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Molecular flip in crystals driven by light creates microrobotic propulsion

Molecular flip in crystals driven by light creates microrobotic propulsion | Amazing Science | Scoop.it

Hokkaido University researchers have designed a crystal material that continually flips between two positions like a paddle, propelling an attached structure, when stimulated by blue light. It could lead to bio-inspired microrobots that deliver drugs to target tissues, for example.

 

The team made azobenzene-oleic acid crystals, composed of an organic compound called azobenzene, commonly used in dye manufacturing, and oleic acid, commonly found in cooking oil. Azobenzene molecules take two structurally different forms: cis and trans, and they were found to switch back and forth when stimulated by the light.

 

The frequency of the motion also increased with increased light intensity. Some crystal complexes they created even exhibited swimming-like motions in the water, the researchers report. Previously reported light-responsive materials have been limited in their ability to deform, the researchers noted.

 

“The importance of this study lies in the realization of macroscopic self-oscillation by the repeated reversible reaction of a molecular machine with the cooperative transformation of a molecular assembly,” the researchers note in a paper published in the journal Angewandte Chemie.

 

“These results provide a fundamental strategy for constructing dynamic self-organizations in supramolecular systems to achieve bioinspired molecular systems.”

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Scientists grow atomically thin transistors and circuits

Scientists grow atomically thin transistors and circuits | Amazing Science | Scoop.it

In an advance that helps pave the way for next-generation electronics and computing technologies—and possibly paper-thin gadgets —scientists with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) developed a way to chemically assemble transistors and circuits that are only a few atoms thick.

 

What's more, their method yields functional structures at a scale large enough to begin thinking about real-world applications and commercial scalability. They report their research online July 11 in the journal Nature Nanotechnology.

 

The scientists controlled the synthesis of a transistor in which narrow channels were etched onto conducting graphene, and a semiconducting material called a transition-metal dichalcogenide, or TMDC, was seeded in the blank channels. Both of these materials are single-layered crystals and atomically thin, so the two-part assembly yielded electronic structures that are essentially two-dimensional. In addition, the synthesis is able to cover an area a few centimeters long and a few millimeters wide.

 

"This is a big step toward a scalable and repeatable way to build atomically thin electronics or pack more computing power in a smaller area," says Xiang Zhang, a senior scientist in Berkeley Lab's Materials Sciences Division who led the study.

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Scientists accidentally create nanorods that harvest water from the air

Scientists accidentally create nanorods that harvest water from the air | Amazing Science | Scoop.it

Learning from your mistakes is a key life lesson, and it's one that researchers at Pacific Northwest National Laboratory (PNNL) can attest to. After unintentionally creating carbon-rich nanorods, the team realized its accidental invention behaves weirdly with water, demonstrating a 20-year old theory and potentially paving the way to low-energy water harvesting systems and sweat-removing fabrics.

 

The researchers note that ordinarily materials will absorb more water as the humidity in the air around them increases. But between 50 and 80 percent relative humidity, these nanorods will actually do the opposite and expel water, a behavior they say is not shared by any other material. Below that range, they behave as normal, so the process is reversible by lowering the humidity again.

 

"Our unusual material behaves a bit like a sponge; it wrings itself out halfway before it's fully saturated with water," says David Lao, PNNL research associate and creator of the material. These nanorods were created by mistake while trying to fabricate magnetic nanowires, and the researchers decided to give the accidents a closer look. On examining them with a vapor analysis instrument, Satish Nune, one of the authors of the research paper, noticed that the structures were actually losing weight as the humidity increased.

 

Assuming the equipment was malfunctioning, the scientists switched to a microscope, and were able to observe water appearing from between the branches of the nanorods, and then evaporating at a higher humidity. On researching why this was the case, the team looked to previous works and found papers from 2012 and 2013 explaining how water can spontaneously vaporize when confined in an area just 1.5 nm wide, or when tightly surrounded by hydrophobic materials. Observations even go as far back as the 1990s, when scientists experimenting with crystallized proteins noticed similar happenings and theorized that some unknown process was allowing the water to rapidly evaporate.

 

The recent research at PNNL appears to be the first time this phenomenon has been directly seen in action. The team's hypothesis was that the water is condensing and drawing the branches of the nanorods together, and when they reach the 1.5 nm threshold, as specified in the previous work, the water quickly evaporates.

 

"Now that we've gotten over the initial shock of this unforeseen behavior, we're imagining the many ways it could be harnessed to improve the quality of our lives," says David Heldebrant, the second author of the paper.

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Artificial optical nanostructure outperforms butterfly wings

Artificial optical nanostructure outperforms butterfly wings | Amazing Science | Scoop.it

"Gyroid" photonic crystal could have a number of technological applications.

 

Using optical two-beam lithography with improved resolution and enhanced mechanical strength, we demonstrate the replication of gyroid photonic nanostructures found in the butterfly Callophrys rubi. These artificial structures are shown to have size, controllability, and uniformity that are superior to those of their biological counterparts. In particular, the elastic Young’s modulus of fabricated nanowires is enhanced by up to 20%. As such, the circular dichroism enabled by the gyroid nanostructures can operate in the near-ultraviolet wavelength region, shorter than that supported by the natural butterfly wings of C. rubi. This fabrication technique provides a unique tool for extracting three-dimensional photonic designs from nature and will aid the investigation of biomimetic nanostructures.

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Built-in miniaturized micro-supercapacitor powers silicon chip

Built-in miniaturized micro-supercapacitor powers silicon chip | Amazing Science | Scoop.it

Finnish researchers have developed a method for building highly efficient miniaturized micro-supercapacitor energy storage directly inside a silicon microcircuit chip, making it possible to power autonomous sensor networks, wearable electronics, and mobile internet-of-things (IoT) devices.

