Researchers grow liquid crystal 'flowers' that can be used as lenses

In continuation of my update on liquid crystals

The researchers' ongoing work with liquid crystals is an example of a growing field of nanotechnology known as "directed assembly," in which scientists and engineers aim to manufacture structures on the smallest scales without having to individually manipulate each component. Rather, they set out precisely defined starting conditions and let the physics and chemistry that govern those components do the rest.

The starting conditions in the researchers previous experiments were templates consisting of tiny posts. In one of their studies, they showed that changing the size, shape or spacing of these posts would result in corresponding changes in the patterns of defects on the surface of the liquid crystal resting on top of them. In another experiment, they showed they could make a "hula hoop" of defects around individual posts, which would then act as a second template for a ring of defects at the surface.

In their latest work, the researchers used a much simpler cue.

"Before we were growing these liquid crystals on something like a trellis, a template with precisely ordered features," Kamien said. "Here, we're just planting a seed."

The seed, in this case, were silica beads -- essentially, polished grains of sand. Planted at the top of a pool of liquid crystal flower-like patterns of defects grow around each bead.

The key difference between the template in this experiment and ones in the research team's earlier work was the shape of the interface between the template and the liquid crystal.

In their experiment that generated grid patterns of defects, those patterns stemmed from cues generated by the templates' microposts. Domains of elastic energy originated on the flat tops and edges of these posts and travelled up the liquid crystal's layers, culminating in defects. Using a bead instead of a post, as the researchers did in their latest experiment, makes it so that the interface is no longer flat.

"Not only is the interface at an angle, it's an angle that keeps changing," Kamien said. "The way the liquid crystal responds to that is that it makes these petal-like shapes at smaller and smaller sizes, trying to match the angle of the bead until everything is flat."

Surface tension on the bead also makes it so these petals are arranged in a tiered, convex fashion. And because the liquid crystal can interact with light, the entire assembly can function as a lens, focusing light to a point underneath the bead.

"It's like an insect's compound eye, or the mirrors on the biggest telescopes," said Kamien. "As we learn more about these systems, we're going to be able to make these kinds of lenses to order and use them to direct light."

Researchers grow liquid crystal 'flowers' that can be used as lenses

Ref : http://prx.aps.org/abstract/PRX/v3/i4/e041026

Researchers split water into hydrogen, oxygen using light, nanoparticles

Researchers from the University of Houston have found a catalyst that can quickly generate hydrogen from water using sunlight, potentially creating a clean and renewable source of energy.

Researchers prepared the nanoparticles in two ways, using femtosecond laser ablation and through mechanical ball milling. Despite some differences, Bao said both worked equally well.

Different sources of light were used, ranging from a laser to white light simulating the solar spectrum. He said he would expect the reaction to work equally well using natural sunlight.

Once the nanoparticles are added and light applied, the water separates into hydrogen and oxygen almost immediately, producing twice as much hydrogen as oxygen, as expected from the 2:1 hydrogen to oxygen ratio in H2O water molecules, Bao said.

The experiment has potential as a source of renewable fuel, but at a solar-to-hydrogen efficiency rate of around 5 percent, the conversion rate is still too low to be commercially viable. Bao suggested a more feasible efficiency rate would be about 10 percent, meaning that 10 percent of the incident solar energy will be converted to hydrogen chemical energy by the process.

Other issues remain to be resolved, as well, including reducing costs and extending the lifespan of cobalt oxide nanoparticles, which the researchers found became deactivated after about an hour of reaction.

"It degrades too quickly," said Bao, who also has appointments in materials engineering and the Department of Chemistry.

Researchers split water into hydrogen, oxygen using light, nanoparticles

Nanotechnology Now - Press Release: "Curing Cancer with Magnetic Nanoparticles"

Curing Cancer with Magnetic Nanoparticles: 

Nanoprobes, Inc. is a nanoparticle research collaborative, dedicated to finding cures for cancer and other diseases. Our technology is helping save lives around the world, at the core of the HER2 breast cancer test. Located in Yaphank, NY, our funding comes from research grants, and sales of nanoparticle products to the scientific community; all profits support our research. 

