Posts belonging to Category photonics



Hydrogen Economy Closer

Washington State University (WSU) researchers have found a way to more efficiently generate hydrogen from water — an important key to making clean energy more viable. Using inexpensive nickel and iron, the researchers developed a very simple, five-minute method to create large amounts of a high-quality catalyst required for the chemical reaction to split water.

Energy conversion and storage is a key to the clean energy economy. Because solar and wind sources produce power only intermittently, there is a critical need for ways to store and save the electricity they create. One of the most promising ideas for storing renewable energy is to use the excess electricity generated from renewables to split water into oxygen and hydrogen. Hydrogen has myriad uses in industry and could be used to power hydrogen fuel-cell carsIndustries have not widely used the water splitting process, however, because of the prohibitive cost of the precious metal catalysts that are required – usually platinum or ruthenium. Many of the methods to split water also require too much energy, or the required catalyst materials break down too quickly.

In their work, the researchers, led by professor Yuehe Lin in the School of Mechanical and Materials Engineering, used two abundantly available and cheap metals to create a porous nanofoam that worked better than most catalysts that currently are used, including those made from the precious metals. The catalyst they created looks like a tiny sponge. With its unique atomic structure and many exposed surfaces throughout the material, the nanofoam can catalyze the important reaction with less energy than other catalysts. The catalyst showed very little loss in activity in a 12-hour stability test.

We took a very simple approach that could be used easily in large-scale production,” said Shaofang Fu, a WSU Ph.D. student who synthesized the catalyst and did most of the activity testing. “The advanced materials characterization facility at the national laboratories provided the deep understanding of the composition and structures of the catalysts,” comments Junhua Song, another WSU Ph.D. student who worked on the catalyst characterization.

The findings are described in the journal Nano Energy.

Source: https://news.wsu.edu/

Flat Lens Boost Virtual Reality

Metalensesflat surfaces that use nanostructures to focus light — promise to revolutionize optics by replacing the bulky, curved lenses currently used in optical devices with a simple, flat surface.  But, these metalenses have remained limited in the spectrum of light they can focus well Now a team of researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) has developed the first single lens that can focus the entire visible spectrum of light — including white light — in the same spot and in high resolution. This has only ever been achieved in conventional lenses by stacking multiple lenses.

Focusing the entire visible spectrum and white light – combination of all the colors of the spectrum — is so challenging because each wavelength moves through materials at different speeds. Red wavelengths, for example, will move through glass faster than the blue, so the two colors will reach the same location at different times resulting in different foci. This creates image distortions known as chromatic aberrations.

Cameras and optical instruments use multiple curved lenses of different thicknesses and materials to correct these aberrations, which, of course, adds to the bulk of the device.

Metalenses have advantages over traditional lenses,” says Federico Capasso, Professor of Applied Physics at SEAS and senior author of the research. “Metalenses are thin, easy to fabricate and cost effective. This breakthrough extends those advantages across the whole visible range of light. This is the next big step. Using our achromatic lens, we are able to perform high quality, white light imaging. This brings us one step closer to the goal of incorporating them into common optical devices such as cameras“.

The research is published in Nature Nanotechnology.

Source: https://www.seas.harvard.edu/

Nano-based Chip Detects Explosives

Technical University of Denmark (DTU) is ready with a prototype for a chemical “sniffer system” for the detection of criminal substances like narcotics and explosivesDogs have an eminent sense of smell. Their snouts use a specific sniffing technique which almost grabs hold of scents. Elephants’ snouts are even better than those of dogs, but obviously these are attached to elephants which are difficult to carry around. Consequently, today dogs are employed to track narcotics, money and explosives. Sometimes dogs are able to sense explosives in very small doses, however, they are not always 100 percent reliable as they are also sensitive to changes in their surroundings. A technological solution is therefore to be preferred in the tracking of stocks of narcotics or explosive materials.

Researchers at DTU have developed the prototype of a chip able to sniff molecular structures from a number of known substances. A special camera visualises the results from the chip (with 24 megapixels per 15 second) and newly developed software interprets these images according to changes in colour (i.e. the difference between two pictures), caused by the impact of the scents in the air.

