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Biodegradable DNA nanoparticles rapidly penetrate mucus barrier for inhaled lung gene therapy

Biodegradable DNA nanoparticles rapidly penetrate mucus barrier for inhaled lung gene therapy | Amazing Science | Scoop.it

A number of lung diseases are resistant to, or only marginally handled by, conventional therapies. Thanks to the discovery of numerous genetic targets, gene therapy provides an alternative or complementary therapeutic option. Over the past two decades or more, a large number of gene delivery systems, based on viruses or man-made nanoparticles, have been developed in order to deliver therapeutic nucleic acids to the target cells in the lung, while preventing these cargos from being degraded by the body's protective enzymes before they reach the target. However, while it is readily accessible via inhalation, the mucus lining the lung airways typically traps inhaled foreign matter that is then removed from the lung by being rapidly and continuously swept up towards the larynx to be swallowed into the stomach and degraded. Although this is a critical host defense mechanism, the same airway mucus also traps inhaled therapeutic nanoparticles, such as gene delivery systems, through steric obstruction and/or adhesive interactions, meaning that therapeutic nanoparticles trapped in airway mucus will be rapidly cleared from the lung and so not be able to reach their target cells in the lung. Indeed, several clinically tested viral and non-viral gene delivery systems have been shown unable to efficiently penetrate human airway mucus. In addition, the physiological environment in the lung renders it hard to retain stability of therapeutic nanoparticles until they reach the target cells. Thus, despite over two decades of effort, therapeutically effective lung gene therapy is yet to be realized.


Scientists at the Center for Nanomedicine at Johns Hopkins University School of Medicine, Baltimore have previously shown that dense surface coatings with hydrophilic (readily absorbing or dissolving in water) and uncharged polyethylene glycol (PEG) polymers render the particle surface muco-inert (that is, resistant to being trapped by mucus via adhesive interactions). However, achieving the high PEG densities required for efficient mucus penetration while retaining the stability of gene delivery nanoparticles is challenging. Recently, however, the same researchers developed a simple strategy using a blend of highly PEGylated and non-PEGylated polymers at an optimal ratio to formulate mucus-penetrating DNA nanoparticles (DNA-MPPs) capable of retaining stability in physiological environments as well as rapidly penetrating human airway mucus.


Dr. Jung Soo Suk discussed the paper that he, Prof. Justin Hanes, Dr. Panagiotis Mastorakos and their colleagues published in Proceedings of the National Academy of Sciences. "Non-viral gene delivery systems, being devoid of one or more of shortcomings of virus-based vectors, constitute an attractive alternative for inhaled gene therapy," Suk tells Medical Xpress. (These systems are typically made with natural or synthetic materials possessing a large number of positive charges that interact with negatively charged nucleic acids to form small nanoparticles – a process known as complexation.) "In particular, biodegradable cationic," or positively charged, "polymers provide a superior in vivo safety profile compared to non-biodegradable or slowly degrading systems while providing timely release of nucleic acid payloads that may lead to improved gene delivery efficacy – both features being due to their hydrolytic nature." Hydrolysis is a chemical process of decomposition involving the splitting of a bond and the addition of the hydrogen cation and the hydroxide anion of water.


However, Suk points out, surfaces of these conventionally designed systems are, typically, positively charged, which makes them unlikely not only to retain their colloidal stability in physiological environments, but also to efficiently penetrate negatively charged biological barriers, such as airway mucus, due to the electrostatically-driven adhesive interactions. "Here," he explains, "we engineered a biodegradable polymer-based platform addressing these problems, thereby leading to highly efficient gene transfer to the lung in vivo, surpassing leading non-viral platforms, including a clinically tested system – and perhaps viral vectors as well."

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Simulations lead to design of near-frictionless material

Simulations lead to design of near-frictionless material | Amazing Science | Scoop.it
Argonne scientists used Mira to identify and improve a new mechanism for eliminating friction, which fed into the development of a hybrid material that exhibited superlubricity at the macroscale for the first time. ALCF researchers helped enable the groundbreaking simulations by overcoming a performance bottleneck that doubled the speed of the team’s code.

While reviewing the simulation results of a promising new lubricant material, Argonne researcher Sanket Deshmukh stumbled upon a phenomenon that had never been observed before.

“I remember Sanket calling me and saying ‘you have got to come over here and see this. I want to show you something really cool,’” said Subramanian Sankaranarayanan, Argonne computational nanoscientist, who led the simulation work at the Argonne Leadership Computing Facility (ALCF), a DOE Office of Science User Facility.

They were amazed by what the computer simulations revealed. When the lubricant materials—graphene and diamond-like carbon (DLC)—slid against each other, the graphene began rolling up to form hollow cylindrical “scrolls” that helped to practically eliminate friction. These so-called nanoscrolls represented a completely new mechanism for superlubricity, a state in which friction essentially disappears.

“The nanoscrolls combat friction in very much the same way that ball bearings do by creating separation between surfaces,” said Deshmukh, who finished his postdoctoral appointment at Argonne in January.

Superlubricity is a highly desirable property. Considering that nearly one-third of every fuel tank is spent overcoming friction in automobiles, a material that can achieve superlubricity would greatly benefit industry and consumers alike. Such materials could also help increase the lifetime of countless mechanical components that wear down due to incessant friction.
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Researchers folded DNA into the shape of a nanoscale bunny and other 3D structures

Researchers folded DNA into the shape of a nanoscale bunny and other 3D structures | Amazing Science | Scoop.it

Folding DNA into the shape of a tiny bunny rabbit is now easier than ever, according to a study published in Nature today. Folding DNA isn’t new — it’s known as DNA origami — but automating the process is. Thanks to a set of computer algorithms, researchers have developed a way to streamline the design phase that comes before the DNA assembly — a substantial step toward 3D printing at the nanoscale.


This has not been done before, it is novel and surprising," says Thorsten Schmidt, a chemist at the Dresden University of Technology who didn't work on the study. "In fact, we have a very related study under review at the moment and the only bad aspect of Björn Högberg’s study is that they were faster than us."


The bunny, while cute, wasn’t the point of the study. Rather, it’s a demonstration that scientists can automatically generate a DNA sequence to form a complex shape — the closest thing to 3D printing on a very tiny scale. "It’s almost a one-click procedure," Högberg says. And if scientists can fully automate the process, they’ll have a real DNA printer at their disposal — one that could, among other things, make drugs easier to deliver to the right places in the body.

