#3d'printouts'at the nanoscale using self-assembling DNA structures A novel way of making 3d nanostructures from DNA is described in a study published in the renowned journal Nature("DNA rendering of polyhedral meshes
at the nanoscale"."The study was led by researchers at Karolinska Institutet who collaborated with a group at Finland's Aalto University.
The new technique makes it possible to synthesize 3d DNA origami structures that are also able to tolerate the low salt concentrations inside the body,
which opens the way for completely new biological applications of DNA NANOTECHNOLOGY. The design process is automated also highly,
which enables the creation of synthetic DNA NANOSTRUCTURES of remarkable complexity. Bjrn Hgberg and Erik Benson The team behind the study likens the new approach to a 3d printer for nanoscale structures.
The user draws the desired structure in the form of a polygon object, in 3d software normally used for computer-aided design or animation.
Graph-theoretic algorithms and optimization techniques are used then to calculate the DNA sequences needed to produce the structure.
When the synthesized DNA sequences are combined in a salt solution, they assemble themselves into the correct structure.
One of the big advantages of building nanostructures out of DNA is that the bases bind to each other through base-paring in a predictable fashion.
This new method makes it very easy to design DNA NANOSTRUCTURES and gives more design freedom,
says study leader Bjrn Hgberg from the Department of Medical Biochemistry and Biophysics at Karolinska Institutet.
We can now make structures that were impossible to design previously and we can do it in the same way as one might draw a 3d structure for printing out in macroscopic scale,
but instead of making it out of plastic, we print it in DNA at the nanoscale.
Using this technique, the team has built a ball, spiral, rod and bottle-shaped structure, and a DNA printout of the so-called Stanford Bunny,
which is a common test model for 3d modelling. Apart from being compared simpler to former ways of making DNA origami
the method importantly does not require high concentrations of magnesium salt. For biological applications, the most crucial difference is that we can now create structures that can be folded in,
and remain viable in, physiological salt concentrations that are more suitable for biological applications of DNA NANOSTRUCTURES,
explains Dr Hgberg. An advantage of the automated design process is that one can now deal systematically with even quite complex structures.
Advanced computing methods are likely to be a key enabler in the scaling of DNA NANOTECHNOLOGY from fundamental studies towards groundbreaking applications,
says Professor Pekka Orponen, who directed the team at the Aalto University Computer science department. The possible applications are many.
The team at Karolinska Institutet has made previously a DNA nano-caliper used for studying cell signalling.
The new technique makes it possible to conduct similar biological experiments in a way that resembles conditions within cells even more closely.
DNA NANOSTRUCTURES have also been used to make targeted capsules able to deliver cancer drugs direct to tumour cells,
which can reduce the amount of drugs needed d
#Magnetic material unnecessary to create spin current (Nanowerk News) It doesn't happen often that a young scientist makes a significant and unexpected discovery,
but postdoctoral researcher Stephen Wu of the U s. Department of energy's Argonne National Laboratory just did exactly that("Paramagnetic Spin Seebeck Effect").
"What he found--that you don't need a magnetic material to create spin current from insulators--has important implications for the field of spintronics and the development of high-speed,
low-power electronics that use electron spin rather than charge to carry information. Typically when referring to electrical current,
However, this work demonstrates that the SSE is limited not to magnetic insulators but also occurs in a class of materials known as paramagnets.
when an external magnetic field is removed, this discovery is unexpected and challenges current theories for the SSE.
New ways of generating spin currents may be important for low-power high-speed spin based computing (spintronics),
The paramagnetic SSE changes the way we think about thermally driven spintronics, allowing for the creation of new devices
and architectures where spin currents are generated without ferromagnetic materials, which have been the centerpiece of all spin-based electronic devices up until this point.
Image: Argonne National Laboratory) Wu's work upends prevailing ideas of how to generate a current of spins."
"This is a discovery in the true sense, "said Anand Bhattacharya, a physicist in Argonne's Materials science Division and the Center for Nanoscale Materials (a DOE Office of Science user facility),
who is the project's principal investigator.""There's no prediction of anything like it.""Spin is a quantum property of electrons that scientists often compare to a tiny bar magnet that points either"up"or"down."
