Light replaces electricity through metatronics

The technological world of the 21^st century owes a tremendous amount to advances in electrical engineering, specifically, the ability to finely control the flow of electrical charges using increasingly small and complicated circuits. And while those electrical advances continue to race ahead, researchers at the University of Pennsylvania are pushing circuitry forward in a different way, by replacing electricity with light.

Different arrangements and combinations of electronic circuits have different functions, ranging from simple light switches to complex supercomputers. These circuits are built of different arrangements of circuit elements, for example resistors, inductors and capacitors, which manipulate the flow of electrons in a circuit in mathematically precise ways.

Now, researchers at Penn have created the first physical demonstration of lumped optical circuit elements. This represents a milestone in a nascent field of science and engineering. In electronics, the lumped designation refers to elements that can be treated as a black box, something that turns a given input to a perfectly predictable output without an engineer having to worry about what exactly is going on inside the element. Optics has always had its own set of elements, things like lenses, waveguides and gratings, but they were never lumped. Those elements are all much larger than the wavelength of light because that's all that could be easily built in the old days. For electronics, the lumped circuit elements were always much smaller than the wavelength of operation, which is in the radio or microwave frequency range.

 Nanotechnology has now opened that possibility for lumped optical circuit elements, allowing construction of structures that have dimensions measured in nanometers. In this experiment's case, the structure was comb-like arrays of rectangular nanorods made of silicon nitrite.

 The "meta" in "metatronics" refers to metamaterials, the relatively new field of research where nanoscale patterns and structures embedded in materials allow them to manipulate waves in ways that were previously impossible. Here, the cross-sections of the nanorods and the gaps between them form a pattern that replicates the function of resistors, inductors and capacitors, three of the most basic circuit elements, but in optical wavelengths.

 In their experiment, the researchers illuminated the nanorods with an optical signal, a wave of light in the mid-infrared range. They then used spectroscopy to measure the wave as it passed through the comb. Repeating the experiment using nanorods with nine different combinations of widths and heights, the researchers showed that the optical current and optical voltage were altered by the optical resistors, inductors and capacitors with parameters corresponding to those differences in size.

A section of the nanorod acts as both an inductor and resistor, and the air gap acts as a capacitor.

 Beyond changing the dimensions and the material the nanorods are made of, the function of these optical circuits can be altered by changing the orientation of the light, giving metatronic circuits access to configurations that would be impossible in traditional electronics. This is because a light wave has polarizations; the electric field that oscillates in the wave has a definable orientation in space. In metatronics, it is that electric field that interacts and is changed by elements, so changing the field's orientation can be like rewiring an electric circuit.

 When the plane of the field is in line with the nanorods, the circuit is wired in parallel and the current passes through the elements simultaneously. When the plane of the electric field crosses both the nanorods and the gaps, the circuit is wired in series and the current passes through the elements sequentially.

This principle could be taken to an even higher level of complexity by building nanorod arrays in three dimensions. An optical signal hitting such a structure's top would encounter a different circuit than a signal hitting its side. Another reason for success in electronics has to do with its modularity.

Smallest transistor ever built: New Beginning of Quantum Computing

The smallest transistor has been created using a single phosphorus atom by an international team of researchers at the University of New South Wales, Purdue University and the University of Melbourne.

Michelle Simmons, group leader and director of the ARC Centre for Quantum Computation and Communication at the University of New South Wales, says the development is less about improving current technology than building future tech.

This is a beautiful demonstration of controlling matter at the atomic scale to make a real device, Simmons says. "Fifty years ago when the first transistor was developed, no one could have predicted the role that computers would play in our society today. As we transition to atomic-scale devices, we are now entering a new paradigm where quantum mechanics promises a similar technological disruption. It is the promise of this future technology that makes this present development so exciting.

Gerhard Klimeck, who directed the Purdue group that ran the simulations, says this is an important development because it shows how small electronic components can be engineered.

Moore’s Law simply stated that the number of transistors that can be placed on a processor will double approximately every 18 months. The latest Intel chip, the "Sandy Bridge," uses a manufacturing process to place 2.3 billion transistors 32 nanometers apart. A single phosphorus atom, by comparison, is just 0.1 nanometers across, which would significantly reduce the size of processors made using this technique, although it may be many years before single-atom processors actually are manufactured. The single-atom transistor does have one serious limitation: It must be kept very cold, at least as cold as liquid nitrogen, or minus 391 degrees Fahrenheit (minus 196 Celsius).