Actually, there are a lot of ideas about how these techniques could be used. In addition to drug delivery, researchers are working on coating the DNA structures with non-biological materials, like gold, that react when the structure comes in contact with light.


But at this point, the bunny and the bottle don't do all that much. "We're not really concerned with the genetic information," Högberg says. "We're using DNA purely as a construction material."


Now that the study has been published, the researchers want to find a way to make their own construction materials. That may mean using natural DNA — taken from a plant or bacteria that they cultivate themselves — instead of synthetic DNA, Högberg says. "We're getting very good at making structures at the nanoscale," Högberg says. Researchers just need to find a way to make lots tiny DNA bunnies cheaply — and all at once.


Via Integrated DNA Technologies
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One the way to breaking the terahertz barrier for graphene nanoelectronics

One the way to breaking the terahertz barrier for graphene nanoelectronics | Amazing Science | Scoop.it

Simple thermodynamics defines the performance of ultrafast graphene transistors and photodetectors.


A team of scientists at the Max Planck Institute for Polymer Research (MPI-P) discovered that electrical conduction in graphene on the picosecond timescale – a picosecond being one thousandth of one billionth of a second – is governed by the same basic laws that describe the thermal properties of gases. This much simpler thermodynamic approach to the electrical conduction in graphene will allow scientists and engineers not only to better understand but also to improve the performance of graphene-based nanoelectronic devices.


The researchers found that the energy of ultrafast electrical currents passing through graphene is very efficiently converted into electron heat, making graphene electrons behave just like a hot gas. “The heat is distributed evenly over all electrons. And the rise in electronic temperature, caused by the passing currents, in turn has a strong effect on the electrical conduction of graphene” explains Professor Mischa Bonn, Director at the MPI-P. The study, entitled “Thermodynamic picture of ultrafast charge transport in graphene”, has recently been published in Nature Communications.


Graphene – a single sheet of carbon atoms – is known to be a very good electrical conductor. As a result, graphene finds a multitude of applications in modern nanoelectronics. They range from highly efficient detectors for optical and wireless communications to transistors operating at very high speeds. A constantly increasing demand for telecommunication bandwidth requires an ever faster operation of electronic devices, pushing their response times to be as short as a picosecond. “The results of this study will help improve the performance of graphene-based nanoelectronic devices such as ultra-high speed transistors and photodetectors” says Professor Dmitry Turchinovich, who led the research at the MPI-P. In particular they show the way for breaking the terahertz operation speed barrier – i.e. one thousand billions of oscillations per second – for graphene transistors.

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Development of smart clothes for personalized cooling and heating

Development of smart clothes for personalized cooling and heating | Amazing Science | Scoop.it

Instead of heating or cooling your whole house, imagine a fabric that will keep your body at a comfortable temperature — regardless of how hot or cold it actually is. That’s the goal of an engineering project called ATTACH (Adaptive Textiles Technology with Active Cooling and Heating) at the University of California, San Diego, funded with a $2.6M grant from the U.S. Department of Energy’s Advanced Research Projects Agency – Energy (ARPA-E).


By regulating the temperature around an individual person, rather than a large room, the smart fabric could potentially cut the energy use of buildings and homes by at least 15 percent, said project leader Joseph Wang, distinguished professor of nanoengineering at UC San Diego.


“In cases where there are only one or two people in a large room, it’s not cost-effective to heat or cool the entire room,” said Wang. “If you can do it locally, like you can in a car by heating just the car seat instead of the entire car, you can save a lot of energy.”


The smart fabric will be designed to regulate the temperature of the wearer’s skin — keeping it at 93° F — by adapting to temperature changes in the room. When the room gets cooler, the fabric will become thicker. When the room gets hotter, the fabric will become thinner, using polymers inside the smart fabric that expand in the cold and shrink in the heat.


“93° F is the average comfortable skin temperature for most people,” added Renkun Chen, assistant professor of mechanical and aerospace engineering at UC San Diego, and one of the collaborators on this project.


The clothing will incorporate printable “thermoelectrics” into specific spots of the smart fabric to regulate the temperature on “hot spots” — such as areas on the back and underneath the feet — that tend to get hotter than other parts of the body when a person is active.


“With the smart fabric, you won’t need to heat the room as much in the winter, and you won’t need to cool the room down as much in the summer. That means less energy is consumed,” said Chen.


The researchers are also designing the smart fabric to power itself, using rechargeable batteries to power the thermoelectrics and biofuel cells that can harvest electrical power from human sweat.


The 3-D printable wearable parts will be thin, stretchable, and flexible to ensure that the smart fabric is not bulky or heavy. The material will also be washable, stretchable, bendable and lightweight. “We also hope to make it look attractive and fashionable to wear,” said Wang.

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Tiny niobium nanowires could provide a big energy boost for intelligent fabrics

Tiny niobium nanowires could provide a big energy boost for intelligent fabrics | Amazing Science | Scoop.it

Yarns of niobium nanowire can make supercapacitors to provide a surge of energy when it’s needed.


Wearable electronic devices for health and fitness monitoring are a rapidly growing area of consumer electronics; one of their biggest limitations is the capacity of their tiny batteries to deliver enough power to transmit data. Now, researchers at MIT and in Canada have found a promising new approach to delivering the short but intense bursts of power needed by such small devices.


The key is a new approach to making supercapacitors — devices that can store and release electrical power in such bursts, which are needed for brief transmissions of data from wearable devices such as heart-rate monitors, computers, or smartphones, the researchers say. They may also be useful for other applications where high power is needed in small volumes, such as autonomous microrobots.


The new approach uses yarns, made from nanowires of the element niobium, as the electrodes in tiny supercapacitors (which are essentially pairs of electrically conducting fibers with an insulator between). The concept is described in a paper in the journal ACS Applied Materials and Interfaces by MIT professor of mechanical engineering Ian W. Hunter, doctoral student Seyed M. Mirvakili, and three others at the University of British Columbia.


Nanotechnology researchers have been working to increase the performance of supercapacitors for the past decade. Among nanomaterials, carbon-based nanoparticles — such as carbon nanotubes and graphene — have shown promising results, but they suffer from relatively low electrical conductivity, Mirvakili says.


In this new work, he and his colleagues have shown that desirable characteristics for such devices, such as high power density, are not unique to carbon-based nanoparticles, and that niobium nanowire yarn is a promising an alternative.


“Imagine you’ve got some kind of wearable health-monitoring system,” Hunter says, “and it needs to broadcast data, for example using Wi-Fi, over a long distance.” At the moment, the coin-sized batteries used in many small electronic devices have very limited ability to deliver a lot of power at once, which is what such data transmissions need.


