Amazing Science
775.1K views | +98 today
Amazing Science
Amazing science facts - 3D_printing • aging • AI • anthropology • art • astronomy • bigdata • bioinformatics • biology • biotech • chemistry • computers • cosmology • education • environment • evolution • future • genetics • genomics • geosciences • green_energy • history • language • map • material_science • math • med • medicine • microscopy • nanotech • neuroscience • paleontology • photography • photonics • physics • postings • robotics • science • technology • video
Your new post is loading...
Scooped by Dr. Stefan Gruenwald!

'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 |
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").

No comment yet.
Scooped by Dr. Stefan Gruenwald!

Microscopic sonic screwdriver invented

Microscopic sonic screwdriver invented | Amazing Science |

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.”

No comment yet.
Rescooped by Dr. Stefan Gruenwald from Research Workshop!

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

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

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
No comment yet.
Scooped by Dr. Stefan Gruenwald!

Artificial muscles created from gold-plated onion cells

Artificial muscles created from gold-plated onion cells | Amazing Science |

Just one well-placed slice into a particularly pungent onion can send even the most seasoned chef running for a box of tissues. Now, this humble root vegetable is proving its strength outside the culinary world as well -- in an artificial muscle created from onion cells. Unlike previous artificial muscles, this one, created by a group of researchers from National Taiwan University, can either expand or contract to bend in different directions depending on the driving voltage applied. The finding is published this week in the journalApplied Physics Letters, from AIP Publishing. "The initial goal was to develop an engineered microstructure in artificial muscles for increasing the actuation deformation [the amount the muscle can bend or stretch when triggered]," said lead researcher Wen-Pin Shih. "One day, we found that the onion's cell structure and its dimensions were similar to what we had been making." Shih lead the study along with graduate student Chien-Chun Chen and their colleagues.

The onion epidermis -- the fragile skin found just beneath the onion's surface -- is a thin, translucent layer of blocky cells arranged in a tightly-packed lattice. Shih and his colleagues thought that onion epidermal cells might be a viable candidate for the tricky task of creating a more versatile muscle that could expand or contract while bending. To date, Shih said, artificial muscles can either bend or contract, but not at the same time.

The researchers treated the cells with acid to remove the hemicellulose, a protein that makes the cell walls rigid. Then, they coated both sides of the onion layer with gold. When current flowed through the gold electrodes, the onion cells bent and stretched much like a muscle. "We intentionally made the top and bottom electrodes a different thickness so that the cell stiffness becomes asymmetric from top to bottom," said Shih. The asymmetry gave the researchers control over the muscle's response: a low voltage made them expand and flex downwards, towards the thicker bottom layer. A high voltage, on the other hand, caused the cells to contract and flex upwards, towards the thinner top layer.

"We found that the single-layer lattice structure can generate unique actuation modes that engineered artificial muscle has never achieved before," said Shih. To demonstrate their device's utility, the researchers combined two onion muscles into a pair of tweezers, which they used to pick up a cotton ball. In the future, they hope to increase the lifting power of their artificial muscles. "Our next step is to reduce the driving voltage and the actuating force," said Shih.

No comment yet.
Scooped by Dr. Stefan Gruenwald!

Scientists tune X-rays with tiny mirrors

Scientists tune X-rays with tiny mirrors | Amazing Science |

The secret of X-ray science – like so much else – is in the timing. Scientists at the U.S. Department of Energy’s (DOE) Argonne National Laboratory have created a new way of manipulating high-intensity X-rays, which will allow researchers to select extremely brief but precise X-ray bursts for their experiments.

The new technology, developed by a team of scientists from Argonne’s Center for Nanoscale Materials (CNM) and the Advanced Photon Source (APS), involves a small microelectromechanical system (MEMS) mirror only as wide as a few hairs.

MEMS are microscale devices fabricated using silicon wafers in facilities that make integrated circuits. The MEMS device acts as an ultrafast mirror reflecting X-rays at precise times and specific angles.

“Extremely compact devices such as this promise a revolution in our ability to manipulate photons coming from synchrotron light sources, not only providing an on-off switch enabling ultrahigh time-resolution studies, but ultimately promising new ways to steer, filter, and shape X-ray pulses as well,” said Stephen Streiffer, Associate Laboratory Director for Photon Sciences and Director of the Advanced Photon Source. “This is a premier example of the innovation that results from collaboration between nanoscientists and X-ray scientists.”

The device that the Argonne researchers developed essentially consists of a tiny diffracting mirror that oscillates at high speeds. As the mirror tilts rapidly back and forth, it creates an optical filter that selects only the X-ray pulses desired for the experiment. Only the light that is diffracted from the mirror goes on to hit the sample, and by adjusting the speed at which the MEMS mirror oscillates, researchers can control the timing of the X-ray pulses.

According to Argonne nanoscientist Daniel Lopez, one of the lead authors on the paper, the device works because of the relationship between the frequency of the mirror’s oscillation and the timing of the positioning of the perfect angle for the incoming X-ray. “If you sit on a Ferris wheel holding a mirror, you will see flashes of light every time the wheel is at the perfect spot for sunlight to hit it. The speed of the Ferris wheel determines the frequency of the flashes you see,” he said.