 

Supercapacitors function similar to standard batteries, but store electrostatic energy instead of chemical energy. The researchers at VTT Technical Research Centre of Finland have developed a hybrid nano-electrode that’s only a few nanometers thick. It consists of porous silicon coated with a titanium nitride layer formed by atomic layer deposition.

 

The nano-electrode design features the highest-ever conductive surface-to-volume ratio. That combined with an ionic liquid (in a microchannel formed in between two electrodes), results in an extremely small form factor and efficient energy storage. That design makes it possible for a silicon-based micro-supercapacitor to achieve higher energy storage (energy density) and faster charge/discharge (power density) than the leading carbon- and graphene-based supercapacitors, according to the researchers.

 

The micro-supercapacitor can store 0.2 joule (55 microwatts of power for one hour) on a one-square-centimeter silicon chip. This design also leaves the surface of the chip available for active integrated microcircuits and sensors.

 

Micro-supercapacitors can also be integrated directly with active microelectronic devices to store electrical energy generated by thermal, light, and vibration energy harvesters to supply electrical energy (see, for example, Wireless device converts ‘lost’ microwave energy into electric power).

 

An open-access paper on the research has been published in Nano Energy journal.

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Nanocars taken for a rough ride: Single molecule cars tested in open air

Nanocars taken for a rough ride: Single molecule cars tested in open air | Amazing Science | Scoop.it

Rice University researchers who developed the first nanocars and colleagues at North Carolina State University found in recent tests that driving their vehicles in ambient conditions -- exposed to open air, rather than a vacuum -- got dicey after a time because the hydrophobic single-molecule cars stuck to the "road" and created what amounted to large speed bumps.

The findings were reported in the American Chemical Society's Journal of Physical Chemistry C.

 

The work by Rice chemist James Tour, NC State analytical chemist Gufeng Wang and their colleagues came as Rice prepares to take part in the first NanoCar Race in Toulouse, France, in October. Rice researchers are members of one of five international teams that plan to enter the competition.

 

Just like in the macro world, driving conditions are important for moving nanocars. Though the race will be run in an ultra-cold vacuum, the Rice researchers thought it wise to study how their latest model of nanocars would fare in a more natural setting.

"Our long-term goal is to make nanomachines that operate in ambient environments," Tour said. "That's when they will show potential to become useful tools for medicine and bottom-up manufacturing."

 

The newest generation of Rice nanocars features adamantane wheels that are slightly hydrophobic (water-repellent). Tour said some hydrophobicity is important to help keep the nanocars attached to a surface, but if the tires are too hydrophobic, the cars could become permanently immobilized. That is because hydrophobic things tend to stick together to minimize the amount of surface area that is in contact with water. Things that are hydrophilic, or water-liking, are more amenable to floating freely in water, Tour said.

 

In the latest Rice tests with the new tires, the nanocars were placed on surfaces that were either clean glass or glass coated with the polymer polyethylene glycol (PEG). Glass is the most frequently used substrate in nanocar research. Tour said the PEG-coated glass slides were used for their anti-fouling -- nonsticky -- properties, while the clean glass slides were treated with hydrogen peroxide so the hydrophobic wheels wouldn't stick.

 

He said the cars weren't so much being driven as undergoing "directed diffusion" in the tests. The point, he said, was to establish the kinetics of nanocar movement and understand the potential energy surface interaction between the car and surface over time. "We wanted to know what makes a nanocar 'hit the brakes' and how much external energy we need to apply to start it moving again," he said. The researchers let their cars run freely on a solid surface exposed to the air and tracked their movements by exciting embedded fluorescent tags.

 

The cars that moved via Brownian diffusion slowed down during the 24 hours that the slides were under observation. Tour said slides absorbed molecules from the air; as more and more of these molecules stuck to the surface, the slides become progressively more "dirty" throughout the experiment. Each nanocar is a single, complex molecule that contains just a few hundred atoms, so any other molecules they encounter on the roadway are huge obstacles that act like sticky foam. Each collision with one of these obstructions makes the nanocar slow down, and eventually the cars become permanently stuck.

 

Wang said that from an energy perspective -- that is, the energetic relationship between the molecular cars and those that make up the road -- molecules adsorbed from air generate many potential energy wells, just like puddles on the potential energy surface. These puddles can slow or permanently trap the nanocars.

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Nanomotors swiftly silence genes

Nanomotors swiftly silence genes | Amazing Science | Scoop.it

The promise of short interfering RNA (siRNA) is that it can be harnessed to turn off harmful genes in the cell. The difficulty is getting siRNA into the cell in the first place. In a new approach, nanoengineers have driven siRNA into the cell on acoustically-propelled nanomotors, silencing genes faster and more completely than with current methods (ACS Nano2016, DOI: 10.1021/acsnano.6b01415).

 

To silence a gene, researchers tap the cell’s own gene suppression system, which quashes the RNA messengers that are produced when a DNA sequence is expressed. The messengers are knocked out by siRNA, complementary to a given messenger RNA, which binds the mRNA and prevents it from being translated into a protein. Scientists can mooch off the cell’s gene suppression infrastructure simply by inserting an engineered siRNA specific to a target into the cell.

 

But that’s easier said than done. The negatively charged siRNA has to cross a negatively-charged cell membrane, traverse the intracellular milieu, and bump into the cell’s silencing complex before degradation enzymes destroy it.

 

The delivery challenge has spawned a bounty of possible siRNA carriers: metal particles, lipid bubbles, hydrogels, and more. Most of these strategies rely on some form of chemical camouflage to enter the cell and on diffusion to do the rest. But Yi Chen and Joseph Wang of the University of California, San Diego, thought that ultrasound-propelled nanowires might produce an siRNA transporter with more oomph.

 

When bombarded with ultrasound, these tiny gold rods—about 4 μm long, 200 nm in diameter, and concave at one end—scurry into motion. They penetrate cells, bounce around like pinballs, and even spin.