“Long-distance Wi-Fi requires a fair amount of power,” says Hunter, the George N. Hatsopoulos Professor in Thermodynamics in MIT’s Department of Mechanical Engineering, “but it may not be needed for very long.” Small batteries are generally poorly suited for such power needs, he adds.


“We know it’s a problem experienced by a number of companies in the health-monitoring or exercise-monitoring space. So an alternative is to go to a combination of a battery and a capacitor,” Hunter says: the battery for long-term, low-power functions, and the capacitor for short bursts of high power. Such a combination should be able to either increase the range of the device, or — perhaps more important in the marketplace — to significantly reduce size requirements.


The new nanowire-based supercapacitor exceeds the performance of existing batteries, while occupying a very small volume. “If you’ve got an Apple Watch and I shave 30 percent off the mass, you may not even notice,” Hunter says. “But if you reduce the volume by 30 percent, that would be a big deal,” he says: Consumers are very sensitive to the size of wearable devices.

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External magnetic field controlled, nanoscale bacteria-like robots could replace stents and angioplasty balloons

External magnetic field controlled, nanoscale bacteria-like robots could replace stents and angioplasty balloons | Amazing Science | Scoop.it

Swarms of microscopic, magnetic, robotic beads could be used within five years by vascular surgeons to clear blocked arteries. These minimally invasive microrobots, which look and move like corkscrew-shaped bacteria, are being developed by an $18-million, 11-institution research initiative headed by the Korea Evaluation Institute of Industrial Technologies (KEIT).


These “microswimmers” are driven and controlled by external magnetic fields, similar to how nanowires from Purdue University and ETH Zurich/Technion (recently covered on KurzweilAI) work, but based on a different design. Instead of wires, they’re made from chains of three or more iron oxide beads, rigidly linked together via chemical bonds and magnetic force. The beads are put in motion by an external magnetic field that causes each of them to rotate. Because they are linked together, their individual rotations cause the chain to twist like a corkscrew and this movement propels the microswimmer. The chains are small enough­­ — the nanoparticles are 50–100 nanometers in diameter — that they can navigate in the bloodstream like a tiny boat, Fantastic Voyage movie style (but without the microscopic humans) via a catheter to navigate directly to the blocked artery, where a drill would clear it completely.


Drilling through plaque:

The inspiration for using the robotic swimmers as tiny drills came from the Borrelia burgdorferi bacteria (shown above), which causes Lyme’s Disease and wreaks havoc inside the body by burrowing through healthy tissue. Its spiral shape enables both its movement and the resultant cellular destruction. By controlling the magnetic field, a surgeon could direct the speed and direction of the microswimmers. The magnetism also allows for joining separate strands of microswimmers together to make longer strings, which can then be propelled with greater force.


Once flow is restored in the artery, the microswimmer chains could disperse and be used to deliver anti-coagulant medication directly to the effected area to prevent future blockage. This procedure could supplant the two most common methods for treating blocked arteries: stenting and angioplasty. Stenting is a way of creating a bypass for blood to flow around the block by inserting a series of tubes into the artery, while angioplasty balloons out the blockage by expanding the artery with help from an inflatable probe.


“Current treatments for chronic total occlusion are only about 60 percent successful,” said MinJun Kim, PhD, a professor in the College of Engineering and director of the Biological Actuation, Sensing & Transport Laboratory (BASTLab) at Drexel University. “We believe that the method we are developing could be as high as 80–90 percent successful and possibly shorten recovery time. The microswimmers are composed of inorganic biodegradable beads so they will not trigger an immune response in the body. We can adjust their size and surface properties to accurately deal with any type of arterial occlusion.” Kim’s research was recently reported in the Journal of Nanoparticle Research.


Mechanical engineers at Drexel University are using these microswimmers as a part of a surgical toolkit being assembled by the Daegu Gyeongbuk Institute of Science and Technology (DGIST)Researchers from other institutions on the project include ETH ZurichSeoul National UniversityHanyang UniversityKorea Institute of Science and Technology, and Samsung Medical Center.


DGIST anticipates testing the technology in lab and clinical settings within the next four years.

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New nanogenerator harvests power from rolling tires

New nanogenerator harvests power from rolling tires | Amazing Science | Scoop.it
A group of University of Wisconsin-Madison engineers and a collaborator from China have developed a nanogenerator that harvests energy from a car's rolling tire friction.


An innovative method of reusing energy, the nanogenerator ultimately could provide automobile manufacturers a new way to squeeze greater efficiency out of their vehicles.


The researchers reported their development, which is the first of its kind, in a paper published May 6, 2015, in the journal Nano Energy.


Xudong Wang, the Harvey D. Spangler fellow and an associate professor of materials science and engineering at UW-Madison, and his PhD student Yanchao Mao have been working on this device for about a year.


The nanogenerator relies on the triboelectric effect to harness energy from the changing electric potential between the pavement and a vehicle's wheels. The triboelectric effect is the electric charge that results from the contact or rubbing together of two dissimilar objects. Wang says the nanogenerator provides an excellent way to take advantage of energy that is usually lost due to friction.


"The friction between the tire and the ground consumes about 10 percent of a vehicle's fuel," he says. "That energy is wasted. So if we can convert that energy, it could give us very good improvement in fuel efficiency." The nanogenerator relies on an electrode integrated into a segment of the tire. When this part of the tire surface comes into contact with the ground, the friction between those two surfaces ultimately produces an electrical charge-a type of contact electrification known as the triboelectric effect.

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Scientists Predict Existence of an Atomically Thin Flat Liquid

Scientists Predict Existence of an Atomically Thin Flat Liquid | Amazing Science | Scoop.it

2D materials were considered impossible until the discovery of graphene around ten years ago. However, they have been observed only in the solid phase, because the thermal atomic motion required for molten materials easily breaks the thin and fragile membrane.

Therefore, the possible existence of an atomically thin flat liquid was considered impossible.


Now, physicists at the University of Jyväskylä have conducted quantum molecular dynamics simulations that predict a liquid phase in atomically thin gold islands that patch small pores of graphene. According to the simulations, gold atoms flow and change places in the plane, while the surrounding graphene template retains the planarity of liquid membrane. “Here the role of graphene is similar to circular rings through which children blow soap bubbles,” said Dr Pekka Koskinen, lead author on the paper published in the journal Nanoscale.


“In general, the existence of a 2D liquid phase requires three conditions. First, the pore template itself has to remain stable at high temperatures, a condition easily met by graphene,” the scientists wrote in the paper.


