You are browsing the archives of Rice University.

Graphene-coated ribbons of vanadium oxide, seen in a scanning electron microscope image, show promise as electrode for lithium-ion batteries, according to researchers at Rice University. (Credit: Ajayan Group/Rice University)

Last week I told you about some fascinating work coming out of the University of Stuttgart on extremely flexible vanadium pentoxide paper like material. Researchers are interested in the material for battery electrode and supercapacitor applications.

Researchers at Rice University also are looking at vanadium oxide for lithium battery electrode applications and recently reported on VO₂-graphene hybrid ribbons for cathodes in an article in Nano Letters published by the American Chemical Society (subscription required).

The work comes out of Pulickel Ajayan’s group. Ajayan is a professor in the Mechanical Engineering and Materials Science Department and in the Chemistry Department and is known for his creative thinking about batteries. Last summer, for example, we told you about his work on paintable batteries.

According to the paper’s abstract, although lithium-ion batteries have high energy density, their full potential in applications is not yet realized because “they lack suitable electrodes capable of rapid charging and discharging to enable a high power density critical for broad applications.” In a press release, Ajayan says that vanadium oxide has long interested the battery research community and that vanadium pentoxide has been used in some Li-ion batteries. However, he points out that oxides generally charge and discharge slowly because their electrical conductivities are low.

Ajayan’s group addressed the slow charge-discharge problem by “baking” high-conductivity graphene on VO₂ ribbons. The graphene forms a web like coating on the ribbons and serves as a “speedy conduit for electrons and channels for ions.”

The team reports promising results. Half-cell tests show that the cathodes fully charge and discharge in 20 seconds and retain 90 percent of their initial charge capacity even after 1,000 cycles. The team says their best cathode samples were up to 84 weight percent “lithium-slurping” VO₂ and held 204 milliamp hours of energy per gram. They also appear to be highly stable. The press release reports the “capacity for lithium storage remained stable after 200 cycles,” even at high temperatures regimes above 75°C, where the effectiveness of other cathode materials tends to attenuate. (I’m not sure how or whether the insulator-to-metal phase transition that VO₂ undergoes at 67°C is a factor. I’ll update this post when I find out.)

The ribbons are made in a simple-sounding hydrothermal process, but in the press release Subin Yang, lead author of the paper, admits, “One challenge to production was controlling the conditions for the co-synthesis of VO₂ ribbons with graphene.” They make the hybrid ribbons by heating a water suspension of graphene oxide nanosheets and vanadium pentoxide powders for hours in an autoclave. The V₂O₅ reduces completely to VO₂ and crystallizes into ribbon like structures that are 10 nanometers thick, up to 600 nanometers wide, and tens of micrometers long. Meanwhile, the graphene oxide reduces into graphene and forms a web like coating on the ribbons.

Ajayan thinks this hybrid material could be used in the paintable batteries his team is working on, too.

Full details are in the paper, “Bottom-up approach toward single-crystalline VO₂-graphene ribbons as cathodes for ultrafast lithium storage,” Shubin Yang, Yongji Gong, Zheng Liu, Liang Zhan, Daniel P. Hashim, Lulu Ma, Robert Vajtai, and Pulickel M. Ajayan, Nano Letters, DOI: 10.1021/nl400001u.

Share

What an active field!

Oxygen tolerance of an in silico-designed bioinspired hydrogen-evolving catalyst in water

(PNAS) Certain bacterial enzymes, the diiron hydrogenases, have turnover numbers for hydrogen production from water as large as 104/s. Their much smaller common active site, composed of earth-abundant materials, has a structure that is an attractive starting point for the design of a practical catalyst for electrocatalytic or solar photocatalytic hydrogen production from water. In earlier work, our group has reported the computational design of [FeFe]P/FeS₂, a hydrogenase-inspired catalyst/electrode complex, which is efficient and stable throughout the production cycle. However, the diiron hydrogenases are highly sensitive to ambient oxygen by a mechanism not yet understood in detail. An issue critical for practical use of [FeFe]P/FeS₂ is whether this catalyst/electrode complex is tolerant to the ambient oxygen. We report demonstration by ab initio simulations that the complex is indeed tolerant to dissolved oxygen over timescales long enough for practical application, reducing it efficiently. This promising hydrogen-producing catalyst, composed of earth-abundant materials and with a diffusion-limited rate in acidified water, is efficient as well as oxygen tolerant.