“The Argonne team’s work is incredibly exciting because it creates a new class of devices for controlling X-rays,” added Paul Evans, a professor of materials science at the University of Wisconsin-Madison. “They have found a way to significantly shrink the optics, which is great because smaller means faster, cheaper to make, and much more versatile.”

No comment yet.
Scooped by Dr. Stefan Gruenwald!

Scientists use nanoscale building blocks and DNA 'glue' to shape 3-D superlattices

Scientists use nanoscale building blocks and DNA 'glue' to shape 3-D superlattices | Amazing Science |
aking child's play with building blocks to a whole new level-the nanometer scale-scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory have constructed 3D "superlattice" multicomponent nanoparticle arrays where the arrangement of particles is driven by the shape of the tiny building blocks. The method uses linker molecules made of complementary strands of DNA to overcome the blocks' tendency to pack together in a way that would separate differently shaped components. The results, published in Nature Communications, are an important step on the path toward designing predictable composite materials for applications in catalysis, other energy technologies, and medicine. "If we want to take advantage of the promising properties of nanoparticles, we need to be able to reliably incorporate them into larger-scale composite materials for real-world applications," explained Brookhaven physicist Oleg Gang, who led the research at Brookhaven's Center for Functional Nanomaterials (CFN), a DOE Office of Science User Facility.

"Our work describes a new way to fabricate structured composite materials using directional bindings of shaped particles for predictable assembly," said Fang Lu, the lead author of the publication.

The research builds on the team's experience linking nanoparticles together using strands of synthetic DNA. Like the molecule that carries the genetic code of living things, these synthetic strands have complementary bases known by the genetic code letters G, C, T, and A, which bind to one another in only one way (G to C; T to A). Gang has previously used complementary DNA tethers attached to nanoparticles to guide the assembly of a range of arrays and structures. The new work explores particle shape as a means of controlling the directionality of these interactions to achieve long-range order in large-scale assemblies and clusters.

Spherical particles, Gang explained, normally pack together to minimize free volume. DNA linkers-using complementary strands to attract particles, or non-complementary strands to keep particles apart-can alter that packing to some degree to achieve different arrangements. For example, scientists have experimented with placing complementary linker strands in strategic locations on the spheres to get the particles to line up and bind in a particular way. But it's not so easy to make nanospheres with precisely placed linker strands.

"We explored an alternate idea: the introduction of shaped nanoscale 'blocks' decorated with DNA tethers on each facet to control the directional binding of spheres with complementary DNA tethers," Gang said.
No comment yet.
Scooped by Dr. Stefan Gruenwald!

Real-time multicolor imaging with luminescent protein-based Nano-lanterns

Real-time multicolor imaging with luminescent protein-based Nano-lanterns | Amazing Science |

While fluorescence imaging (in which external light is used to excite a specimen that then emits light in response) is essential in cell biology, it has a number of significant drawbacks, including autofluorescence, phototoxicity and photobleaching, resulting from that excitation light. In addition, fluorescence imaging has the unfortunate side effect of triggering cellular activation when combined with optogenetics – an otherwise extremely valuable tool. On the other hand, luminescence (in this case, a type of chemiluminescence called bioluminescence) imaging doesn't require light activation, and so eschews these issues – but currently suffers from low brightness and poor color variants.

Recently, however, scientists at RIKEN and Osaka University extended their previous development of a bright yellowish-green luminescent protein Nano-lantern to devise bright cyan and orange luminescent proteins some 20 times brighter than previously possible with wild-type (i.e., naturally-occurring) Renilla luciferase, or Rluc – an oxidative enzyme associated with a luciferin-binding protein – found in a type of soft coral known as a sea pansy. (Luciferins are organic substances, found in luminescent organisms, which produce a near-heatless light upon oxidation.) Specifically, the researchers accomplished this by bioluminescence resonance energy transfer (BRET) from enhanced Renilla luciferase to a fluorescent protein, stating that their proof-of-principle experiments show that luminescence imaging has become a practical alternative when the side effects by the excitation light are not negligible – for example, when the samples are very sensitive to photodamage – and that the most effective future application of luminescence imaging lies in combining it with optogenetics, since the latter's external light illumination can be reserved for optical stimulation.

Dr. Yasushi Okada discussed the paper that he, Dr. Akira Takai, Dr. Takeharu Nagai, and their colleagues published in Proceedings of the National Academy of Sciences, starting with the challenges of developing cyan and orange luminescent proteins approximately 20 times brighter than wild-type Renilla luciferase. "Making the cyan version was straightforward," Okada tells "We acquired the best available cyan fluorescent protein, mTurquoise2," or mTq2, "from Dr Joachim Goedhart at University of Amsterdam. I was so impressed with the title of his paper1 that I immediately requested the plasmid – and he said that my request was the first he received. Several weeks after, we started working with our colleague Dr. Takeharu Nagai on yellow lanterns and soon came up with the idea of swapping the mVenus used in the yellow Nano-lantern," or YNL, "with mTq2 – and it worked excellently, producing the cyan Nano-lantern," or CNL.

Okada adds that developing the orange Nano-lantern (ONL) took trial-and-error. "We initially planned to use a large Stokes shift orange fluorescent protein like LSSmOrange2, but it didn't work well." A Stokes shift, which is essential in fluorescence imaging, refers to the difference between the energy (i.e., wavelength) of the excitation and emitted photons – and a large Stokes shift typically indicates a greater difference and thereby easier detection. "We therefore tested all possible combinations of available orange to red fluorescent proteins and Rluc variants – hundreds of them – and we finally identified the best combination." That combination became the orange Nano-lantern.

