Science & Technology News (925)
Posted: May 29, 2015 02:26PM
Sometimes science can involve shooting something, but the process does not end there as one has to determine why whatever happened, happened. For decades it has been known that shooting ions at an iron-based superconductor can positively affect its properties, but the exact mechanics involved have been somewhat mysterious. That is until now, thanks to researchers at Brookhaven National Laboratory and their spectroscopic-imaging scanning tunneling microscope (SI-STM).
Superconductors are materials capable of carrying electrical currents without resistance, but require very low temperatures to do so. They can also require that the area be free of strong magnetic fields. This is the case with iron-based superconductors as the magnetic fields can cause the formation of vortices within the material, and these vortices inhibit the free flow of electrons. In the 1970's though, it was discovered that shooting high-energy ions at the superconductor can, sometimes, prevent these vortices from moving, and thus mitigate their impact. Now we know the reason is because the damage from the ions leaves either holes, just a few nanometers wide in the crystal structure, or elongated streaks, which trap the vortices.
The hope is to take advantage of this damage and control the vortices, potentially allowing for control over currents at different temperatures or varying magnetic field strengths. To perform this study though required the SI-STM because only it was able to measure the damage the ions do to the structure at the atomic scale and how it impacts superconductivity, within the material, atom-by-atom.
Source: Brookhaven National Laboratory
Posted: May 29, 2015 05:44AM
According to the Theories of Relativity, the Universe has the speed of light as its speed limit, and this rules our day-to-day life. Quantum mechanics however, likes getting around such rules and has been caught doing so, which begs the question of if it is violating relativity or going around it? Researchers at the Australian National University believe they have the answer with regard to tunneling.
Quantum tunneling is an interesting phenomenon that is important in many places, including the nuclear fusion at the core of stars, scanning tunneling microscope, and FLASH memory. It involves particles acting like waves and skipping over barriers that would otherwise block them, thanks to their position not being well-defined. The question has been if tunneling has a speed that surpasses the speed of light, and according to the researchers it does not because that rule does not exactly apply. The math apparently works out so that the time it takes to tunnel across a barrier is a complex value, with an imaginary part, so the tunneling velocity must also be imaginary. What this translates to is that the tunneling must occur instantaneously, as imaginary values do not really work in our real Universe.
This discovery should have a number of impacts by allowing technology to reach faster speeds and smaller size, where tunneling plays an important factor for leakage. It also solves problems with some attosecond scale (10-18) observations, such as a delay between a photon striking an atom and an electron being ejected from it. Based on the researchers' calculations, this delay is caused by the nucleus trying to pulling the electron back in, and not from tunneling.
Posted: May 28, 2015 04:26PM
Correcting errors is important for the reliable operation of any computing device. For modern computers, we have it down pretty well, but for future quantum computers, the challenge is completely different. Researchers at MIT though have managed to overcome one significant aspect of the challenge, by breaking the limit others suffer.
Quantum computers get their name and extraordinary power from quantum mechanics, which presents a special challenge. In classical mechanics, measuring a system tends not to change it, but in a quantum mechanical system can change it, as demonstrated by Schrodinger's Cat. Because of this there was a time when researchers believed it would be impossible to correct errors in a quantum computer, because measuring the values of qubits would cause them to collapse, defeating the purpose. Despite those concerns, error correction systems have been developed that do not actually measure the qubits' value, but their relationship to others. All of these systems are limited to only working on a square root of the total number of qubits (so you could only correct eight qubits in a 64-qubit computer). The new MIT method breaks that limit by using a special qubit bank and time. As the qubits are manipulated in the computer and take on new states, a bank of qubits is assigned to each state. By analyzing relationships within the banks, it is possible to determine where an error occurred and to fix it.
Ironically, this approach does not prevent errors and could even introduce them, but what errors there are must obey certain rules, which is why they can be corrected later. This approach allows for an arbitrary fraction of the qubits in a quantum computer to be checked for errors, and thus breaks the square root limit. Now the question is how much redundancy is needed amongst the qubit banks, and if fewer can be used, simplifying the system.
Posted: May 28, 2015 06:42AM
For humans, when something is too difficult to do we can enlist the help of others to get the job done, but for robots it is not as simple. For multiple robots to work together their actions may need to be coordinated and the results can be very efficient, in a controlled environment. In other settings, the efficiency can vanish because of how complex the computational work is, but researchers at MIT have found a solution to this problem.
