Posts belonging to Category Universities

A Step Towards Invisibility

Controlling and bending light around an object so it appears invisible to the naked eye is the theory behind fictional invisibility cloaks. It may seem easy in Hollywood movies, but is hard to create in real life because no material in nature has the properties necessary to bend light in such a way. Scientists have managed to create artificial nanostructures that can do the job, called metamaterials. But the challenge has been making enough of the material to turn science fiction into a practical reality. The work of Debashis Chanda at the University of Central Florida (UCF), however, may have just cracked that barrier. The cover story in the March edition of the journal Advanced Optical Materials, explains how Chanda and fellow optical and nanotech experts were able to develop a larger swath of multilayer 3-D metamaterial operating in the visible spectral range. They accomplished this feat by using nanotransfer printing, which can potentially be engineered to modify surrounding refractive index needed for controlling propagation of light.

Such large-area fabrication of metamaterials following a simple printing technique will enable realization of novel devices based on engineered optical responses at the nanoscale,” said Chanda, an assistant professor at UCF.

Stealth aricraft
By improving the technique, the team hopes to be able to create larger pieces of the material with engineered optical properties, which would make it practical to produce for real-life device applications. For example, the team could develop large-area metamaterial absorbers, which would enable fighter jets to remain invisible from detection systems.


How To Measure Risks From Nanomaterials In Contact With Cells

Scientists at the Center for Nanotechnology and Nanotoxicology at Harvard School of Public Health (HSPH) have discovered a fast, simple, and inexpensive method to measure the effective density of engineered nanoparticles in physiological fluids, thereby making it possible to accurately determine the amount of nanomaterials that come into contact with cells and tissue in culture. The new discovery will have a major impact on the hazard assessment of engineered nanoparticles, enabling risk assessors to perform accurate hazard rankings of nanomaterials using cellular systems. Furthermore, by measuring the composition of nanomaterial agglomerates in physiologic fluids, it will allow scientists to design more effective nano-based drug delivery systems for nanomedicine applications.
nanohazardThousands of consumer products containing engineered nanoparticles — microscopic particles found in everyday items from cosmetics and clothing to building materials — enter the market every year. Concerns about possible environmental health and safety issues of these nano-enabled products continue to grow with scientists struggling to come up with fast, cheap, and easy-to-use cellular screening systems to determine possible hazards of vast libraries of engineered nanomaterials. However, determining how much exposure to engineered nanoparticles could be unsafe for humans requires precise knowledge of the amount (dose) of nanomaterials interacting with cells and tissues such as lungs and skin

The biggest challenge we have in assessing possible health effects associated with nano exposures is deciding when something is hazardous and when it is not, based on the dose level. At low levels, the risks are probably miniscule,” said senior author Philip Demokritou, associate professor of aerosol physics in the Department of Environmental Health at HSPH. “The question is: At what dose level does nano-exposure become problematic? The same question applies to nano-based drugs when we test their efficiency using cellular systems. How much of the administered nano-drug will come in contact with cells and tissue? This will determine the effective dose needed for a given cellular response,” Demokritou said.


Cheap Batteries Last 3 Times Longer, Recharge in 10 minutes

Researchers at the University of Southernn California (USC) have developed a new lithium-ion battery design that uses porous silicon nanoparticles in place of the traditional graphite anodes to provide superior performance.

The new batteries — which could be used in anything from cellphones to hybrid cars — hold three times as much energy as comparable graphite-based designs and recharge within 10 minutes. The design, currently under a provisional patent, could be commercially available within two to three years.
silicon nanoparticlesOn the left, a vial of the silicon nanoparticles; on the right, silicon nanoparticles viewed under magnification
It’s an exciting research. It opens the door for the design of the next generation lithium-ion batteries,” said Chongwu Zhou, professor at the USC Viterbi School of Engineering, who led the team that developed the battery.

Zhou worked with USC graduate students Mingyuan Ge, Jiepeng Rong, Xin Fang and Anyi Zhang, as well as Yunhao Lu of Zhejiang University in China. Their research was published in Nano Research in January.


