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Stanford engineers have developed an improved process for making flexible circuits that use carbon nanotube transistors, a development that paves the way for a new generation of bendable electronic devices. (Bao Lab / Stanford University)

Engineers would love to create flexible electronic devices, such as e-readers that could be folded to fit into a pocket. One approach involves designing circuits based on electronic fibers, known as carbon nanotubes (CNTs), instead of rigid silicon chips. But reliability is essential. Most silicon chips are based on a type of circuit design that allows them to function flawlessly even when the device experiences power fluctuations. However, it is much more challenging to do so with CNT circuits. But now a team at Stanford University has developed a process to create flexible chips that can tolerate power fluctuations in much the same way as silicon circuitry. This is the first time anyone has designed flexible CNT circuits that have both high immunity to electrical noise and low power consumption," said Zhenan Bao, a professor of chemical engineering at Stanford.  In principle, CNTs should be ideal for making flexible electronic circuitry. These ultra-thin carbon filaments have the physical strength to take the wear and tear of bending and the electrical conductivity to perform any electronic task. But until this recent work from the Stanford team, flexible CNT circuits didn't have the reliability and power-efficiency of rigid silicon chips. The Stanford process also has some potential application to rigid CNTs. Although other engineers have previously doped rigid CNTs to create this immunity to electrical noise, the precise and finely tuned Stanford process out-performs these prior efforts, suggesting that it could be useful for both flexible and rigid CNT circuitry. Bao has focused her research on flexible CNTs, which compete with other experimental materials, such as specially formulated plastics, to become the foundation for bendable electronics, just as silicon has been the basis for rigid electronics.

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Image, courtesy of Dr. Matthew Lefebre and Professor Jorge Galan (Yale University), shows parts of nanoinjectors from Salmonella as seen under an electron microscope. Image Source: University of Kansas Press.

If you’ve ever suffered the misery of food poisoning from a bacterium like Shigella or Salmonella, then your cells have been on the receiving end of “nanoinjectors” — microscopic spikes made from proteins through which pathogens secrete effector proteins into human host cells, causing infection. Many bacteria use nanoinjectors to infect millions of people around the world every year. Today, Roberto De Guzman, associate professor of molecular biosciences at the University of Kansas, is leading a research group that is evaluating the potential of nanoinjectors as a target for a new class of antibiotics. Their work is funded by a five-year, $1.8 million grant from the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health. “This grant will support our studies on elucidating how bacterial nanoinjectors are assembled,” said De Guzman. “Nanoinjectors are protein machinery used by bacterial pathogens to inject virulence proteins into human cells to cause infectious diseases. They are nanoscale is size — they look like needles and bacteria use them to inject virulence proteins into host cells — so I called them nanoinjectors. In microbiology, they are known as part of the type III secretion system, a protein delivery machinery.” The KU researcher said nanoinjectors are unique to pathogenic bacteria and are absolutely required for infectivity. Most people have heard of the diseases caused by bacterial pathogens that employ nanoinjectors — several of which have changed the course of the human experience for the worse.

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Researchers with the University of Florida’s Institute of Food and Agricultural Sciences took what some would consider garbage and made a remarkable scientific tool, one that could someday help to correct genetic disorders or treat cancer without chemotherapy’s nasty side effects. Wilfred Vermerris, an associate professor in UF’s department of microbiology and cell science, and Elena Ten, a postdoctoral research associate, created from plant waste a novel nanotube, one that is much more flexible than rigid carbon nanotubes currently used. The researchers say the lignin nanotubes – about 500 times smaller than a human eyelash – can deliver DNA directly into the nucleus of human cells in tissue culture, where this DNA could then correct genetic conditions. Experiments with DNA injection are currently being done with carbon nanotubes, as well. “That was a surprising result,” Vermerris said. “If you can do this in actual human beings you could fix defective genes that cause disease symptoms and replace them with functional DNA delivered with these nanotubes.” The nanotube is made up of lignin from plant material obtained from a UF biofuel pilot facility in Perry, Fla. Lignin is an integral part of the secondary cell walls of plants and enables water movement from the roots to the leaves, but it is not used to make biofuels and would otherwise be burned to generate heat or electricity at the biofuel plant. The lignin nanotubes can be made from a variety of plant residues, including sorghum, poplar, loblolly pine and sugar cane.

