The researchers studied a representative sampling of three classes of nanoparticles: metal, metal oxides and carbon-based. “We did not do polymeric nanoparticles because the type of polymers you can possibly have is endless,” Li explained.
They examined the toxicity of each nanoparticle at four concentrations. Their results showed C-60 fullerenes, fullerol (a fullerene derivative), titanium dioxide, titanium dioxide-decorated nanotubes and cerium dioxide were the least damaging to worm populations.
Their “fitness” assay confirmed dose-dependent toxicity for carbon black, single- and multiwalled carbon nanotubes, graphene, graphene oxide, gold nanoparticles and fumed silicon dioxide.
They also determined the degree to which surface chemistry affected the toxicity of some particles. While amine-functionalized multiwalled nanotubes proved highly toxic, hydroxylated nanotubes had the least toxicity, with significant differences in fitness, body length and lifespan.
A complete and interactive toxicity chart for all of the tested materials is available online.
Zhong said the method could prove its worth as a rapid way for drug or other companies to narrow the range of nanoparticles they wish to put through more expensive, dedicated toxicology testing.
“Next, we hope to add environmental variables to the assays, for example, to mimic ultraviolet exposure or river water conditions in the solution to see how they affect toxicity,” she said. “We also want to study the biological mechanism by which some particles are toxic to worms.”
Here’s a citation for the paper and links to the paper and to the researchers’ website,
Rice University (Texas, US) researchers have published a study which follows quantum dot nanoparticles as they enter the water supply and are taken up by plant roots and leaves and eaten by caterpillars. From a Dec. 16, 2014 news item on ScienceDaily,
In one of the most comprehensive laboratory studies of its kind, Rice University scientists traced the uptake and accumulation of quantum dot nanoparticles from water to plant roots, plant leaves and leaf-eating caterpillars.
The study, one of the first to examine how nanoparticles move through human-relevant food chains, found that nanoparticle accumulation in both plants and animals varied significantly depending upon the type of surface coating applied to the particles. The research is available online in the American Chemical Society’s journal Environmental Science & Technology.
“With industrial use of nanoparticles on the rise, there are increasing questions about how they move through the environment and whether they may accumulate in high levels in plants and animals that people eat,” said study co-author Janet Braam, professor and chair of the Department of BioSciences at Rice.
Braam and colleagues studied the uptake of fluorescent quantum dots by Arabidopsis thaliana, an oft-studied plant species that is a relative of mustard, broccoli and kale. In particular, the team looked at how various surface coatings affected how quantum dots moved from roots to leaves as well as how the particles accumulated in leaves. The team also studied how quantum dots behaved when caterpillars called cabbage loopers (Trichoplusia ni) fed upon plant leaves containing quantum dots.
“The impact of nanoparticle uptake on plants themselves and on the herbivores that feed upon them is an open question,” said study first author Yeonjong Koo, a postdoctoral research associate in Braam’s lab. “Very little work has been done in this area, especially in terrestrial plants, which are the cornerstone of human food webs.”
Some toxins, like mercury and DDT, tend to accumulate in higher concentrations as they move up the food chain from plants to animals. It is unknown whether nanoparticles may also be subject to this process, known as biomagnification.
While there are hundreds of types of nanoparticles in use, Koo chose to study quantum dots, submicroscopic bits of semiconductors that glow brightly under ultraviolet light. The fluorescent particles — which contained cadmium, selenium, zinc and sulfur — could easily be measured and imaged in the tests. In addition, the team treated the surface of the quantum dots with three different polymer coatings — one positively charged, one negatively charged and one neutral.
“In industrial applications, nanoparticles are often coated with a polymer to increase solubility, improve stability, enhance properties and for other reasons,” said study co-author Pedro Alvarez, professor and chair of Rice’s Department of Civil and Environmental Engineering. “We expect surface coatings to play a significant role in whether and how nanomaterials may accumulate in food webs.”
Previous lab studies had suggested that the neutral coatings might cause the nanoparticles to aggregate and form clumps that were so large that they would not readily move from a plant’s roots to its leaves. The experiments bore this out. Of the three particle types, only those with charged coatings moved readily through the plants, and only the negatively charged particles avoided clumping altogether. The study also found that the type of coating impacted the plants’ ability to biodegrade, or break down, the quantum dots.