No comment yet.
Scooped by Dr. Stefan Gruenwald!

Nanotubes self-organize and wiggle: Evolution of a non-equilibrium system shows maximum entropy production

Nanotubes self-organize and wiggle: Evolution of a non-equilibrium system shows maximum entropy production | Amazing Science |

Physicists Alexey BezryadinAlfred Hubler, and Andrey Belkin from the University of Illinois at Urbana-Champaign, have demonstrated the emergence of self-organized structures that drive the evolution of a non-equilibrium system to a state of maximum entropy production. The authors suggest MEPP underlies the evolution of the artificial system’s self-organization, in the same way that it underlies the evolution of ordered systems (biological life) on Earth. The team’s results are published in Nature Publishing Group’s online journal Scientific Reports.

MEPP may have profound implications for our understanding of the evolution of biological life on Earth and of the underlying rules that govern the behavior and evolution of all nonequilibrium systems. Life emerged on Earth from the strongly nonequilibrium energy distribution created by the Sun’s hot photons striking a cooler planet. Plants evolved to capture high energy photons and produce heat, generating entropy. Then animals evolved to eat plants increasing the dissipation of heat energy and maximizing entropy production.

In their experiment, the researchers suspended a large number of carbon nanotubes in a non-conducting non-polar fluid and drove the system out of equilibrium by applying a strong electric field. Once electrically charged, the system evolved toward maximum entropy through two distinct intermediate states, with the spontaneous emergence of self-assembled conducting nanotube chains.

In the first state, the “avalanche” regime, the conductive chains aligned themselves according to the polarity of the applied voltage, allowing the system to carry current and thus to dissipate heat and produce entropy. The chains appeared to sprout appendages as nanotubes aligned themselves so as to adjoin adjacent parallel chains, effectively increasing entropy production. But frequently, this self-organization was destroyed through avalanches triggered by the heating and charging that emanates from the emerging electric current streams. (Watch the video.)

“The avalanches were apparent in the changes of the electric current over time,” said Bezryadin.

No comment yet.
Scooped by Dr. Stefan Gruenwald!

Evolution-in-materio: ‘Training’ carbon-nanotube composites in ‘unconventional’ computing

Evolution-in-materio: ‘Training’ carbon-nanotube composites in ‘unconventional’ computing | Amazing Science |

Researchers from Durham University and the University of São Paulo-USP have  developed a method of using single-walled carbon nanotube (SWCNT) composites in “unconventional” computing. By studying the mechanical and electrical properties of the materials, they discovered a correlation between SWCNT concentration /viscosity/ conductivity and the computational capability of the composite.

“Instead of creating circuits from arrays of discrete components (transistors in digital electronics), our work takes a random disordered material and then ‘trains’ the material to produce a desired output,” said Mark K. Massey, research associate, School of Engineering and Computing Sciences at Durham University. This emerging field of research is known as “evolution-in-materio,” a term coined by Julian Miller at the University of York.

It combines materials science, engineering, and computer science. It uses an approach similar to biological evolution: materials can be “trained” to mimic electronic circuits — without needing to design the material structure in a specific way. “The material we use in our work is a mixture of [conducting] carbon nanotubes and [insulating] polymer, which creates a complex electrical structure,” explained Massey.

“When voltages (stimuli) are applied at points of the material, its electrical properties change. When the correct signals are applied to the material, it can be trained or ‘evolved’ to perform a useful function.”

The research “could lead to new techniques for making electronics devices for analog signal processing or low-power, low-cost devices in the future.” The research is describe in a paper in the Journal of Applied Physics.

No comment yet.
Scooped by Dr. Stefan Gruenwald!

This yarn conducts electricity and can be used for smart fabrics and bionic implants

This yarn conducts electricity and can be used for smart fabrics and bionic implants | Amazing Science |

Right now, wearable fitness trackers and bionic devices like electronic skin look cool, but they’re a bit clunky. One reason is that rigid wires tend to lose their conductivity after being bent, limiting the range of flexibility for wearables. Now, researchers report the creation of an ultrathin, fabric circuit that keeps high conductivity even while bending and stretching as much as yoga pants. The fiber’s core mimics spandex, consisting of an elastic synthetic thread—polyurethane—twinned by two cotton yarns.

These stretchy strings were then dipped in silver nanoparticles to instill conductivity and then liquid silicone to encase everything. This silver nanoyarn could stretch as much as spandex—500% of its original length—and retain a high conductivity (688 siemens per centimeter), the team reports online this month in ACS Nano. That’s 34 times the conductivity and five times the flexibility seen with prior attempts at nanowires made from grapheneThe fibers kept high conductivity after being bent 1000 times or wrapped around fingers. The team used their yarn to link light-emitting diodes within foldable plastic (shown above), meaning the fibers might serve as flexible wiring in new-age curved TVs, stretchable digital screens, or electronic clothing. The team tested the biocompatibility of these nanowires by surgically embedding them in the skin of mice for 8 weeks. No inflammation surfaced, suggesting that this silver yarn could be used to wire bionic implants in the future.

No comment yet.
Scooped by Dr. Stefan Gruenwald!