Contact Lens To See During Night

The first room-temperature light detector that can sense the full infrared spectrum has the potential to put heat vision technology into a contact lens. Unlike comparable mid- and far-infrared detectors currently on the market, the detector developed by University of Michigan engineering researchers doesn’t need bulky cooling equipment to work. Infrared vision may be best known for spotting people and animals in the dark and heat leaks in houses, but it can also help doctors monitor blood flow, identify chemicals in the environment and allow art historians to see Paul Gauguin’s sketches under layers of paint. Graphene, a single layer of carbon atoms, could sense the whole infrared spectrum — plus visible and ultraviolet light. But until now, it hasn’t been viable for infrared detection because it can’t capture enough light to generate a detectable electrical signal. With one-atom thickness, it only absorbs about 2.3 percent of the light that hits it. If the light can’t produce an electrical signal, graphene can’t be used as a sensor.
To overcome that hurdle, Zhong and Ted Norris, the Gerard A. Mourou Professor of Electrical Engineering and Computer Science, worked with graduate students to design a new way of generating the electrical signal.

infra red night visionWe can make the entire design super-thin,” said Zhaohui Zhong, assistant professor of electrical and computer engineering. “It can be stacked on a contact lens or integrated with a cell phone.
The challenge for the current generation of graphene-based detectors is that their sensitivity is typically very poor.”It’s a hundred to a thousand times lower than what a commercial device would require.” “Our work pioneered a new way to detect light“. “We envision that people will be able to adopt this same mechanism in other material and device platforms” Zhong said.

The device is already smaller than a pinky nail and is easily scaled down. Zhong suggests arrays of them as infrared cameras.


Watch Nanoparticles Grow

Danish scientists from Arhus University – Netherlands – , led by Dr. Dipanka Saha, have observed the growth of nanoparticles live. To obtain this result, the team used the DESY’s X-ray light source PETRA III, a German Synchrotron. The study shows how tungsten oxide nanoparticles are forming from solution. These particles are used for example for smart windows, which become opaque at the flick of a switch, and they are also used in particular solar cells.

watch nanoparticles growLeft: Structure of the ammonium metatungstate dissolved in water on atomic length scale. The octahedra consisting of the tungsten ion in the centre and the six surrounding oxygen ions partly share corners and edges. Right: Structure of the nanoparticles in the ordered crystalline phase. The octahedra exclusively share corners

The team around lead author Dr. Dipankar Saha from Århus University present their observations in the scientific journal “Angewandte Chemie – International Edition“.

Flexible E-readers In Your Pocket

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 has developed a process to create flexible chips that can tolerate power fluctuations in much the same way as silicon circuitry.
bendable smartphone
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.

Huiliang (Evan) Wang, a graduate student in Bao’s lab, and Peng Wei, a previous postdoctoral scholar in Bao’s lab, were the lead authors of the paper. Bao’s team also included Yi Cui, an associate professor of materials science at Stanford, and Hye Ryoung Lee, a graduate student in his lab.
The Bao Lab reported its findings in the Proceedings of the National Academy of Sciences.


How To Detect Infections At Extremely Low Cost

Detecting HIV/AIDS, tuberculosis, malaria and other deadly infectious diseases as early as possible helps to prevent their rapid spread and allows for more effective treatments. But current detection methods are cost-prohibitive in most areas of the world. Now a new nanotechnology method—employing common, everyday shrink wrap— may make highly sensitive, extremely low-cost diagnosis of infectious disease agents possible. The research team conducted by co-author Michelle Khine, a biomedical engineering professor at the University of California, Irvine (UC Irvine) found that the shrink wrap’s wrinkles significantly enhanced the intensity of the signals emitted by the biomarkers. The enhanced emission, Khine says, is due to the excitation of localized surface plasmons—coherent oscillations of the free electrons in the metal. When researchers shined a light on their wrinkled creation, the electromagnetic field was amplified within the nanoscale gaps between the shrink wrap’s folds, Khine said. This produced “hotspots”—areas characterized by sudden bursts of intense fluorescence signals from the biomarkers.

Using commodity shrink wrap and bulk manufacturing processes, we can make low-cost nanostructures to enable fluorescence enhancements greater than a thousand-fold, allowing for significantly lower limits of detection,” said Michelle Khine,. “If you have a solution with very few molecules that you are trying to detect—as in the case of infectious diseases — this platform will help amplify the signal so that a single molecule can be detected.The technique should work with measuring fluorescent markers in biological samples, but we have not yet tested bodily fluids,” said Khine, who cautions that the technique is far from ready for clinical use.