We have conducted experiments by sucking air from smaller containers like e.g. handbags or pieces of luggage and from large industrial sized containers typically used for smuggling. In both cases, we arrived at promising results”, says Mogens Havsteen Jakobsen, Senior Researcher at DTU Nanotech.

By using the so-called colorimetric sensing technique, the artificial nose is able to detect different substances like explosives, narcotics, the ripeness of cheese, rotten meat and fish, the quality of wine and coffee or bad indoor climate of a room.

The project has specifically targeted explosives which are a growing safety risk in our society. The Chemical Division of the Danish Emergency Management Agency has been an important collaborator because they are authorised to produce and handle explosives. “We have test laboratories which have been made available during the course of the project”, says Jesper Mogensen, civil engineer and analysis chemist at the Chemical Division and therefore used to handling explosives.

There will be some evident advantages in using a technology such as CRIM-TRACK, compared to the instruments available today,” Jesper Mogensen says. “Firstly, the preparation time is short in that what you largely need to do is switch on the tracker and use it. This is valuable time saved. Secondly and perhaps the most important advantage is the fact that the EOD (the Explosive Ordnance Disposal) does not need to collect a sample. Today when we are called to a ransacking if e.g. a kilo of white powder has been found and we have to analyse its chemistry by way of GC-MS (i.e. gas chromatography-mass spectrometry), a sample of the substance must be collected on a fibre. In other words, it is necessary to collect physically a sample with all the risks this entails. With DTU’s sniffer system, it is possible to collect samples in the air. It sniffs for the drug much like a dog and indicates whether there are any explosives or not. This will increase the safety of our EOD”.

Source: http://www.nanotech.dtu.dk/

How To Store Solar Energy In A Non-Electric Battery

Materials chemists have been trying for years to make a new type of battery that can store solar or other light-sourced energy in chemical bonds rather than electrons, one that will release the energy on demand as heat instead of electricity–addressing the need for long-term, stable, efficient storage of solar power.

Now a group of materials chemists at the University of Massachusetts Amherst led by Dhandapani Venkataraman, with Ph.D. student and first author Seung Pyo Jeong, Ph.D. students Larry Renna, Connor Boyle and others, report that they have solved one of the major hurdles in the field by developing a polymer-based system. It can yield energy storage density – the amount of energy stored – more than two times higher than previous polymer systems. Details appear in the current issue of Scientific Reports.

Venkataraman and Boyle say that previous high energy storage density achieved in a polymeric system was in the range of 200 Joules per gram, while their new system is able to reach an average of 510 Joules per gram, with a maximum of 690. Venkataraman says, “Theory says that we should be able to achieve 800 Joules per gram, but nobody could do it. This paper reports that we’ve reached one of the highest energy densities stored per gram in a polymeric system, and how we did it.”

Source: https://www.umass.edu/

Lenses Provide Nano Scale X-ray Microscopy

Scientists at DESY (Germany) have developed novel lenses that enable X-ray microscopy with record resolution in the nanometre regime. Using new materials, the research team led by DESY scientist Saša Bajt from the Center for Free-Electron Laser Science (CFEL) has perfected the design of specialised X-ray optics and achieved a focus spot size with a diameter of less than ten nanometres. A nanometre is a millionths of a millimetre and is smaller than most virus particles. They successfully used their lenses to image samples of marine plankton.

Modern particle accelerators provide ultra-bright and high-quality X-ray beams. The short wavelength and the penetrating nature of X-rays are ideal for the microscopic investigation of complex materials. However, taking full advantage of these properties requires highly efficient and almost perfect optics in the X-ray regime. Despite extensive efforts worldwide this turned out to be more difficult than expected, and achieving an X-ray microscope that can resolve features smaller than 10 nm is still a big challenge.