The atom sits in a well or channel, and for it to operate as a transistor the electrons must stay in that channel. At higher temperatures, the electrons move more and go outside of the channel. For this atom to act like a metal you have to contain the electrons to the channel. If someone develops a technique to contain the electrons, this technique could be used to build a computer that would work at room temperature. But this is a fundamental question for this technology.

Although single atoms serving as transistors have been observed before, this is the first time a single-atom transistor has been controllably engineered with atomic precision. The structure even has markers that allow researchers to attach contacts and apply a voltage. The thing that is unique about what is done here, with atomic precision, individual atom is positioned within the device.

Simmons says this control is the key step in making a single-atom device. By achieving the placement of a single atom, we have, at the same time, developed a technique that will allow us to be able to place several of these single-atom devices towards the goal of a developing a scalable system.

The single-atom transistor could lead the way to building a quantum computer that works by controlling the electrons and thereby the quantum information, or quantum bits. Some scientists, however, have doubts that such a device can ever be built.

 Whilst this result is a major milestone in scalable silicon quantum computing, it does not answer the question of whether quantum computing is possible or not," Simmons says. The answer to this lies in whether quantum coherence can be controlled over large numbers of quantum bits. The technique developed is potentially scalable, using the same materials as the silicon industry, but more time is needed to realize this goal.

Nanoscale wires defy quantum predictions

http://www.nature.com/news/nanoscale-wires-defy-quantum-predictions-1.9747

Miracle Antennas for Optical Innovations

Researchers have shown how arrays of tiny plasmonic nanoantennas are able to precisely manipulate light in new ways that could make possible a range of optical innovations such as more powerful microscopes, telecommunications and computers.

The researchers at Purdue University used the nanoantennas to abruptly change the phase of light phase. Light is transmitted as waves analogous to waves of water, which have high and low points. The phase defines these high and low points of light.

By abruptly changing the phase light propagates opens up the possibility of many potential applications. , Harvard researchers modified Snell's law, a long-held formula used to describe how light reflects and refracts, or bends, while passing from one material into another.

Until now, Snell's law has implied that when light passes from one material to another there are no abrupt phase changes along the interface between the materials. Harvard researchers, however, conducted experiments showing that the phase of light and the propagation direction can be changed dramatically by using new types of structures called metamaterials, which in this case were based on an array of antennas.

The wavelength size manipulated by the antennas in the Purdue experiment ranges from 1 to 1.9 microns.

The near infrared, specifically a wavelength of 1.5 microns, is essential for telecommunications. Information is transmitted across optical fibers using this wavelength, which makes this innovation potentially practical for advances in telecommunications.

The Harvard researchers predicted how to modify Snell's law and demonstrated the principle at one wavelength.

The innovation could bring technologies for steering and shaping laser beams for military and communications applications, nanocircuits for computers that use light to process information, and new types of powerful lenses for microscopes.

Critical to the advance is the ability to alter light so that it exhibits anomalous behaviour: notably, it bends in ways not possible using conventional materials by radically altering its refraction, a process that occurs as electromagnetic waves, including light, bend when passing from one material into another.

Scientists measure this bending of radiation by its index of refraction. Refraction causes the bent-stick-in-water effect, which occurs when a stick placed in a glass of water appears bent when viewed from the outside. Each material has its own refraction index, which describes how much light will bend in that particular material. All natural materials, such as glass, air and water, have positive refractive indices. However, the nanoantenna arrays can cause light to bend in a wide range of angles including negative angles of refraction.

Importantly, such dramatic deviation from the conventional Snell's law governing reflection and refraction occurs when light passes through structures that are actually much thinner than the width of the light's wavelengths, which is not possible using natural materials. Also, not only the bending effect, refraction, but also the reflection of light can be dramatically modified by the antenna arrays on the interface, as the experiments showed.