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Combining nanotextured surfaces with the Leidenfrost effect for extreme water repellency

Combining nanotextured surfaces with the Leidenfrost effect for extreme water repellency | Amazing Science | Scoop.it

Combining superhydrophobic surfaces with Leidenfrost levitation--picture a water droplet hovering over a hot surface rather than making physical contact with it--has been explored extensively for the past decade by researchers hoping to uncover the holy grail of water-repellent surfaces.

 

In a new twist, a group of South Korean researchers from Seoul National University and Dankook University report an anomalous water droplet-bouncing phenomenon generated by Leidenfrost levitation on nano-textured surfaces in Applied Physics Letters.

 

"Wettability plays a key role in determining the equilibrium contact angles, contact angle hysteresis, and adhesion between a solid surface and liquid, as well as the retraction process of a liquid droplet impinged on the surface," explained Doo Jin Lee, lead author, and a postdoctoral researcher in the Department of Materials and Engineering at Seoul National University.

 

Non-wetting surfaces tend to be created by one of two methods. "First, textured surfaces enable non-wettability because a liquid can't penetrate into the micro- or nano-features, thanks to air entrapment between asperities on the textured materials," Lee said.

 

Or, second, the Leidenfrost effect "can help produce a liquid droplet dancing on a hot surface by floating it on a cushion of its own vapor," he added. "The vapor film between the droplet and heated surface allows the droplet to bounce off the surface--also known as the 'dynamic Leidenfrost phenomenon.'"

 

Lee and colleagues developed a special "non-wetting, nano-textured surface" so they could delve into the dynamic Leidenfrost effect's impact on the material.

 

"Our nano-textured surface was verified to be 'non-wetting' via thermodynamic analysis," Lee elaborated. "This analytical approach shows that the water droplet isn't likely to penetrate into the surface's nanoholes, which is advantageous for designing non-wetting, water-repellant systems. And the water droplet bouncing was powered by the synergetic combination of the non-wetting surface--often called a 'Cassie surface'--and the Leidenfrost effect."

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New method to improve photoluminescence efficiency of 2-D semiconductors

New method to improve photoluminescence efficiency of 2-D semiconductors | Amazing Science | Scoop.it
A team led by researchers from the National University of Singapore has developed a method to enhance the photoluminescence efficiency of tungsten diselenide, a two-dimensional semiconductor, paving the way for the application of such semiconductors in advanced optoelectronic and photonic devices.

 

Tungsten diselenide is a single-molecule-thick semiconductor that is part of an emerging class of materials called transition metal dichalcogenides (TMDCs), which have the ability to convert light to electricity and vice versa, making them strong potential candidates for optoelectronic devices such as thin film solar cells, photodetectors flexible logic circuits and sensors. However, its atomically thin structure reduces its absorption and photoluminescence properties, thereby limiting its practical applications.

 

By incorporating monolayers of tungsten diselenide onto gold substrates with nanosized trenches, the research team, led by Professor Andrew Wee of the Department of Physics at the NUS Faculty of Science, successfully enhanced the nanomaterial's photoluminescence by up to 20,000-fold. This technological breakthrough creates new opportunities of applying tungsten diselenide as a novel semiconductor material for advanced applications.

 

Ms Wang Zhuo, a PhD candidate from the NUS Graduate School for Integrative Sciences and Engineering (NGS) and first author of the paper, explained, "This is the first work to demonstrate the use of gold plasmonic nanostructures to improve the photo-luminescence of tungsten diselenide, and we have managed to achieve an unprecedented enhancement of the light absorption and emission efficiency of this nanomaterial."

 

Elaborating on the significance of the novel method, Prof Wee said, "The key to this work is the design of the gold plasmonic nanoarray templates. In our system, the resonances can be tuned to be matched with the pump laser wavelength by varying the pitch of the structures. This is critical for plasmon coupling with light to achieve optimal field confinement."


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Researchers create 1-step graphene patterning method

Researchers create 1-step graphene patterning method | Amazing Science | Scoop.it

Researchers from the University of Illinois at Urbana-Champaign have developed a one-step, facile method to pattern graphene by using stencil mask and oxygen plasma reactive-ion etching, and subsequent polymer-free direct transfer to flexible substrates.

 

Graphene, a two-dimensional carbon allotrope, has received immense scientific and technological interest. Combining exceptional mechanical properties, superior carrier mobility, high thermal conductivity, hydrophobicity, and potentially low manufacturing cost, graphene provides a superior base material for next generation bioelectrical, electromechanical, optoelectronic, and thermal management applications.

 

"Significant progress has been made in the direct synthesis of large-area, uniform, high quality graphene films using chemical vapor deposition (CVD) with various precursors and catalyst substrates," explained SungWoo Nam, an assistant professor of mechanical science and engineering at Illinois. "However, to date, the infrastructure requirements on post-synthesis processing--patterning and transfer--for creating interconnects, transistor channels, or device terminals have slowed the implementation of graphene in a wider range of applications."

 

"In conjunction with the recent evolution of additive and subtractive manufacturing techniques such as 3D printing and computer numerical control milling, we developed a simple and scalable graphene patterning technique using a stencil mask fabricated via a laser cutter," stated Keong Yong, a graduate student and first author of the paper, "Rapid Stencil Mask Fabrication Enabled One-Step Polymer-Free Graphene Patterning and Direct Transfer for Flexible Graphene Devices appearing in Scientific Reports.

 

"Our approach to patterning graphene is based on a shadow mask technique that has been employed for contact metal deposition," Yong added. "Not only are these stencil masks easily and rapidly manufactured for iterative rapid prototyping, they are also reusable, enabling cost-effective pattern replication. And since our approach involves neither a polymeric transfer layer nor organic solvents, we are able to obtain contamination-free graphene patterns directly on various flexible substrates."