“Second, edge interactions need to favor planar bonding and be robust enough to endure high temperatures. Our supplementary calculations showed that the gold-carbon interface has bending rigidity comparable to that of the 2D gold membrane, which is sufficient to retain the patch steady under gold diffusion.”


“Third, the membrane itself has to display 2D diffusion before out-of-plane fluctuations grow too large and initiate rupturing.”


Currently the flat liquid exists only in computers and is still waiting for experimental confirmation. “Unfortunately, simulations suggest that the flat liquid is volatile,” Dr Koskinen said. “In experiments the liquid membrane might burst too early, like a soap bubble that bursts before one gets a proper look at it.” “But again, even graphene was previously considered too unstable to exist.”

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Toward nanorobots that swim through blood to deliver drugs

Toward nanorobots that swim through blood to deliver drugs | Amazing Science | Scoop.it

Someday, treating patients with nanorobots could become standard practice to deliver medicine specifically to parts of the body affected by disease. But merely injecting drug-loaded nanoparticles might not always be enough to get them where they need to go. Now scientists are reporting in the ACS journal Nano Letters the development of new nanoswimmers that can move easily through body fluids to their targets.


Tiny robots could have many benefits for patients. For example, they could be programmed to specifically wipe out cancer cells, which would lower the risk of complications, reduce the need for invasive surgery and lead to faster recoveries. It’s a burgeoning field of study with early-stage models currently in development in laboratories. But one of the challenges to making these robots work well is getting them to move through body fluids, which are like molasses to something as small as a nanorobot. Bradley J. Nelson, Salvador Pané, Yizhar Or and colleagues wanted to address this problem.


The researchers strung together three links in a chain about as long as a silk fiber is wide. One segment was a polymer, and two were magnetic, metallic nanowires. They put the tiny devices in a fluid even thicker than blood. And when they applied an oscillating magnetic field, the nanoswimmer moved in an S-like, undulatory motion at the speed of nearly one body length per second. The magnetic field also can direct the swimmers to reach targets.


Watch the nanoswimmers in this video.

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'No-Ink' color printing with nanomaterials that is only visible with high-powered electron microscopy

'No-Ink' color printing with nanomaterials that is only visible with high-powered electron microscopy | Amazing Science | Scoop.it
Researchers at Missouri University of Science and Technology are giving new meaning to the term 'read the fine print' with their demonstration of a color printing process using nanomaterials.


this case, the print features are very fine – visible only with the aid of a high-powered electron microscope. The researchers describe their "no-ink" printing method in the latest issue of the Nature Publishing Group journal Scientific Reports and illustrate their technique by reproducing the Missouri S&T athletic logo on a nanometer-scale surface. A nanometer is one billionth of a meter, and some nanomaterials are only a few atoms in size.


The method described in the Scientific Reports article "Structural color printing based on plasmonic metasurfaces of perfect light absorption" involves the use of thin sandwiches of nanometer-scale metal-dielectric materials known as metamaterials that interact with light in ways not seen in nature. Experimenting with the interplay of white light on sandwich-like structures, or plasmonic interfaces, the researchers developed what they call "a simple but efficient structural color printing platform" at the nanometer-scale level. They believe the process holds promise for future applications, including nanoscale visual arts, security marking and information storage.


The researchers' printing surface consists of a sandwich-like structure made up of two thin films of silver separated by a "spacer" film of silica. The top layer of silver film is 25 nanometers thick and is punctured with tiny holes created by a microfabrication process known as focused ion beam milling. The bottom layer of silver is four times thicker than the top layer but still minuscule at 100 nanometers. Between the top and bottom films lies a 45-nanometer silica dielectric spacer.


The researchers created a scaled-down template of the athletic logo and drilled out tiny perforations on the top layer of the metamaterial structure. Under a scanning electron microscope, the template looks like a needlepoint pattern of the logo. The researchers then beamed light through the holes to create the logo using no ink – only the interaction of the materials and light.


By adjusting the hole size of the top layer, light at the desired frequency was beamed into the material with a perfect absorption. This allowed researchers to create different colors in the reflected light and thereby accurately reproduce the S&T athletic logo with nanoscale color palettes. The researchers further adjusted the holes to alter the logo's official green and gold color scheme to introduce four new colors (an orange ampersand, magenta "S" and "T," cyan pickaxe symbol and navy blue "Missouri").

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Microscopic sonic screwdriver invented

Microscopic sonic screwdriver invented | Amazing Science | Scoop.it

The research by academics from the University of Bristol’s Department of Mechanical Engineering and Northwestern Polytechnical University in China, is published in Physical Review Letters.


The researchers have shown that acoustic vortices act like tornados of sound, causing microparticles to rotate and drawing them to the vortex core. Like a tornado, what happens to the particles depends strongly on their size.


Bruce Drinkwater, Professor of Ultrasonics in the Department of Mechanical Engineering and one of the authors of the study, said: “We have now shown that these vortices can rotate microparticles, which opens up potential applications such as the creation of microscopic centrifuges for biological cell sorting or small-scale, low-power water purification.


“If the large-scale acoustic vortex devices were thought of as sonic screwdrivers, we have invented the watchmakers sonic screwdriver.” The research team used a number of tiny ultra-sonic loudspeakers arranged in a circle to create the swirling sound waves. They found that when a mixture of small microparticles (less than 1 micron) and water were introduced they rotated slowly about the vortex core. However, larger microparticles (household flour) were drawn into the core and were seen to spin at high speeds or become stuck in a series of circular rings due to acoustic radiation forces.


Dr ZhenYu Hong, of the Department of Applied Physics at Northwestern Polytechnical University in China, added: “Previously researchers have shown that much larger objects, centimeters in scale, could be rotated with acoustic vortices, proving that they carry rotational momentum.”

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Toxin-absorbing nanosponges could be used to soak up localized infections

Toxin-absorbing nanosponges could be used to soak up localized infections | Amazing Science | Scoop.it

Back in 2013, we heard that nanoengineers at the University of California, San Diago (UC San Diego) had successfully used nanosponges to soak up toxins in the bloodstream. Fast-forward two years and the team is back with more nanospongey goodness, now using hydrogel to keep the tiny fellas in place, allowing them to tackle infections such as MRSA, without the need for antibiotics.


Let's start with a quick recap. In 2013, a team of researchers announced that they'd successfully managed to create nanosponges – nanoparticles coated in red blood cell membranes – that flow through the bloodstream, removing harmful toxins as they go. The red blood cell coating tricks the immune system into ignoring the nanoparticles, but the disguise also attracts pore-forming toxins that kill cells by perforating their outer membranes.