Instead of requiring the robots to build a comprehensive plan, this new method breaks it up into single actions. At first these actions are evaluated to determine if the one robot involved will be able to complete the task successfully, and then checked to see if they are compatible with the steps before and after, and the additional robots involved in those steps. If the robots cannot determine a viable solution to the step, it will just skip the step and move on, coming back to it later. This deferment is actually critical to the method as it allows the actions to be interrupted at any point, and it also allows the parts the robots are carrying to be freely dropped and regrasped as needed.
The resulting sequence of actions may not be the optimal solution, but it works and can be found significantly faster. In fact some optimal solutions would take thousands of years of computation to discover, so by just finding a viable solution, this method should prove very powerful for robots in the real-world, outside of factories and such.
Posted: May 27, 2015 03:05PM
Augmented reality systems are technologies that somehow affect our view of the world for some purpose. One example would be smartphone keyboards that use a camera to display the ground you are not seeing while walking, and glasses that layer information onto our environment. Recently at Marine Corps Base Quantico, the Augmented Immersive Team Trainer (AITT) was tested with glasses, rendering a non-existent battleground onto a golf course.
The glasses, or optical see-through components, were only recently finished and this marks the first time they were integrated into the AITT system. While there are comparable see-through systems available commercially, this system offers are larger field of view and has been likened to having an HD screen in front of your eyes. The Marines do already use HUDs, but this is able to integrate more complex information into the scene than that technology.
The AITT program has been running for five years now, and is set to end in the Fall, when it will become part of the Marine Corps Program Manager for Training Systems. At this point, it will continue to be tested for improving situational awareness in training and operations.
Source: Office of Naval Research
Posted: May 27, 2015 05:39AM
If there is one thing you do not expect to turn into fertilizer, it is our computers and other electronics, but that may be changing though, thanks to researchers at the University of Wisconsin-Madison. These researchers have worked to replace the plastic substrate material commonly used with a biological material with suitable properties.
The bulk of a computer chip is not the circuitry but the substrate that supports it all. What the researchers have done is replaced the usual substrate with one made of cellulose nanofibril (CNF), which is flexible and biodegradable. Like paper, it is made from wood, but where the fibers in paper are on the micrometer scale, there are on the nanoscale for CNF. One of the issues the researchers had to overcome with it was preventing it from absorbing moisture from the air. This was achieved by applying an epoxy coating, which also improved its surface smoothness.
A chip made from this material could, when it needs to be disposed of, could be put somewhere that fungi could find and grow on, enjoying their cellulose dinner. Before that happens though, the chip would be able to perform comparably to modern chips.
Source: University of Wisconsin-Madison
Posted: May 26, 2015 03:13PM
As amazing as a material may be, it is not until it is easily accessible that it can really shine. Graphene was discovered years ago and researchers have been discovering possible uses for it since then, while also searching for new ways to make it. Researchers at MIT have recently developed a roll-to-roll means to create large graphene sheets, only limited in size by the size of the foil substrate and deposition chambers used.
Graphene is an atom-thick sheet of carbon atoms that has many extraordinary properties, but producing it in large quantities is very difficult. Typically it requires either pulling it off of pieces of graphite or furnaces with chemical vapor deposition (CVD) that only put out stamp-sized pieces. This new means though is an adaptation of the CVD method that uses two concentric tubes for the vacuum chamber, and allows a foil substrate to be run through. The foil winds around the inner tube as it moves through the system, and holes in the inner tube allows the necessary mixture of vapors to reach the substrate, to prepare it to grow the graphene, and to actually grow it. Throughout the process, the whole chamber is heated to 1000 ºC.
Thus far the system has only been built on a laboratory scale and the foil had to move through at just one inch per minute to create high-quality graphene. It is possible to go faster, but that degrades the quality of the graphene, and while lower-quality graphene may still have applications, the researchers want to see if they can push the speed, while also scaling the system up. Though the focus was on graphene, this process could be adapted for growing other 2D materials and even carbon nanotubes.