Engineers create stretchable structures tougher than bulletproof vests

Engineers create stretchable structures tougher than bulletproof vests | Amazing Science |

Researchers at University of Texas at Dallas (UT Dallas) have created a material made from nanofibers that can stretch to up to seven times its length while remaining tougher than Kevlar. These structures absorb up to 98 joules per gram. Kevlar, often used to make bulletproof vests, can absorb up to 80 joules per gram. The researchers hope the structures will one day form material that can reinforce itself at points of high stress and could potentially be used in military airplanes or other defense applications.

In a study published by ACS Applied Materials and Interfaces, a journal of the American Chemical Society, researchers twisted nanofiber into yarns and coils. The electricity generated by stretching the twisted nanofiber formed an attraction ten times stronger than a hydrogen bond, which is considered one of the strongest forces formed between molecules.

Researchers sought to mimic their earlier work on the piezoelectric action (how pressure forms electric charges) of collagen fibers found inside bone in hopes of creating high-performance materials that can reinforce itself, said Dr. Majid Minary, an assistant professor of mechanical engineering in the University’s Erik Jonsson School of Engineering and Computer Science and senior author of the study.

“We reproduced this process in nanofibers by manipulating the creation of electric charges to result in a lightweight, flexible, yet strong material,” said Minary, who is also a member of the Alan G. MacDiarmid NanoTech Institute. “Our country needs such materials on a large scale for industrial and defense applications.”

Alberto Mazarro's curator insight, July 9, 2015 1:02 PM

El desarrollo y combinación de materiales compuestos con nanopartículas da propiedades impensables hasta hoy

Scooped by Dr. Stefan Gruenwald!

Designer's toolkit for dynamic DNA: Arm-waving nanorobot signals new flexibility in DNA origami

Designer's toolkit for dynamic DNA: Arm-waving nanorobot signals new flexibility in DNA origami | Amazing Science |

The latest DNA nanodevices created at the Technische Universitaet Muenchen (TUM) - including a robot with movable arms, a book that opens and closes, a switchable gear, and an actuator - may be intriguing in their own right, but that's not the point. They demonstrate a breakthrough in the science of using DNA as a programmable building material for nanometer-scale structures and machines. Results published in the journalScience reveal a new approach to joining - and reconfiguring - modular 3D building units, by snapping together complementary shapes instead of zipping together strings of base pairs. This not only opens the way for practical nanomachines with moving parts, but also offers a toolkit that makes it easier to program their self-assembly.

The field popularly known as "DNA origami," in reference to the traditional Japanese art of paper folding, is advancing quickly toward practical applications, according to TUM Prof. Hendrik Dietz. Earlier this month, Dietz was awarded Germany's most important research award, the Gottfried Wilhelm Leibniz Prize, for his role in this progress.

In recent years, Dietz and his team have been responsible for major steps in the direction of applications: experimental devices including a synthetic membrane channel made from DNA; discoveries that cut the time needed for self-assembly processes from a week to a few hours and enable yields approaching 100%; proof that extremely complex structures can be assembled, as designed, with subnanometer precision. Yet all those advances employed "base-pairing" to determine how individual strands and assemblies of DNA would join up with others in solution. What's new is the "glue."

"Once you build a unit with base pairs," Dietz explains, "it's hard to break apart. So dynamic structures made using that approach tended to be structurally simple." To enable a wider range of DNA nanomachines with moving parts and potentially useful capabilities, the team adapted two more techniques from nature's biomolecular toolkit: the way proteins use shape complementarity to simplify docking with other molecules, and their tendency to form relatively weak bonds that can be readily broken when no longer needed.

For the experiments reported in Science, Dietz and his co-authors took inspiration from a mechanism that allows nucleic acid molecules to bond through interactions weaker than base-pairing. In nature, weak bonds can be formed when the RNA-based enzyme RNase P "recognizes" so-called transfer RNA; the molecules are guided into close enough range, like docking spacecraft, by their complementary shapes.

The new technology from Dietz's lab imitates this approach. To create a dynamic DNA nanomachine, the researchers begin by programming the self-assembly of 3D building blocks that are shaped to fit together. A weak, short-ranged binding mechanism called nucleobase stacking can then be activated to snap these units in place. Three different methods are available to control the shape and action of devices made in this way.

What this has given us is a tiered hierarchy of interaction strengths," Dietz says, "and the ability to position - precisely where we need them - stable domains that can recognize and interact with binding partners." The team produced a series of DNA devices - ranging from micrometer-scale filaments that might prefigure technological "flagella" to nanoscale machines with moving parts - to demonstrate the possibilities and begin testing the limits.

For example, transmission electron micrographs of a three-dimensional, nanoscale humanoid robot confirm that the pieces fit together exactly as designed. In addition, they show how a simple control method - changing the concentration of positive ions in solution - can actively switch between different configurations: assembled or disassembled, with "arms" open wide or resting at the robot's side.

No comment yet.
Scooped by Dr. Stefan Gruenwald!

First Graphene Cytobot: Graphene Quantum Dots Interfaced with A Single Bacterial Spore

First Graphene Cytobot: Graphene Quantum Dots Interfaced with A Single Bacterial Spore | Amazing Science |

UIC researchers created an electromechanical device--a humidity sensor--on a bacterial spore. They call it NERD, for Nano-Electro-Robotic Device. The report is online at Scientific Reports, a Nature open access journal.

