Home > University News
Bookmark and Share

Computer simulations show that when a light particle (blue wave on left) hits a crystal of a high-pressure form of silicon, it releases two electron-hole pairs (red circles/green rings), which generate electric current. (Stefan Wippermann/UC Davis photo)

Using an exotic form of silicon could substantially improve the efficiency of solar cells, according to computer simulations by researchers at the University of California, Davis, and in Hungary. Solar cells are based on the photoelectric effect: a photon, or particle of light, hits a silicon crystal and generates a negatively charged electron and a positively charged hole. Collecting those electron-hole pairs generates electric current. “Conventional solar cells generate one electron-hole pair per incoming photon, and have a theoretical maximum efficiency of 33 percent. One exciting new route to improved efficiency is to generate more than one electron-hole pair per photon,” said Giulia Galli, professor of chemistry at UC Davis. "This approach is capable of increasing the maximum efficiency to 42 percent, beyond any solar cell available today, which would be a pretty big deal," said Stefan Wippermann, a postdoctoral researcher at UC Davis. "In fact, there is reason to believe that if parabolic mirrors are used to focus the sunlight on such a new-paradigm solar cell, its efficiency could reach as high as 70 percent," Wippermann said. Galli said that nanoparticles have a size of nanometers, typically just a few atoms across. Because of their small size, many of their properties are different from bulk materials. In particular, the probability of generating more than one electron-hole pair is much enhanced, driven by an effect called "quantum confinement." Experiments to explore this paradigm are being pursued by researchers at the Los Alamos National Laboratory, the National Renewable Energy Laboratory in Golden, Colo., as well as at UC Davis. The researchers simulated the behavior of a structure of silicon called silicon BC8, which is formed under high pressure but is stable at normal pressures, much as diamond is a form of carbon formed under high pressure but stable at normal pressures.

Bookmark and Share

Jim Smith, of civil and environmental engineering, and Dr. Rebecca Dillingham, director of the Center for Global Health, co-direct PureMadi. (Photo Credit: University of Virginia, Dan Addison)

PureMadi, a nonprofit University of Virginia organization, has announced a new invention – a simple ceramic water purification tablet .  Called MadiDrop, the tablet – developed and extensively tested at U.Va. – is a small ceramic disk impregnated with silver or copper nanoparticles. It can repeatedly disinfect water for up to six months simply by resting in a vessel where water is poured. It is being developed for use in communities in South Africa that have little or no access to clean water.  During the past year, PureMadi has established a water filter factory in Limpopo province, South Africa, employing local workers. The factory produced several hundred flowerpot-like water filters, according to James Smith, a U.Va. civil and environmental engineer who co-leads the project with Dr. Rebecca Dillingham, director of U.Va.’s Center for Global Health. “Eventually that factory will be capable of producing about 500 to 1,000 filters per month, and our 10-year plan is to build 10 to 12 factories in South Africa and other countries,” Smith said. “Each filter can serve a family of five or six for two to five years, so we plan to eventually serve at least 500,000 people per year with new filters.” The idea is to create sustainable businesses that serve their communities and employ local workers. A small percentage of the profits go back to PureMadi and will be used to help establish more factories. The filters produced at the factory are made of a ceramic design refined and extensively tested at U.Va. The filters are made of local clay, sawdust and water. Those materials are mixed and pressed into a mold. The result is a flowerpot-shaped filter, which is then fired in a kiln. The firing burns off the sawdust, leaving a ceramic with very fine pores. The filter is then painted with a thin solution of silver or copper nanoparticles that serve as a highly effective disinfectant for waterborne pathogens, the type of which can cause severe diarrhea, vomiting and dehydration.

Bookmark and Share

An up-close look at the “hyperbolic metamaterial waveguide,” which catches and ultimately absorbs wavelengths (or color) in a vertical direction. (Image credit: University of Buffalo)

University at Buffalo engineers have created a more efficient way to catch rainbows, an advancement in photonics that could lead to technological breakthroughs in solar energy, stealth technology and other areas of research. Qiaoqiang Gan, PhD, an assistant professor of electrical engineering at UB, and a team of graduate students developed a “hyperbolic metamaterial waveguide,” which is essentially an advanced microchip made of alternate ultra-thin films of metal and semiconductors and/or insulators. The waveguide halts and ultimately absorbs each frequency of light, at slightly different places in a vertical direction (see the figure to the right), to catch a “rainbow” of wavelengths. Gan is a researcher within UB’s new Center of Excellence in Materials Informatics. “Electromagnetic absorbers have been studied for many years, especially for military radar systems,” Gan said. “Right now, researchers are developing compact light absorbers based on optically thick semiconductors or carbon nanotubes. However, it is still challenging to realize the perfect absorber in ultra-thin films with tunable absorption band. “We are developing ultra-thin films that will slow the light and therefore allow much more efficient absorption, which will address the long existing challenge, he added.” The research could lead to advancements in an array of fields. For example, in electronics there is a phenomenon known as crosstalk, in which a signal transmitted on one circuit or channel creates an undesired effect in another circuit or channel. The on-chip absorber could potentially prevent this.