Posted: May 26, 2015 04:59AM
One of the larger mysteries of physics currently is likely the barrier between classical and quantum mechanics. At some point the rules change and discovering that point could allow us to eventually understand how the world we live in arises from the quantum world. Researchers at McGill University, the University of Vermont, and Leipzig University have recently performed an experiment that should help uncover the transition point.
Superfluid is a curious state a matter that is currently only known to exist for very cold liquid helium. In this state, the liquid flows without viscosity, which allows it to do some weird things, like move through small pores normal fluids could not. Normal fluids will also speed up as they travel through a small channel, like a river through rapids, but according to the Tomonaga-Luttinger theory, a superfluid will actually slow down if the pore size is small enough. It took a pore size less than 30 atoms wide, but the researchers finally observed such a slowdown.
It took a long time and an accident to finally make this experiment happens, as cutting the pores required using an electron beam and only after a student left a valve open during a run did they solve a problem with containments. Now that the nano-faucet is working though, it could be applied to help explore the region between quantum and classical mechanics, by observing behaviors at pores of different sizes. It could also be used to develop advanced nano-sensors.
Source: McGill University
Posted: May 22, 2015 05:21AM
Graphene is almost certainly going to be a wonder material of our time, with its amazing properties and many potential applications. Different applications pose different challenges for the material though. An example of this is polymer composites that contain graphene, but researchers at ORNL have found a solution to some of the problems.
The idea with polymer composites is to add flakes of graphene to the mix, so that they can add strength and conductivity. Graphene, despite being an atom-thick sheet of carbon, is exceedingly strong and tremendous electron mobility. When added to polymers though, the tiny flakes can clump together and not disperse correctly. The ORNL researchers' solution was to use chemical vapor deposition to create larger laminates of graphene. This resulted in the desired electrical conductance despite using only half as much graphene. Being large pieces, approximately two inches by two inches, the graphene also will not stick together.
Polymer composites with graphene could find many uses from aerospace and land vehicles to electronics and the energy sector. Before that can happen though, the researchers have to bring down costs and show the process can be scaled up, to meet manufacturing needs.
Source: Oak Ridge National Laboratory
Posted: May 21, 2015 02:37PM
Streaming and cloud services has become a popular solution for many people as a means to access media they otherwise would not be able to, at least not at the same quality or quantity. One problem with streaming content though is running into data caps, especially if someone is using a cloud gaming service. Researchers at Duke University, however, have deployed a technique that can significantly cut the data transmitted, without degrading quality.
The tool the researchers developed is named Kahawai, the Hawaiian word for stream, and what makes it special is collaborative rendering. Typical cloud gaming services work by doing all of the rendering on the remote servers, with the local client only being for display and input. Collaborative rendering splits the workload between the server and the local device, which could be a smartphone or tablet. While the finer details will still be rendered by the remote server, the local device still renders a rougher view for each frame, or a few highly detailed frames with the remote server filling in as needed. Either way, by having the local device do part of the work, the same visual quality can be achieved while cutting bandwidth down to one-sixth what current methods allow.
Another advantage over traditional streaming methods is that Kahawai can work offline by just showing the lower quality graphics the local device renders. While gaming is a logical place to start applying Kahawai, the researchers see it finding uses in other fields, such as medical imaging and CAD.
Source: Duke University
Posted: May 21, 2015 06:37AM
We may not realize it, because we cannot see it, but wireless congestion is an issue that limits rates and the number of users connecting to a single access point. It does not help matters that devices must transmit and receive on different channels. That may change soon though, thanks to researchers at the University of Bristol developing a duplexer small enough and cheap enough to integrate into phones.
The reason devices have to transmit and receive on different channels is because the emissions would interfere with each other if they were on the same frequency. A duplexer allows for the same frequency to be used by effectively removing this interference. The prototype made at Bristol suppressed the interference by a factor of over 100 million, all while using inexpensive and small components that can fit in mobile devices.
With this duplexer, filtering components could be removed from the devices, which would open up the possibility for unrestricted global roaming by allowing the devices to use any frequency band. This in turn could reduce costs as a single model could be manufactured for the entire world, and thus take advantage of the economics of scale.
Source: University of Bristol
Posted: May 20, 2015 02:29PM
Many of the devices we use every day rely on antennas, even though manufacturers have gotten quite good at hiding them. This achievement is actually not a little one as longer antennas can have desirable properties. As reported in the American Institute of Physics' Journal of Applied Physics, researchers at North Carolina State University have developed a tunable liquid antenna that may give us the best of both worlds.