The nanoantennas are V-shaped structures made of gold and formed on top of a silicon layer. They are an example of metamaterials, which typically include so-called plasmonic structures that conduct clouds of electrons called plasmons. The antennas themselves have a width of 40 nanometers, or billionths of a meter, and researchers have demonstrated they are able to transmit light through an ultrathin plasmonic nanoantenna layer about 50 times smaller than the wavelength of light it is transmitting.

 This ultrathin layer of plasmonic nanoantennas makes the phase of light change strongly and abruptly, causing light to change its propagation direction, as required by the momentum conservation for light passing through the interface between materials.

Solar cell paint developed

Suppose if the next coat of paint you put on the outside of your home generates electricity from light -- electricity that can be used to power the appliances and equipment on the inside.

A team of researchers at the University of Notre Dame has made a major advance toward this vision by creating an inexpensive material that uses semiconducting nanoparticles to produce energy.

By incorporating power-producing nanoparticles, called quantum dots, into a spreadable compound, a one-coat solar paint was produced that can be applied to any conductive surface without special equipment.

The team's search for the new material, described in the journal ACS Nano, centered on nano-sized particles of titanium dioxide, which were coated with either cadmium sulfide or cadmium selenide. The particles were then suspended in a water-alcohol mixture to create a paste. When the paste was brushed onto a transparent conducting material and exposed to light, it created electricity.

The best light-to-energy conversion efficiency achieved by this is 1 percent, which is well behind the usual 10 to 15 percent efficiency of commercial silicon solar cells; but this paint can be made cheaply and in large quantities. If efficiency can be improved, it would be worthwhile to use in day-today activities.

Nanomechanical oscillator

Physicists, have shown how a nanomechanical oscillator can be used for detection and amplification of feeble radio waves or microwaves. A measurement using such a tiny device, resembling a miniaturized guitar string, can be performed with the least possible disturbance.

The researchers cooled the nanomechanical oscillator, thousand times thinner than a human hair, down to a low temperature near the absolute zero at -273 centigrade. Under such extreme conditions, even nearly macroscopic sized objects follow the laws of quantum physics which often contradict common sense. In the Low Temperature Laboratory experiments, the nearly billion atoms comprising the nanomechanical resonator were oscillating in pace in their shared quantum state.

The scientists had fabricated the device in contact with a superconducting cavity resonator, which exchanges energy with the nanomechanical resonator. This allowed amplification of their resonant motion. This is very similar to what happens in a guitar, where the string and the echo chamber resonate at the same frequency. Instead of the musician playing the guitar string, the energy source was provided by a microwave laser.

Newest Energy Material: Application in Computer, Lighting Technologies

Arizona State University researchers have created a new compound crystal material that promises to help produce advances in a range of scientific and technological pursuits.

The newest material, called erbium chloride silicate, can be used to develop the next generations of computers, improve the capabilities of the internet, increase the efficiency of silicon-based photovoltaic cells to convert sunlight into electrical energy, and enhance the quality of solid-state lighting and sensor technology.

Ning's research team of team of students and post-doctoral degree assistants help synthesize the new compound in ASU's Nanophotonics Lab in the School of Electrical, Computer and Energy Engineering, one of the university's Ira A. Fulton Schools of Engineering.

The breakthrough involves the first-ever synthesis of a new erbium compound in the form of a single-crystal nanowire, which has superior properties compared to erbium compounds in other forms.

Erbium is one of the most important members of the rare earth family in the periodic table of chemical elements. It emits photons in the wavelength range of 1.5 micrometers, which are used in the optical fibers essential to high-quality performance of the Internet and telephones.

Erbium is used in doping optical fibers to amplify the signal of the internet and telephones in telecommunications systems. Doping is the term used to describe the process of inserting low concentrations of various elements into other substances as a way to alter the electrical or optical properties of the substances to produce desired results. The elements used in such processes are referred to as dopants.

With the new erbium compound, 1,000 times more erbium atoms are contained in the compound. This means many devices can be integrated into a chip-scale system. Thus the new compound materials containing erbium can be integrated with silicon to combine computing and communication functionalities on the same inexpensive silicon platform to increase the speed of computing and internet operation at the same time. Erbium materials can also be used to increase the energy-conversion efficiency of silicon solar cells.