"Until now scientists and engineers have relied on shrinking electronics to make them faster, but now increasingly clever methods must be used to sustain the continued progression of electronics technology,
as we reach the limit of how small we can create a transistor. One such method is to separate the flow of electron spin from the flow of electron current,
upending the idea that information needs to be carried on wires and instead flowing it through insulators.
scientists have kept typically electrons stationary in a lattice made of an insulating ferromagnetic material, such as yttrium iron garnet (YIG.
When they apply a heat gradient across the material, the spins begin to"move"--that is,
Wu set out to build on previous work with spin currents, expanding it to different materials using a new technique he'd developed.
Wu looked at a layer of ferromagnetic YIG on a substrate of paramagnetic gadolinium gallium garnet (GGG.
They generate no magnetic field, produce no magnons, and there appears to be no way for the spins to communicate with one another.
"We don't know the way this works, "said Bhattacharya.""There's an opportunity here for somebody to come up with a theory for this."
"The scientists also want to look for other materials that display this effect.""We think that there may be other new physics working here,
"We've just taken ferromagnetism off its pedestal. In a spintronic device you don't have to use a ferromagnet.
You can use either a paramagnetic metal or a paramagnetic insulator to do it now
#Superfast fluorescence sets new speed record (Nanowerk News) Researchers have developed an ultrafast light-emitting device that can flip on and off 90 billion times a second
and could form the basis of optical computing. At its most basic level, your smart phone's battery is powering billions of transistors using electrons to flip on and off billions of times per second.
But if microchips could use photons instead of electrons to process and transmit data, computers could operate even faster.
But first engineers must build a light source that can be turned on and off that rapidly.
While lasers can fit this requirement they are too energy-hungry and unwieldy to integrate into computer chips.
Duke university researchers are now one step closer to such a light source. In a new study, a team from the Pratt School of engineering pushed semiconductor quantum dots to emit light at more than 90 billion gigahertz.
This so-called plasmonic device could one day be used in optical computing chips or for optical communication between traditional electronic microchips.
TEM Nanocube A nanoscale view of the new superfast fluorescent system using a transmission electron microscope.
The silver cube is just 75-nanometers wide. The quantum dots (red) are sandwiched between the silver cube and a thin gold foil.
The study was published online on July 27 in Nature Communications("Ultrafast Spontaneous Emission Source Using Plasmonic Nanoantennas"."
""This is something that the scientific community has wanted to do for a long time, "said Maiken Mikkelsen, an assistant professor of electrical and computer engineering and physics at Duke."
"We can now start to think about making fast-switching devices based on this research, so there's a lot of excitement about this demonstration."
"The new speed record was set using plasmonics. When a laser shines on the surface of a silver cube just 75 nanometers wide,
the free electrons on its surface begin to oscillate together in a wave. These oscillations create their own light,
which reacts again with the free electrons. Energy trapped on the surface of the nanocube in this fashion is called a plasmon.
The plasmon creates an intense electromagnetic field between the silver nanocube and a thin sheet of gold placed a mere 20 atoms away.
This field interacts with quantum dots--spheres of semiconducting material just six nanometers wide--that are sandwiched in between the nanocube and the gold.
The quantum dots in turn, produce a directional, efficient emission of photons that can be turned on and off at more than 90 gigahertz."
"There is great interest in replacing lasers with LEDS for short-distance optical communication, but these ideas have always been limited by the slow emission rate of fluorescent materials,
lack of efficiency and inability to direct the photons, "said Gleb Akselrod, a postdoctoral research in Mikkelsen's laboratory."
including funding agencies, is pushing pretty hard for.""The group is now working to use the plasmonic structure to create a single photon source--a necessity for extremely secure quantum communications--by sandwiching a single quantum dot in the gap between the silver nanocube and gold foil.
They are also trying to precisely place and orient the quantum dots to create the fastest fluorescence rates possible.
Aside from its potential technological impacts, the research demonstrates that well-known materials need not be limited by their intrinsic properties."
