Monthly Archives: January 2019
Antireflection (AR) coatings on plastics have a multitude of practical applications, including glare reduction on eyeglasses, computer monitors and the display on your smart-phone when outdoors. Now, researchers at Penn State have developed an AR coating that improves on existing coatings to the extent that it can make transparent plastics, such as Plexiglas, virtually invisible.
Plastic dome coated with a new antireflection coating (right), and uncoated dome (left)
“This discovery came about as we were trying to make higher-efficiency solar panels,” said Chris Giebink, associate professor of electrical engineering, Penn State. “Our approach involved concentrating light onto small, high-efficiency solar cells using plastic lenses, and we needed to minimize their reflection loss.”
They needed an antireflection coating that worked well over the entire solar spectrum and at multiple angles as the sun crossed the sky. They also needed a coating that could stand up to weather over long periods of time outdoors. “We would have liked to find an off-the-shelf solution, but there wasn’t one that met our performance requirements,” he said. “So, we started looking for our own solution.”
That was a tall order. Although it is comparatively easy to make a coating that will eliminate reflection at a particular wavelength or in a particular direction, one that could fit all their criteria did not exist. For instance, eyeglass AR coatings are targeted to the narrow visible portion of the spectrum. But the solar spectrum is about five times as broad as the visible spectrum, so such a coating would not perform well for a concentrating solar cell system.
Reflections occur when light travels from one medium, such as air, into a second medium, in this case plastic. If the difference in their refractive index, which specifies how fast light travels in a particular material, is large — air has a refractive index of 1 and plastic 1.5 — then there will be a lot of reflection. The lowest index for a natural coating material such as magnesium fluoride or Teflon is about 1.3. The refractive index can be graded — slowly varied — between 1.3 and 1.5 by blending different materials, but the gap between 1.3 and 1 remains.
In a paper recently posted online ahead of print in the journal Nano Letters, Giebink and coauthors describe a new process to bridge the gap between Teflon and air. They used a sacrificial molecule to create nanoscale pores in evaporated Teflon, thereby creating a graded index Teflon-air film that fools light into seeing a smooth transition from 1 to 1.5, eliminating essentially all reflections.
“The interesting thing about Teflon, which is a polymer, is when you heat it up in a crucible, the large polymer chains cleave into smaller fragments that are small enough to volatize and send up a vapor flux. When these land on a substrate they can repolymerize and form Teflon,” Giebink explained.
“We’ve been interacting with a number of companies that are looking for improved antireflection coatings for plastic, and some of the applications have been surprising,” he said. “They range from eliminating glare from the plastic domes that protect security cameras to eliminating stray reflections inside virtual/augmented -reality headsets.”
Chemical engineering scientist Christian Hulteberg, from Lund University, has used the black liquor residue from pulp and paper manufacturing to create a polymer called lignin.
After purification and filtration, that is then turned into a gasoline mixture.
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“We’re actually using the stuff of the wood that they don’t use when they make paper and pulp… It adds value to low-value components of the tree,” he told Reuters.
In environmental terms, he says that gives it an advantage over other biofuels such as ethanol. “A lot of the controversy with ethanol production has been the use of feedstock that you can actually eat,” he said.
Lead-based perovskites are quite promising in applications of large-scale photovoltaic technology. However, toxicity is one of the crucial issues in these materials.
In the search for Lead-free perovskite, UNIST scientists have taken a major step forward toward a new generation of solar cells. They have developed new perovskite material that works as a charge regenerator with dye‐sensitized solar cells and have higher efficiency and stability.
Scientists used the vacancy‐ordered double perovskite (Cs2SnI6). They primarily examined the charge transfer mechanism of Cs2SnI6 with the aim of clarifying the function of its surface state.
For this reason, a 3‐electrode system was produced to observe charge exchange through the surface state of Cs2SnI6. “Due to a high volume of electrical charges in organic dyes that show high connectivity with the surface state of Cs2SnI6, more electric current was generated,” said Byung-Man Kim from the Department of Chemistry at UNIST. “Consequently, Cs2SnI6 shows efficient charge transfer with a thermodynamically favorable charge acceptor level, achieving a 79% enhancement in the photocurrent density compared with that of a conventional liquid electrolyte.”
Immunotherapy’s promise in the fight against cancer drew international attention after two scientists won a Nobel Prize this year for unleashing the ability of the immune system to eliminate tumor cells.
But their approach, which keeps cancer cells from shutting off the immune system’s powerful T-cells before they can fight tumors, is just one way to use the body’s natural defenses against deadly disease. A team of Vanderbilt University bioengineers today announced a major breakthrough in another: penetrating tumor-infiltrating immune cells and flipping on a switch that tells them to start fighting. The team designed a nanoscale particle to do that and found early success using it on human melanoma tissue.
“Tumors are pretty conniving and have evolved many ways to evade detection from our immune system,” said John T. Wilson, assistant professor of chemical and biomolecular engineering and biomedical engineering. “Our goal is to rearm the immune system with the tools it needs to destroy cancer cells. “Checkpoint blockade has been a major breakthrough, but despite the huge impact it continues to have, we also know that there are a lot of patients who don’t respond to these therapies. We’ve developed a nanoparticle to find tumors and deliver a specific type of molecule that’s produced naturally by our bodies to fight off cancer.”