This breakthrough was ideal if you wanted to deal with harmful toxins in the bloodstream, such as snake venom, but it didn't allow for a sustained attack in a localized region. Since the initial announcement, the team has been working on improving the method, with the new study focusing on adapting it to clear up antibiotic-resistant bacterial infections.


In order to keep the nanosponges tied to a specific area, the team turned to hydrogel – a gel made of water and polymers. The team mixed the nanosponges into the hydrogel, which then holds them in place at an infected spot, allowing for all of the toxins to be removed.


Nanosponges are some three thousand times smaller than red blood cells, allowing billions to be held in every milliliter of hydrogel. The gel's pores are small enough to keep the nanosponges in, but also large enough to allow the toxins to pass through, making it an ideal agent for delivery of the treatment.


As the method doesn't involve antibiotics, it's thought that it won't be affected by existing bacterial antibiotic resistance, and the bacteria shouldn't develop any new resistance in response to the treatment.

The nanosponge/hydrogel combination was tested on MRSA-infected mice, with the team observing significantly smaller lesions on treated as opposed to untreated subjects. The tests also confirmed that hydrogel was effective at holding the nanosponges in place, with 80 percent remaining at the site of infection two days after being injected.

The UC San Diego researchers posted the results of their study in the journal Advanced Materials.


Via Jocelyn Stoller
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New Nanotech Device Will Be Able To Target And Destroy Blood Clots

New Nanotech Device Will Be Able To Target And Destroy Blood Clots | Amazing Science | Scoop.it

One problem following a heart attack incident or a stroke is the presence of blood clots. These can make the severity of the condition worse or can trigger a recurrence. Medical procedures to address these life-threatening events need to be carried out in specialist hospital units and, in some cases due to the risk of internal bleeding, they cannot be performed. A blood clot is technically known as a venous thromboembolism (VTE). It is a serious medical condition and some groups of people are more at risk than others.


A research group have come up with a novel method based on nanotechnology to deal with blood clots. The method is easy to administer and it could be potentially given by medical staff on arriving to deal with a medical issue.


The developed device is a nanoparticle packed with a clot destroying compound. The outer shell of the nanoparticle is equipped with an antibody that is designed to target activated platelets (the cells that form blood clots.) The nanoparticles are given the lengthy name “poly(2-oxazoline) (POx)-based multifunctional polymer capsules.”


Once the nanoparticle reaches the blood clot, thrombin (a molecule at the center of the clotting process) breaks the shell of the nanocapsule. This releases the drug that wipes out the blood clots and prevents blockage to a blood vessel.


Speaking with International Business Times, lead researcher Professor Hagemeyer said of the nanoparticle method: “This can be given in the ambulance straight away so you really save a lot of time and restore the blood flow to the critical organs much faster than currently possible.” The nanotech device is at the early design stage. However, trials on animals have been successful and the objective is to move to human trials in the near future.


The research was carried out between Baker IDI Heart and the University of Melbourne. The study was funded by the National Heart Foundation of Australia. The findings have been published in the journal Advanced Materials, in a paper headed “Multifunctional Thrombin-Activatable Polymer Capsules for Specific Targeting to Activated Platelets.”

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Nanotechnology research leads to super-elastic conducting fibers

Nanotechnology research leads to super-elastic conducting fibers | Amazing Science | Scoop.it

An international research team based at The University of Texas at Dallas has made electrically conducting fibers that can be reversibly stretched to over 14 times their initial length and whose electrical conductivity increases 200-fold when stretched. The research team is using the new fibers to make artificial muscles, as well as capacitors whose energy storage capacity increases about tenfold when the fibers are stretched. Fibers and cables derived from the invention might one day be used as interconnects for super-elastic electronic circuits; robots and exoskeletons having great reach; morphing aircraft; giant-range strain sensors; failure-free pacemaker leads; and super-stretchy charger cords for electronic devices.


The new fibers differ from conventional materials in several ways. For example, when conventional fibers are stretched, the resulting increase in length and decrease in cross-sectional area restricts the flow of electrons through the material. But even a “giant” stretch of the new conducting sheath-core fibers causes little change in their electrical resistance, said Dr. Ray Baughman, senior author of the paper and director of the Alan G. MacDiarmid NanoTech Institute at UT Dallas.


One key to the performance of the new conducting elastic fibers is the introduction of buckling into the carbon nanotube sheets. Because the rubber core is stretched along its length as the sheets are being wrapped around it, when the wrapped rubber relaxes, the carbon nanofibers form a complex buckled structure, which allows for repeated stretching of the fiber.


“Think of the buckling that occurs when an accordion is compressed, which makes the inelastic material of the accordion stretchable,” said Baughman, the Robert A. Welch Distinguished Chair in Chemistry at UT Dallas.


“We make the inelastic carbon nanotube sheaths of our sheath-core fibers super stretchable by modulating large buckles with small buckles, so that the elongation of both buckle types can contribute to elasticity. These amazing fibers maintain the same electrical resistance, even when stretched by giant amounts, because electrons can travel over such a hierarchically buckled sheath as easily as they can traverse a straight sheath.”


Dr. Zunfeng Liu, lead author of the study and a research associate in the NanoTech Institute, said the structure of the sheath-core fibers “has further interesting and important complexity.” Buckles form not only along the fiber’s length, but also around its circumference.


“Shrinking the fiber’s circumference during fiber stretch causes this second type of reversible hierarchical buckling around its circumference, even as the buckling in the fiber direction temporarily disappears,” Liu said. “This novel combination of buckling in two dimensions avoids misalignment of nanotube and rubber core directions, enabling the electrical resistance of the sheath-core fiber to be insensitive to stretch.”


By adding a thin overcoat of rubber to the sheath-core fibers and then another carbon nanotube sheath, the researchers made strain sensors and artificial muscles in which the buckled nanotube sheaths serve as electrodes and the thin rubber layer is a dielectric, resulting in a fiber capacitor. These fiber capacitors exhibited a capacitance change of 860 percent when the fiber was stretched 950 percent.


Via CineversityTV
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Nanowires give 'solar fuel cell' efficiency a tenfold boost

Nanowires give 'solar fuel cell' efficiency a tenfold boost | Amazing Science | Scoop.it

Researchers make important step towards a solar cell that generates hydrogen.