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Fluorescent nanoreporters created at Rice University can tell oil producers how “sour” a reservoir is based on its hydrogen sulfide content. (Credit: Chih-Chau Hwang/Rice University)

Scientists at Rice University have created a nanoscale detector that checks for and reports on the presence of hydrogen sulfide in crude oil and natural gas while they’re still in the ground. The nanoreporter is based on nanometer-sized carbon material developed by a consortium of Rice labs led by chemist James Tour. Limited exposure to hydrogen sulfide causes sore throats, shortness of breath and dizziness, according to the researchers. The human nose quickly becomes desensitized to hydrogen sulfide, leading to an inability to detect higher concentrations. That can be fatal, they said. On the flip side, hydrogen sulfide is also a biologically important signaling molecule in processes that include pain and inflammation. Tour said chemists have synthesized fluorescent probes to detect it in the body. The Rice team capitalized on that work by using the probes to create downhole detectors for oil fields. Crude oil and natural gas inherently contain hydrogen sulfide, which gives off a “rotten egg” smell. Even a 1 percent trace of sulfur turns oil into what’s known as “sour crude,” which is toxic and corrodes pipelines and transportation vessels, Tour said. The extra steps required to turn the sour into “sweet” crude are costly. So it’s important to know the content of what you’re pumping out of the ground, and the earlier the better,” Tour said. Led by Rice professors Tour, Michael Wong and Mason Tomson and researcher Amy Kan, the university has pioneered efforts to gather information from oil fields through the use of nanoreporters. The nanoreporters were designed to detect and report on the presence and amount of oil in a well that might otherwise be hard to assess.

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The ability to move single atoms, one of the smallest particles of any element in the universe, is crucial to IBM's research in the field of atomic-scale memory. In 2012, IBM scientists announced the creation of the world's smallest magnetic memory bit, made of just 12 atoms. This breakthrough could transform computing by providing the world with devices that have access to unprecedented levels of data storage. But even nanophysicists need to have a little fun. In that spirit, the scientists moved atoms by using their scanning tunneling microscope to make … a movie, which has been verified by Guinness World Records™ as The World’s Smallest Stop-Motion Film.  A behind the scenes short shows how the work was done.

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Biodegradable plastic molecules (orange) self-assemble with DNA molecules (intertwined, black circles) to form tiny nanoparticles that can carry genes to cancer cells. Image Source: The John Hopkins University; Credit: Stephany Tzeng.

Working together, Johns Hopkins biomedical engineers and neurosurgeons report that they have created tiny, biodegradable “nanoparticles” able to carry DNA to brain cancer cells in mice. The team says the results of their proof of principle experiment suggest that such particles loaded with “death genes” might one day be given to brain cancer patients during neurosurgery to selectively kill off any remaining tumor cells without damaging normal brain tissue.

“In our experiments, our nanoparticles successfully delivered a test gene to brain cancer cells in mice, where it was then turned on,” says Jordan Green, Ph.D., an assistant professor of biomedical engineering and neurosurgery at the Johns Hopkins University School of Medicine. “We now have evidence that these tiny Trojan horses will also be able to carry genes that selectively induce death in cancer cells, while leaving healthy cells healthy.” Green and his colleagues focused on glioblastomas, the most lethal and aggressive form of brain cancer. With standard treatments of surgery, chemotherapy and radiation, the median survival time is only 14.6 months, and improvement will only come with the ability to kill tumor cells resistant to standard treatments, according to Alfredo Quiñones-Hinojosa, M.D., a professor of neurosurgery who treats brain cancer patients at the Johns Hopkins Kimmel Cancer Center. Because nature protects the brain by making it difficult to reach its cells through the blood, efforts turned to the use of particles that could carry tumor-destroying DNA instructions directly to cancer cells during surgery.

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An enveloped virus (left) coats itself with lipid as part of its life cycle. New lipid-coated DNA nanodevices (right) closely resemble those viruses and evade the immune defenses of mice. Credit: Steven Perrault/Harvard's Wyss Institute

It's a familiar trope in science fiction: In enemy territory, activate your cloaking device. And real-world viruses use similar tactics to make themselves invisible to the immune system. Now scientists at Harvard's Wyss Institute for Biologically Inspired Engineering have mimicked these viral tactics to build the first DNA nanodevices that survive the body's immune defenses. The results pave the way for smart DNA nanorobots that could use logic to diagnose cancer earlier and more accurately than doctors can today; target drugs to tumors, or even manufacture drugs on the spot to cripple cancer, the researchers report. The same cloaking strategy could also be used to make artificial microscopic containers called protocells that could act as biosensors to detect pathogens in food or toxic chemicals in drinking water. The scientists designed their nanodevices to mimic a type of virus that protects its genome by enclosing it in a solid protein case, then layering on an oily coating identical to that in membranes that surround living cells. That coating, or envelope, contains a double layer (bilayer) of phospholipid that helps the viruses evade the immune system and delivers them to the cell interior.