America’s Growing Minerals Deficit

(ProEdgeWire/WSJ) After every election, there’s a mad scramble in Washington over the must-make-it-happen agenda for the newly inaugurated president and Congress. There are welcome signs from the White House’s own Material Genome Initiative that securing America’s access to critical metals and minerals will be high on the list. A good thing, too. Jobs and capital increasingly flow to countries that command the resources to power modern manufacturing, and American manufacturing is more dependent on metals and minerals access than ever before. Yet there is no country on the planet where it takes longer to get a permit for domestic mining. Among other consequences of this red tape, there are now 19 strategic metals and minerals for which the U.S. is currently 100 percent import-dependent-and for 11 of them a single country, China, is among the top three providers.

Researchers developing nanosensor to detect CO₂

Researchers at the Universities of Toronto and St. Francis Xavier, Canada, are developing an affordable, energy efficient and ultrasensitive nanosensor that has the potential to detect even one molecule of carbon dioxide. Current sensors used to detect CO2 at surface sites are either very expensive or they use a lot of energy. And they’re not as accurate as they could be. Improving the accuracy of measuring and monitoring stored CO₂ is seen as key to winning public acceptance of carbon capture and storage as a greenhouse gas mitigation method. With funding from Carbon Management Canada, Harry Ruda of the Centre for Nanotechnology at UT and David Risk of StFX are working on single-nanowire transistors that should have unprecedented sensitivity for detecting CO₂ emissions. CMC, a national network that supports game-changing research to reduce CO₂ emissions in the fossil energy industry as well as from other large stationary emitters, is providing Ruda and his team $350,000 over three years. The grant is part of CMC’s third round of funding which saw the network award $3.75 million to Canadian researchers working on eight different projects. Risk is also using a CMC grant to work on marrying specialized sensor-housings, called forced diffusion chambers, with fiber-optic CO2 sensors.

Flat boron by the numbers: Rice researchers calculate what it would take to make new 2D material

It would be a terrible thing if laboratories striving to grow graphene from carbon atoms kept winding up with big pesky diamonds. “That would be trouble, cleaning out the diamonds so you could do some real work,” says Rice University theoretical physicist Boris Yakobson, chuckling at the absurd image. Yet something like that keeps happening to experimentalists working to grow two-dimensional boron. Boron atoms have a strong preference to clump into 3D shapes rather than assemble into pristine single-atom sheets, like carbon does when it becomes graphene. And boron clumps aren’t nearly as sparkly. Yakobson and his Rice colleagues have made progress toward 2D boron through theoretical work that suggests the most practical ways to make the material and put it to work. Earlier calculations by the group indicated 2D born would conduct electricity better than graphene. Through first-principle calculations of the interaction of boron atoms with various substrates, the team came up with several possible paths experimentalists may take toward 2D boron. Yakobson feels the work may point the way toward other useful 2D materials.

Diamond defects shrink MRI to the nanoscale

(Nature) Diamond-based quantum devices can now make nuclear magnetic resonance measurements on the molecular scale. Work by two independent groups will make it easier to find out the structure of single biological molecules such as proteins without destroying or freezing them. Nuclear magnetic resonance (NMR) and its close cousin magnetic resonance imaging (MRI) give information about a sample’s structure by detecting the weak magnetic forces in certain atomic nuclei, such as hydrogen. They work by detecting how molecules collectively resonate—like guitar strings that vibrate together—with electromagnetic waves of specific wavelengths. The techniques provide information about the structure of samples without damaging them, which is particularly important if the sample is a human body. But to some researchers, whole bodies are less interesting than the molecules that they are made up of. “I want to push NMR and MRI to the molecular level,” says Friedemann Reinhard, a physicist at the University of Stuttgart in Germany. His team is one of two that have used NMR to detect hydrogen atoms in samples measuring just a few nanometres across. The second team was led by Daniel Rugar, manager of nanoscale studies at IBM’s Almaden Research Center in San Jose, Calif. Both studies are published in Science.