Silicon does not absorb solar radiation with wavelengths longer than 1.1 microns, which results in waste of energy -- making solar cells less efficient. Erbium materials can remedy the situation by converting two or more photons carrying small amounts of energy into one photon that is carrying a larger amount of energy. The single, more powerful photon can then be absorbed by silicon, thus increasing the efficiency of solar cells.

Erbium materials also help absorb ultraviolet light from the sun and convert it into photons carrying small amounts of energy, which can then be more efficiently converted into electricity by silicon cells. This color-conversion function of turning ultraviolet light into other visible colors of light is also important in generating white light for solid-state lighting devices.

While erbium's importance is well-recognized, producing erbium materials of high quality has been challenging. The standard approach is to introduce erbium as a dopant into various host materials, such as silicon oxide, silicon, and many other crystals and glasses. One big problem has been that we have not been able to enough erbium atoms could not be introduced into crystals and glasses without degrading optical quality, because too many of these kinds of dopants would cluster, which lowers the optical quality.

What is unique about the new erbium material synthesized here is that erbium is no longer randomly introduced as a dopant. Instead, erbium is part of a uniform compound and the number of erbium atoms is a factor of 1,000 more than the maximum amount that can be introduced in other erbium-doped materials. Increasing the number of erbium atoms provides more optical activity to produce stronger lighting. It also enhances the conversion of different colors of light into white light to produce higher-quality solid-state lighting and enables solar cells to more efficiently convert sunlight in electrical energy. In addition, since erbium atoms are organized in a periodic array, they do not cluster in this new compound. The fact that the material has been produced in a high-quality single-crystal form makes the optical quality superior to the other doped materials.

This new erbium compound can be used for various applications, such as increasing silicon solar cell efficiency and making miniaturized optical amplifiers for chip-scale photonic systems for computers and high-speed internet.

New Improved Rechargeable batteries

A team of engineers has created an electrode for lithium-ion batteries -- rechargeable batteries such as those found in cellphones and iPods -- that allows the batteries to hold a charge up to 10 times greater than current technology. Batteries with the new electrode also can charge 10 times faster than current batteries.

The researchers combined two chemical engineering approaches to address two major battery limitations -- energy capacity and charge rate -- in one fell swoop. In addition to better batteries for cellphones and iPods, the technology could pave the way for more efficient, smaller batteries for electric cars.

The technology could be seen in the marketplace in the next three to five years, the researchers said.

Lithium-ion batteries charge through a chemical reaction in which lithium ions are sent between two ends of the battery, the anode and the cathode. As energy in the battery is used, the lithium ions travel from the anode, through the electrolyte, and to the cathode; as the battery is recharged, they travel in the reverse direction.

With current technology, the performance of a lithium-ion battery is limited in two ways. Its energy capacity -- how long a battery can maintain its charge -- is limited by the charge density, or how many lithium ions can be packed into the anode or cathode. Meanwhile, a battery's charge rate -- the speed at which it recharges -- is limited by another factor: the speed at which the lithium ions can make their way from the electrolyte into the anode.

In current rechargeable batteries, the anode -- made of layer upon layer of carbon-based graphene sheets -- can only accommodate one lithium atom for every six carbon atoms. To increase energy capacity, scientists have previously experimented with replacing the carbon with silicon, as silicon can accommodate much more lithium: four lithium atoms for every silicon atom. However, silicon expands and contracts dramatically in the charging process, causing fragmentation and losing its charge capacity rapidly.

Currently, the speed of a battery's charge rate is hindered by the shape of the graphene sheets: they are extremely thin -- just one carbon atom thick -- but by comparison, very long. During the charging process, a lithium ion must travel all the way to the outer edges of the graphene sheet before entering and coming to rest between the sheets. And because it takes so long for lithium to travel to the middle of the graphene sheet, a sort of ionic traffic jam occurs around the edges of the material.

Now, research team has combined two techniques to combat both these problems. First, to stabilize the silicon in order to maintain maximum charge capacity, they sandwiched clusters of silicon between the graphene sheets. This allowed for a greater number of lithium atoms in the electrode while utilizing the flexibility of graphene sheets to accommodate the volume changes of silicon during use. Thus much higher energy density have been achieved of the silicon, and the sandwiching reduces the capacity loss caused by the silicon expanding and contracting. Even if the silicon clusters break up, the silicon won't be lost.