"We've taken a spore from a bacteria, and put graphene quantum dots on its surface--and then attached two electrodes on either side of the spore," said Vikas Berry, UIC associate professor of chemical engineering and principal investigator on the study.

"Then we change the humidity around the spore," he said. When the humidity drops, the spore shrinks as water is pushed out. As it shrinks, the quantum dots come closer together, increasing their conductivity, as measured by the electrodes. "We get a very clean response--a very sharp change the moment we change humidity," Berry said. The response was 10 times faster, he said, than a sensor made with the most advanced man-made water-absorbing polymers.

A sensitive and reproducible electron-tunneling width modulation of 1.63 nm within a network of GQDs chemically-secured on a spore was achieved via sporal hydraulics with a driving force of 299.75 Torrs (21.7% water at GQD junctions). The electron-transport activation energy and the Coulomb blockade threshold for the GQD network were 35 meV and 31 meV, respectively; while the inter-GQD capacitance increased by 1.12 folds at maximum hydraulic force.

This is the first example of nano/bio interfacing with spores and will lead to the evolution of next-generation bio-derived microarchitectures, probes for cellular/biochemical processes, biomicrorobotic-mechanisms, and membranes for micromechanical actuation.

No comment yet.
Scooped by Dr. Stefan Gruenwald!

World’s smallest spirals could guard against identity theft

World’s smallest spirals could guard against identity theft | Amazing Science |
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.”

No comment yet.
Scooped by Dr. Stefan Gruenwald!

One step closer to single-molecule devices

One step closer to single-molecule devices | Amazing Science |

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.

No comment yet.
Scooped by Dr. Stefan Gruenwald!

New technique for exploring structural dynamics in the nanoworld

New technique for exploring structural dynamics in the nanoworld | Amazing Science |

A new technique for visualizing the rapidly changing electronic structures of atomic-scale materials as they twist, tumble and traipse across the nanoworld is taking shape at the California Institute of Technology. There, researchers have for the first time successfully combined two existing methods to visualize the structural dynamics of a thin film of graphite.

Described this week in the journal Structural Dynamics, from AIP Publishing and the American Crystallographic Association, their approach integrated a highly specific structural analysis technique known as "core-loss spectroscopy" with another approach known as ultrafast four-dimensional (4-D) electron microscopy—a technique pioneered by the Caltech laboratory, which is headed by Nobel laureate Ahmed Zewail.

In core-loss spectroscopy, the high-speed probing electrons can selectively excite core electrons of a specific atom in a material (core electrons are those bound most tightly to the atomic nucleus). The amount of energy that the core electrons gain gives insight into the local electronic structure, but the technique is limited in the time resolution it can achieve—traditionally too slow for fast catalytic reactions. 4-D electron microscopy also reveals the structural dynamics of materials over time by using short pulses of high-energy electrons to probe samples, and it is engineered for ultrafast time resolution.

Combining these two techniques allowed the team to precisely track local changes in electronic structure over time with ultrafast time resolution.

"In this work, we demonstrate for the first time that we can probe deep core electrons with rather high binding energies exceeding 100 eV," said Renske van der Veen, one of the authors of the new study. "We are equipped with an ultrafast probing tool that can investigate, for example, the relaxation processes in photocatalytic nanoparticles, photoinduced phase transitions in nanoscale materials or the charge transfer dynamics at interfaces."

No comment yet.
Scooped by Dr. Stefan Gruenwald!

Scientists use shape-fixing nanoreactor to make a better fuel cell catalyst

Scientists use shape-fixing nanoreactor to make a better fuel cell catalyst | Amazing Science |
Proton-exchange membrane fuel cells (PEMFCs) are lightweight fuel cells being developed for applications in vehicles and portable electronics. One of the biggest challenges facing their development is the need for expensive platinum-based catalysts. In an effort to lower the cost, scientists are looking for ways to either reduce the amount of platinum required or completely replace the platinum with a less expensive material. But so far, alternative materials have not performed nearly as well as platinum, mainly because they have fewer and less accessible "active sites"—locations where the catalyzed reactions can occur.

To address this challenge, scientists in a new study have developed a way to synthesize materials with a large number of active sites that also ensures that the active sites are accessible to all of the species (electrons, protons, oxygen, and water molecules, etc.) involved in the reactions. They've done this by synthesizing highly porous carbon nanomaterials, in which the pores act as open channels to transport various species to their particular active sites within the carbon framework.

The resulting catalyst, when incorporated into a PEMFC, has a peak power (600 mW/cm2) that is among the best of the non-platinum, non-precious-metal catalysts developed to date. In addition, the researchers explain that the method stands out because it produces the catalysts at a higher yield than any other previous method, in which most products are lost at high temperatures.

The researchers, led by Zidong Wei, Professor of Chemistry at Chongqing University in China, have published their work on the new PEMFC catalyst in a recent issue of the Journal of the American Chemical SocietyThe researchers describe the new high-yield method as "shape fixing" because it allows for the construction ofcarbon nanomaterials with a similar structure and morphology as their polymer precursors. The process of shape-fixing involves pouring a supersaturated sodium chloride (NaCl) solution onto a 3D polyaniline (PANI) carbon-based polymer in a beaker, which results in the water evaporating and NaCl recrystallizing around the PANI until the PANI is fully covered by crystals, almost appearing as if it is buried in a block of ice.