The antenna in question is made of a liquid metal, which normally would require a pump to manipulate. Pumps are not exactly easy to integrate into devices like phones though, but the researchers have found an electrochemical solution that does the trick. When a voltage is applied to the liquid metal, the oxide layer on its surface is affected, which in turn impacts its surface tension. When a positive voltage is applied, the surface tensions weakens, allowing the liquid metal to flow into a capillary, lengthening the antenna, while a negative voltage does just the opposite. This allows the antenna's properties to be altered on the fly, such as increasing the range of frequencies it can operate over.
The next step for the researchers is to see what else they can do with this discovery. Potentially other tunable, liquid components could be made, such as filters, but they also want to see if more complicated shapes can be made, than one dimensional antennas.
Posted: May 20, 2015 05:22AM
Some believe that the future for some technologies will involve more directly linking them, and we already see something like this with television content that our phones can listen and react to. The trick for such a future is keeping this communication hidden from the viewer, or at least unobtrusive. Researchers at Dartmouth College have achieved just that, while still encoding information directly into the video displayed on screen.
Some attempts to encode data into video have been made before, but one does not necessarily want a QR code to appear on top of whatever they are watching. The Darthmouth researchers' solution, called HiLight, is to use the alpha channel of the image, so the information can be found in pixel translucency changes. This way the communication and screen content is separated, hiding it from the users, yet still allowing for real-time communication. Also, because it uses the visible part of the spectrum, there is not electromagnetic interference.
Source: Dartmouth College
Posted: May 19, 2015 02:43PM
For energy storage, most people think of batteries, but we may soon see some serious competition from supercapacitors. These energy storages systems are able to charge and discharge very quickly, can be flexible and cheap to make, and can even be safer to work with. Now researchers at Rice University have found a way to significantly increase the energy density of flexible microsupercapacitors made of graphene by adding boron to the mix.
Capacitors work by storing electrical charges on separated conductors, which allows them to charge up and release energy very rapidly. Supercapacitors bring with them higher energy capacities, similar to that of batteries, so one day they could see use in many applications where batteries now dominate. To create the microsupercapacitors they used, the Rice researchers used a laser to burn patterns into common polymers, resulting in the formation of a matrix of graphene flakes. From previous work they knew a commercial polyimide was the best choice, but this new study revealed that dissolving boric acid into polyamic acid, so that the polyimide sheet was boron infused, quadrupled the supercapacitor's storage capability.
With just a two-step process, the researchers are able to create microsupercapacitors with four times the storage ability and five to ten times the energy density of boron-free microsupercapacitors. Beyond that, the supercapacitors survived over 12,000 cycles while retaining 90% capacitance and after 8000 bending cycles, there was no performance loss. That flexibility could be an especially important aspect of this technique, by enabling industrial-scale roll-to-roll production.
Source: Rice University
Posted: May 19, 2015 05:49AM
Black silicon is a special form of silicon that has surface features that cause it to absorb much of the light that hits it, hence the name. Naturally there is interest in using it for solar cells and now researchers at Aalto University and Universitat Politècnica de Catalunya have set a new efficiency record of 22.1%.
To achieve this record the researchers used atomic vapor deposition to add a thin passivating film onto the black surface structures and by moving the metal contacts to the back of the cell. The film had the effect of limiting surface recombination, instead of it limiting the energized electrons that can be pulled away by the contacts for work. This is the first time the recombination issue of black silicon has been removed from such a system. Additional work may actually push the efficiency higher as the type of silicon used, p-type, is known to suffer from impurity-related degradation, so n-type silicon or more advanced cell structures could go even higher.
While the improved efficiency is definitely important and noteworthy, there is more to the operation of black solar cells than that. When tested against traditional solar cells of similar efficiency, the researchers found the black silicon cells generated more electricity because they are better at capturing light at low angles. This is important in northern areas, where the Sun shines at lower angles for a good portion of the year.