"By tailoring the environment around a material, like we've done here with semiconductors, we can create new designer materials with almost any optical properties we desire,
"said Mikkelsen.""And that's an emerging area that's fascinating to think about
#Wafer-thin material heralds future of wearable technology (Nanowerk News) UOW Institute for Superconducting and Electronic Materials (ISEM) has pioneered successfully a way to construct a flexible,
foldable and lightweight energy storage device that provides the building blocks for next-generation batteries needed to power wearable electronics and implantable medical devices (ACS Central Science,"Self-Assembled Multifunctional Hybrids:
Toward Developing High-performance Graphene-Based Architectures for Energy storage devices"."The conundrum researchers have faced in developing miniature energy storage devices,
such as batteries and supercapacitors, has been figuring out how to increase the surface area of the device, to store more charge,
without making it larger. mong all modern electronic devices, portable electronics are some of the most exciting,
ISEM Phd student Monirul Islam said. ut the biggest challenge is to charge storage in a small volume as well as being able to deliver that charge quickly on demand.
To solve this problem, a team of Phd students, led by Dr Konstantin Konstantinov under the patronage of ISEM Director Professor Shi Xue Dou and with the support of Professor Hua Kun Liu,
the head of ISEM Energy storage Division, have developed a three-dimensional structure using a flat-pack self-assembly of three components:
graphene, a conductive polymer and carbon nanotubes, which are atom-thick latticelike networks of carbon formed into cylinders.
Graphene, made from single atom-thick layers of graphite, was a suitable candidate due its electronic performance
and mechanical strength. e knew in theory that if you can make a sort of carbon skeleton you have a greater surface area and greater surface area means more charge,
Dr Konstantinov said. f we could efficiently separate the layers of carbon we could then use both surfaces of each layer for charge accumulation.
The graphene in liquid form was mixed with the conductive polymer and reduced to solid and the carbon nanotubes carefully inserted between the graphene layers to form a self-assembled flat-packed,
wafer-thin supercapacitor material. he real challenge was how to assemble these three components into a single structure with the best use of the space available,
Phd student Monirul Islam said. etting the proportions or ratios of the components appropriately in order to obtain a composite material with maximum energy storage performance was another challenge.
Wrong proportions of either ingredient result in a lumpy mess, or a 3d shape that isn strong enough to retain the needed flexibility as well as the charge storage ability.
There also elegance in the simplicity of the team design: the researchers dispersed the components in liquid crystalline,
The result was a 3d shape with, thanks to the carbon nanotubes, a massive surface area, excellent charge capacity that is also foldable.
or sophisticated equipment. ur graphene-based flexible composite is highly conductive, lightweight, is able to fold like a roll
or stack like a paper in electronic devices to store a huge amount of charge, Monirul said. his material can store charge in a second
and will be more lightweight than traditional batteries used in present day electronics. The ISEM study has been supported financially by the Automotive Australia 2020 CRC as part of its research into electric vehicles.
ISEM is the program leader for electrification and plays crucial role for design of next generation electric vehicles A key to unlocking the electric vehicle capability is a lightweight and powerful battery pack. ur simple fabrication method of eco-friendly materials
with increased performance has great potential to be scaled up for use supercapacitor and battery technology. Our next step is to use this material to fabricate flexible wearable supercapacitors with high power density and energy density as well as large scale supercapacitors for electric vehicles. u
#Smart hydrogel coating creates'stick-slip'control of capillary action Coating the inside of glass microtubes with a polymer hydrogel material dramatically alters the way capillary forces draw water into the tiny structures,
researchers have found. The discovery could provide a new way to control microfluidic systems, including popular lab-on-a-chip devices.
Capillary action draws water and other liquids into confined spaces such as tubes, straws, wicks and paper towels,
and the flow rate can be predicted using a simple hydrodynamic analysis . But a chance observation by researchers at the Georgia Institute of technology will cause a recalculation of those predictions for conditions in which hydrogel films line the tubes carrying water-based liquids."
"Rather than moving according to conventional expectations, water-based liquids slip to a new location in the tube,
"explained Andrei Fedorov, a professor in the George W. Woodruff School of Mechanical engineering at Georgia Tech."
