Articles from March 2014

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.

We 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.

Left: 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.

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.

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.

The 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“.


Ear: How To Tune In To A Single Voice

Even in a crowded room full of background noise, the human ear is remarkably adept at tuning in to a single voice — a feat that has proved remarkably difficult for computers to match. A new analysis of the underlying mechanisms, conducted by researchers at MIT, has provided insights that could ultimately lead to better machine hearing, and perhaps to better hearing aids as well.

Our ears’ selectivity, it turns out, arises from evolution’s precise tuning of a tiny membrane, inside the inner ear, called the tectorial membrane. The viscosity of this membrane — its firmness, or lack thereof — depends on the size and distribution of tiny pores, just a few tens of nanometers wide. This, in turn, provides mechanical filtering that helps to sort out specific sounds.
This optical microscope image depicts wave motion in a cross-section of the tectorial membrane, part of the inner ear. This membrane is a microscale gel, smaller in width than a single human hair, and it plays a key role in stimulating sensory receptors of the inner ear. Waves traveling on this membrane control our ability to separate sounds of varying pitch and intensity
The new findings are reported in the Biophysical Journal.

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.

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.


How to Observe Neurons In The Brain

The term a “brighter future” might be a cliché, but in the case of ultra-small probes for lighting up individual proteins, it is now most appropriate. Researchers at the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) have discovered surprising new rules for creating ultra-bright light-emitting crystals that are less than 10 nanometers in diameter. These ultra-tiny but ultra-bright nanoprobes should be a big asset for biological imaging, especially deep-tissue optical imaging of neurons in the brain.

Working at the Molecular Foundry, a DOE national nanoscience center hosted at Berkeley Lab, a multidisciplinary team of researchers led by James Schuck and Bruce Cohen, both with Berkeley Lab’s Materials Sciences Division, used advanced single-particle characterization and theoretical modeling to study what are known as “upconverting nanoparticles” or UCNPs. Upconversion is the process by which a molecule absorbs two or more photons at a lower energy and emits them at higher energies.

Researchers at Berkeley Lab’s Molecular Foundry created upconverting nanoparticles (UCNPs) from nanocrystals of sodium yttrium fluoride (NaYF4) doped with ytterbium and erbium that can be safely used to image single proteins in a cell without disrupting the protein’s activity

The widely accepted conventional wisdom for designing bright UCNPs has been that you want to use a high concentration of sensitizer ions and a relatively small concentration of emitter ions, since too many emitters will result in self-quenching that leads to lower brightness, says Schuck, who directs the Molecular Foundry’s Imaging and Manipulation of Nanostructures Facility.

Schuck and Cohen are the corresponding authors of a paper describing this research in Nature Nanotechnology.

Has The Milk Turned Sour?

A color-coded smart tag could tell consumers whether a carton of milk has turned sour or a can of green beans has spoiled without opening the containers, according to researchers. The tag, which would appear on the packaging, also could be used to determine if medications and other perishable products were still active or fresh, they said. This report on the color-changing food deterioration tags was presented today as part of the 247th National Meeting & Exposition of the American Chemical Society (ACS). It is being held at the Dallas Convention Center.

The green smart tag on the bottle above indicates that the product is no longer fresh
This tag, which has a gel-like consistency, is really inexpensive and safe, and can be widely programmed to mimic almost all ambient-temperature deterioration processes in foods,” said Chao Zhang, Ph.D., the lead researcher of the study. Use of the tags could potentially solve the problem of knowing how fresh packaged, perishable foods remain over time, he added. And a real advantage, Zhang said, is that even when manufacturers, grocery-store owners and consumers do not know if the food has been unduly exposed to higher temperatures, which could cause unexpected spoilage, “the tag still gives a reliable indication of the quality of the product.”

Nanoparticles Attack Cervical Cancer

Infection with the human papillomavirus (HPV) is the main risk factor and a necessary cause of cervical cancer. Worldwide, around 275,000 women are estimated to have died from cervical cancer last year. It is rare for young women to die from cervical cancer; almost three-quarters of all cervical cancer deaths occur in women aged 50 and over. To underscore: cervical cancer death rates have decreased by 71% since the early 1970s.
One of the most promising technologies for the treatment of various cancers is nanotechnology, creating drugs that directly attack the cancer cells without damaging other tissues’ development. The Laboratory of Cellular Oncology at the Research Unit in Cell Differentiation and Cancer, of the Faculty of Higher Studies (FES) Zaragoza UNAM (National Autonomous University of Mexico) developed a therapy to attack cervical cancer tumors.

The treatment, which has been tested in animal models, consists of a nanostructured composition encapsulating a protein called interleukin-2 (IL -2), lethal to cancer cells

According to the researcher Rosalva Rangel Corona, head of the project, the antitumor effect of interleukin in cervical cancer is because their cells express receptors for interleukin-2 that “fit together ” like puzzle pieces with the protein to activate an antitumor response .

The scientist explains that the nanoparticle works as a bridge of antitumor activation between tumor cells and T lymphocytes. The nanoparticle has interleukin 2 on its surface, so when the protein is around it acts as a switch, a contact with the cancer cell to bind to the receptor and to carry out its biological action.

Furthermore, the nanoparticle concentrates interleukin 2 in the tumor site, which allows its accumulation near the tumor growth. It is not circulating in the blood stream, is “out there” in action.


Bigger DNA Cages Enclose Drugs

Scientists at the Harvard’s Wyss Institute have built a set of self-assembling DNA cages one-tenth as wide as a bacterium. The structures are some of the largest and most complex ever constructed solely from DNA. DNA is best known as a keeper of genetic information. But scientists in the emerging field of DNA nanotechnology are exploring ways to use it to build tiny structures for a variety of applications. . In the future, scientists could potentially coat the DNA cages to enclose their contents, packaging drugs for delivery to tissues. And, like a roomy closet, the cage could be modified with chemical hooks that could be used to hang other components such as proteins or gold nanoparticles. This could help scientists build a variety of technologies, including tiny power plants, miniscule factories that produce specialty chemicals, or high-sensitivity photonic sensors that diagnose disease by detecting molecules produced by abnormal tissue.

The five cage-shaped DNA polyhedra here have struts stabilizing their legs, and this innovation allowed a Wyss Institute team to build by far the largest and sturdiest DNA cages yet. The largest, a hexagonal prism (right), is one-tenth the size of an average bacterium
Bioengineers interested in advancing the field of nanotechnology need to devise manufacturing methods that build sturdy components in a highly robust manner, and develop self-assembly methods that enable formation of nanoscale devices with defined structures and functions,” said Wyss Institute Founding Director Don Ingber, M.D., Ph.D. “DNA cages and the methods for visualizing the process in solution represent major advances along this path.”

I see exciting possibilities for this technology,” said Peng Yin, Ph.D., a Core Faculty member at the Wyss Institute and Assistant Professor of Systems Biology at Harvard Medical School, and senior author of the study.

The findings have been published in the online edition of Science.