Source: Aalto University
Posted: May 18, 2015 02:28PM
Many people believe that 3D printing could lead to a revolution, as it allows for the efficient production of items, but it could also revolutionize medicine. Already we have seen 3D printers used to build a replacement windpipe for an infant, bow we could see it applied to repairing soft-tissue. Researchers at Technische Universitaet Muenchen have demonstrated that the 3D printing technique melt electrospinning writing could be used to build scaffolds that support human cartilage cells.
Attempts to build cartilage supporting scaffolds have been made before, but what makes this different is that melt electrospinning writing. It allows for filaments to be made just five micrometers in diameter. This produces the necessary stiffness while also being small enough for cells to grow around the hydrogel scaffolding.
Joint repair is one obvious use for this technology, but it could also be applied for heart tissue engineering and breast reconstruction. Naturally more study is needed before this is applied, but it is a very promising breakthrough.
Source: Technische Universitaet Muenchen
Posted: May 18, 2015 05:22AM
If you are reading this on a flatscreen display, like an LCD or OLED display, chances are you are staring through indium tin oxide (ITO) a transparent conductor. While ITO has the necessary transparency and conductivity, it is also expensive and fragile, so many are working on replacements. Among the possibilities are networks of nanowires, which are flexible and cheap as well as conductive and transparent, and now researchers at Lehigh University have made a discovery that should improve them.
The orientation of nanowires in the network is, as you would expect, very important to the network's properties. If you think that a network with strictly oriented nanowires would be the best conductor though, you would be wrong. The Lehigh researchers have built computers models of the networks and found that those with a degree of randomness are actually better conductors. The nanowires still need some restrictions on their orientation, but just the right amount will beat out heavily ordered networks.
To test the model, the researchers applied it to previously published papers, which is a common practice, and found that it accurately explains the results. This discovery could lead to improvements for many optoelectronic devices and flexible electronics.
Posted: May 15, 2015 02:28PM
Spin is a property of many particles and is at the heart of various technologies, but working with it can be challenging. Typically very powerful fields are necessary to measure it. That may be changing soon though, thanks to researchers at the Universities of Waterloo and Basel, and RWTH Aachen University.
One of the technologies that measures spin is Magnetic Resonance Imaging (MRI) or Nuclear Magnetic Resonance (NMR) and doing so takes very powerful magnets, with those in MRI machines actually being superconducting electromagnets. This is despite the fact that the spin of particles produces weak magnetic fields. Ideally weak fields could also be used to measure it, but because of the weakness and noise, this has been impossible until now. According to the researcher's work, a small ferromagnetic particle could amplify the weak field, allowing a nitrogen-vacancy qubit to detect it from 30 nm away, and at room temperature. Without the particle, the distance would have to be 1-2 nm, which is infeasible.
The hope is that this theoretical work could be used to develop superior NMR techniques for imaging biological materials, but more still needs to be done. At least this actually classical technique should be less fragile than other, quantum schemes.
Source: University of Waterloo
Posted: May 15, 2015 06:03AM
Typically when a material's temperature crosses a transition point, it will change phase, but there are ways around this, allowing a phase to persist when you would not expect it. Researchers at the University of Michigan have demonstrated this quite elegantly when they balanced two opposing crystallization mechanisms in a material. This resulted in the material staying liquid about 200 ºF below its freezing point.
The material the researchers were working with is part of a family of organic materials commonly used as pigments in electronics. They all feature a rigid core with two flexible side chains, and depending on the length of the chains, the molecules will take on one crystal structure or another. What the researchers did is balance the chains' length to cause the two modes to counter each other. Normally the material crystalizes at 273 ºF but this balance allowed it to stay liquid at 41 ºF, and cooling it further caused it to solidify into a gas. While in its supercooled state, the material was sensitive to pressure, depending on its temperature. At high temperatures even the weight of a cell would cause it to crystallize, but at room temperature and lower, a stylus was required. Even then, the crystallization was so sluggish that the researchers could write messages in the material, as the crystallized regions glowed under UV light.
This material could have some interesting uses, including as a biosensor and as an optical memory. Its ability to encode information optically could be useful, but much more work is required to develop its potential.
Source: University of Michigan
Posted: May 14, 2015 02:35PM
Researchers at MIT have managed to corral electrons in graphene in a new way that allows for tunability and high quality. Corrals have been made before, but these were always static and thus had limited potential. With this new technique though, the researchers were able to create a resonator that could have more applications than can be imagined currently.