A safer next-gen battery is used with solar panels for the first time

(GigaOm) But the next generation of lithium ion batteries are promising to be safer, and a few of them are already starting to be used in real-world situations in the power grid, electric vehicles and gadgets… So what makes Seeo’s batteries safer? It largely involves improvements to the electrolyte, or the medium that shuttles lithium ions back and forth between the cathode and the anode to charge and discharge the battery. Traditional lithium-ion battery electrolytes are mostly made of liquids, while Seeo is using a solid dry polymer based electrolyte, which feels like plastic to the touch. The polymer is non-flammable and when combined with using lithium foil as the anode, the battery can be ultra light weight and also have a high energy density, or amount of energy that can be stored per a given weight. If traditional lithium ion batteries are overcharged they can have a margin of error in the danger zone of about 20 percent above the max voltage of the battery, explained Zarem. In contrast, Seeo batteries have a margin of error of 100 percent over the voltage. The batteries also won’t burst into flames if something penetrates it (for example, during a car crash).

Share

So much to read, so little time. Maybe try anyway:

Scientists discover novel way to ‘heal’ defects in materials

In a paper published in Nature Materials, a team of researchers report they have succeeded in creating a defect in the structure of a single-layer crystal by simply inserting an extra particle, and then watching as the crystal “heals” itself. The trick to this self-healing property is that the crystal, an array of microscopic particles, must be curved. This effect, which carries important implications for improving the conductivity of electronics and other realms of materials science, was predicted six years ago by physicist Mark Bowick of Syracuse University, along with David Nelson, Homin Shin and Alex Travesset, in research supported by the National Science Foundation. NSF also funded the new study. In order to prove their prediction experimentally, Bowick sought out Paul M. Chaikin of the Center for Soft Matter Research at New York University. Chaikin enlisted the help of Irvine while he was a postdoctoral scientist working in Chaikin’s laboratory. All three researchers specialize in the branch of materials science called “soft matter,” which studies a wide range of semi-solid substances such as gels, foams and liquid crystals.

Apple files disappearing-feature iPhone patent

(The Register) Apple has filed a patent application for the ability to hide some of a device’s components, such as its camera, biometric sensors, or even its entire display, until they are needed. “Electronic devices are becoming more and more sophisticated, capable of performing a multitude of tasks from image capture to identity verification through biometric sensors,” patent application 20120258773 notes. That’s the good news; the bad news is that each new sensor clutters up the seamless shiny-shiny of an iDevice. The solution to this visual junkiness? Hide the sensors needed to accomplish those tasks behind switchable curtains such as those enabled by a polymer-dispersed liquid crystal window, and make them visible only when needed. In addition to hiding sensors, those switchable windows—as you might assume—would be appropriately color-matched to blend seamlessly with the device’s case when they’re hiding the components behind them.

‘Lava dots’ made from molten metal salt

(Futurity) Thanks to a chance discovery, scientists now know how to make hollow, coated versions of a nanotech staple called quantum dots. The new “lava dot” particles were discovered accidentally by researchers using molten droplets of metal salt. The results appear in the journal Nanotechnology. The researchers also found that lava dots arrange themselves in evenly spaced patterns on flat surfaces, thanks in part to a soft outer coating that can alter its shape when the particles are tightly packed. “We’re exploring potential of using these particles as catalysts for hydrogen production, as chemical sensors, and as components in solar cells, but the main point of this paper is how we make these materials,” says coauthor Michael Wong, professor of chemical and biomolecular engineering at Rice University. “We came up with this ‘molten-droplet synthesis’ technique and found we can use the same process to make hollow nano-size particles out of several kinds of elements. The upshot is that this discovery is about a whole family of particles rather than one specific composition.” Like their quantum dot cousins, lava dots can be made of semiconductors like cadmium selenide and zinc sulfide.