Koo and colleagues found caterpillars that fed on plants containing quantum dots gained less weight and grew more slowly than caterpillars that fed on untainted leaves. By examining the caterpillar’s excrement, the scientists were also able to estimate whether cadmium, selenium and intact quantum dots might be accumulating in the animals. Again, the coating played an important role.
“Our tests were not specifically designed to measure bioaccumulation in caterpillars, but the data we collected suggest that particles with positively charged coatings may accumulate in cells and pose a risk of bioaccumulation,” Koo said. “Based on our findings, more tests should be conducted to determine the extent of this risk under a broader set of ecological conditions.”
The researchers have a couple of images illustrating their work,
The buildup of fluorescent quantum dots in the leaves of Arabidopsis plants is apparent in this photograph of the plants under ultraviolet light. Credit: Y. Koo/Rice University
This paper is open access but you must be registered on the website.
One final thought about the research, it did take place in a laboratory environment and there doesn’t seem to have been any soil involved so the uptake can not be directly compared (as I understand matters) to the uptake characteristics where plant cultivation requires soil. This seems to have been a study involving hydroponic framing practices.
Queensland University of Technology* (QUT; Australia) researchers are hopeful they can adapt supercapacitors in the form of a fine film tor use in electric vehicles making them more energy-efficient. From a Nov. 6, 2014 news item on ScienceDaily,
A car powered by its own body panels could soon be driving on our roads after a breakthrough in nanotechnology research by a QUT team.
Researchers have developed lightweight “supercapacitors” that can be combined with regular batteries to dramatically boost the power of an electric car.
The discovery was made by Postdoctoral Research Fellow Dr Jinzhang Liu, Professor Nunzio Motta and PhD researcher Marco Notarianni, from QUT’s Science and Engineering Faculty — Institute for Future Environments, and PhD researcher Francesca Mirri and Professor Matteo Pasquali, from Rice University in Houston, in the United States.
A Nov. 6, 2014 QUT news release, which originated the news item, describes supercapacitors, the research, and the need for this research in more detail,
The supercapacitors – a “sandwich” of electrolyte between two all-carbon electrodes – were made into a thin and extremely strong film with a high power density.
The film could be embedded in a car’s body panels, roof, doors, bonnet and floor – storing enough energy to turbocharge an electric car’s battery in just a few minutes.
“Vehicles need an extra energy spurt for acceleration, and this is where supercapacitors come in. They hold a limited amount of charge, but they are able to deliver it very quickly, making them the perfect complement to mass-storage batteries,” he said.
“Supercapacitors offer a high power output in a short time, meaning a faster acceleration rate of the car and a charging time of just a few minutes, compared to several hours for a standard electric car battery.”
Dr Liu said currently the “energy density” of a supercapacitor is lower than a standard lithium ion (Li-Ion) battery, but its “high power density”, or ability to release power in a short time, is “far beyond” a conventional battery.
“Supercapacitors are presently combined with standard Li-Ion batteries to power electric cars, with a substantial weight reduction and increase in performance,” he said.
“In the future, it is hoped the supercapacitor will be developed to store more energy than a Li-Ion battery while retaining the ability to release its energy up to 10 times faster – meaning the car could be entirely powered by the supercapacitors in its body panels.
“After one full charge this car should be able to run up to 500km – similar to a petrol-powered car and more than double the current limit of an electric car.”
Dr Liu said the technology would also potentially be used for rapid charges of other battery-powered devices.
“For example, by putting the film on the back of a smart phone to charge it extremely quickly,” he said.
The discovery may be a game-changer for the automotive industry, with significant impacts on financial, as well as environmental, factors.
“We are using cheap carbon materials to make supercapacitors and the price of industry scale production will be low,” Professor Motta said.
“The price of Li-Ion batteries cannot decrease a lot because the price of Lithium remains high. This technique does not rely on metals and other toxic materials either, so it is environmentally friendly if it needs to be disposed of.”
Rice University scientist Matteo Pasquali and his team contributed to two new papers that suggest the nano-infused body of a car may someday power the car itself.
Rice supplied high-performance carbon nanotube films and input on the device design to scientists at the Queensland University of Technology in Australia for the creation of lightweight films containing supercapacitors that charge quickly and store energy. The inventors hope to use the films as part of composite car doors, fenders, roofs and other body panels to significantly boost the power of electric vehicles.
Researchers in the Queensland lab of scientist Nunzio Motta combined exfoliated graphene and entangled multiwalled carbon nanotubes combined with plastic, paper and a gelled electrolyte to produce the flexible, solid-state supercapacitors.