Scientists at Nanoprobes, Inc. are heralding a major breakthrough in cancer research, using their new magnetic nanoparticles. After a quick intravenous injection and just three minutes inside a magnetic field, 80% of test animals are completely cured of cancer. Their spectacular results have just been published in The International Journal of Nanomedicine.

Six years of research were built on a simple idea: iron particles inside an alternating magnetic field will spin back and forth, and generate significant heat. If enough iron particles were delivered to a tumor, you could cook the cancer. For many years, however, researchers had been stymied by the toxic amount of iron required. To avoid poisoning the body, researchers had tried injecting iron particles directly into tumors, but areas missed would always regrow.

At Nanoprobes, a different approach held the key. Senior scientist Dr. James F. Hainfeld, one of the original fathers of the nanoparticle, decided to make the iron itself non-toxic. Together with colleague Hui Huang, he engineered a nanoparticle with an iron core and a biocompatible shell, which could safely be injected into the bloodstream. Sized to specifically leak out of newly-formed blood vessels in tumors, these iron nanoparticles will find and load cancerous tissue anywhere in the body, even targeting metastases.

The iron-laden cancer is then easily heated in a magnetic field; the tumors actually liquefy, while adjacent, healthy tissue stays cool and unharmed. Afterwards, the neutralized liquid is quickly absorbed by the body, while the nanoparticles break down slowly, allowing the iron to be safely assimilated. The research team has achieved a cure rate of 78-90% in mice, ablating tumors with an accuracy finer than a surgeon's knife.

It's also great news for combination therapy, where pre-treatment with heat (hyperthermia), greatly amplifies chemotherapy and radiation. Since magnetic fields easily pass through the human body, these iron nanoparticles will heat previously inaccessible, deep tumors. Brain cancer too is in their sights: where nothing else works, the lab has achieved highly specific iron loading of brain tumors. The precision of magnetic heating would vitally spare healthy brain tissue, compared to the collateral damage of radiation or surgery.

The National Institutes of Health recently granted the research group roughly a million dollars' worth of laboratory testing, in preparation for FDA approval. "We need to bring this to patients, as soon as possible," says Huang, now in medical school and soon to be treating patients himself. Nanoprobes is currently organizing funding for the clinical trials to come.

"After so many years in the trenches, I tend to be cautious," says Dr. Hainfeld, "but I've never seen such promising results. We're very hopeful." Because, he adds, "No one should ever have to hear, "There's nothing more we can do."

Nanotechnology Now - Press Release:

"Curing Cancer with Magnetic Nanoparticles"

Nanotechnology Now - Press Release: "Graphene-based nano-antennas may enable networks of tiny machines"

With antennas made from conventional materials like copper, communication between low-power nanomachines would be virtually impossible. But by taking advantage of the unique electronic properties of the material known as graphene, researchers now believe they're on track to connect devices powered by small amounts of scavenged energy.

Based on a honeycomb network of carbon atoms, graphene could generate a type of electronic surface wave that would allow antennas just one micron long and 10 to 100 nanometers wide to do the work of much larger antennas. While operating graphene nano-antennas have yet to be demonstrated, the researchers say their modeling and simulations show that nano-networks using the new approach are feasible with the alternative material.

"We are exploiting the peculiar propagation of electrons in graphene to make a very small antenna that can radiate at much lower frequencies than classical metallic antennas of the same size," said Ian Akyildiz, a Ken Byers Chair professor in Telecommunications in the School of Electrical and Computer Engineering at the Georgia Institute of Technology. "We believe that this is just the beginning of a new networking and communications paradigm based on the use of graphene."

Sponsored by the National Science Foundation, the research is scheduled to be reported in the journal IEEE Journal of Selected Areas in Communications (IEEE JSAC). In addition to the nanoscale antennas, the researchers are also working on graphene-based nanoscale transceivers and the transmission protocols that would be necessary for communication between nanomachines.

The communications challenge is that at the micron scale, metallic antennas would have to operate at frequencies of hundreds of terahertz. While those frequencies might offer advantages in communication speed, their range would be limited by propagation losses to just a few micrometers. And they'd require lots of power – more power than nanomachines are likely to have.