Cartilage made easy with novel hybrid printer

The printing of 3D tissue has taken a major step forward with the creation at Wake Forest University of a novel hybrid printer that simplifies the process of creating implantable cartilage. The printer was recently described in IOP Publishing’s journal Biofabrication, and was used to create cartilage constructs that could eventually be implanted into injured patients to help regrow cartilage in specific areas, such as the joints. The printer is a combination of two low-cost fabrication techniques: a traditional ink jet printer and an electrospinning machine. Combining these systems allowed the scientists to build a structure made from natural and synthetic materials. Synthetic materials ensure the strength of the construct and natural gel materials provide an environment that promotes cell growth. In this study, the hybrid system produced cartilage constructs with increased mechanical stability compared to those created by an ink jet printer using gel material alone. The constructs were also shown to maintain their functional characteristics in the laboratory and a real-life system. The constructs were also inserted into mice for two, four and eight weeks to see how they performed in a real life system. After eight weeks of implantation, the constructs appeared to have developed the structures and properties that are typical of elastic cartilage, demonstrating their potential for insertion into a patient.

With sensors, apps & data, my smartphone is (almost) my doctor

(GigaOm) If you think the Jawbone Up and Nike FuelBand are changing our perception of personal health, then wait until you see what Scanadu, a Mountain View, Calif.-based company, has planned for you. The two-year-old old company is the brainchild of Walter de Brouwer, a Belgian-born serial entrepreneur (EUnet-Quest and Star Lab) and member of TED, who in the recent past worked with Nicholas Negroponte on the One Laptop Per Child project. His team of a dozen-odd people, including biologists, chemists, data scientists and semiconductor engineers, is planning to develop a series of personalized health products that want to capitalize on the rapidly falling prices of sensors and other technologies and combine them with data and easy to use smartphone apps. It wants scientists and developers to figure out a handheld device that can diagnose 15 medical ailments based on sensors in the device. De Brouwer’s crew has come up Scanadu Scout, a square shaped device. that can be held next to the left temple when holding it with thumb and the index finger of the left thumb. The device communicates with your iPhone via bluetooth and a few seconds later you get a readout of your vitals such as heart rate, level of oxygen in your blood, pulse and body temperature. It is one of the many devices the company plans to build.

New technique reveals lithium in action

Exactly what goes inside advanced lithium-air batteries as they charge and discharge has always been impossible to observe directly. Now, a new technique developed by MIT researchers promises to change that, allowing study of this electrochemical activity as it happens. The reactions that take place inside a conventional lithium-air battery are complex, says MIT professor Yang Shao-Horn. “We focused on finding out what really happens during charging and discharging,” she says. Doing that required the use of a special kind of high-intensity X-ray illumination at one of only two facilities in the world capable of producing such an experiment: the Advanced Light Source at the Lawrence Berkeley National Lab in California. That facility made it possible to study the electrochemical reactions taking place at the surface of electrodes, and to show the reactions between lithium and oxygen as the voltage applied to the cell was changed. The tests used a novel solid-state version of a lithium-air battery made possible via collaboration with Nancy Dudney and colleagues at Oak Ridge National Lab. Using ALS, researchers were able to produce detailed spectra of how the reaction unfolds, and show that this reaction is reversible on metal oxide surfaces. This study showed that using metal oxides as the oxygen electrode could potentially enable a lithium-air battery to maintain its performance over many cycles of operation.