Researchers have developed a very promising prototype of a new solar celll. The material gallium phosphide enables their solar cell to produce the clean fuel hydrogen gas from liquid water. Processing the gallium phosphide in the form of very small nanowires is novel and helps to boost the yield by a factor of ten. And does so using ten thousand times less precious material.


According to Bakkers, it's not simply about the yield -- where there is still a lot of scope for improvement he points out: "For the nanowires we needed ten thousand less precious GaP material than in cells with a flat surface. That makes these kinds of cells potentially a great deal cheaper," Bakkers says. "In addition, GaP is also able to extract oxygen from the water -- so you then actually have a fuel cell in which you can temporarily store your solar energy. In short, for a solar fuels future we cannot ignore gallium phosphide any longer."


GaP has good electrical properties but the drawback that it cannot easily absorb light when it is a large flat surface as used in GaP solar cells. The researchers have overcome this problem by making a grid of very small GaP nanowires, measuring five hundred nanometers (a millionth of a millimeter) long and ninety nanometers thick. This immediately boosted the yield of hydrogen by a factor of ten to 2.9 percent. A record for GaP cells, even though this is still some way off the fifteen percent achieved by silicon cells coupled to a battery.

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Nanoscale device that can emit light as powerfully as an object 10,000 times its size

Nanoscale device that can emit light as powerfully as an object 10,000 times its size | Amazing Science | Scoop.it
University of Wisconsin-Madison engineers have created a nanoscale device that can emit light as powerfully as an object 10,000 times its size. It's an advance that could have huge implications for a variety of imaging and energy applications.


In a paper published July 10, 2015 in the journal Physical Review Letters, Zongfu Yu, an assistant professor of electrical and computer engineering at UW-Madison, and his collaborators describe nanoscale device that  that drastically outpaces previous technology in its ability to scatter light.  They showed how a single nanoresonator can manipulate light to cast a very large "reflection."  The nanoresonator's capacity to absorb and emit light energy is such that it can make itself—and, in applications, other very small things—appear 10,000 times as large as its physical size.


"Making an object look much 10,000 times larger than its physical size has lots of implications in technologies related to light," Yu says. The researchers realized the advance through materials innovation and a keen understanding of the physics of light. Much like sound, light can resonate, amplifying itself as the surrounding environment manipulates the physical properties of its wave energy. The researchers took advantage of this by creating an artificial material in which the wavelength of light is much larger than in a vacuum, which allows light waves to resonate more powerfully.


In a paper published July 10, 2015 in the journal Physical Review Letters, Zongfu Yu, an assistant professor of electrical and computer engineering at UW-Madison, and his collaborators describe nanoscale device that  that drastically outpaces previous technology in its ability to scatter light.  They showed how a single nanoresonator can manipulate light to cast a very large "reflection."


The nanoresonator's capacity to absorb and emit light energy is such that it can make itself—and, in applications, other very small things—appear 10,000 times as large as its physical size.


"Making an object look much 10,000 times larger than its physical size has lots of implications in technologies related to light," Yu says. The researchers realized the advance through materials innovation and a keen understanding of the physics of light. Much like sound, light can resonate, amplifying itself as the surrounding environment manipulates the physical properties of its wave energy. The researchers took advantage of this by creating an artificial material in which the wavelength of light is much larger than in a vacuum, which allows light waves to resonate more powerfully.

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Gecko-inspired adhesives helps humans to climb glass walls and may provide a better grip for robotic arms

Gecko-inspired adhesives helps humans to climb glass walls and may provide a better grip for robotic arms | Amazing Science | Scoop.it

Forget Spider-man, and meet Geckoman. Researchers at Stanford University have created a gecko-inspired human climbing system that allowed a grad student to scale a glass wall using two hand-sized sticky pads. The researchers, led by engineer Mark Cutkosky, also hope to use the adhesives in manufacturing equipment, making grippers for manipulating huge solar panels, displays, and other objects without the need for suction power or chemical glues. The team is also working with NASA’s Jet Propulsion Laboratory to adapt the adhesive for use by robots.


Gecko toes are incredibly sticky because they are covered with groups of long, thin spatula-shaped structures called setae that increase surface area and amplify weak electrical attractions between the toes and a surface. Gecko feet stick well but are readily released when the animal shifts its weight; and of course, they can stick again and again, unlike most man-made adhesive tapes.


Researchers have made various artificial adhesives that work the same way, using clusters of carbon nanotubes or microscale wedges of molded rubber to mimic the high surface area of the setae on gecko feet. But these mechanisms have only worked well for small weights. Carrying larger weights requires materials with larger surface areas.


Using previous materials, a 70 kilogram human would require gecko-foot-like pads 10 times larger than a normal human hand in order to scale a wall. “Scaling gecko adhesion is a challenge,” says Cutkosky.


In 2015, the United States Defense Advanced Research Projects Agency (DARPAannounced that its Z-Man program had, for the first time, made a gecko-adhesive-based climbing system that enabled a person to scale a wall. Although DARPA didn’t provide details on how this was accomplished, the Stanford group, which participated in the Z-Man work, has made a similar demonstration using its own adhesive system. The work is described in research published today in the Journal of the Royal Society Interface.


To make the climbing system, the researchers started with an existing adhesive based on molded microwedges made from a polymer material called PDMS. They attached tiles of this material to a flat, hexagonal, hand-sized gripper. Each gripper was backed with a spring that distributed weight across the pad, and absorbed some of the force involved in climbing. To make climbing easier, the researchers also linked the grippers to platform for a person’s feet, thereby transferring the work of climbing to the legs.


Jeffrey Karp, a bioengineer at Brigham and Women’s Hospital in Boston, notes that the test situation involved a very smooth, clean, flat surface. Karp, who cofounded a company called Gecko Biomedical to commercialize a bioinspired surgical adhesive, says the Stanford researchers will need to show that their system works in less ideal environments. In the real world, a climbing system is liable to be exposed to humidity, rain, pollen, dust, and other contaminants, he notes.


The Stanford group hopes to test the adhesive in especially extreme conditions. This month they tested it in a zero-gravity airplane with NASA and found that it still worked.

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Lucile Debethune's curator insight, July 15, 2015 7:35 AM

l'homme augmenté pourra bientot grimper sur des surfaces verticales.. avec le même système que les gecko (de petites impulsions electrique, de très grande surfaces adhésives, et une capacité à faire passer la charge d'un endroit à l'autre facilement, et de manière quasi illimité . Waow

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The bioprinted ‘play dough’ capable of cell and protein transfer

The bioprinted ‘play dough’ capable of cell and protein transfer | Amazing Science | Scoop.it
Scientists have developed a new technique allowing the bioprinting at ambient temperatures of a strong paste similar to ‘play dough’ capable of incorporating protein-releasing microspheres.