Scientist also used a chemical oxidation process to create miniscule holes (10 to 20 nanometers) in the graphene sheets termed in-plane defects so the lithium ions would have a "shortcut" into the anode and be stored there by reaction with silicon. This reduced the time it takes the battery to recharge by up to 10 times.

This research was all focused on the anode; next, the researchers will begin studying changes in the cathode that could further increase effectiveness of the batteries. They also will look into developing an electrolyte system that will allow the battery to automatically and reversibly shut off at high temperatures - a safety mechanism that could prove vital in electric car applications.

Nanotubes for Microscopic Mechanics

In the latest issue of Elsevier's Materials Today, researchers from Spain and Belgium reported on the innovative use of carbon nanotubes to create mechanical components for use in a new generation of micro-machines. While the electronics industry has excelled in miniaturizing components, with individual elements approaching the nanoscale (or a billionth of a meter), reducing the size of mechanical systems has proved much more challenging.

One of the difficulties of shrinking mechanical devices is that the conventional techniques used to produce individual components are not useful when it comes to creating intricate shapes on the microscale. One promising technique is electrical discharge machining (EDM), which uses a spark of electricity to blast away the unwanted material to create complex shapes. However, this method requires that the target material is electrically conductive, limiting the use of EDM on hard, ceramic materials.

But now, by implanting carbon nanotubes in silicon nitride, the ceramic of choice, Manuel Belmonte and colleagues have been able to increase the electrical conductivity of the material by 13 orders of magnitude and have used EDM to produce a microgear without compromising the production time or integrity of the apparatus.

 Carbon nanotubes rose to prominence in the early 1990s when their range of remarkable properties became apparent. These include phenomenal strength and electrical properties that can be tailored to suit. Each tube is made from a rolled up sheet of carbon atoms in a honeycomb-like structure. Unrolled, this sheet is also known as graphene, the innovative material which was the subject of the 2010 Nobel Prize in Physics. Implanted inside a ceramic, these nanotubes form a conductive network that greatly reduces electrical resistance.

 The electrical conductivity of the composite material is much higher, while the mechanical properties of the ceramic are preserved and wear resistance is significantly improved. As the corresponding author, Dr Manuel Belmonte clarifies this breakthrough will allow the manufacture of intricate 3D components, widening the potential use of advanced ceramics and other insulating materials. The team hopes that such nanocomposite materials will find use in emerging applications, such as, microturbines, microreactors, and bioimplants.

Ill effect of Carbon Nanoparticles

A study by researchers from the schools of science and medicine at Indiana University-Purdue University Indianapolis examines the effects of carbon nanoparticles (CNPs) on living cells. This work is among the first to study concentrations of these tiny particles that are low enough to mimic the actual exposure of an ordinary individual.

 The effects on the human body of exposure to CNPs -- minute chemicals with rapidly growing applications in electronics, medicine, and many other fields -- is just beginning to be revealed. Exposure at the level studied by the IUPUI researchers is approximately equivalent to what might be the result of improperly disposing of an item such as a television or computer monitor containing CNPs, living near a CNP producing facility, or working with CNPs.

The research focuses on the effect of low concentration CNP exposure on the cells that line the renal nephron, a tubular structure inside the kidney that makes urine. The investigators found the role of the CNPs in this part of the body to be significant and potentially worrisome.

Unlike many other studies,  low concentrations of CNPs have been used that are typically appear in the body after ingesting them from environmental contamination or even from breathing air with CNPs. These minute particles cause leakage in the cellular lining of the renal nephron.

Breaching this biological barrier cause great concerns because things that should be retained in the forming urine can leak back into the blood stream and things in the blood can leak into the urine. Normal biological substances as well as waste products are dangerous if they go where they are not supposed to be.

These CNPs don't kill cells; so they are not lethal, but they do affect cells, and in this case it's an adverse effect. Biological barriers are very important to human health. The two researchers note that these incredibly strong particles, visible only under an electron microscope, perform useful functions including roles in drug delivery and are responsible for many advances in electronics such as the impressive colors seen on plasma televisions and computer monitors. What they worry about is when CNPs enter the air and the environment and eventually the human body from inappropriate disposal or from manufacture of products containing the particles.