“Nunzio’s team is making important advances in the energy-storage area, and we were glad to see that our carbon nanotube film technology was able to provide breakthrough current collection capability to further improve their devices,” said Pasquali, a Rice professor of chemical and biomolecular engineering and chemistry. “This nice collaboration is definitely bottom-up, as one of Nunzio’s Ph.D. students, Marco Notarianni, spent a year in our lab during his Master of Science research period a few years ago.”
“We built on our earlier work on CNT films published in ACS Nano, where we developed a solution-based technique to produce carbon nanotube films for transparent electrodes in displays,” said Francesca Mirri, a graduate student in Pasquali’s research group and co-author of the papers. “Now we see that carbon nanotube films produced by the solution-processing method can be applied in several areas.”
As currently designed, the supercapacitors can be charged through regenerative braking and are intended to work alongside the lithium-ion batteries in electric vehicles, said co-author Notarianni, a Queensland graduate student.
“Vehicles need an extra energy spurt for acceleration, and this is where supercapacitors come in. They hold a limited amount of charge, but with their high power density, deliver it very quickly, making them the perfect complement to mass-storage batteries,” he said.
Because hundreds of film supercapacitors are used in the panel, the electric energy required to power the car’s battery can be stored in the car body. “Supercapacitors offer a high power output in a short time, meaning a faster acceleration rate of the car and a charging time of just a few minutes, compared with several hours for a standard electric car battery,” Notarianni said.
The researchers foresee such panels will eventually replace standard lithium-ion batteries. “In the future, it is hoped the supercapacitor will be developed to store more energy than an ionic battery while retaining the ability to release its energy up to 10 times faster – meaning the car would be powered by the supercapacitors in its body panels,” said Queensland postdoctoral researcher Jinzhang Liu.
Here’s an image of graphene infused with carbon nantoubes used in the supercapacitor film,
A scanning electron microscope image shows freestanding graphene film with carbon nanotubes attached. The material is part of a project to create lightweight films containing super capacitors that charge quickly and store energy. Courtesy of Nunzio Motta/Queensland University of Technology
Here are links to and citations for the two papers published by the researchers,
One final note, Dexter Johnson provides some insight into issues with graphene-based supercapacitors and what makes this proposed application attractive in his Nov. 7, 2014 post on the Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers] website; Note: Links have been removed),
The hope has been that someone could make graphene electrodes for supercapacitors that would boost their energy density into the range of chemical-based batteries. The supercapacitors currently on the market have on average an energy density around 28 Wh/kg, whereas a Li-ion battery holds about 200Wh/kg. That’s a big gap to fill.
The research in the field thus far has indicated that graphene’s achievable surface area in real devices—the factor that determines how many ions a supercapacitor electrode can store, and therefore its energy density—is not any better than traditional activated carbon. In fact, it may not be much better than a used cigarette butt.
Though graphene may not help increase supercapacitors’ energy density, its usefulness in this application may lie in the fact that its natural high conductivity will allow superconductors to operate at higher frequencies than those that are currently on the market. Another likely benefit that graphene will yield comes from the fact that it can be structured and scaled down, unlike other supercapacitor materials.
I recommend reading Dexter’s commentary in its entirety.
*’University of Queensland’ corrected to “Queensland University of Technology’ on Nov. 10, 2014 at 1335 PST.
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.
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,
Australian start-up company, Fabricor Workwear launched a Kickstarter campaign on Sept. 18, 2014 to raise funds for a stain-proof and water-repellent chef’s jacket according to a Sept. 25, 2014 news item on Azonano,
An Australian startup is using a patented nanotechnology to create ‘hydrophobic’ chef jackets and aprons. Fabricor says this means uniforms that stay clean for longer, and saving time and money.
The company was started because cofounder and MasterChef mentor Adrian Li, was frustrated with keeping his chef jackets and aprons clean.
“As a chef I find it really difficult to keep my chef jacket white, and we like our jackets white,” Li said. …
The nanotechnology application works by modifying the fabric at a molecular level by permanently attaching hydrophobic ‘whiskers’ to individual fibres which elevate liquids, causing them to bead up and roll off.
The fabric’s patented technology can extend the life of the apparel is because the apparel doesn’t have to be washed as often and can be washed in cooler temperatures, the company stated.
Fabricor’s products are not made with spray-application like many on the market which can destroy fabrics and contain carcinogenic chemical. Its hydrophobic properties are embedded into the weave during the production of the fabric.