"The findings resulted from research sponsored by the Air force Office of Scientific research (AFOSR) through the BIONIC center at Georgia Tech,
the liquid begins to flow into the tube, pulled by a combination of surface tension in the liquid and adhesion between the liquid and the walls of the tube.
a so-called"smart"polymer (PNIPAM), everything changes. Water entering a tube coated on the inside with a dry hydrogel film must first wet the film
while the polymer layer locally deforms. The meniscus then rapidly slides for a short distance before the process repeats.
"The researchers-who included graduate students James Silva, Drew Loney and Ren Geryak and senior research engineer Peter Kottke-tried the experiment again using glycerol,
After using high-resolution optical visualization to study the meniscus propagation while the polymer swelled, the researchers realized they could put this previously-unknown behavior to good use.
including labs-on-a-chip. The transition temperature can be controlled by varying the chemical composition of the hydrogel."
or cooling the polymer inside a microfluidic chamber, you can either speed up the filling process
That would allow precise control of fluid flow on demand using external stimuli to change polymer film behavior."
which the desired rate of molecule delivery could be tuned dynamically over time to achieve the optimal therapeutic outcome.
In future work, Fedorov and his team hope to learn more about the physics of the hydrogel-modified capillaries
They also want to explore other"smart"polymers which change the flow rate in response to different stimuli,
or the induction of mechanical stress-all of which can change the properties of a particular hydrogel designed to be responsive to those triggers."
dynamically evolving polymer interfaces in which the system creates an energy barrier to further motion through elasto-capillary deformation,
and then lowers the barrier through diffusive softening, "the paper's authors wrote.""This insight has implications for optimal design of microfluidic and lab-on-a-chip devices based on stimuli-responsive smart polymers
#A new type of modulator for the future of data transmission In February 1880 in his laboratory in Washington the American inventor Alexander graham bell developed a device
which he himself called his greatest achievement, greater even than the telephone: the"photophone"."Bell's idea to transmit spoken words over large distances using light was the forerunner of a technology without
which the modern internet would be unthinkable. Today, huge amounts of data are sent incredibly fast through fibre optic-cables cables as light pulses.
For that purpose they first have to be converted from electrical signals, which are used by computers and telephones, into optical signals.
In Bell's days it was a simple, very thin mirror that turned sound waves into modulated light.
Today's electro-optic modulators are complicated more, but they do have one thing in common with their distant ancestor:
especially when compared with electronic devices that can be as small as a few micrometers. In a seminal paper in the scientific journal Nature Photonics("All-plasmonic Mach-Zehnder modulator enabling optical high-speed communication at the microscale"),Juerg Leuthold, professor of photonics and communications
at ETH Zurich, and his colleagues now present a novel modulator that is a hundred times smaller and that can,
therefore, be integrated easily into electronic circuits. Moreover, the new modulator is considerably cheaper and faster than common models,
and it uses far less energy. The plasmon-trick For this sleight of hand the researchers led by Leuthold and his doctoral student Christian Haffner
who contributed to the development of the modulator, use a technical trick. In order to build the smallest possible modulator they first need to focus a light beam
Modern telecommunications use laser light with a wavelength of one and a half micrometers, which accordingly is the lower limit for the size of a modulator.
the light is turned first into so-called surface-plasmon-polaritons. Plasmon-polaritons are a combination of electromagnetic fields
and electrons that propagate along a surface of a metal strip. At the end of the strip they are converted back to light once again.
The advantage of this detour is that plasmon-polaritons can be confined in a much smaller space than the light they originated from.
Refractive index changed from the outside In order to control the power of the light that exits the device,
and thus to create the pulses necessary for data transfer, the researchers use the working principle of an interferometer.
A change in phase can result from a difference in the refractive index, which determines the speed of the waves.
whose refractive index can be changed from the outside, the relative phase of the two waves can be controlled
but rather plasmon-polaritons that are sent through an interferometer that is only half a micrometer wide.