 

The silica shell of the diatom Actinoptychus senarius, measuring only 0.1 mm across, is revealed in fine detail in this X-ray hologram recorded at 5000-fold magnification with the new lenses. The lenses focused an X-ray beam to a spot of approximately eight nanometres diameter – smaller than a single virus – which then expanded to illuminate the diatom and form the hologram

The new lenses consist of over 10 000 alternating layers of a new material combination, tungsten carbide and silicon carbide. “The selection of the right material pair was critical for the success,” emphasises Bajt. “It does not exclude other material combinations but it is definitely the best we know now.” The resolution of the new lenses is about five times better than achievable with typical state-of-the-art lenses.

We produced the world’s smallest X-ray focus using high efficiency lenses,” says Bajt. The new lenses have an efficiency of more than 80 per cent. This high efficiency is achieved with the layered structures that make up the lens and which act like an artificial crystal to diffract X-rays in a controlled way.

The researchers have reported their work in the journal Light: Science and Applications.

Source: http://www.desy.de/

Nanotechnology Boosts CyberSecurity Against Hackers

The next generation of electronic hardware security may be at hand as researchers at New York University Tandon School of Engineering  (NYU Tandon) introduce a new class of unclonable cybersecurity security primitives made of a low-cost nanomaterial with the highest possible level of structural randomness. Randomness is highly desirable for constructing the security primitives that encrypt and thereby secure computer hardware and data physically, rather than by programming.

In a paper published in the journal ACS Nano, Assistant Professor of Electrical and Computer Engineering Davood Shahrjerdi and his team at NYU Tandon offer the first proof of complete spatial randomness in atomically thin molybdenum disulfide (MoS2). The researchers grew the nanomaterial in layers, each roughly one million times thinner than a human hair. By varying the thickness of each layer, Shahrjerdi explained, they tuned the size and type of energy band structure, which in turn affects the properties of the material.

(a) At monolayer thickness, this material has the optical properties of a semiconductor that emits light. At multilayer, the properties change and the material doesn’t emit light. (b) Varying the thickness of each layer results in a thin film speckled with randomly occurring regions that alternately emit or block light. (c) Upon exposure to light, this pattern can be translated into a one-of-a-kind authentication key that could secure hardware components at minimal cost.

This property is unique to this material,” underscores Shahrjerdi. By tuning the material growth process, the resulting thin film is speckled with randomly occurring regions that alternately emit or do not emit light. When exposed to light, this pattern translates into a one-of-a-kind authentication key that could secure hardware components at minimal cost.

Source: http://engineering.nyu.edu/

Glass Blocks Generate Electricity Using Solar Energy

Buildings consume more than forty percent of global electricity and reportedly cause at least a third of carbon emissions. Scientists want to cut this drastically – and create a net-zero energy future for new buildings. Build Solar want to help. The firm has created a glass brick containing small solar cells.

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On top of this we have placed in some intelligent optics which are able to focus the incoming sunlight onto these solar cells almost throughout the day. When we do that we are able to generate a higher amount of electrical output from each solar cell that we are using,” says Dr Hasan Baig, founder of Build Solar.
As well as converting the sun’s power to electricity, the bricks have other abilities.
The product is aligned to provide three different things, including electricity, daylighting, and thermal insulation which is generally required by any kind of construction product. More importantly it is aesthetic in its look, so it fits in very well within the building architecture,” adds Dr Baig.
Using Building Integrated Photovoltaics, the technology would be used in addition to existing solar roof panels. The University of Exeter spin-off is fine-tuning the design, which works in many colours. The company says the product could be market ready by the end of next year.

Source: https://www.buildsolar.co.uk/

Graphene Ripples, Clean And Limitless Energy Source

Graphene is a seemingly impossible material. For years, scientists had theorized that lifting a single layer of carbon atoms from a chunk of graphite could produce the first two-dimensional material, which they called graphene. Finally, in 2004, this was accomplished by two physicists at the University of Manchester, who earned the Nobel Prize in Physics for this breakthrough. There was a problem, however: two dimensional materials violate the laws of physics. Without the support of a substrate, physics predicts they would tear apart or melt, even at a temperature of absolute zero. Physicists had to find a loophole to explain their existence.