This new method is surprisingly simple as it just places the tip of a scanning tunneling microscope over the graphene. This causes a circular barrier to form around the tip, which acts as a curved mirror and creates a whispering gallery effect. In optics, whispering gallery resonators have been used for sensing, spectroscopy, and communication, but have the issue of not being tunable. This is however, as the junction between the positive and negative regions the tip produces can be controlled. Also the tip can be moved around the graphene sheet, which opens up other possibilities. Even without that though, such a resonator could be turned into various devices, including electron lenses that could observe systems a thousand times smaller than light is able to, but without the high-energy electron beams of electron microscopy.
Using the tip of an electron microscope comes with two benefits for this and future work. One is that the tip can both create the resonator and be used to observe the system. The other is that the tips are a well-established technology already, which should make deploying this technology easier.
Posted: May 14, 2015 07:08AM
In general, simplifying a process by reducing steps is a good thing for a number of reasons, such as reducing costs and improving scalability. Researchers at Rice University have recently discovered a way to remove some steps to the production of black silicon for use as solar cells. This discovery could bring the technology closer to commercialization.
Black silicon is silicon with a special textured surface with features smaller than the wavelength of light. This makes it very efficient at capturing light at any angle. The Rice researchers have been working to fine tune the creation process for a while, but were surprised to find that the electrodes were actually able to catalyze the etching process, removing the need for other catalyst particles. Normally the metal electrodes are added last, but when the researchers had applied the electrodes earlier, and then repeated the process without the catalyst, they found black silicon formed near the electrodes.
Interestingly the etching always occurred the same distance from the electrodes, which was actually a tip-off to what was happening. An electrochemical process is causing the etching and the distance away from the electrodes is determined by the conductivity of the silicon, because after a point the charge carriers cannot move any farther. Now the trick is to optimize the process further, which the researchers suggest could be by applying a thin layer of gold on top of the silicon, with titanium sandwiched between, because it bonds well to both.
Source: Rice University
Posted: May 13, 2015 02:35PM
Despite it surrounding us and being within us, recreating Nature can be very difficult. For a long time there was no way to simulate cell membranes, but in 2010 researchers discovered how to replace a key molecule with some easier to create and work with. Now researchers at the University of Pennsylvania have succeeded in modelling how sugars on membranes can influence the behavior and interactions of cells.
Cell membranes are made of two layers of phospholipids, which are molecules with a water-loving head and water-hating tail. This allows them to self-assemble into so simple membranes just by being placed in water. In 2010 it was discovered that a class of molecules called dendrimers could replace the phospholipids, and they can be precisely tuned. On the surface of natural membranes though are sugars that are crucial for how cells interact with each other, so the question was if these artificial membranes could support sugars. The researchers have found they can by constructing a library of dendrimers that are chemically bonded to glycan sugars.
What all of this translates to is a new ability to model cell membranes, which could lead to various advances in medicine and biophysics. Some illnesses are believed to be related to mutations in proteins that interact with these sugars, such as rheumatoid arthritis, so by better understanding the processes involved, better treatments may be developed with this and much more.
Source: University of Pennsylvania
Posted: May 13, 2015 05:29AM
Bread, apples, and ducks float on water and now some metals can too. Researchers at New York University and Deep Springs Technology have created a metal matrix composite that can float on water but is still very strong. This combination could see it being used in boats and even cars, where weight can be a factor.
The material is what is called a syntactic foam, which is made by using hollow particles to reduce weight. In this case the solid material is a magnesium alloy and the hollow particles are silicon carbide spheres. These spheres can withstand pressures of 25,000 PSI before rupturing, which contributes to the metal's strength both in what they can withstand but also by absorbing energy when they do rupture. The result is a metal that has a density of just 0.92 grams per cubic centimeter, which is just under the 1.0 of water. That means a boat made of this material would still float, even after suffering serious structural damage.
A lot of work has been done over recent years to find strong and light materials, as a means to conserve energy, but being a metal, this stands apart from the plastics normally getting the attention. Metals can withstand high temperatures, which is necessary for components of engines and exhaust systems.