The scientists demonstrated that the bioprinted material, in the form of a micro-particle paste capable of being injected via a syringe, could sustain stresses and strains similar to cancellous bone – the ‘spongy’ bone tissue typically found at the end of long bones.

This work, published today (3 July 2015) in the journal Biofabrication, suggests that bioprinting at ambient temperatures is a viable route to the production of materials for bone repair which would allow the inclusion of cells and proteins capable of accelerating the healing of large fractures.

“Bioprinting is a hot research area in tissue engineering,” explains Dr Jing Yang, of the University of Nottingham, a lead author on the paper. “However it usually requires a printing environment that isn’t compatible with living cells – and those materials that are compatible with living cells usually don’t have sufficient mechanical properties for certain applications.”

“Initially we’re targeting the clinical application of this material as injectable bone defect filler,” continues Dr Yang, “but we’ve postulated that its properties would make it highly suitable for use as a scaffold to reconstruct larger shapes, which could help with more complicated reconstructions – such as nasal reconstruction.”

Typically, bioprinting techniques involve high temperature processes, or the application of ultraviolet light or organic solvents, all of which prevent the incorporation of cells and therapeutic biomolecules during the fabrication process.

This technique involved blending poly(L-lactic-co-glycolic acid) and polyethylene glycol with carrier fluids at room temperature to form a micro-particulate extrudable paste that can be formed to desired shapes. These pastes were incubated at 37 °C to form porous solid constructs. The next steps of the process will be to apply this process in a clinical application.
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Researchers develop 100-fold cheaper and faster way to make graphene

Researchers develop 100-fold cheaper and faster way to make graphene | Amazing Science | Scoop.it

Scientists at the University of Exeter say they've developed a way to make graphene better, cheaper, faster -- and at mass scale. Lead researcher Monica Craciun says the technology, known as the nanoCVD system, promises to usher in "a graphene-driven industrial revolution."


Graphene is a single layer of carbon atoms, organized a honeycomb like structure. The material is super strong, flexible and conductive.


"The vision for a 'graphene-driven industrial revolution' is motivating intensive research on the synthesis of high quality and low cost graphene," Craciun said in a press release. "Currently, industrial graphene is produced using a technique called chemical vapor deposition (CVD). Although there have been significant advances in recent years in this technique, it is still an expensive and time consuming process."


Craciun and her colleagues, in cooperation with U.K.-based graphene company Moorfield, have tweaked CVD technology to develop a "cold wall" device. CVD technology mixes volatile vapors to create a desired deposited material (like a film of graphene) on a substrate.


The research team's new nanoCVD system reportedly grows graphene at a rate 100 times faster than traditional methods, and at one percent of the cost.


"We are very excited about the potential of this breakthrough using Moorfield's technology and look forward to seeing where it can take the graphene industry in the future," said Jon Edgeworth, the company's technical director.
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New “corner cloak” directs light around sharp edges

New “corner cloak” directs light around sharp edges | Amazing Science | Scoop.it

From fun-house mirrors to holograms, we have all experienced incredible optical illusions. Right now, scientists are fascinated by the prospect of finding a way to perform an even more challenging trick: hiding things in plain sight. We've made some metamaterials that have refractive indices that can redirect particular wavelengths of light. But one issue scientists have found particularly difficult to address is how to mask corners. Sharp corners are pretty common, and it's difficult to figure out ways to guide the surface waves of light around corners, as the light experiences scattering loss when encountering sharp corners. 


That's because there is a large mismatch in momentum of the light waves at the surface of an object before and after passing around the corner of an extremely compact shape. Though scientists have successfully developed a few materials that can perform scattering-free guidance of surface waves around corners, these methods are limited. They rely on photonic crystals with a large magnetic response, which limits the types of waves it can influence.


When waves encounter a sharp corner, they pass through compact space, which causes the change in momentum (yes, photons have momentum). More advanced cloaking methods have focused on compensating for this change in momentum by curving the electromagnetic space in a way that tricks light waves into behaving as if they're moving in a straight line. Through this method, transformative optics has made strides towards developing a real invisibility cloak.


In the new work, scientists have demonstrated a way of bending surface light waves around sharp corners, one that works across a broad range of wavelengths, exhibiting almost ideal transmission. This method is able to bend the waves in a way that does not disturb other wave properties, such as the amplitude and phase. This could actually allow for the development of an invisibility cloak.


The scientists created bending adaptors that were essentially “corner cloaks”—able to hide corners as the waves traveled around them. Physically, the corner cloaks are triangular pieces that can be placed over a sharp corner. The cloaks are made of layered structures of subwavelength foam and ceramic materials that had a refractive index that's able to redirect light. Experimental results show that the cloaks almost completely conceal their presence from anyone looking at the light that passed through them. It appears that the ultimate Harry Potter fantasy might be right around the corner for some of us.


PNAS, 2015. DOI: 10.1073/pnas.1508777112  (About DOIs).

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Tunable luminescent carbon nanospheres with well-defined nanoscale chemistry for synchronized imaging and therapy

Tunable luminescent carbon nanospheres with well-defined nanoscale chemistry for synchronized imaging and therapy | Amazing Science | Scoop.it

Researchers have found an easy way to produce carbon nanoparticles that are small enough to evade the body’s immune system, reflect light in the near-infrared range for easy detection, and carry payloads of pharmaceutical drugs to targeted tissues. 

Unlike other methods of making carbon nanoparticles – which require expensive equipment and purification processes that can take days – the new approach generates the particles in a few hours and uses only a handful of ingredients, including store-bought molasses. 

The researchers, led by University of Illinois bioengineering professors Dipanjan Pan and Rohit Bhargavareport their findings in the journal Small. 

“If you have a microwave and honey or molasses, you can pretty much make these particles at home,” Pan said. “You just mix them together and cook it for a few minutes, and you get something that looks like char, but that is nanoparticles with high luminescence. This is one of the simplest systems that we can think of. It is safe and highly scalable for eventual clinical use.”

These “next-generation” carbon spheres have several attractive properties, the researchers found. They naturally scatter light in a manner that makes them easy to differentiate from human tissues, eliminating the need for added dyes or fluorescing molecules to help detect them in the body. 

The nanoparticles are coated with polymers that fine-tune their optical properties and their rate of degradation in the body. The polymers can be loaded with drugs that are gradually released.