This study is part of the team's larger body of work, which looks at the effect of CNPs on barriers throughout the body including those of the airways and large intestine.

CNPs have many beneficial qualities, but also pose potential risks. These particles are so small that when they get into various organs or systems they can bind to many things. A further study is required for what they look like in various parts of the body, how they affect protein expression, as well as what they do when they cross a barrier or are excreted.

Cool rollerball-pen ink to draw circuits!

Two professors from the University of Illinois have combined their talents to use the idea of printing circuits onto non-standard materials by developing a conductive ink that can be used in a traditional roller ball ink pen to draw circuits by hand onto paper and other porous materials. In their paper published in Advanced Materials, team leads Jennifer Lewis, Jennifer Bernhard and colleagues describe how they were able to make a type of ink from silver nanoparticles that would remain a liquid while in the pen, but would dry like regular ink once applied. The pen could was then used to draw a functioning LCD display and an antenna.

To make the ink, the team produced silver nanoparticles by reducing a silver nitrate solution along with an acid to prevent the particles from growing too large. Afterwards the acid was removed and the viscosity of the ink modified using hydroxyethyl cellulose to get just the right consistency. The result is a sort of liquid metal that dries on contact and which can be used to conduct electricity, hence its ability to be used in the creation of a circuit.

  

Up till now, most research on printing circuits onto non-standard materials, such as paper, have been done using inkjet printers or even airbrushes. This new approach would allow circuits to be drawn quicker and much cheaper, or even on-the-fly, as no other hardware is needed. Such a low cost device might create a market for throwaway circuits or even super cheap batteries. Paper was used in the study because it is considered to be the most suitable non-standard material for printing circuits due to its wide availability, low cost, ability to be bent and shaped, and the fact that it is biodegradable.

The paper used in study was folded after testing to see how the circuit would hold up, and discovered it took folding several thousand times before the ink pathways were broken.

The team next plans to look into other types of materials that might be used to make conductive ink for their pen, hoping to open up the door to all kinds of inks that can be used for a wide variety of purposes.

Nanotechnology leads to massive increase in memory capacity

There are two very exciting recent advances in nanotechnology may soon result in a massive increase in memory capacities of your DVDs and iPods. Researchers at the Centre for Micro-Photonics at the Swinburne University of Technology in Victoria, Australia, created a new material that could lead to new discs that can store 10,000 times more data than your average DVDs.

The material is made up of layers of gold nanorods suspended in clear plastic spun flat on a glass substrate. Multiple data patterns can be written and read within the same area in the material without interfering with each other. Using three wavelengths and two polarizations of light, the Australian researchers have written six different patterns within the same area. They've further increased the storage density to 1.1 terabytes per cubic centimeter by writing data to stacks of as many as 10 nanorod layers.

Also Berkeley researcher  created a physical memory cell composed of an iron nanoparticle that can be moved back and forth in a nanotube. The position of the iron particle represents the state of the bit, which leads to very dense and highly stabile memory arrays, resulting in very long lifetime.

Silicon Optical Chips by nanofabrication tools

In an effort to make it easier to build inexpensive, next-generation silicon-based electro-optical chips, which allow computers to move information with light and electricity, a University of Washington photonics professor, Dr. Michael Hochberg and his research team are developing design tools and using commercial nanofabrication tools.

Silicon optical chips are critical to the Air Force because of their size, weight, power, rapid cycle time, program risk reduction and the improvements they can offer in data communications, lasers and detectors. 

The UW researchers are working on system design and validation so they can imitate what's been done in electronics by stabilizing and characterizing some processes so that the transition from photonics to systems can be smooth.

Silicon photonics has developed over the last decade, and the transition from using devices to systems is something that has only recently occurred.

The digital electronics revolution over the past 40 years has had a transformative effect on how the Air Force systems are built, and hopefully it has similar impact on photonic systems.The researchers' current goal is to work first on test runs for the new optical chips for commercial uses and on developing some software tools that will make the design process easier.

AFOSR program manager, Dr. Gernot S. Pomrenke, agrees with Prof. Hochberg. "Integrating silicon photonics will impact Air Force, DoD and commercial avionics," he said. "AFRL has been a leader in developing and supporting this technology over the last two decades and the OpSIS program will help in transitioning silicon photonics into new system capabilities."