Li said chefs spend too much money on chef jackets that are poorly designed and don’t last. The long-lasting fabric in Fabricor’s chef’s apparel retains its natural softness and breathability.
It seems to me that the claim about fewer washes can be made for all superhydrophobic textiles. As for carcinogenic chemicals in other superhydrophobic textiles, it’s the first I’ve heard of it, which may or may not be significant. I.e., I look at a lot of material but don’t focus on superhydrophobic textiles here and do not seek out research on risks specific to these textiles.
Teijin Aramid/Rice University
Still talking about textile fibres but on a completely different track, I received a news release this morning (Sept. 25, 2014) from Teijin Aramid about carbon nanotubes and fibres,
Researchers of Teijin Aramid, based in the Netherlands, and Rice University in the USA are awarded with the honorary ‘Paul Schlack Man-Made Fibers Prize’ for corporate-academic partnerships in fiber research. Their new super fibers are now driving innovation in aerospace, healthcare, automotive, and (smart) clothing.
The honorary Paul Schlack prize was granted by the European Man-made Fibers Association to Dr. Marcin Otto, Business Development Manager at Teijin Aramid and Prof. Dr. Matteo Pasquali from Rice University Texas, for the development of a new generation super fibers using carbon nanotubes (CNT). The new super fibers combine high thermal and electrical conductivity, as seen in metals, with the flexibility, robust handling and strength of textile fibers.
“The introduction of carbon nanotube fibers marked the beginning of a series of innovations in various industries”, says Marcin Otto, Business Development Manager at Teijin Aramid. “For example, CNT fibers can be lifesaving for heart patients: one string of CNT fiber in the cardiac muscle suffices to transmit vital electrical pulses to the heart. Or by replacing copper in data cables and light power cables by CNT fibers it’s possible to make satellites, aircraft and high end cars lighter and more robust at the same time.”
Since 1971, the Paul Schlack foundation annually grants one monetary prize to an individual young researcher for outstanding research in the field of fiber research, and an honorary prize to the leader(s) of excellent academic and corporate research partnerships to promote research at universities and research institutes.
For several years, leading researchers at Rice University and Teijin Aramid worked together on the development of CNT production. Teijin Aramid and Rice University published their research findings on carbon nanotubes fibers in the leading scientific journal, Science, beginning of 2013.
The material is made of graphene nanoribbons, atom-thick strips of carbon created by splitting nanotubes, a process also invented by the Tour lab. Whether sprayed, painted or spin-coated, the ribbons are transparent and conduct both heat and electricity.
Last year the Rice group created films of overlapping nanoribbons and polyurethane paint to melt ice on sensitive military radar domes, which need to be kept clear of ice to keep them at peak performance. The material would replace a bulky and energy-hungry metal oxide framework.
The graphene-infused paint worked well, Tour said, but where it was thickest, it would break down when exposed to high-powered radio signals. “At extremely high RF, the thicker portions were absorbing the signal,” he said. “That caused degradation of the film. Those spots got so hot that they burned up.”
The answer was to make the films more consistent. The new films are between 50 and 200 nanometers thick – a human hair is about 50,000 nanometers thick – and retain their ability to heat when a voltage is applied. The researchers were also able to preserve their transparency. The films are still useful for deicing applications but can be used to coat glass and plastic as well as radar domes and antennas.
In the previous process, the nanoribbons were mixed with polyurethane, but testing showed the graphene nanoribbons themselves formed an active network when applied directly to a surface. They were subsequently coated with a thin layer of polyurethane for protection. Samples were spread onto glass slides that were then iced. When voltage was applied to either side of the slide, the ice melted within minutes even when kept in a minus-20-degree Celsius environment, the researchers reported.
“One can now think of using these films in automobile glass as an invisible deicer, and even in skyscrapers,” Tour said. “Glass skyscrapers could be kept free of fog and ice, but also be transparent to radio frequencies. It’s really frustrating these days to find yourself in a building where your cellphone doesn’t work. This could help alleviate that problem.”
Tour noted future generations of long-range Wi-Fi may also benefit. “It’s going to be important, as Wi-Fi becomes more ubiquitous, especially in cities. Signals can’t get through anything that’s metallic in nature, but these layers are so thin they won’t have any trouble penetrating.”
He said nanoribbon films also open a path toward embedding electronic circuits in glass that are both optically and RF transparent.