Manufacturing activity in developing countries encourages use of superhard materials in machine tools, according to new report

Global Industry Analysts announces the release of a comprehensive global report on Superhard Materials markets. Global Superhard Materials market is projected to reach $20.2 billion by 2018, driven by healthy economic, industrial and manufacturing activity in developing countries and the ensuing increased demand for highly efficient metal machining, boring, grinding, and nonmetal machining tools. Developing economies, on the road towards rapid industrialization, will continue to drive growth in the world market, especially in the machine tools sector. For instance, China is emerging into a major market for industrial diamonds encouraged by its low-cost export oriented manufacturing prowess. Technology innovations are also poised to benefit the market in the upcoming years. Growing demand for new abrasive products in manufacturing plants as a result of increased precision grinding needs in most end-user manufacturing sectors, is driving R&D investments in superhard materials. For instance, increased research focus is being shed on substitute materials to the traditional diamond such as, cubic boron nitride and polycrystalline boron nitride for cutting, grinding and machining applications. Rising environmental awareness and the ensuing focus on common rail diesel injection systems, given their ability to reduce carbon dioxide emissions, will create demand for superhard materials, such as ceramics in the manufacture of glow plugs, and piezoelectric-stacks in diesel engines. Also, as the diesel engine technology continues to develop in the future, ceramics will find potential applications in components, such as, turbocharger valve train components, glow plugs, piston, cap cylinders, exhaust train insulation, liners, air bearings, high-temperature bearings, and low friction liquid, lubricant-free bearings, among others.

Researchers develop new way to determine amount of charge remaining in battery

Researchers from North Carolina State University have developed a new technique that allows users to better determine the amount of charge remaining in a battery in real time. That’s good news for electric vehicle drivers, since it gives them a better idea of when their car may run out of juice. The research is also good news for battery developers. “This improved accuracy will also give us additional insight into the dynamics of the battery, which we can use to develop techniques that will lead to more efficient battery management,” says Mo-Yuen Chow, a professor of electrical and computer engineering at NC State. At present, it is difficult to determine how much charge a battery has left. Existing computer models for estimating the remaining charge are not very accurate. The inaccuracy stems, in part, from the number of variables that must be plugged in to the models. But now researchers have developed software that identifies and processes data that can be used to update the computer model in real time, allowing the model to estimate the remaining charge in a battery much more accurately. While the technique was developed specifically for batteries in plug-in electric vehicles, the approach is also applicable to battery use in any other application. Using the new technique, models are able to estimate remaining charge within 5 percent. In other words, if a model using the new technique estimates a battery’s state of charge at 48 percent, the real state of charge would be between 43 and 53 percent (5 percent above or below the estimate).

Share

Lot’s of good stories here:

India-Japan join hands to challenge China’s rare earth monopoly

The Indian Prime Minister was forced to cancel his planned visit to Japan this month after the Japanese government dissolved the lower house of parliament and announced early elections. An important trade pact in respect of rare earth materials was proposed to be signed during the visit. Fortunately, the cancellation of the Indian Prime Minister’s visit has not come in the way of the realisation of this pact. On Nov. 16, a trade pact allowing the import of 4,100 tons of rare earth elements material (amounts to roughly 10 to 15 percent of Japan’s peak annual demand) from India has been signed by the two countries. India is known to be the second largest producer of REEs. According to one estimate made in 2010, China produced 1.3 lakh tons of REEs while India’s output was 2,700 tons. India, in spite of being a small player in comparison with China, has been in the business of REEs since the 1950s when Indian Rare Earths Ltd. was established. The recent agreement between Japan and India on REEs could also be viewed as a continuation of their existing relationship in the field of REEs. Japan has already made investments in this regard in India. The most interesting aspect of India and Japan coming together is that they are also proposing to engage with other states where REEs are available for excavation. India and Japan want to develop a joint venture in third countries, particularly in underdeveloped states, such as Afghanistan and Kazakhstan.