Because the NaCl fully seals the PANI, the researchers explain that the NaCl can be thought of as a nanoreactor. Inside this nanoreactor, the PANI is heated in the processes of pyrolysis and gasification, while various raw materials are added. In the end, the gasification of the various materials in the enclosed space causes the formation of many pores, and the carbonized PANI retains its original 3D shape due to previously being shape-fixed by the NaCl crystal. Further, as the researchers explain, the active sites created in this method are especially highly active.

No comment yet.
Scooped by Dr. Stefan Gruenwald!

New VR Technology Lets You Explore Worlds at the Nanoscale

New VR Technology Lets You Explore Worlds at the Nanoscale | Amazing Science |

Nanotronics Imaging, an Ohio-based company backed by PayPal founder and early Facebook investor Peter Thiel, makes atomic-scale microscopes that both researchers and industrial manufacturers can use in the production of nanoscale materials. Today at the Tribeca Disruptive Innovation Awards the company announced a new endeavor: the ability to view the microscopes’ output using virtual reality headsets like the Rift.

The new product, nVisible, will enable Nanotronics users to do virtual walkthroughs of nano-structures, which the company says will enable them to better visualize and understand the materials they’re working with. But most importantly, it could help manufacturers create more reliable processes for building nanoscale products—which has historically been a huge hurdle in working with such incredibly small materials.

No comment yet.
Scooped by Dr. Stefan Gruenwald!

Glassy Butterflies: Low-reflection Wings Make Butterflies Nearly Invisible

Glassy Butterflies: Low-reflection Wings Make Butterflies Nearly Invisible | Amazing Science |

The effect is known from the smart phone: Sun is reflected by the display and hardly anything can be seen. In contrast to this, the glasswing butterfly hardly reflects any light in spite of its transparent wings. As a result, it is difficult for predatory birds to track the butterfly during the flight. Researchers of KIT under the direction of Hendrik Hölscher found that irregular nanostructures on the surface of the butterfly wing cause the low reflection. In theoretical experiments, they succeeded in reproducing the effect that opens up fascinating application options, e.g. for displays of mobile phones or laptops.

Transparent materials such as glass, always reflect part of the incident light. Some animals with transparent surfaces, such as the moth with its eyes, succeed in keeping the reflections small, but only when the view angle is vertical to the surface. The wings of the glasswing butterfly that lives mainly in Central America, however, also have a very low reflection when looking onto them under higher angles. Depending on the view angle, specular reflection varies between two and five percent. For comparison: As a function of the view angle, a flat glass plane reflects between eight and 100 percent, i.e. reflection exceeds that of the butterfly wing by several factors. Interestingly, the butterfly wing does not only exhibit a low reflection of the light spectrum visible to humans, but also suppresses the infrared and ultraviolet radiation that can be perceived by animals. This is important to the survival of the butterfly.

For research into this so far unstudied phenomenon, the scientists examined glasswings by scanning electron microscopy. Earlier studies revealed that regular pillar-like nanostructures are responsible for the low reflections of other animals. The scientists now also found nanopillars on the butterfly wings. In contrast to previous findings, however, they are arranged irregularly and feature a random height. Typical height of the pillars varies between 400 and 600 nanometers, the distance of the pillars ranges between 100 and 140 nanometers. This corresponds to about one thousandth of a human hair.

In simulations, the researchers mathematically modeled this irregularity of the nanopillars in height and arrangement. They found that the calculated reflected amount of light exactly corresponds to the observed amount at variable view angles. In this way, they proved that the low reflection at variable view angles is caused by this irregularity of the nanopillars. Hölscher’s doctoral student Radwanul Hasan Siddique, who discovered this effect, considers the glasswing butterfly a fascinating animal: “Not only optically with its transparent wings, but also scientifically. In contrast to other natural phenomena, where regularity is of top priority, the glasswing butterfly uses an apparent chaos to reach effects that are also fascinating for us humans.”

No comment yet.
Scooped by Dr. Stefan Gruenwald!

Venus flytrap-inspired shape-shifting plastics take shape

Venus flytrap-inspired shape-shifting plastics take shape | Amazing Science |

Shape-shifting plastics which respond to external stimuli, similar to how Venus flytraps ensnare prey and touch-me-nots fold their leaves inwards when touched, have come a step closer thanks to a new polymer developed by US researchers. The work could lead to new classes of plastics with many applications including smart responsive coatings, sensors and controlled release vehicles.

Polymers have previously been made to reversibly change shape from triggers such as light and temperature. Now, Scott Phillips' team at Pennsylvania State University, US, has broadened the scope by creating a polymer, Pcl2PA [poly(4,5-dichlorophthalaldehyde], that depolymerises from head to tail in response to multiple stimuli.

'The field of head-to-tail depolymerisable polymers is really just emerging, with only a selection of polymers showing rapid and selective depolymerisation,' says Phillips. 'This depolymerisation response, however, is critical for enabling the multi-stimuli-responsive 3D materials in this work.'

Previous research on the parent polymer poly(phthalaldehyde) (PPA) showed it to continuously depolymerise quickly in response to specific applied molecular signals.2 But its thermal instability and high sensitivity to mild acids and bases prevented manufacture of 3D materials using thermal-based manufacturing processes such as selective laser sintering (SLS), which fuses particles of the polymer together using a laser.