 

Nam stated that this approach demonstrates a new possibility to overcome limitations imposed by existing post-synthesis processes to achieve graphene micro-patterning. Yong envisions this facile approach to graphene patterning sets forth transformative changes in "do It yourself" (DIY) graphene-based device development for broad applications including flexible circuits/devices and wearable electronics.

 

"This method allows rapid design iterations and pattern replications, and the polymer-free patterning technique promotes graphene of cleaner quality than other fabrication techniques," Nam said. "We have shown that graphene can be patterned into varying geometrical shapes and sizes, and we have explored various substrates for the direct transfer of the patterned graphene."

 

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Route to Carbyne: Scientists Create Ultra-Long 1D Carbon Chains

Route to Carbyne: Scientists Create Ultra-Long 1D Carbon Chains | Amazing Science | Scoop.it

Even in its elemental form, the high bond versatility of carbon allows for many different well-known materials, including diamond and graphite. A single layer of graphite, named graphene, can then be rolled or folded into carbon nanotubes or fullerenes, respectively. To date, Nobel prizes have been awarded for both graphene and fullerenes.

 

Although the existence of carbyne, an infinitely long carbon chain, was proposed in 1885 by Adolf von Baeyer, scientists have not yet been able to synthesize this material. Von Baeyer even suggested that carbyne (also known as linear acetylenic carbon) would remain elusive as its high reactivity would always lead to its immediate destruction. Nevertheless, carbon chains of increasing length have been successfully synthesized over the last five decades, with a record of around 100 carbon atoms.

To grow even longer carbon chains – up to 6,000 carbon atoms long – on a bulk scale, Dr. Pichler and his colleagues used the confined space inside a double-walled carbon nanotube as a nano-reactor.

 

“The direct experimental proof of confined ultra-long linear carbon chains, which are more than an order of magnitude longer than the longest proven chains so far, can be seen as a promising step towards the final goal of unraveling the ‘holy grail’ of carbon allotropes, carbyne,” said team member Lei Shi, from the Faculty of Physics at the University of Vienna. “Carbyne is very stable inside double-walled carbon nanotubes,” the scientists said. “This property is crucial for its eventual application in future materials and devices.”

 

“According to theoretical models, carbyne’s mechanical properties exceed all known materials, outperforming both graphene and diamond.”

 

“Carbyne’s electrical properties suggest novel nanoelectronic applications in quantum spin transport and magnetic semiconductors.” The results were published online April 4, 2016 in the journal Nature Materials (arXiv.org preprint).

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Penn Engineers Develop First Transistors Made Entirely of Nanocrystal Ink

Penn Engineers Develop First Transistors Made Entirely of Nanocrystal Ink | Amazing Science | Scoop.it

The transistor is the most fundamental building block of electronics, used to build circuits capable of amplifying electrical signals or switching them between the 0s and 1s at the heart of digital computation. Transistor fabrication is a highly complex process, however, requiring high-temperature, high-vacuum equipment. 

 

Now, University of Pennsylvania engineers have shown a new approach for making these devices: sequentially depositing their components in the form of liquid nanocrystal “inks.” Their new study, published in Science, opens the door for electrical components to be built into flexible or wearable applications, as the lower-temperature process is compatible with a wide array of materials and can be applied to larger areas. The researchers’ nanocrystal-based field effect transistors were patterned onto flexible plastic backings using spin coating but could eventually be constructed by additive manufacturing systems, like 3-D printers.

 

The study was lead by Cherie Kagan, the Stephen J. Angello Professor in the School of Engineering and Applied Science, and Ji-Hyuk Choi, then a member of her lab, now a senior researcher at the Korea Institute of Geoscience and Mineral Resources. Han Wang, Soong Ju Oh, Taejong Paik and Pil Sung Jo of the Kagan lab contributed to the work. They collaborated with Christopher Murray, a Penn Integrates Knowledge Professor with appointments in the School of Arts & Sciences and Penn Engineering; Murray lab members Xingchen Ye and Benjamin Diroll; and Jinwoo Sung of Korea’s Yonsei University.

The researchers began by taking nanocrystals, or roughly spherical nanoscale particles, with the electrical qualities necessary for a transistor and dispersing these particles in a liquid, making nanocrystal inks.

 

Kagan’s group developed a library of four of these inks: a conductor (silver), an insulator (aluminum oxide), a semiconductor (cadmium selenide) and a conductor combined with a dopant (a mixture of silver and indium). “Doping” the semiconductor layer of the transistor with impurities controls whether the device transmits a positive or negative charge. “These materials are colloids just like the ink in your inkjet printer,” Kagan said, “but you can get all the characteristics that you want and expect from the analogous bulk materials, such as whether they’re conductors, semiconductors or insulators.

 

“Our question was whether you could lay them down on a surface in such a way that they work together to form functional transistors.”

 

The electrical properties of several of these nanocrystal inks had been independently verified, but they had never been combined into full devices. “This is the first work,” Choi said, “showing that all the components, the metallic, insulating, and semiconducting layers of the transistors, and even the doping of the semiconductor could be made from nanocrystals.”

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Adding a topological fold to origami metamaterials

Adding a topological fold to origami metamaterials | Amazing Science | Scoop.it
Topological mechanics could play a key role in developing "smart" materials of the future

 

A metamaterial that is soft along one edge and rigid along the other, yet also displays mechanical topological properties, has been developed by an international team of researchers. This is the first time that topological origami and kirigami techniques have been applied experimentally to metamaterials – artificial materials with tunable, well-defined properties. Apart from having developed a metamaterial with two distinct topological phases, the team is also working on theoretical guidelines for the future design and development of such materials.