That molecule is called cGAMP, and it’s the primary way to switch on what’s known as the stimulator of interferon genes (STING) pathway: a natural mechanism the body uses to mount an immune response that can fight viruses or bacteria or clear out malignant cells. Wilson said his team’s nanoparticle delivers cGAMP in a way that jump-starts the immune response inside the tumor, resulting in the generation of T-cells that can destroy the tumor from the inside and also improve responses to checkpoint blockade.
While the Vanderbilt team’s research focused on melanoma, their work also indicates that this could impact treatment of many cancers, Wilson said, including breast, kidney, head and neck, neuroblastoma, colorectal and lung cancer.
The findings are reported in the journal Nature Nanotechnology.
Scientists at EPFL and ETH Zurich in Switzerland have developed tiny elastic robots that can change shape depending on their surroundings. Modeled after bacteria and fully biocompatible, these robots optimize their movements so as to get to hard-to-reach areas of the human body. They stand to revolutionize targeted drug delivery.
One day we may be able to ingest tiny robots that deliver drugs directly to diseased tissue, thanks to research being carried out at EPFL and ETH Zurich.
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The robots are modeled after bacteria and fully biocompatible© 2019 EPFL/ ETHZ
The group of scientists – led by Selman Sakar at EPFL and Bradley Nelson at ETH Zurich – drew inspiration from bacteria to design smart, biocompatible microrobots that are highly flexible. Because these devices are able to swim through fluids and modify their shape when needed, they can pass through narrow blood vessels and intricate systems without compromising on speed or maneuverability. They are made of hydrogel nanocomposites that contain magnetic nanoparticles allowing them to be controlled via an electromagnetic field.
In an article appearing in Science Advances, the scientists describe the method they have developed for “programming” the robot’s shape so that it can easily travel through fluids that are dense, viscous or moving at rapid speeds. When we think of robots, we generally think of bulky machines equipped with complex systems of electronics, sensors, batteries and actuators. But on a microscopic scale, robots are entirely different.
Fabricating miniaturized robots presents a host of challenges, which the scientists addressed using an origami-based folding method. Their novel locomotion strategy employs embodied intelligence, which is an alternative to the classical computation paradigm that is performed by embedded electronic systems. “Our robots have a special composition and structure that allow them to adapt to the characteristics of the fluid they are moving through. For instance, if they encounter a change in viscosity or osmotic concentration, they modify their shape to maintain their speed and maneuverability without losing control of the direction of motion,” says Sakar.
These deformations can be “programmed” in advance so as to maximize performance without the use of cumbersome sensors or actuators. The robots can be either controlled using an electromagnetic field or left to navigate on their own through cavities by utilizing fluid flow. Either way, they will automatically morph into the most efficient shape.
Researchers at Queen’s University Belfast have developed a highly innovative new enzyme biomarker test that has the potential to indicate diseases and bacterial contamination saving time, money and possibly lives. The test, developed by scientists at the Institute for Global Food Security at Queen’s, can detect enzyme markers of disease known as proteases in humans, animals and food products.
Proteases are crucial for microorganism growth and are responsible for the progression of many diseases. Levels of proteases can be highly elevated in the urine of patients with diabetic kidney disease, or at the sites of infected wounds. Similarly, in cows, an elevation of proteases in their milk can reveal diseases such as bovine mastitis, a type of mammary gland infection. In food, proteases produced by bacteria contaminated in meat and dairy products can lead to rancidity, as well as decreased shelf life and quality. Current protease detection methods are costly, time-consuming and are not always effective. Scientists at Queen’s Institute for Global Food Security have developed a nanosensor which has resulted in sensitive, fast and cost effective protease detection in milk and urine.
“Not only is the test cheap to produce, but it can be used anywhere and is not reliant on laboratory conditions. Eliminating the need to carry out tests in a laboratory setting is life-changing. As well as being cost-effective, it means faster diagnosis,” says Dr Claire McVey, Queen’s researcher and co-author on the study.
The gold-nanoparticle based nanosensor devised by Queen’s researchers indicates when proteases are present through a visible colour-change reaction. Gold nanoparticles are well known for their capability in speeding up the oxidization of a chemical called tetramethylbenzidine (TMB), visible through a vivid blue-colour formation.
“When we add TMB to the casein-covered gold nanoparticles, we can tell virtually instantly if proteases are present by whether or not the solution turns blue. Normally such testing takes much longer,” explains Dr Cuong Cao, the lead academic on the study.
Using this approach, proteases can be detected within 90 minutes without the need for complicated or expensive laboratory equipment.
The findings have been published in the journal Nano Research,
The British company Bristol Braille Technology is developing Canute 360, the world’s first multi-line digital Braille e-reader. Developed with, by, and for the blind community, Canute 360 will make reading digital Braille books affordable, practical and enjoyable.
Canute 360 is a standalone desktop multi-line Braille e-reader. Compatible with all six-dot Braille codes, Canute 360 can condense an entire Braille library into one device.
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- 360 cells: nine lines of forty characters of Braille
- Supports all six-dot Braille codes (including music, maths and foreign languages) and tactile graphics
- Dimensions: 36.5 X 18.5 X 8 cm (approx 14 x 7 x 1.5 inches), 2.8KG
- 2 X USB A; 1 X USB A; Video out; SD Card slot;
- 3.55mm audio out
- 3 page navigation buttons
- 9 line select keys
- Contextual help button