Improving the thermal stability of the Pcl2PA they synthesised allowed the team to make 3D objects with a simple SLS technique. They were able to create depolymerisable objects, including those that changed their shape and function in different ways in response to different chemical stimuli. The depolymerisation of the polymer works by end-capping the polymers with functionality – for example with tert-Butyldimethylsilyl ethers and allyl carbonates that respond to specific signals. Cleavage of the end-caps results in the polymer becoming thermodynamically unstable, leading to rapid depolymerisation to the monomer.

'This may be important for specialty polymers which require the ability to depolymerise from one end of the chain in the presence of certain sensitising species, and it might be important in diblock copolymers or comb polymers where the end sequences can be readily removed,' says Wayne Cook who investigates responsive polymers at Monash University, Australia.

No comment yet.
Scooped by Dr. Stefan Gruenwald!

Scientists create invisible objects in the microwave range without metamaterial cloaking

Scientists create invisible objects in the microwave range without metamaterial cloaking | Amazing Science |
Physicists have managed to make homogenous cylindrical objects completely invisible in the microwave range. Contrary to the now prevailing notion of invisibility that relies on metamaterial coatings, the scientists achieved the result using a homogenous object without any additional coating layers. The method is based on a new understanding of electromagnetic wave scattering.

The scientists studied light scattering from a glass cylinder filled with water. In essence, such an experiment represents a two-dimensional analog of a classical problem of scattering from a homogeneous sphere (Mie scattering), the solution to which is known for almost a century. However, this classical problem contains unusual physics that manifests itself when materials with high values of refractive index are involved. In the study, the scientists used ordinary water whose refractive index can be regulated by changing temperature.

As it turned out, high refractive index is associated with two scattering mechanisms: resonant scattering, which is related to the localization of light inside the cylinder, and non-resonant, which is characterized by smooth dependence on the wave frequency. The interaction between these mechanisms is referred to as Fano resonances. The researchers discovered that at certain frequencies waves scattered via resonant and non-resonant mechanisms have opposite phases and are mutually destroyed, thus making the object invisible.

The work led to the first experimental observation of an invisible homogeneous object by means of scattering cancellation. Importantly, the developed technique made it possible to switch from visibility to invisibility regimes at the same frequency of 1.9 GHz by simply changing the temperature of the water in the cylinder from 90 °C to 50 °C.

"Our theoretical calculations were successfully tested in microwave experiments. What matters is that the invisibility idea we implemented in our work can be applied to other electromagnetic wave ranges, including to the visible range. Materials with corresponding refractive index are either long known or can be developed at will," said Mikhail Rybin, first author of the paper and senior researcher at the Metamaterials Laboratory in ITMO University.

The discovery of invisibility phenomenon in a homogenous object and not an object covered with additional coating layers is also important from the engineering point of view. Because it is much easier to produce a homogeneous cylinder, the discovery could prompt further development of nanoantennas, wherein invisible structural elements could help reduce disturbances. For instance, invisible rods could be used as supports for a miniature antenna complex connecting two optical chips.

No comment yet.
Scooped by Dr. Stefan Gruenwald!

Light-Powered Gyroscope is World’s Smallest and Promises a Powerful Spin for Navigation Technologies

Light-Powered Gyroscope is World’s Smallest and Promises a Powerful Spin for Navigation Technologies | Amazing Science |

A pair of light waves – one zipping clockwise the other counterclockwise around a microscopic track – may hold the key to creating the world’s smallest gyroscope: one a fraction of the width of a human hair. By bringing this essential technology down to an entirely new scale, a team of applied physicists hopes to enable a new generation of phenomenally compact gyroscope-based navigation systems, among other intriguing applications.

“We have found a new detection scheme that may lead to the world's smallest gyroscope,” said Li Ge, The Graduate Center and Staten Island College, City University of New York. “Though these so-called optical gyroscopes are not new, our approach is remarkable both in its super-small size and potential sensitivity.”

Ge and his colleagues – physicist Hui Cao and her student Raktim Sarma, both at Yale University in New Haven, Connecticut – recently published their results in The Optical Society’s (OSA) new high-impact journal Optica.

More than creative learning toys, gyroscopes are indispensable components in a number of technologies, including inertial guidance systems, which monitor an object’s motion and orientation. Space probes, satellites, and rockets continuously rely on these systems for accurate flight control. But like so many other essential pieces of aerospace technology, weight is a perennial problem. According to NASA, it costs about $10,000 for every pound lifted into orbit, so designing essential components that are smaller and lighter is a constant struggle for engineers and project managers.

If the size of an optical gyroscope is reduced to just a fraction of a millimeter, as is presented in the new paper, it could then be integrated into optical circuit boards, which are similar to a conventional electric circuit board but use light to carry information instead of electric currents. This could drastically reduce the equipment cost in space missions, opening the possibility for a new generation of micro-payloads.

No comment yet.
Scooped by Dr. Stefan Gruenwald!

Radio-frequency-heated iron-oxide nanoparticles open the blood-brain barrier

Radio-frequency-heated iron-oxide nanoparticles open the blood-brain barrier | Amazing Science |

A new method of opening the blood-brain barrier (BBB) to deliver therapeutic molecules directly to the brain has been developed by researchers from the University of MontrealPolytechnique Montréal, and CHU Sainte-JustineThe BBB protects the brain from elements circulating in the blood that may be toxic to the brain, but currently, 98% of therapeutic molecules are unable to cross the BBB.