Akyildiz has studied nanonetworks since the late 1990s, and had concluded that traditional electromagnetic communication between these machines might not be possible. But then he and his Ph.D. student, Josep Jornet - who graduated in August 2013 and is now an assistant professor at the State University of New York at Buffalo - began reading about the amazing properties of graphene. They were especially interested in how electrons behave in single-layer sheets of the material.

"When electrons in graphene are excited by an incoming electromagnetic wave, for instance, they start moving back and forth," explained Akyildiz. "Because of the unique properties of the graphene, this global oscillation of electrical charge results in a confined electromagnetic wave on top of the graphene layer."

Known technically as a surface plasmon polariton (SPP) wave, the effect will allow the nano-antennas to operate at the low end of the terahertz frequency range, between 0.1 and 10 terahertz - instead of at 150 terahertz required by traditional copper antennas at nanoscale sizes. For transmitting, the SPP waves can be created by injecting electrons into the dielectric layer beneath the graphene sheet.

Materials such as gold, silver and other noble metals also can support the propagation of SPP waves, but only at much higher frequencies than graphene. Conventional materials such as copper don't support the waves.

By allowing electromagnetic propagation at lower terahertz frequencies, the SPP waves require less power - putting them within range of what might be feasible for nanomachines operated by energy harvesting technology pioneered by Zhong Lin Wang, a professor in Georgia Tech's School of Materials Science and Engineering.

"With this antenna, we can cut the frequency by two orders of magnitude and cut the power needs by four orders of magnitude," said Jornet. "Using this antenna, we believe the energy-harvesting techniques developed by Dr. Wang would give us enough power to create a communications link between nanomachines."

The nanomachines in the network that Akyildiz and Jornet envision would include several integrated components. In addition to the energy-harvesting nanogenerators, there would be nanoscale sensing, processing and memory, technologies that are under development by other groups. The nanoscale antenna and transceiver work being done at Georgia Tech would allow the devices to communicate the information they sense and process to the outside world.

"Each one of these components would have a nanoscale measurement, but in total we would have a machine measuring a few micrometers," said Jornet. "There would be lots of tradeoffs in energy use and size”.

Beyond giving nanomachines the ability to communicate, hundreds or thousands of graphene antenna-transceiver sets might be combined to help full-size cellular phones and Internet based laptops communicate faster.

"The terahertz band can boost current data rates in wireless networks by more than two orders of magnitude," Akyildiz noted. "The data rates in current cellular systems are up to one gigabit-per-second in LTE advanced networks or 10 gigabits-per-second in the so-called millimeter wave or 60 gigahertz systems. We expect data rates on the order of terabits-per-second in the terahertz band."

The unique properties of graphene, Akyildiz says, are critical to this antenna - and other future electronic devices.

"
The researchers have so far evaluated numerous nano-antenna designs using modeling and simulation techniques in their laboratory. The next step will be to actually fabricate a graphene nano-antenna and operate it using a transceiver also based on graphene.

Nanotechnology Now - Press Release: "Graphene-based nano-antennas may enable networks of tiny machines"

Turning waste into power with bacteria — and loofahs

Loofahs, best known for their use in exfoliating skin to soft, radiant perfection, have emerged as a new potential tool to advance sustainability efforts on two fronts at the same time: energy and waste. The study describes the pairing of loofahs with bacteria to create a power-generating microbial fuel cell (MFC) and appears in the ACS journal Environmental Science & Technology.

Shungui Zhou and colleagues note that MFCs, which harness the ability of some bacteria to convert waste into electric power, could help address both the world’s growing waste problem and its need for clean power. Current MFC devices can be expensive and complicated to make. In addition, the holes, or pores, in the cells’ electrodes are often too small for bacteria to spread out in. Recently, researchers have turned to plant materials as a low-cost alternative, but pore size has still been an issue. Loofahs, which come from the fully ripened fruit of loofah plants, are commonly used as bathing sponges. They have very large pores, yet are still inexpensive. That’s why Zhou’s team decided to investigate their potential use in MFCs.