That loophole turned out to be related to a phenomenon known as Brownian motion, small random fluctuations of the carbon atoms that make up graphene. This causes the material to ripple into the third dimension, similar to waves moving across the surface of the ocean. These movements in and out of the flat surface allow graphene to stay comfortably within the laws of physics.

Ever since Robert Brown discovered Brownian motion in 1827, scientists have wondered whether they could harvest this motion as a source of energy. The research of Paul Thibado, professor of physics at the University of Arkansas, provides strong evidence that the motion of graphene could indeed be used as a source of clean, limitless energy. Other researchers have theorized that temperature-induced curvature inversion in graphene could be used as an energy source, and even predicted the amount of energy they could produce. What sets Thibado’s work apart is his discovery that graphene has naturally occurring ripples that invert their curvature as the atoms vibrate in response to the ambient temperature.

This is the key to using the motion of 2D materials as a source of harvestable energy,” Thibado said. Unlike atoms in a liquid, which move in a random directions, atoms connected in a sheet of graphene move together. This means their energy can be collected using existing nanotechnology.

These results have been published in the journal Physical Review Letters.

Source: https://researchfrontiers.uark.edu

Printed 3D Nanostructures Against Counterfeiting

Security features are to protect bank notes, documents, and branded products against counterfeiting. Losses caused by product forgery and counterfeiting may be enormous. According to the German Engineering Association, the damage caused in 2016 in its branch alone amounted to EUR 7.3 billion. In the Advanced Materials Technologies journal, researchers of Karlsruhe Institute of Technology (KIT) and the ZEISS company now propose to use printed 3D microstructures instead of 2D structures, such as holograms, to improve counterfeit protection.

Today, optical security features, such as holograms, are frequently based on two-dimensional microstructures,” says Professor Martin Wegener, expert for 3D printing of microstructures at the Institute of Nanotechnology of KIT. “By using 3D-printed fluorescent microstructures, counterfeit protection can be increased.” The new security features have a side length of about 100 µm and are barely visible with the eye or a conventional microscope. For their production and application, Wegener and his team have developed an innovative method that covers all processes from microstructure fabrication to the readout of information.

The microstructures consist of a 3D cross-grid scaffold and dots that fluoresce in different colors and can be arranged variably in three dimensions within this grid. To produce and print such microstructures, the experts use a rapid and precise laser lithography device developed and commercialized by the Nanoscribe company, a spinoff of KIT. It enables highly precise manufacture of voluminous structures of a few millimeters edge length or of microstructured surfaces of several cm² in dimension. The special 3D printer produces the structures layer by layer from non-fluorescent and two fluorescent photoresists. A laser beam very precisely passes certain points of the liquid photoresist. The material is exposed and hardened at the focus point of the laser beam. The resulting filigree structure is then embedded in a transparent polymer in order to protect it against damage.

Source: http://www.kit.edu/

How To Use Computers Heat To Generate Electricity

Electronic devices such as computers generate heat that mostly goes to waste. Physicists at Bielefeld University (Germany) have found a way to use this energy: They apply the heat to generate magnetic signals known as ‘spin currents’. In future, these signals could replace some of the electrical current in electronic components. In a new study, the physicists tested which materials can generate this spin current most effectively from heat. The research was carried out in cooperation with colleagues from the University of Greifswald, Gießen University, and the Leibniz Institute for Solid State and Materials Research in Dresden.

The Bielefeld physicists are working on the basic principles for making data processing more effective and energy-efficient in the young field of ‘spin caloritronics’. They are members of the ‘Thin Films & Physics of Nanostructures’ research group headed by Professor Dr. Günter Reiss. Their new study determines the strength of the spin current for various combinations of thin films.

A spin current is produced by differences in temperature between two ends of an electronic component. These components are extremely small and only one millionth of a millimetre thick. Because they are composed of magnetic materials such as iron, cobalt, or nickel, they are called magnetic nanostructures.

The physicists take two such nanofilms and place a layer of metal oxide between them that is only a few atoms thick. They heat up one of the external films – for example, with a hot nanowire or a focused laser. Electrons with a specific spin orientation then pass through the metal oxide. This produces the spin current. A spin can be conceived as electrons spinning on their own axes – either clockwise or anti-clockwise.