 

Researchers have become increasingly interested in recent years in using he ancient Japanese arts of paper folding and cutting – origami and kirigami, respectively – to build and create a variety of metamaterials. Indeed, Bryan Gin-ge Chen, at the University of Massachusetts Amherst, who led the latest work, sees origami as one of the earliest examples of a metamaterial. "All designs are folded from a square sheet of paper, but many different shapes and structures can result, which is exactly in line with the principle that a metamaterials' properties come from structure rather than composition," he explains.

 

Chen and colleagues in the US and the Netherlands were inspired by the novel idea of "topological mechanics", developed in 2014 by Charles Kane and Tom Lubensky from the University of Pennsylvania. Originating from the topological states seen in quantum physics, the idea was extended by Kane and Lubensky, who showed that there is a special class of mechanical structures that can be "polarized" so they are soft or floppy along one side, while being hard or rigid along the other.

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Researchers generate 3D images using just one photon per pixel

Researchers generate 3D images using just one photon per pixel | Amazing Science | Scoop.it

Every time you take a photograph, your camera detects more than a billion photons. For a basic one-megapixel camera, that's more than 1,000 photons per pixel. Now in a new study, researchers have developed an algorithm that is so efficient that it can generate high-quality 3D images using a single-photon camera that detects just one signal photon per pixel.

 

The researchers, led by Jeffrey Shapiro, a professor of electrical engineering and computer science at the Massachusetts Institute of Technology (MIT), along with coauthors at MIT, Politecnico di Milano, and Boston University, have published a paper on the new photon-efficient approach to imaging with a single-photon camera in a recent issue of Nature Communications.

 

"Our work shows that we can use these new photon-counting cameras at much lower fluxes and much higher efficiencies than previously thought," Shapiro explains. Compared to other camera-based 3D imaging techniques that have recently been developed, the new framework has the highest photon efficiency to date, resulting in a visibly better reconstruction accuracy and an order of magnitude better depth resolution.

 

To demonstrate how the new single-photon imaging algorithm works in low-light environments, the researchers illuminated a scene of interest (such as a mannequin and sunflower) with a pulsed laser that emits low-light pulses every 50 nanoseconds. A light diffuser spatially spreads out the pulses so that they flood the entire scene.

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Tiny DNA 'legs' walk with record fuel efficiency

Tiny DNA 'legs' walk with record fuel efficiency | Amazing Science | Scoop.it

For the first time, researchers have demonstrated a DNA nanomotor that can "walk" along a track with sustainable motion. The nanomotor also has the highest fuel efficiency for any type of walking nanomotor so far built.

 

Researchers Meihan Liu et al. at the National University of Singapore have published a paper on the DNA nanowalker in a recent issue of ACS Nano.

 

The tiny motor illustrates how purely physical effects can enable the efficient harvest of chemical energy at the single-molecule level. By operating on chemical energy, the new motor functions completely differently than any macroscopic motor, and brings researchers a step closer to replicating the highly efficient biomotors that transport cargo in living cells.

 

An important characteristic of the new nanowalker is that, like biomotors in living cells, it is an enzyme. This means that it helps initiate the fuel-producing chemical reaction that generates its motion without permanently changing itself or its track. This trait enables repeated, sustainable motion, which has not been achieved by any chemically powered synthetic nanowalker before now. Most other nanowalkers have been "burn-bridge motors," meaning they are not enzymes but instead consume their tracks as their fuel.

 

Creating enzymatic nanowalkers is very challenging, and so progress in this area has been relatively slow over the past few years. The only other demonstration of an enzymatic walker was in 2009, when researchers designed a nanowalker that, despite being enzymatic, cannot achieve sustainable motion because its track coils over time and eventually halts the motor. This nanowalker uses more than two fuel molecules per step, and studies since then have suggested that two fuel molecules per step is a general threshold for enzymatic nanomotors.

 

With its capability of sustainable motion and a fuel efficiency of approximately one molecule per step, the new nanowalker represents a leap of progress in this area.

 

The key to this achievement was finding a physical mechanism for efficiently harvesting chemical energy at the single-molecule level. This mechanism consists of three "chemomechanical gates" that basically ensure that the nanowalker walks by always picking up its back leg and not its front leg.

 

To do this, these gates physically control the order in which the products are released in the chemical reaction that propels the nanowalker forward. As a result, the DNA nanowalker's back leg dissociates from the track first and takes a step forward before the front leg dissociates. Then when the front leg becomes the back leg, that leg takes a step forward, and the walking cycle repeats. The dissociation of each leg occurs when an enzyme "cuts" one fuel molecule that is bound to the leg, so that one molecule is all that is needed to take one step. Using a fluorescence microscope, the researchers observed that the 20-nm-long nanowalker could move at speeds of up to 3 nm per minute.

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The ultimate discovery power of the gene chip is coming to nanotechnology

The ultimate discovery power of the gene chip is coming to nanotechnology | Amazing Science | Scoop.it

The discovery power of the gene chip is coming to nanotechnology, as a Northwestern University research team develops a  tool to rapidly test millions — and perhaps even billions — of different nanoparticles at one time to zero in on the best nanoparticle for a specific use.

 

When materials are miniaturized, their properties — optical, structural, electrical, mechanical and chemical — change, offering new possibilities. But determining what nanoparticle size and composition are best for a given application, such as catalysts, biodiagnostic labels, pharmaceuticals and electronic devices, is a daunting task.

 

“As scientists, we’ve only just begun to investigate what materials can be made on the nanoscale,” said Northwestern’s Chad A. Mirkin, a world leader in nanotechnology research and its application, who led the study. “Screening a million potentially useful nanoparticles, for example, could take several lifetimes. Once optimized, our tool will enable researchers to pick the winner much faster than conventional methods. We have the ultimate discovery tool.”

 

Combinatorial libraries of nanoparticles - more than half never existed on Earth.