When the scientists put nitrogen-enriched carbon nanoparticles on loofahs and loaded them with bacteria, the resulting MFC performed better than traditional MFCs. “This study introduces a promising method for the fabrication of high-performance anodes from low-cost, sustainable natural materials,” the researchers state.

Turning waste into power with bacteria — and loofahs

DNA nanotechnology opens new path to super-high-resolution molecular imaging : Wyss Institute at Harvard

The DNA-based microscopy method could potentially lead to new ways of diagnosing disease by distinguishing healthy and diseased cells based on sophisticated molecular details. It could also help scientists uncover how the cell's components carry out their work inside the cell.

"If you want to study physiology and disease, you want to see how the molecules work, and it's important to see them in their native environments," said Peng Yin, Ph.D., a core faculty member at the Wyss Institute and Assistant Professor of Systems Biology at Harvard Medical School. Yin will lead the project, and he will collaborate with Samie Jaffrey, M.D., Ph.D., a Professor of Pharmacology at Weill Cornell Medical College, and Ralf Jungmann, Ph.D., a postdoctoral scholar in Yin's Wyss Institute lab, among others.

Biologists have used microscopes to reveal how tiny structures inside cells prop them up and help them move, reproduce, activate genes, and much more. But although microscope makers have honed the technology for centuries to get ever-clearer images, they have been limited by the laws of physics. When two objects are closer than about 0.2 micrometers, or about one five-hundredth the width of a human hair, the scientists can no longer distinguish them using traditional light microscopes. As a result, the viewer sees one blurry blob where in reality there are two objects. This behavior occurs because of the way light rays bend around objects, and is known as the diffraction limit.

Molecules such as enzymes, receptors, RNA and DNA that do most of the work of the cell are typically far smaller than 0.2 micrometers, and to visualize them microscopists have struggled to overcome this limitation. They have developed several clever methods that accomplish this, but some of them require special microscopes that tend to be very expensive, and others require cumbersome procedures. What's more, today's methods can only reveal a handful of distinct molecule species at a time, and the images remain blurrier than many scientists would like.

The Wyss Institute-led team plans to overcome these challenges by combining single-molecule imaging methods with molecular tools from DNA nanotechnology. Using an imaging method called DNA-PAINT, they created so-called "imager strands" by tagging small pieces of DNA with a fluorescent dye. Each of these imager strands binds transiently to a matching DNA strand that is attached to a target molecule, which makes the target appear to blink. Such blinking, when done right, enables scientists to beat the diffraction limit and obtain sharper images of the targets than otherwise possible.

"The powerful thing about using DNA lies in its amazing programmability," Yin said. "We plan to use that capability to make molecules in cells blink in a programmable and autonomous way. This will allow us to see things that were previously invisible."

DNA nanotechnology opens new path to super-high-resolution molecular imaging : Wyss Institute at Harvard

Advances in nanotechnology's fight against cancer

Advances in nanotechnology's fight against cancer

Bioinspired self-repairing slippery surfaces with pressure-stable omniphobicity : Nature : Nature Publishing Group

To address the challenges like limited oleophobicity, researchers have reported a strategy to create self-healing, slippery liquid-infused porous surface(s) (SLIPS) with exceptional liquid- and ice-repellency, pressure stability and enhanced optical transparency.  Researchers claim  that the properties are insensitive to the precise geometry of the underlying substrate, making their approach applicable to various inexpensive, low-surface-energy structured materials (such as porous Teflon membrane). Researchers envision that the  slippery surfaces will be useful in fluid handling and transportation, optical sensing, medicine, and as self-cleaning and anti-fouling materials operating in extreme environments.

Bioinspired self-repairing slippery surfaces with pressure-stable omniphobicity : Nature : Nature Publishing Group

Researchers design a new catalyst to produce hydrogen from water and sunlight — Sala de Premsa - Universitat Politècnica de Catalunya (UPC)

The scientists behind the project have fused the optical properties of three dimensionalphotonic crystals (inverse opals of titanium dioxide, TiO2) and 2-3 nm gold nanoparticles to develop a highly active catalyst powder. The research paper has been published in Scientific Reports, the open-access journal of Nature.