KurzweilAI has reported a number of recently developed techniques for delivering drugs to the blood-brain barrier, ranging from protein-based nanoparticles to most recently, ultrasound. But according to principal investigator Sylvain Martel, “previous techniques either open the BBB too wide, exposing the brain to great risks, or they are not precise enough, leading to scattering of the drugs and possible unwanted side effects.”

To open the BBB, the researchers used a cannulation technique to deliver iron-oxide magnetic nanoparticles to the surface of the middle cerebral artery of mice. In a previous study they showed that MRI could guide nanoparticles to a desired location. Then they applied a radio-frequency field, heating the nanoparticles, which then dissipated the heat, creating a mechanical stress on the BBB. That allowed for a temporary and localized opening of the barrier for diffusion of a visually identifiable dye (representing a drug) for approximately two hours into the brain.


CineversityTV's curator insight, April 6, 2015 5:39 PM

Opening Pandora's Box.

Scooped by Dr. Stefan Gruenwald!

‘Nanoneedles’ generate new blood vessels in mice, paving the way for new regenerative medicine

‘Nanoneedles’ generate new blood vessels in mice, paving the way for new regenerative medicine | Amazing Science |
Scientists have developed “nanoneedles” that have successfully prompted parts of the body to generate new blood vessels, in a trial in mice.

The researchers, from Imperial College London and Houston Methodist Research Institute in the USA, hope their nanoneedle technique could ultimately help damaged organs and nerves repair themselves and help transplanted organs  thrive.

In a trial described in Nature Materials, the team showed they could deliver nucleic acids DNA and siRNA to back muscles in mice. After seven days there was a six-fold increase in the formation of new blood vessels in the mouse back muscles, and blood vessels continued to form over a 14 day period.

The nanoneedles are tiny porous structures that act as a sponge to load significantly more nucleic acids than solid structures. This makes them more effective at delivering their payload. They can penetrate the cell, bypassing its outer membrane, to deliver nucleic acids without harming or killing the cell.

The nanoneedles are made from biodegradable silicon, meaning that they can be left in the body without leaving a toxic residue behind. The silicon degrades in about two days, leaving behind only a negligible amount of a harmless substance called orthosilicic acid.

The hope is that one day scientists will be able to help promote the generation of new blood vessels in people, using nanoneedles, to provide transplanted organs or future artificial organ implants with the necessary connections to the rest of the body, so that they can function properly with a minimal chance of being rejected.

“This is a quantum leap compared to existing technologies for the delivery of genetic material to cells and tissues,” said Ennio Tasciotti, Co-Chair, Department of Nanomedicine at Houston Methodist Research Institute and co-corresponding author of the paper.

No comment yet.
Scooped by Dr. Stefan Gruenwald!

Organic LEDs and carbon nanotubes may light up future fabrics

Organic LEDs and carbon nanotubes may light up future fabrics | Amazing Science |

With the emergence of wearable electronics that monitor fitness and health, there is a growing need for more flexible light-emitting devices. One option that researchers have been interested in is developing fabrics with integrated light-emitting devices. Unfortunately, fabrics themselves are not a suitable surface for current light-emitting materials. However, a team of scientists have found a way around this issue by integrating the light-emitting devices directly into fabrics using a new technology: light-emitting device fibers.

These research team, based in China, worked with polymer light-emitting electrochemical cells (PLECs). Like many other light-emitting devices, PLECs have a structure that is composed of two metal electrodes connected to a thin organic layer that acts as a semiconductor. Because PLECs have mobile ions incorporated into the semiconductor, they have many benefits compared to other light-emitting diodes (LEDs): low operating voltage, high efficiency in converting electrons to photons, and high power efficiency. PLECs are also a good option because they do not require the use of metals that are sensitive to air and they can be used on rougher surfaces; these characteristics make them suitable for large-scale manufacturing.

These fiber-shaped PLECs have a coaxial structure with four layers. Using a solution-based processing, a steel wire, which acts as the base of this fiber, is dip-coated with a thin layer of ZnO nanoparticles. This layer has two key functions: protecting the light-emitting layer that's applied next; and decreasing the leakage of the current, thus enhancing current efficiency.

Next, the electroluminescent polymer layer is deposited onto the wire using dip-coating. Finally, a sheet of aligned carbon nanotubes is wrapped around the bundle using a dry-drawn form of spinnable carbon nanotubes. Because the carbon nanotubes were highly aligned, they provided the fiber with high electrical conductivities. Imaging revealed that the fibers had a uniform diameter and a smooth outer surface.

The scientists who created these fibers determined the lifetime of the devices. They found that the fibers gradually light up over a 21-minute period and gradually dim over a four-hour period; in these studies, the light emitted by the fibers was blue. The fiber lit up when a voltage of 5.6V was applied and reached a peak intensity at 13V. When the fiber is pre-charged, it displays a rapid turn-on response that is similar to conventional LEDs.

The brightness of the light emitted by the fibers was almost entirely independent of viewing angle. When the fibers were bent, they maintained their brightness above 90 percent and no obvious damage was observed. Though only blue light was explored in these studies, the team believes other colors could be displayed as well.

No comment yet.