The nanoparticles also can be made quite small, less than eight nanometers in diameter (a human hair is 80,000 to 100,000 nanometers thick). 

“Our immune system fails to recognize anything under 10 nanometers,” Pan said. “So, these tiny particles are kind of camouflaged, I would say; they are hiding from the human immune system.”

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Three-dimensional Nanowire Structures for Ultra-Fast Separation of DNA, Protein and RNA

Three-dimensional Nanowire Structures for Ultra-Fast Separation of DNA, Protein and RNA | Amazing Science | Scoop.it

Separation and analysis of biomolecules represent crucial processes for biological and biomedical engineering development. However, separation resolution and speed for biomolecules analysis still require improvements. To achieve separation and analysis of biomolecules in a short time, the use of highly-ordered nanostructures fabricated by top-down or bottom-up approaches have been proposed. Here, a group of scientists reported on the use of three-dimensional (3D) nanowire structures embedded in microchannels fabricated by a bottom-up approach for ultrafast separation of small biomolecules, such as DNA, protein, and RNA molecules. The 3D nanowire structures could analyze a mixture of DNA molecules (50–1000 bp) within 50 s, a mixture of protein molecules (20–340 kDa) within 5 s, and a mixture of RNA molecules (100–1000 bases) within 25 s. The researchers observed the electrophoretic mobility difference of biomolecules as a function of molecular size in the 3D nanowire structures. Since the present methodology allows users to control the pore size of sieving materials by varying the number of cycles for nanowire growth, the 3D nanowire structures have a good potential for use as alternatives for other sieving materials. The presented method allows researchers to control the pore size between nanowires by varying the number of nanowire growth cycles and to select the pore size of the nanowires based on the analytical range of the target biomolecules.

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World’s smallest spirals could guard against identity theft

World’s smallest spirals could guard against identity theft | Amazing Science | Scoop.it
Vanderbilt researchers have made the world’s smallest spirals and found they have unique optical properties that are nearly impossible to counterfeit.


Take gold spirals about the size of a dime…and shrink them down about six million times. The result is the world’s smallest continuous spirals: “nano-spirals” with unique optical properties that would be almost impossible to counterfeit if they were added to identity cards, currency and other important objects.


Students and faculty at Vanderbilt University fabricated these tiny Archimedes’ spirals and then used ultrafast lasers at Vanderbilt and the Pacific Northwest National Laboratory in Richland, Washington, to characterize their optical properties. The results are reported in a paper published online by the Journal of Nanophotonics on May 21.


“They are certainly smaller than any of the spirals we’ve found reported in the scientific literature,” said Roderick Davidson II, the Vanderbilt doctoral student who figured out how to study their optical behavior. The spirals were designed and made at Vanderbilt by another doctoral student, Jed Ziegler, now at the Naval Research Laboratory.


When these spirals are shrunk to sizes smaller than the wavelength of visible light, they develop unusual optical properties. For example, when they are illuminated with infrared laser light, they emit visible blue light. A number of crystals produce this effect, called frequency doubling or harmonic generation, to various degrees. The strongest frequency doubler previously known is the synthetic crystal beta barium borate, but the nano-spirals produce four times more blue light per unit volume.


When infrared laser light strikes the tiny spirals, it is absorbed by electrons in the gold arms. The arms are so thin that the electrons are forced to move along the spiral. Electrons that are driven toward the center absorb enough energy so that some of them emit blue light at double the frequency of the incoming infrared light.


“This is similar to what happens with a violin string when it is bowed vigorously,” said Stevenson Professor of Physics Richard Haglund, who directed the research. “If you bow a violin string very lightly it produces a single tone. But, if you bow it vigorously, it also begins producing higher harmonics, or overtones. The electrons at the center of the spirals are driven pretty vigorously by the laser’s electric field. The blue light is exactly an octave higher than the infrared – the second harmonic.”

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One step closer to single-molecule devices

One step closer to single-molecule devices | Amazing Science | Scoop.it

Columbia Engineering researchers have created the first single-molecule diode — the ultimate in miniaturization for electronic devices — with potential for real-world applications in electronic systems. The diode that has a high (>250) rectification and a high “on” current (~ 0.1 microamps), says Latha Venkataraman, associate professor of applied physics. “Constructing a device where the active elements are only a single molecule … which has been the ‘holy grail’ of molecular electronics, represents the ultimate in functional miniaturization that can be achieved for an electronic device,” he said.


With electronic devices becoming smaller every day, the field of molecular electronics has become ever more critical in solving the problem of further miniaturization, and single molecules represent the limit of miniaturization. The idea of creating a single-molecule diode was suggested by Arieh Aviram and Mark Ratner who theorized in 1974 that a molecule could act as a rectifier, a one-way conductor of electric current.


Researchers have since been exploring the charge-transport properties of molecules. They have shown that single-molecules attached to metal electrodes (single-molecule junctions) can be made to act as a variety of circuit elements, including resistors, switches, transistors, and, indeed, diodes. They have learned that it is possible to see quantum mechanical effects, such as interference, manifest in the conductance properties of molecular junctions.


Since a diode acts as an electricity valve, its structure needs to be asymmetric so that electricity flowing in one direction experiences a different environment than electricity flowing in the other direction. To develop a single-molecule diode, researchers have simply designed molecules that have asymmetric structures. “While such asymmetric molecules do indeed display some diode-like properties, they are not effective,” explains Brian Capozzi, a PhD student working with Venkataraman and lead author of the paper.


“A well-designed diode should only allow current to flow in one direction, and it should allow a lot of current to flow in that direction. Asymmetric molecular designs have typically suffered from very low current flow in both ‘on’ and ‘off’ directions, and the ratio of current flow in the two has typically been low. Ideally, the ratio of ‘on’ current to ‘off’ current, the rectification ratio, should be very high.”


To overcome the issues associated with asymmetric molecular design, Venkataraman and her colleagues — Chemistry Assistant Professor Luis Campos’ group at Columbia and Jeffrey Neaton’s group at the Molecular Foundry at UC Berkeley — focused on developing an asymmetry in the environment around the molecular junction. They created an environmental asymmetry through a rather simple method: they surrounded the active molecule with an ionic solution and used gold metal electrodes of different sizes to contact the molecule. Their results achieved rectification ratios as high as 250 — 50 times higher than earlier designs. The “on” current flow in their devices can be more than 0.1 microamps, which, Venkataraman notes, is a lot of current to be passing through a single-molecule. And, because this new technique is so easily implemented, it can be applied to all nanoscale devices of all types, including those that are made with graphene electrodes.

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