Stronger than a speeding bullet

(R&D News) Providing protection against impacts from bullets and other high-speed projectiles is more than just a matter of brute strength. While traditional shields have been made of bulky materials such as steel, newer body armor made of lightweight material such as Kevlar has shown that thickness and weight are not necessary for absorbing the energy of impacts. Now, a new study by researchers at MIT and Rice University has shown that even lighter materials may be capable of doing the job just as effectively. The key is to use composites made of two or more materials whose stiffness and flexibility are structured in very specific ways-such as in alternating layers just a few nanometers thick. The research team produced miniature high-speed projectiles and measured the effects they had on the impact-absorbing material. The team developed a self-assembling polymer with a layer-cake structure: rubbery layers, which provide resilience, alternating with glassy layers, which provide strength. They then developed a method for shooting glass beads at the material at high speed by using a laser pulse to rapidly evaporate a layer of material just below its surface. Though the beads were tiny-just millionths of a meter in diameter-they were still hundreds of times larger than the layers of the polymer they impacted: big enough to simulate impacts by larger objects, such as bullets, but small enough so the effects of the impacts could be studied in detail using an electron microscope.

Storm damage opportunity to consider autoclave aerated concrete?

Although widespread rebuilding in the hard-hit New York metro region from Super Storm Sandy has not yet begun, New Jersey Institute of Technology Assistant Professor Mohamed Mahgoub says when the hammers start swinging, it’s time to look at autoclaved aerated concrete. The material, best known as AAC, has been heralded as the building material of the new millennium. It’s a lightweight, easily-crafted manufactured stone, strong enough to withstand earthquakes and hurricanes when reinforced with steel. The material is used widely worldwide, says Mahgoub. Mahgoub is also the coordinator of the NJIT Concrete Industry Management program, which is only one of a select few programs of its kind across the United States. This semester CIM students are testing and analyzing AAC. “It is an environmentally-friendly solution for future building problems and it is also an extremely efficient, specialty fabrication material,” he says. “Cuts can easily be factory controlled. AAC is available throughout the U.S. and Canada. There is currently one U.S. manufacturer in Florida with plans to open another manufacturing operation in New Jersey.” AAC is workable and lightweight like wood.  It can provide outstanding thermal insulation, is resistant to fire, termites and decay.  A concrete product, AAC consists of finely ground sand, cement, quick lime, gypsum, aluminum and water.  “Most sand is too coarse for the manufacturing of AAC,” notes Mahgoub.

Experimental ‘bio-concrete’ that patches up cracks by itself is to undergo outdoor testing.

(BBC) A concrete that contains limestone-producing bacteria, which are activated by corrosive rainwater working its way into the structure, could potentially increase the service life of the concrete—with considerable cost savings as a result. The work is taking place at Delft Technical University, Netherlands. It is the brainchild of microbiologist Henk Jonkers and concrete technologist Eric Schlangen. If all goes well, Jonkers says they could start the process of commercializing the system in 2-3 years. Bacterial spores and the nutrients they will need to feed on are added as granules into the concrete mix. But water is the missing ingredient required for the microbes to grow. So the spores remain dormant until rainwater works its way into the cracks and activates them. The harmless bacteria, belonging to the Bacillus genus, then feed on the nutrients to produce limestone. The bacterial food incorporated into the healing agent is calcium lactate—a component of milk. The microbes used in the granules are able to tolerate the highly alkaline environment of the concrete. ”In the lab we have been able to show healing of cracks with a width of 0.5 mm, 2-3 times higher than the norms state,” Jonkers explained. ”Now we are upscaling. We have to produce the self-healing agent in huge quantities and we are starting to do outdoor tests, looking at different constructions, different types of concrete to see if this concept really works in practice.” The main challenge is to ensure the healing agent is robust enough to survive the mixing process. But, in order to do so, says Jonkers, “we have to apply a coating to the particles, which is very expensive”. The team is currently trying to reduce the cost this adds to the process. But he expects an improved system to be ready in about six months. The outdoor tests should begin after this; the team is already talking to several construction firms that could provide help. The concrete will then have to be monitored for a minimum of two years to see how it behaves in this real-world setting.