 

Using a Northwestern technique that deposits materials on a surface, Mirkin and his team figured out how to make combinatorial libraries of nanoparticles in a controlled way. (A combinatorial library is a collection of systematically varied structures encoded at specific sites on a surface.) Their study was published today (June 24) by the journal Science.

The nanoparticle libraries are much like a gene chip, Mirkin says, where thousands of different spots of DNA are used to identify the presence of a disease or toxin. Thousands of reactions can be done simultaneously, providing results in just a few hours. Similarly, Mirkin and his team’s libraries will enable scientists to rapidly make and screen millions to billions of nanoparticles of different compositions and sizes for desirable physical and chemical properties.

 

“The ability to make libraries of nanoparticles will open a new field of nanocombinatorics, where size — on a scale that matters — and composition become tunable parameters,” Mirkin said. “This is a powerful approach to discovery science.”

Mirkin is the George B. Rathmann Professor of Chemistry in the Weinberg College of Arts and Sciences and founding director of Northwestern’s International Institute for Nanotechnology.

 

Using just five metallic elements — gold, silver, cobalt, copper and nickel — Mirkin and his team developed an array of unique structures by varying every elemental combination. In previous work, the researchers had shown that particle diameter also can be varied deliberately on the 1- to 100-nanometer length scale.

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Study shows band structure engineering is possible with organic semiconductors

Study shows band structure engineering is possible with organic semiconductors | Amazing Science | Scoop.it

A team of researchers with members from institutions in Germany and Switzerland has shown that band structure engineering is possible when designing organic semiconductors. In their paper published in the journal Science, the team describes a technique that involves long-range Coulomb interactions that are loosely bound by van der Walls forces. Nobuo Ueno with Chiba University, in Japan offers a deeper look at the work done by the team in a Perspective commentary in the same journal issue.

 

As Ueno notes, one of the most basic principles underlying semiconductor devices is the band gap—which is a measure of the energy needed to excite a material enough to make it conduct electricity. Much work has been done over the years to control the band gap in inorganic (non-carbon based) materials such as gallium, arsenide and of course silicon, by creating different alloys and putting them together in different ways to allow for tuning—success in this area meant that many different types of semiconductor based devices could be created. In recent years researchers have looked more and more at applying similar techniques to organic semiconductors, which as their name implies are semiconductors made from materials that are carbon based. Holding up such work has been an inability to find a way around the strong localization of the electronic states in them. In this new effort, the researchers report that they have developed a means at long last for engineering organic semiconductors.

 

The new approach involved taking note of the influence of Coulomb interactions (interactions that occur between electrically charged particles) which up to now, the team points out, have been mostly ignored by other researchers attempting to control band gaps in organic semiconductors. They found that the ionization energies of crystalline organic semiconductors could be tuned continuously over a large number of options by mixing them with their halogenated derivatives. In addition they showed that the photovoltaic gap and open-circuit voltage of organic solar cells could be tuned on a continuous basis by mixing the ratio of the donors.

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Study: Molecular motors shape chromosome structure

Study: Molecular motors shape chromosome structure | Amazing Science | Scoop.it

Human cells contain 23 pairs of chromosomes that form a loosely organized cluster in the cell nucleus. When cells divide, they must first condense these chromosomes — each of which when fully extended is a thousand times longer than the cell’s nucleus and physically indistinguishable from the others — into compact structures that can be easily separated and packaged into their offspring.

 

An MIT-led team has now developed a model that explains how cells handle this difficult task. In computer simulations, the researchers demonstrate that certain molecular “machines” can transform chromosomes from a loosely tangled rope into a series of tiny loops that condense each chromosome and allow it to extricate itself from the others. Moreover, the researchers demonstrate that a similar model explains how chromosomes are organized when cells are not dividing, and they hypothesize that loop extrusion by molecular motors splits chromosomes into separate domains, helping to control which genes are expressed in a given cell.

 

This mechanism, outlined in three recent papers published in Cell Reports, eLife, and Biophysical Journal, suggests that chromosome organization relies on proteins that act as molecular motors that pull strands of DNA into progressively larger loops. The MIT team suggests that two proteins thought to function primarily as “staples” that hold DNA together, cohesin and condensin, can also actively manipulate DNA.

 

“Nobody has ever directly observed this mechanism of loop extrusion. If it exists, it will solve lots of problems,” says Leonid Mirny, a professor of physics in MIT’s Institute for Medical Engineering and Sciences, who led the research. “We will know how chromosomes condense, how they segregate, how genes talk to enhancers. Lots of things can be solved by this mechanism.”

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Scientists Find a Better Way to Make Structures to Create DNA Based Tech

Scientists Find a Better Way to Make Structures to Create DNA Based Tech | Amazing Science | Scoop.it
Researchers have designed a new algorithm that automates the manipulation and sculpting of DNA into different shapes—a process known as DNA origami.

 

A team of researchers from MIT, Arizona State University, and Baylor University have devised a new computer algorithm that does all the hard work for you. The results of their research have been published in the journal Science.

 

“The paper turns the problem around from one in which an expert designs the DNA needed to synthesize the object, to one in which the object itself is the starting point, with the DNA sequences that are needed automatically defined by the algorithm,” says Mark Bathe, associate professor of biological engineering at MIT, and lead researcher for the study.

 

The new algorithm, which the team has called DAEDALUS, automates the entire business of sculpting DNA shapes; essentially, you begin with the desired shape (which must have a closed surface) and feed it into the algorithm, which then maps out the order of bases (adenine, guanine, cytosine and thymine) needed to produce the DNA “scaffold.”

 

DAEDALUS means “open source” DNA origami, enabling anyone with the inclination and access to the algorithm to design and create their own DNA-based, nanoscale objects. What Henry Ford’s assembly line concept did for manufacturing, DAEDALUS promises to do for nanoscale structures.