Bookmark and Share

Bioengineering researchers at University of California, Santa Barbara have found that changing the shape of chemotherapy drug nanoparticles from spherical to rod-shaped made them up to 10,000 times more effective at specifically targeting and delivering anti-cancer drugs to breast cancer cells. Their findings could have a game-changing impact on the effectiveness of anti-cancer therapies and reducing the side effects of chemotherapy, according to the researchers.

Conventional anti-cancer drugs accumulate in the liver, lungs and spleen instead of the cancer cell site due to inefficient interactions with the cancer cell membrane,” explained Samir Mitragotri, professor of chemical engineering and Director of the Center for BioEngineering at UCSB. “We have found our strategy greatly enhances the specificity of anti-cancer drugs to cancer cells.”

Bookmark and Share

Professor Novoselov addressing the audience at the University of Manchester.

The University of Manchester launched a £50,000 enterprise competition for students with new graphene ideas at a staff event attended by more than 500 people. The event was held to showcase and appeal for new ideas for graphene, a wonder material that is the world’s thinnest, strongest and most conductive material with the potential to revolutionise a huge number of diverse applications; from smartphones and ultrafast broadband to drug delivery and computer chips. Andre Geim and Kostya Novoselov isolated graphene at the University in 2004 and were awarded the 2010 Nobel prize in Physics. The University is building the £61 million National Graphene Institute to develop the material. A packed audience in University Place heard from a range of graphene researchers, including Professor Novoselov, about the key sectors that graphene can potentially revolutionise.  The 2013 competition is open to final year PhD students and Postdoctoral Research Associates at the University. It will be awarded to the candidate who can demonstrate outstanding potential in establishing a new enterprise related to graphene and who now wishes to embark on an entrepreneurial career in innovation and commercialisation. Applications will be judged on the strength of their business plan to develop a new graphene-related business.

Bookmark and Share

With a new technique that uses tightly-focused sound waves for micro-surgery, University of Michigan engineering researchers drilled a 150-micrometer hole in a confetti-sized artificial kidney stone. Image Credit: University of Michigan/Hyoung Won Baac

A carbon-nanotube-coated lens that converts light to sound can focus high-pressure sound waves to finer points than ever before. The University of Michigan engineering researchers who developed the new therapeutic ultrasound approach say it could lead to an invisible knife for noninvasive surgery. Today's ultrasound technology enables far more than glimpses into the womb. Doctors routinely use focused sound waves to blast apart kidney stones and prostate tumors, for example. The tools work primarily by focusing sound waves tightly enough to generate heat, says Jay Guo, a professor of electrical engineering and computer science, mechanical engineering, and macromolecular science and engineering. But, the beams that today's technology produces can be unwieldy, says Hyoung Won Baac, a research fellow at Harvard Medical School who worked on this project as a doctoral student in Guo's lab. The team was able to concentrate high-amplitude sound waves to a speck just 75 by 400 micrometers (a micrometer is one-thousandth of a millimeter). Their beam can blast and cut with pressure, rather than heat. Guo speculates that it might be able to operate painlessly because its beam is so finely focused it could avoid nerve fibers. The device hasn't been tested in animals or humans yet, though.

Bookmark and Share

When a DNA strand is captured and pulled through a nanopore, it’s much more likely to start the journey at one of its ends (top left) rather than being grabbed somewhere in the middle and pulled through in a folded configuration. Image Credit: Stein lab/Brown University