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Researchers at Washington University School of Medicine in St. Louis have demonstrated a new approach to treating muscular dystrophy. Mice with a form of this muscle-weakening disease showed improved strength and heart function when treated with nanoparticles loaded with rapamycin, an immunosuppressive drug recently found to improve recycling of cellular waste. The investigators, including Kristin P. Bibee, MD, PhD, looked at a mouse model of Duchenne muscular dystrophy, the most severe inherited form of the disease. Duchenne exclusively affects boys who have to rely on wheelchairs by age 12 and die from heart or respiratory failure in their 20s. When treated with rapamycin nanoparticles, the mice showed a 30 percent increase in grip strength and a significant improvement in cardiac function, based on an increase in the volume of blood the heart pumped. The nanoparticle used in the study consists of an inert core made of perfluorocarbon, originally designed as a blood substitute. The particles are about 200 nanometers in diameter—500 times smaller than the thickness of a human hair. The surface of the nanoparticle is coated with rapamycin, which suppresses the immune system. The drug typically is used to help prevent organ rejection in transplant patients. It is known for its anti-inflammatory properties and, more recently, for its role in activating autophagy.

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Often touted as a wonder material, graphene is a one-atom thick layer of carbon with remarkable, record breaking properties. Until now its ability to absorb electromagnetic radiation – energy from across the radio frequency spectrum – was not known.  Recently, scientists from the Queen Mary University of London and the Cambridge Graphene Centre demonstrated that the transparent material increased the absorption of electromagnetic energy by 90 per cent at a wide bandwidth. “The technological potential of graphene is well-known. This paper demonstrates one example of how that potential can translate into a practical application,” said Yang Hao, co-author of the study and Professor of Antennas and Electromagnetics at Queen Mary’s School of Electronic Engineering and Computer Science. “The transparent material could be added as a coating to car windows or buildings to stop radio waves from travelling through the structure. This, in turn, could be used to improve secure wireless network environments, for example.” The researchers placed a stack of layers of graphene supported by a metal plate and the mineral quartz to absorb the signals from a millimetre wave source, which allows the efficient control of wave propagation in complex environments. Co-author Bian Wu, who is at Queen Mary from Xidian University in China on a scholarship from China Scholarship Council, added: “The stacking configuration gives us better control of the interaction between radio waves and the graphene.”  The group is now developing prototypes like wireless networks, which are aimed to take the graphene from lab-based research to engineering applications.

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An atomic-scale model of a nanophononic metamaterial. The vibrations caused by the pillar slow down the horizontal flow of heat through the thin film. (Image Credit: University of Colorado Boulder)

University of Colorado Boulder scientists have found a creative way to radically improve thermoelectric materials, a finding that could one day lead to the development of improved solar panels, more energy-efficient cooling equipment, and even the creation of new devices that could turn the vast amounts of heat wasted at power plants into more electricity. The technique—building an array of tiny pillars on top of a sheet of thermoelectric material—represents an entirely new way of attacking a century-old problem, said Mahmoud Hussein, an assistant professor of aerospace engineering sciences who pioneered the discovery. The thermoelectric effect, first discovered in the 1800s, refers to the ability to generate an electric current from a temperature difference between one side of a material and the other. Conversely, applying an electric voltage to a thermoelectric material can cause one side of the material to heat up while the other stays cool, or, alternatively, one side to cool down while the other stays hot. Devices that incorporate thermoelectric materials have been used in both ways: to create electricity from a heat source, such as the sun, for example, or to cool precision instruments by consuming electricity. However, the widespread use of thermoelectric materials has been hindered by a fundamental problem that has kept scientists busy for decades. Materials that allow electricity to flow through them also allow heat to flow through them. This means that at the same time a temperature difference creates an electric potential, the temperature difference itself begins to dissipate, weakening the current it created. Using nanotechnology, material physicists began creating barriers in thermoelectric materials—such as holes or particles—that impeded the flow of heat more than the flow of electricity. But even under the best scenario, the flow of electrons—which carry electric energy—also was slowed. In a new study, Hussein and doctoral student Bruce Davis demonstrate that nanotechnology could be used in an entirely different way to slow the heat transfer without affecting the motion of electrons. The new concept involves building an array of nanoscale pillars on top of a sheet of a thermoelectric material, such as silicon, to form what the authors call a “nanophononic metamaterial.” Heat is carried through the material as a series of vibrations, known as phonons. The atoms making up the miniature pillars also vibrate at a variety of frequencies. Davis and Hussein used a computer model to show that the vibrations of the pillars would interact with the vibrations of the phonons, slowing down the flow of heat. The pillar vibrations are not expected to affect the electric current. The team estimates that their nanoscale pillars could reduce the heat flow through a material by half, but the reduction could be significantly stronger because the calculations were made very conservatively, Hussein said.

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