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Self-healing, flexible electronic material restores functions after many breaks

Self-healing, flexible electronic material restores functions after many breaks | Amazing Science | Scoop.it

Electronic materials have been a major stumbling block for the advance of flexible electronics because existing materials do not function well after breaking and healing. A new electronic material created by an international team, however, can heal all its functions automatically even after breaking multiple times. This material could improve the durability of wearable electronics.

 

"Wearable and bendable electronics are subject to mechanical deformation over time, which could destroy or break them," said Qing Wang, professor of materials science and engineering, Penn State. "We wanted to find an electronic material that would repair itself to restore all of its functionality, and do so after multiple breaks."

 

Self-healable materials are those that, after withstanding physical deformation such as being cut in half, naturally repair themselves with little to no external influence.

 

In the past, researchers have been able to create self-healable materials that can restore one function after breaking, but restoring a suite of functions is critical for creating effective wearable electronics. For example, if a dielectric material retains its electrical resistivity after self-healing but not its thermal conductivity, that could put electronics at risk of overheating.

 

The material that Wang and his team created restores all properties needed for use as a dielectric in wearable electronics -- mechanical strength, breakdown strength to protect against surges, electrical resistivity, thermal conductivity and dielectric, or insulating, properties. They published their findings online in Advanced Functional Materials.

 

Most self-healable materials are soft or "gum-like," said Wang, but the material he and his colleagues created is very tough in comparison. His team added boron nitride nanosheets to a base material of plastic polymer. Like graphene, boron nitride nanosheets are two dimensional, but instead of conducting electricity like graphene they resist and insulate against it.

 


Via Mariaschnee, CineversityTV
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Two-beam super-resolution lithography to make 3D photonic 'gyroid' nanostructures

Two-beam super-resolution lithography to make 3D photonic 'gyroid' nanostructures | Amazing Science | Scoop.it

"A team of researchers with Swinburne University of Technology in Australia has found a way to use two-beam super-resolution lithography to create 3D photonic "gyroid" nanostructures—similar to those found in butterfly wings. In their paper published in the journal Science Advances, the team describes their technique and some applications to which it might be applied.


Scientists have known for some time that butterfly wings have "gyroid" nanostructures in them (arranged in grid patterns), that serve the butterflies by manipulating light in useful ways. In addition to their photonic properties, the structures, which are made of intertwining curved surfaces, were also found to be very strong for their size, which has caused scientists to see if they might find a way to create them artificially. Up till now, such efforts have left a lot to be desired—most do not have a high enough resolution or are too fragile. In this new effort, the researchers report that rather than rely on traditional methods, such as two-photon polymerization, the team went with optical two-beam super-resolution lithography—they compare it to direct laser writing techniques, noting that it has two major advantages over other techniques used in the past. The first is that it offers much better resolution and the second is that the resulting structure has more mechanical strength."


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The next step in DNA computing: GPS mapping?

The next step in DNA computing: GPS mapping? | Amazing Science | Scoop.it

Conventional silicon-based computing, which has advanced by leaps and bounds in recent decades, is pushing against its practical limits. DNA computing could help take the digital era to the next level. Scientists are now reporting progress toward that goal with the development of a novel DNA-based GPS. They describe their advance in ACS' The Journal of Physical Chemistry B.

 

Jian-Jun Shu and colleagues note that Moore's law, which marked its 50thanniversary in April, posited that the number of transistors on a computer chip would double every year. This doubling has enabled smartphone and tablet technology that has revolutionized computing, but continuing the pattern will come with high costs. In search of a more affordable way forward, scientists are exploring the use of DNA for its programmability, fast processing speeds and tiny size. So far, they have been able to store and process information with the genetic material and perform basic computing tasks. Shu's team set out to take the next step.

 

The researchers built a programmable DNA-based processor that performs two computing tasks at the same time. On a map of six locations and multiple possible paths, it calculated the shortest routes between two different starting points and two destinations. The researchers say that in addition to cost- and time-savings over other DNA-based computers, their system could help scientists understand how the brain's "internal GPS" works.

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Injectable nanoparticles deliver cancer therapy in mice

Injectable nanoparticles deliver cancer therapy in mice | Amazing Science | Scoop.it

Researchers designed and tested a system that delivered nanometer-sized particles of a cancer drug to tumors in mice, improving survival.

 

Many drugs for treating cancer work by slowing or stopping the growth of cancerous cells. However, there are numerous barriers that can hinder a drug’s ability to work successfully. A drug needs to reach and get inside cancerous cells—whether they’re in the liver, breast, or lung. The drug must also avoid damaging healthy, non-cancerous tissues—such as the heart and kidneys—to prevent side effects.

 

A team led by Drs. Mauro Ferrari and Haifa Shen at Houston Methodist Research Institute has been working to overcome the many hurdles to successful cancer treatment by harnessing nanotechnology to deliver drugs directly into cancerous cells. The group set out to develop and test an injectable carrier of nanoparticles that contain a chemotherapy drug. The work was funded in part by NIH’s National Cancer Institute. Results were published on March 14, 2016, in Nature Biotechnology.

 

The scientists turned to doxorubicin (dox), a drug used to treat many cancer types. They attached dox to string-like molecules, known as poly(L-glutamic acid), through a pH-sensitive link. This formed a drug complex called pDox. The team made disk-shaped, micrometer-sized silicon particles to serve as a carrier for the pDox. The pDox was loaded into the particles through nanometer-sized pores.

 

When the researchers injected pDox-containing silicon particles intravenously into mice with cancerous tumors, the particles traveled through the blood stream and accumulated at the site of tumors, where blood vessels are leakier. The silicon, which was designed to degrade, released pDox molecules at the tumor site. These molecules spontaneously formed nanoparticles, which were then taken up by tumor cells.