This new photocatalyst produces more hydrogen than others developed so far by harnessing the properties of both photonic crystals and nanoparticles of a metal. According to Jordi Llorca, a researcher at the UPC's Institute of Energy Technology, the process involves "tuning" the two materials to amplify the effect. "You have to choose the right photonic crystal and the right nanoparticles", he adds.

  

In any photocatalyst made from gold nanoparticles and titanium dioxide crystals using ultraviolet light, which is only a small part of solar radiation (less than 3%), the process is the same: light excites the TiO2 electrons and promotes them to the conduction band, leaving holes on the other side. The electrons interact with the gold nanoparticles and are captured by them. According to the scientists, the novelty in this case is the use of a 3D photonic crystal that captures the visible part of the solar spectrum, precisely at the energy level at which the gold nanoparticles "resonate". As a result, it's possible to take advantage of the visible part of the solar spectrum rather than just the ultraviolet part. This translates into a significant boost in the performance of the process.

The new catalyst has great potential for application in industrial processes. According to researcher Jordi Llorca, making the move from the laboratory to an industrial plant would mean designing a reactor to operate outdoors in the sun, and using a solar collector to capture more sunlight.

A conventional plant for the production of hydrogen from natural gas generates about 300 tons of hydrogen a day. With the new catalyst developed at the UPC, researchers have managed to produce 0.025 litres of hydrogen in one hour using one gram of catalyst. Assuming eight hours of sunlight a day, the scientists estimate that an area measuring 10 x 10 km would be needed to produce hydrogen on an industrial scale.

More

Researchers design a new catalyst to produce hydrogen from water and sunlight — Sala de Premsa - Universitat Politècnica de Catalunya (UPC)

KIT - Visiting - Current Topics - Press Releases - PI 2013 - POPUP – Novel Organic Solar Cells

Future solar cells will be light and mechanically flexible. They will be produced at low costs with the help of printing processes. POPUP, the new BMBF-funded research project, aims at developing more efficient materials and new architectures for organic photovoltaic devices. An interdisciplinary team headed by Dr. Alexander Colsmann of the KIT Light Technology Institute (LTI) works on improving the basic understanding and developing new architectures for semitransparent and non-transparent solar cells and modules. 

Depending on the application, solar cells are manufactured on flexible plastic foils or rigid glass carriers. In the area of organic photovoltaics, KIT scientists work on two objectives, namely, full printability of solar cells and replacing indium tin oxide (ITO) as the electrode material. Instead, the scientists use conductive and transparent foils for flexible carriers. For glass carriers, they study the deposition of transparent electrodes from metallic microstructures and conductive buffer layers. In addition, the KIT team studies highly efficient semi-transparent solar cells in mini-modules made of organic semiconductors. Hence, KIT research concentrates on one of the key technologies of organic photovoltaics.

In the medium and long term, the industry partners plan to manufacture organic solar modules by competitive mass production methods. Later on, the solar modules are planned to be integrated into vehicles for electricity supply to onboard electronics, in buildings and glass facades, for energy supply of free-standing buildings and devices, emergency systems, transport and navigation aids. The novel technologies will also be used for off-grid electricity supply in the leisure activity sector or for charging mobile consumer devices. The results obtained by the KIT researchers will have direct impact on various applications.

The POPUP consortium comprises ten partners who have many years of experience in the organic photovoltaics field and are technology leaders in their respective areas of work: Merck, Darmstadt; Center for Applied Energy Systems, Erlangen; PolyIC GmbH & Co. KG, Fürth; Karlsruhe Institute of Technology, Karlsruhe; Leonhard Kurz Stiftung & Co. KG, Fürth; Belectric OPV GmbH, Nuremberg; Webasto Group, Stockdorf; Siemens AG, Erlangen; Centrosolar Glas GmbH & Co. KG, Fürth; Center for Solar Energy and Hydrogen Research, Stuttgart. The companies, universities and institutes are cooperating along a cross-sectoral and multidisciplinary value chain characterized by the division of labor.

KIT - Visiting - Current Topics - Press Releases - PI 2013 - POPUP – Novel Organic Solar Cells

The promise of nanotechnology

The promise of nanotechnology