Source: New York University
Posted: May 12, 2015 02:38PM
There are some materials that are surprisingly prolific, thanks to their various special properties. Many believe graphene will come to be such a material, once some challenges it has are overcome. One area it may be used in is water purification, and researchers at MIT have made that more possible than ever now, by finding ways to fix the defects in graphene membranes.
Graphene is an atom-thick sheet of carbon with a variety of useful properties, including high strength and conductivity. Membranes of the material could significantly improve water purification systems, because of how much thinner the membranes would be, at one atom thick versus 200 nm thick. The problem is that the graphene membranes must first be made on a substrate like copper, which is not porous, so the graphene must be removed. This causes tears in the membrane, in addition to intrinsic defects the membrane will have. For these defects the researchers found that they could be fixed by placing the graphene in a vacuum chamber with hafnium oxide. Normally the material would not interact with graphene, but is attracted to these small defects. The larger tears can be plugged by using interfacial polymerization, which submerges the membrane between two solutions that will react together to form nylon. After the repairs are made, the researchers etch small holes into the membrane, to let water through.
With the defects and tears dealt with, and the pores etched in, the researchers found the graphene membrane could block up to 90% of larger molecules, even though it still let salt though. Additional work is needed, but graphene could become a realistic alternative to current filtration membranes, providing clean water to more places, amongst other applications.
Posted: May 12, 2015 07:01AM
Batteries are necessary for a great many systems, including micro-devices, but because of the large sizes of the energy storage devices, they must be kept off of the chips used. This could change thanks to the work of researchers at the University of Illinois, Urbana-Champaign though, as they have developed a powerful microbattery that can be easily integrated onto chips. The manufacturing processes involved can even allow for large-scale production.
To create the new battery, the researchers use 3D holographic lithography and 2D photolithography. Holographic lithography utilizes multiple light beams that interfere within a photoresist, creating the desired, interior structure. Recent work has made this process simpler to the point of making it highly scalable. The 2D photolithography is used to create the shape of the electrodes that connect to the battery, which the researchers found is particularly important. Structural parameters including size, shape, surface area, porosity, and tortuosity all impact the microbattery's performance.
As the methods used to create the microbattery are compatible with those used to create chips, the expectation is that they can be integrated directly onto chips. The fact that the miniature battery is also high-power, comparable to supercapacitors in that regard, make it very desirable for various applications from wireless sensors and transmitters and medical devices, to monitors and actuators.
Posted: May 11, 2015 07:36AM
We may not think about light very much, but in our day to day lives, we probably consider it to be somewhat simple. On the scale we live at, light is not necessarily complicated, but at the nanoscale, it can be very different from what one expects. Researchers at Aalto University have confirmed this by discovering a new way to couple light with magnetic materials that may have applications in telecommunications and more.
Normally when light strikes a material, you except it to reflect or scatter off, but on the nanoscale quantum mechanics can be involved, if the materials are ferromagnetic. Metallic nanoparticles can act like antennas for visible light, and thereby interact with the light, possibly shifting its polarization axis or intensity. The researchers applied this and built an array of ferromagnetic nanoparticles that exploits surface lattice resonances. This causes all of the particles to radiate together, creating a much more significant impact on the polarization change. By having the spacing between the particles differ, based on direction, the researchers were even able to change the frequency this effect occurs at away from the frequency the particles themselves most interact with.
This work opens new possibilities for magneto-optical effects, as previously one would not work with ferromagnetic materials, due to their high resistance. By working with the array of nanoparticles though, this issue is mitigated.
Source: Aalto University
Posted: May 8, 2015 02:01PM
There are many possibilities for the future of computing, but while the systems involved can be very different, many of them rely on optics in one way or another. Naturally this makes it important to find ways to precisely create the light being used, and researchers at the University of Rochester have made a significant discovery to achieving that. They have found how to make quantum dots in a two-dimensional semiconductor, which has never been accomplished before.
Quantum dots are occasionally referred to as artificial atoms because we are able to engineer their properties, such as the color of light they absorb and emit. Naturally there is great interest in them for photonic devices, such as those that may be used in some future computer systems. Before that can happen though we will need to find ways to integrate them into chips, which is where this discovery comes in. The Rochester researchers discovered that by layering atomically-thin sheets of tungsten disulfide on top of each other, the points where they overlap create quantum dots. By controlling the applied voltage the researchers can already tune the brightness of the quantum dot, and the next step is to adjust the frequency by manipulating the voltage.