 

Once inside cancerous cells, the pDox was transported to the area around the nucleus through vesicular transport. Due to the acidic environment near the nucleus, the dox was cleaved from its attachment to the poly(L-glutamic acid). This resulted in a high concentration of dox within the nuclei of the cancerous cells.

 

In contrast, when the researchers injected the drug dox alone, high levels appeared in non-cancerous tissues, such as the heart, leading to damage.

 

The team tested the therapy in several mouse cancer models, including triple-negative breast cancer, which is difficult to treat. Mice treated with the pDox-containing particles had much smaller and fewer tumors. They also had a longer survival time than mice given a saline control. The group found that 40-50% of cancer-bearing mice given the treatment showed no signs of metastatic tumors 8 months later. “We invented a method that actually makes the nanoparticles inside the cancer and releases the drug particles at the site of the cellular nucleus,” Ferrari says.

 

The silicon-based carrier could transport other chemicals, or combinations of chemicals, besides dox. The team plans to begin safety and efficacy studies in humans in the future.


Via Krishan Maggon
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Wafer-scale Nanotube Film Is Finally Here

Wafer-scale Nanotube Film Is Finally Here | Amazing Science | Scoop.it
Wafer-scale production technique could lead to single-walled carbon nanotubes finally fulfilling their promise in a range of applications

 

Single-walled carbon nanotubes (SWCNTs) used to be the darling of those who were looking for an alternative to silicon in digital electronics. The first SWCNT-based transistors were fashioned almost twenty years ago, but scaling up the use of SWCNTs since then to very large scale integration (VLSI) processes has remained elusive.

 

There were two persistent problems with SWCNTs that led to much of theresearch community pursuing graphene instead of SWCNTs as the next great post-silicon hope: an inconsistency between semiconducting and metallic nanotubes and the frustration of trying to get all of the nanotubes to align on a wafer.

 

Now researchers at Rice University claim that they have struck upon a method that produces a uniform and wafer-scale film of highly aligned and densely packed SWCNTs that may finally deliver on the long-promised potential of SWCNTs.

 

In research published in the journal Nature Nanotechnology, the Rice researchers’ method starts by preparing a well-dispersed CNT suspension, which requires getting just the right concentration of CNT powder with a surfactant in water. The next step involves a vacuum filtration method that has long been the established technique for creating wafer-scale films of CNTs with controllable thickness. The CNT suspension is poured into a filtration funnel with small pores. Pressure pushes the suspension through those pores so that CNTs are left behind on the filter membrane.

 

The SWCNTs spontaneously align as long as both the surfactant level in the dispersion and the CNT concentration are just right and the filtration process is done slowly and carefully. When these criteria are met, a wafer-scale, uniform and aligned SWCNT film forms on the filter membrane.

 

The film can be easily transferred onto a substrate by dissolving the filter membrane on the substrate, which leaves perfectly aligned SWCNTs in place. In addition to the problem of alignment, many methods that have been used for aligning SWCNTs result in low density. However, in this method the density is quite high with 1×106 CNTs found in a cross-sectional area of 1 square micrometer. Finally, the film can be patterned by standardphotolithography methods.

 

The researchers have put the resulting material to the test by producing terahertz/infrared polarizers using a mix of metallic and semiconductor CNTs; and they fabricated thin-film transistors, polarized light-emission devices and polarization-sensitive photodetectors using only semiconducting CNTs.

 

The Rice team believes that this method should create not only new avenues for fundamental research in physics, chemistry and materials science, but will also enable the use of SWCNTs in electronics, optoelectronics, sensing, imaging and medicine.

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Artificial DNA could build new generation of cancer drugs

Artificial DNA could build new generation of cancer drugs | Amazing Science | Scoop.it

Scientists have built the first 3D nano-sized objects using artificial DNA, which could be used to deploy cancer treatments inside tumor cells. The team from The Institute of Cancer Research, London, and the University of Cambridge created microscopic pyramid- and diamond-shaped 3D ‘packets’ by folding together artificial nucleic acid building blocks called Xeno nucleic acids (XNAs).

 

They saw that XNA made pyramid packets that were more stable in biological environments than DNA-made structures, keeping their shape for eight days compared with DNA nanostructures, which degraded after two.

 

The research was published in ChemBioChem and funded by the Medical Research Council and the Biotechnology and Biological Sciences Research Council, with additional support from Cancer Research UK and the European Science Foundation.

 

DNA nanotechnology is an exciting new way to manipulate genetic material, which could have huge benefits for biomedical research and clinical care.

 

Strands of DNA or RNA can be folded to make microscopic packets which could detect important biological markers of cancer, or be used to transport cancer treatments into cells to make them more effective. However, DNA-cutting enzymes in human tissue can break down these nanostructures very rapidly, limiting their use as medical treatments.

 

The 3D nanostructures using XNA building blocks – in which the sugar backbone of human nucleic acid strands is chemically altered in ways that do not occur in nature – were first developed by the University of Cambridge and had greater bio-stability and wider ranging physical and chemical properties than DNA.

 

They saw that XNAs behaved in a similar way to DNA nanostructures, folding to produce 3D tetrahedrons (pyramid shaped) and octahedrons (diamond shaped) as intended, which ICR researchers confirmed using electron microscopy.

 

When tested inside cell cultures, tetrahedral XNA packets kept their shape inside for eight days, compared with structures made from DNA which degraded after two days.

 

Dr Edward Morris, Leader of the ICR’s Structural Electron Microscopy team, said: “DNA has shown great promise as a potential building material for nano-molecular scale objects, but unfortunately they tend to get broken down quite quickly by our bodies and this may limit their clinical use. Our research with scientists from the University of Cambridge shows that you can make robust microscopic 3D shapes using this novel XNA chemistry which can stand up to conditions inside the body.


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