In the 1960s, Nobel laureate Pierre-Gilles de Gennes postulated that someday researchers could test his theories of polymer networks by observing single molecules. Researchers at Brown University observed single molecules of DNA being drawn through nanopores by electrical current and figured out why they most often travel head first. The research looks at the dynamics of how DNA molecules are captured by solid-state nanopores, tiny holes that soon may help sequence DNA at lightning speed. The study found that when a DNA strand is captured and pulled through a nanopore, it’s much more likely to start the journey at one of its ends, rather than being grabbed somewhere in the middle and pulled through in a folded configuration. “We think this is an important advance for understanding how DNA molecules interact with these nanopores,” said Derek Stein, assistant professor of physics at Brown, who performed the research with graduate student Mirna Mihovilovic and undergraduate Nick Hagerty. “If you want to do sequencing or some other analysis, you want the molecule going through the pore head to tail.”  Research into DNA sequencing with nanopores started a little over 15 years ago. The concept is fairly simple. A little hole, a few billionths of a meter across, is poked in a barrier separating two pools of salt water. An electric current is applied across the hole, which occasionally attracts a DNA molecule floating in the water. When that happens, the molecule is whipped through the pore in a fraction of a second. Scientists can then use sensors on the pore or other means to identify nucleotide bases, the building blocks of the genetic code. The technology is advancing quickly, and the first nanopore sequencing devices are expected to be on the market very soon. But there are still basic questions about how molecules behave at the moment they’re captured and before.

Bookmark and Share

Rice University’s latest nanotechnology breakthrough was more than 10 years in the making, but it still came with a shock. Scientists from Rice, the Dutch firm Teijin Aramid, the U.S. Air Force and Israel’s Technion Institute recently unveiled a new carbon nanotube (CNT) fiber that looks and acts like textile thread and conducts electricity and heat like a metal wire. In this week’s issue of Science, the researchers describe an industrially scalable process for making the threadlike fibers, which outperform commercially available high-performance materials in a number of ways. “We finally have a nanotube fiber with properties that don’t exist in any other material,” said lead researcher Matteo Pasquali, professor of chemical and biomolecular engineering and chemistry at Rice. “It looks like black cotton thread but behaves like both metal wires and strong carbon fibers.” The research team includes academic, government and industrial scientists from Rice; Teijin Aramid’s headquarters in Arnhem, the Netherlands; the Technion-Israel Institute of Technology in Haifa, Israel; and the Air Force Research Laboratory (AFRL) in Dayton, Ohio. “The new CNT fibers have a thermal conductivity approaching that of the best graphite fibers but with 10 times greater electrical conductivity,” said study co-author Marcin Otto, business development manager at Teijin Aramid. “Graphite fibers are also brittle, while the new CNT fibers are as flexible and tough as a textile thread. We expect this combination of properties will lead to new products with unique capabilities for the aerospace, automotive, medical and smart-clothing markets.”    

Bookmark and Share

A centre for research on graphene, a material which has the potential to revolutionise numerous industries, ranging from healthcare to electronics, is to be created at the University of Cambridge. The University has been a hub for graphene engineering from the very start and now aims to make this “wonder material” work in real-life applications. The Cambridge Graphene Centre will start its activities on February 1st 2013, with a dedicated facility due to open at the end of the year. Its objective is to take graphene to the next level, bridging the gap between academia and industry. It will also be a shared research facility with state-of-the-art equipment, which any scientist researching graphene will have the opportunity to use. The Centre’s activities will be funded by a Government grant worth more than £12 million, which was allocated to the University in December by the Engineering and Physical Sciences Research Council (EPSRC). The rest of this money will support projects focusing both on how to manufacture high-quality graphene on an industrial scale, and on developing some of its potential applications.

Bookmark and Share

A close-up of spherical silicon nanoparticles about 10 nanometers in diameter. University at Buffalo scientists report that these particles could form the basis of new technologies that generate hydrogen for portable power applications. (Image Credit: Swihart Research Group, University at Buffalo)

Super-small particles of silicon react with water to produce hydrogen almost instantaneously, according to University at Buffalo researchers. In a series of experiments, the scientists created spherical silicon particles about 10 nanometers in diameter. When combined with water, these particles reacted to form silicic acid (a nontoxic byproduct) and hydrogen — a potential source of energy for fuel cells. The reaction didn’t require any light, heat or electricity, and also created hydrogen about 150 times faster than similar reactions using silicon particles 100 nanometers wide, and 1,000 times faster than bulk silicon, according to the study.  The scientists were able to verify that the hydrogen they made was relatively pure by testing it successfully in a small fuel cell that powered a fan. “When it comes to splitting water to produce hydrogen, nanosized silicon may be better than more obvious choices that people have studied for a while, such as aluminum,” said researcher Mark T. Swihart, UB professor of chemical and biological engineering and director of the university’s Strategic Strength in Integrated Nanostructured Systems.

Pages