Nanomaterial copies butterfly colors, repels water

Researchers have figured out how to recreate the bright, beautiful colors of butterfly wings, as well as their ability to strongly repel water. The colors of a butterfly’s wings are the result of an unusual trait-the way they reflect light is fundamentally different from how color works most of the time. A team of researchers at the University of Pennsylvania has found a way to generate this kind of “structural color.” Shu Yang, associate professor in the department of materials science and engineering, led the research. She and colleagues report their findings in the journal Advanced Functional Materials. The two qualities-structural color and superhydrophobicity-are related by structures. Structural color is the result of periodic patterns, while superhydrophobicity is the result of surface roughness. While trying to combine these traits, engineers have to go through complicated, multi-step processes, first to create color-providing 3D structures out of a polymer, followed by additional steps to make them rough in the nanoscale.

An electric motor that’s ditched the rare earth materials

(GigaOm) A Chicago startup is ready to commercialize an electric motor that presents an alternative to the conventional motors that require the use of rare earth materials. HEVT hopes to raise money to scale up production. Political battles over rare earth materials - which are crucial for many energy components, like lighting, batteries and motors - have spawned efforts to create technologies free of these materials. A startup called HEVT (or Hybrid Electric Vehicle Technologies), which recently won the national Cleantech competition, has developed a rare earth-free electrical motor and is looking to deliver its technology to market first in electric bicycles. The Chicago-based company has engineered a high-performance “switched reluctance motor” and says it has solved the noise and vibration problem that has crippled efforts in the past to commercialize it, according to Heidi Lubin, CEO of HEVT. The motor presents an alternative to conventional induction and magnet motors, which require rare earth elements that can be hard to secure. HEVT is part of a team, led by the University of Texas at Dallas, to design a switch reluctance motor with nearly $3 million from the ARPA-E program. Rare earth mining and processing also can be environmentally unfriendly. HEVT was founded in 2005 within the Illinois Institute of Technology to target electric hybrids and plug-in electric cars and trucks. But that market is hard to crack. The pace of electric car adoption hasn’t taken off as quickly as some proponents would’ve liked to see, and some battery makers in particular have had trouble meeting their sales projections. So HEVT wants to tackle the more established electric bicycle market first.

Silica ‘nano-wiffle-ball’ cancer therapy wins inventors competition

For work toward a safer approach to treating cancer, electrical engineering PhD student Inanc Ortac from the University of California, San Diego has won first prize in the graduate student category at the 2012 Collegiate Inventors Competition. Ortac’s winning entry offers a new approach for delivering cancer drugs just to the areas where the drugs are needed. This kind of targeted drug delivery minimizes collateral damage to non-cancerous cells. “With our nano-wiffle-ball technology, we expect that the lethal side effects to chemotherapy can be greatly reduced, the efficacy of the therapy can be increased, and the quality of life of patients can be improved,” said Ortac. The proposed nano-wiffle-ball approach for the treatment of solid tumors and metastatic cancers would involve multiple steps. First, the nano-wiffle-balls, which are nano-scale capsules made of silica, are filled with foreign enzymes. The nano-wiffle-balls encapsulate the enzymes and effectively hide them from the body’s immune system. Trillions of nano-wiffle balls loaded with foreign enzymes would then travel through the blood stream and accumulate at the cancer sites. Next, a doctor would administer a non-toxic, inactive drug precursor (prodrug) that enters these nanocapsules reacts with the enzyme cargo. These reactions activate the prodrug, turning it into an active cancer-fighting drug. Preclinical trials for a number of cancer types including colorectal cancer, pancreatic cancer, acute lymphoblastic leukemia, and metastatic breast cancer are under way and clinical studies will follow, according to Ortac.

To build a better bone graft, rough it up

Coating a bone graft with an inorganic compound found in bones and teeth may significantly increase the likelihood of a successful implant, new research from Penn State shows. Natural bone grafts need to be sterilized and processed with chemicals and radiation before implantation into the body to make sure disease isn’t transmitted by the graft. Human bones have a rough surface. However, once a graft is sterilized the surface changes and doesn’t work as well at stimulating bone formation in the body. Researchers developed a way to create a rough surface on bone grafts that is similar in texture to the surface of an untreated bone that promotes healing. By coating a bone with hydroxyapatite using physical vapor deposition, they could closely mimic the rough surface of an untreated bone. To find the optimum thickness of hydroxyapatite, the group sterilized the graft samples. After sterilization, physical vapor deposition layered different amounts of hydroxyapatite on the grafts.