Their findings have been  published  in the research journal ‘Nature Communications’.

Source: https://ekvv.uni-bielefeld.de/

Invisible Glass

If you have ever watched television in anything but total darkness, used a computer while sitting underneath overhead lighting or near a window, or taken a photo outside on a sunny day with your smartphone, you have experienced a major nuisance of modern display screens: glare. Most of today’s electronics devices are equipped with glass or plastic covers for protection against dust, moisture, and other environmental contaminants, but light reflection from these surfaces can make information displayed on the screens difficult to see. Now, scientists at the Center for Functional Nanomaterials (CFN) — a U.S. Department of Energy Office of Science User Facility at Brookhaven National Laboratory — have demonstrated a method for reducing the surface reflections from glass surfaces to nearly zero by etching tiny nanoscale features into them.

Whenever light encounters an abrupt change in refractive index (how much a ray of light bends as it crosses from one material to another, such as between air and glass), a portion of the light is reflected. The nanoscale features have the effect of making the refractive index change gradually from that of air to that of glass, thereby avoiding reflections. The ultra-transparent nanotextured glass is antireflective over a broad wavelength range (the entire visible and near-infrared spectrum) and across a wide range of viewing angles. Reflections are reduced so much that the glass essentially becomes invisible.

This “invisible glass” could do more than improve the user experience for consumer electronic displays. It could enhance the energy-conversion efficiency of solar cells by minimizing the amount of sunlight lost to refection. It could also be a promising alternative to the damage-prone antireflective coatings conventionally used in lasers that emit powerful pulses of light, such as those applied to the manufacture of medical devices and aerospace components.

We’re excited about the possibilities,” said CFN Director Charles Black, corresponding author on the paper published online on October 30 in Applied Physics Letters. “Not only is the performance of these nanostructured materials extremely high, but we’re also implementing ideas from nanoscience in a manner that we believe is conducive to large-scale manufacturing.”

Our role in the CFN is to demonstrate how nanoscience can facilitate the design of new materials with improved properties,” concluded Black. “This work is a great example of that–we’d love to find a partner to help advance these remarkable materials toward technology.”

Source: https://www.eurekalert.org/

Using Brain-Machine Interfaces, Mental Power Can Move Objects

A unique citizen science project in which volunteers will be trained to move a piece of steel machinery using the power of their mind begins on October 27. The Mental Work project uses brain-machine interfaces developed at EPFL (Ecole polytechnique fédérale de Lausanne) in Switzerland, a convergence of science, art, and design .

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At the mental work factory the public can come and we equip them with an EEG helmet which will read the mental activity, the electrical activity, that’s in their brain. These helmets are dry, so we don’t need gel for conductivity and they’re also wireless so they can walk through the mental factory and engage with four of our machines activating them with only their mental activity,  explains Michael Mitchell , who is one of the three co-founders of Mental Work.

The data that will be collected during the mental worker’s trajectory throughout our factory floor will then be made anonymous and given to the brain machine interface community to improve the interfaces for the future. “We think that we’re on the cusp of a cognitive revolution. Now a cognitive revolution is going to be a world where our brains are intimately connected to our physical world around us. With the development of these brain machine interfaces we think that we are really at the beginning of a moment in time where man is going to become the centre of all this technology. His brain activity is going to interact with the physical world around him in ways that we can hardly imagine today. “So I think it’s understandable if people are a little apprehensive about this technology because some people may think ‘oh, it can read my thoughts and then what are we going to do with those thoughts. Where’s the privacy level here?’ But in fact we’re only asking you to modulate your brain activity according to your own will. So it’s as simple as sending a command to a computer using a mouse or a keyboard. But this time we’re using asking you to use your brain. Now we want to bring this technology to the public at a early phase of its development so that we can create a dialogue about what kind of relationship we want to have with this technology in particular but also with man’s relationship to technology in general.

Source: https://actu.epfl.ch/