It is an important advantage that tungsten disulfide is a 2D semiconductor, as these tend to be easier to integrate into electronics. The researchers also found that the quantum dots do not interfere with the semiconductor's electrical or optical properties, which will also prove invaluable for integration with electronics.
Source: University of Rochester
Posted: May 8, 2015 05:12AM
In my experience, people love chocolate unless they have an allergy or are actually sticking to a diet. We love it, until it has the white layer on it that looks like nothing you would want to eat. Even though these blooms are well known about, there is little understanding about them, which is why a team of researchers from DESY, the Hamburg University of Technology, and Nestle decided to study chocolate more closely.
That white layer is actually a fat bloom and, believe it or not, is completely harmless, but it still causes people to dispose of the chocolate and even file complaints. The bloom occurs when the liquid fat in the chocolate finds its way to the surface and crystallizes there. To understand the exact processes involved, the researchers pulverized samples of chocolate and shined X-rays through it to examine fat crystals and pores. Dropping sunflower oil on the samples allowed them to also watch the fat migrate, and they found the oil quickly penetrated even the smallest pores. As it dissolved into the chocolate, it affected the chocolate's structure, making it softer and easier for more fat to migrate, which could then lead to fat blooms.
Based on this study, which is the first to study the dynamics of fat blooms developing, the researchers suggest three ways to reduce the occurrence of fat blooms. One is to reduce the porosity of the chocolate, so fat migrates more slowly. The second is to keep the chocolate at a cool temperature, to limit the liquid fat. Finally the researchers suggest controlling the crystal structures of the fat in the chocolate, as this directly influences the amount of liquid fat in the chocolate. Cocoa butter has six crystal structures it can form, and some may be better than others.
Posted: May 7, 2015 02:10PM
Carbon nanotubes are an amazing material with great potential for various applications. This is thanks to their amazing strength and electrical properties, but getting them into usable forms can be difficult. Researchers at North Carolina State University and the Suzhou Institute of Nano-Science and Nano-Biotics in China have succeeded in developing a method to create large films of CNTs stronger than any that came before it.
Carbon nanotubes are a form of pure carbon and are among the strongest materials known to man, despite also being among the smallest. To utilize this strength, they have to be made into larger structures, like threads or films. The better aligned the nanotubes are within these structures, the better the properties of the final structure will be, but aligning a bunch of nanotubes a thousand times smaller than human hair tends not to be easy. Yet that is what the researchers have achieved by exploiting the imperfections of surgical blades. To the naked eye, these blades will look perfectly straight, but if one looks closer with a microscope, microscale fissures will become visible along the cutting edge. The researchers realized these fissures could be used as a kind of comb to straighten the nanotubes, just by drawing them over the blades.
The resulting films made from the microcombed nanotubes have more than double the tensile strength of regular CNT films, at over 3 gigapascals, compared to just 1.5, and some 80% better conductance. Despite that though, there is still room for improvement with this method. Right now though, the researchers are looking for an industry partner to help scale up the method for large-scale production, which, theoretically, should be easy.
Source: North Carolina State University
Posted: May 7, 2015 05:40AM
As powerful as our computers get, there are some things they will simply never be able to do because the operations involved are too complicated. For many of these problems, quantum computers may be able to provide the solutions, but we are not able to build such a computer. We are getting closer all the time though with new developments, such as a new chip architecture set to appear in the Journal of Applied Physics.
The key to quantum computers is the use of quantum bits, or qubits, which are able to represent both 0 and 1 at the same time, as opposed to electronic bits that are one or the other. There are many candidates for qubits, including ions trapped in vacuum chambers that lasers manipulate, but it is difficult to scale up the technologies involved. This is because the electrodes needed to create the trapping fields are attached to the perimeter of the chip, which has only so much room. The researchers' new solution was to switch to a ball grid array (BGA), like some computer chips use. This moves the electrodes from the perimeter to the more spacious area of the chip, significantly increasing the density of the connections.
Besides the shift to BGA, the researchers also changed the kind of capacitors commonly used from surface or edge capacitors to trench capacitors, and rewired the connections. While this is a large and valuable step forward, there is still a lot of work to be done before quantum computers can come to be.