Share

Researchers create solar steam using nanoparticles at Rice University. Credit: Rice Univ.

From Futurity.org:

New technology that uses nanoparticles to convert solar energy directly into steam is so effective it even works with icy cold water.

The solar steam method has an overall energy efficiency of 24 percent. Photovoltaic solar panels, by comparison, typically have an overall energy efficiency around 15 percent. Inventors of solar steam expect the first uses of the new technology won’t be for electricity generation but rather for sanitation and water purification in developing countries.

“This is about a lot more than electricity,” says Naomi Halas of the Laboratory for Nanophotonics at Rice University. “With this technology, we are beginning to think about solar thermal power in a completely different way.”

As reported in ACS Nano (”Solar Vapor Generation Enabled by Nanoparticles, doi:10.1021/nn304948h), the efficiency of solar steam is due to the light-capturing nanoshells and nanoparticles that convert sunlight into heat. The researchers tested solutions containing two materials: 1) SiO₂/Au nanoshells and 2) water soluble N115 carbon nanoparticles with equivalent integrated optical densities (from 400 nm to 1300 nm in wavelength)When submerged in water and exposed to sunlight, the particles heat up so quickly they instantly vaporize water and create steam. Halas says the solar steam’s overall energy efficiency can probably be increased as the technology is refined.

“We’re going from heating water on the macro scale to heating it at the nanoscale,” Halas says. “Our particles are very small-even smaller than a wavelength of light-which means they have an extremely small surface area to dissipate heat. This intense heating allows us to generate steam locally, right at the surface of the particle, and the idea of generating steam locally is really counterintuitive.”

To show just how counterintuitive, Rice graduate student Oara Neumann videotaped a solar steam demonstration {above) in which a test tube of water containing light-activated nanoparticles was submerged into a bath of ice water. Using a lens to concentrate sunlight onto the near-freezing mixture in the tube, Neumann showed she could create steam from nearly frozen water.

Steam is one of the world’s most-used industrial fluids. About 90 percent of electricity is produced from steam, and steam is also used to sterilize medical waste and surgical instruments, to prepare food, and to purify water.

Most industrial steam is produced in large boilers-solar steam’s efficiency could allow it to become economical on a much smaller scale.

People in developing countries will be among the first to see the benefits of solar steam. Rice engineering undergraduates have already created a solar steam-powered autoclave that’s capable of sterilizing medical and dental instruments at clinics that lack electricity. Halas also won a Grand Challenges grant from the Bill and Melinda Gates Foundation to create an ultra-small-scale system for treating human waste in areas without sewer systems or electricity.

“Solar steam is remarkable because of its efficiency,” says Neumann, the lead co-author on the paper. “It does not require acres of mirrors or solar panels. In fact, the footprint can be very small. For example, the light window in our demonstration autoclave was just a few square centimeters.”

Another potential use could be in powering hybrid air-conditioning and heating systems that run off of sunlight during the day and electricity at night. Halas, Neumann, and colleagues have also conducted distillation experiments and found that solar steam is about two-and-a-half times more efficient than existing distillation columns.

Halas, a professor in electrical and computer engineering and of physics, chemistry, and biomedical engineering, specializes in creating and studying light-activated particles. One of her creations, gold nanoshells, is the subject of several clinical trials for cancer treatment.

For the cancer treatment technology and many other applications, Halas’ team chooses particles that interact with just a few wavelengths of light. For the solar steam project, Halas and Neumann set out to design a particle that would interact with the widest possible spectrum of sunlight energy. Their new nanoparticles are activated by both visible sunlight and shorter wavelengths that humans cannot see.

“We’re not changing any of the laws of thermodynamics,” Halas says. “We’re just boiling water in a radically different way.”

The research was supported by the Welch Foundation and the Bill and Melinda Gates Foundation.

Share