The findings have been described in a paper published in The Optical Society’s (OSA) journal Optical Materials Express.


Use Your Smartphone As A Movies Projector

Imagine that you are in a meeting with coworkers or at a gathering of friends. You pull out your cell phone to show a presentation or a video on YouTube. But you don’t use the tiny screen; your phone projects a bright, clear image onto a wall or a big screen. Such a technology may be on its way, thanks to a new light-bending silicon chip developed by researchers at Caltech.

The chip was developed by Ali Hajimiri, Thomas G. Myers Professor of Electrical Engineering, and researchers in his laboratory. The results were presented at the Optical Fiber Communication (OFC) conference in San Francisco on March 10.

Traditional projectors—like those used to project a film or classroom lecture notes—pass a beam of light through a tiny image, using lenses to map each point of the small picture to corresponding, yet expanded, points on a large screen. The Caltech chip eliminates the need for bulky and expensive lenses and bulbs and instead uses a so-called integrated optical phased array (OPA) to project the image electronically with only a single laser diode as light source and no mechanically moving parts.

Hajimiri and his colleagues were able to bypass traditional optics by manipulating the coherence of light — a property that allows the researchers to “bend” the light waves on the surface of the chip without lenses or the use of any mechanical movement. If two waves are coherent in the direction of propagation — meaning that the peaks and troughs of one wave are exactly aligned with those of the second wave—the waves combine, resulting in one wave, a beam with twice the amplitude and four times the energy as the initial wave, moving in the direction of the coherent waves.

bending the light Caltech

By changing the relative timing of the waves, you can change the direction of the light beam
For example, if 10 people kneeling in line by a swimming pool slap the water at the exact same instant, they will make one big wave that travels directly away from them. But if the 10 separate slaps are staggered—each person hitting the water a half a second after the last — there will still be one big, combined wave, but with the wave bending to travel at an angle, says Hajimiri.


How To Triple Service Life Of Aircraft Engines

Researchers at University West in Sweden have started using nanoparticles in the heat-insulating surface layer that protects aircraft engines from heat. In tests, this increased the service life of the coating by 300%. This is something that interests the aircraft industry to a very great degree, and the hope is that motors with the new layers will be in production within two years.

To increase the service life of aircraft engines, a heat-insulating surface layer is sprayed on top of the metal components. Thanks to this extra layer, the engine is shielded from heat. The temperature can also be raised, which leads to increased efficiency, reduced emissions, and decreased fuel consumption.

The goal of the University West research group is to be able to control the structure of the surface layer in order to increase its service life and insulating capability. They have used different materials in their work.

A350 AirbusThe ceramic layer is subjected to great stress when the enormous changes in temperature make the material alternately expand and contract. Making the layer elastic is therefore important. Over the last few years, the researchers have focused on further refining the microstructure, all so that the layer will be of interest for the industry to use

The base is a ceramic powder, but we have also tested adding plastic to generate pores that make the material more elastic,” says Nicholas Curry, who has just presented his doctoral thesis on the subject.

We have tested the use of a layer that is formed from nanoparticles. The particles are so fine that we aren’t able to spray the powder directly onto a surface. Instead, we first mix the powder with a liquid that is then sprayed. This is called suspension plasma spray application“.


Solar Cells: Huge Efficiency Boost

In a new study, a team of physicists and chemists at Umeå University – Sweden – have joined forces to produce nano-engineered carbon nanotubes networks with novel properties.
For the first time, the researchers show that carbon nanotubes can be engineered into complex network architectures, and with controlled nano-scale dimensions inside a polymer matrix.
Carbon nanotubes are becoming increasingly attractive for photovoltaic solar cells as a replacement to silicon. Researchers at Umeå University have discovered that controlled placement of the carbon nanotubes into nano-structures produces a huge boost in electronic performance.

solar cells
Carbon nanotubes, CNTs, are one dimensional nanoscale cylinders made of carbon atoms that possess very unique properties. For example, they have very high tensile strength and exceptional electron mobility, which make them very attractive for the next generation of organic and carbon-based electronic devices
We have found that the resulting nano networks possess exceptional ability to transport charges, up to 100 million times higher than previously measured carbon nanotube random networks produced by conventional methods,” says Dr David Barbero, leader of the project and assistant professor at the Department of Physics at Umeå University.

Their groundbreaking results are published in the prestigious journal Advanced Materials.