By applying a voltage the refractive index and hence the velocity of the plasmons in one arm of the interferometer can be varied,
which in turn changes their amplitude of oscillation at the exit. After that, the plasmons are reconverted into light,
which is fed into a fibre optic cable for further transmission. Faster communication with less energy The modulator built by Leuthold
and his colleagues has several advantages at once.""It's incredibly small and simple, and on top of that it's also the cheapest modulator ever built,
consisting of a gold layer on glass that is only 150 nanometers thick and an organic material
whose refractive index changes when an electric voltage is applied and that thus modulates the plasmons inside the interferometer.
As such a modulator is much smaller than conventional devices it consumes very little energy-only a few thousandth of Watts at a data transmission rate of 70 Gigabits per second.
This corresponds to merely a hundredth of the consumption of commercial models. In that sense it contributes to the protection of the environment
given that the amount of energy used worldwide for data transmission is considerable-after all, there are modulators in every single fibre optic line.
Every year increasing amounts of data need to be transmitted at ever higher speed, which leads to an increasing energy consumption.
A hundredfold energy saving would, therefore, be more than welcome.""Our modulator provides more communication with less energy,
"as the ETH professor puts it in a nutshell. At present the reliability of the modulator is being tested in long term trials,
which is a crucial step towards making it fit for commercial use e
#Making polymer nanostructures from a greenhouse gas (Nanowerk News) A future where power plants feed their carbon dioxide directly into an adjacent production facility instead of spewing it up a chimney
and into the atmosphere is definitely possible, because CO2 isnt just an undesirable greenhouse gas; it is also a good source of carbon for processes like polymer production.
In the journal Angewandte Chemie("Construction of Versatile and Functional Nanostructures Derived from CO2-based Polycarbonates),
"American scientists have introduced now a two-step, one-pot conversion of CO2 and epoxides to polycarbonate block copolymers that contain both water-soluble and hydrophobic regions
and can aggregate into nanoparticles or micelles. Versatile nanostructures made from CO2 based polycarbonates. Wiley-VCH) CO2 and epoxides (highly reactive compounds with a three-membered ring made of two carbon atoms
and one oxygen atom) can be polymerized to form polycarbonates in reactions that use special catalysts.
These processes are a more environmentally friendly alternative to conventional production processes and have already been introduced by several companies.
However, because current CO2-based polycarbonates are hydrophobic and have no functional groups, their applications are limited.
In particular, biomedical applications, an area where the use of biocompatible polycarbonates is established well, have been left out.
A team led by Donald J. Darensbourg along with graduate student Yanyan Wang at Texas A&m University (USA) has provided a solution.
For the first time the researchers have been able to produce amphiphilic polycarbonate block copolymers in which both the hydrophilic and hydrophobic regions are based on CO2.
They were also able to incorporate a variety of functional and charged groups into the polymers.
Because it is very difficult to find building blocks to make hydrophilic polycarbonates, the researchers used a trick:
they polymerized first and attached the water-soluble groups afterwards. The entire process is even a one-pot reaction:
The researchers first produce the hydrophobic regions by polymerizing CO2 and propylene oxide (as the epoxide component.
In the same vessel, they then change to a different building block, allyl glycidyl ether (AGE), an epoxide with a double bond in its side chain,
and continue the polymerization. The AGE-containing polymer grows on both ends of the existing polycarbonate, leading to a triblock copolymer.
The length of the blocks can be controlled precisely. Subsequently a thiolene click reaction can be used to simply click a water-soluble group into place at the double bond.
This makes it possible to attach acidic and/or basic groups that carry a positive or negative charge in certain ph ranges.
Some of the amphiphilic polycarbonates made by this method are able to aggregate into particles or micelles in a self-organization process.
This and the ability to attach bioactive substances, for example, could provide many more possibilities for biomedical applications n
#New material opens possibilities for super-long-acting pills (Nanowerk News) Medical devices designed to reside in the stomach have a variety of applications,
including prolonged drug delivery, electronic monitoring, and weight-loss intervention. However, these devices, often created with nondegradable elastic polymers, bear an inherent risk of intestinal obstruction as a result of accidental fracture or migration.
As such, they are designed usually to remain in the stomach for a limited time. Now, researchers at MITS Koch Institute for Integrative Cancer Research and Massachusetts General Hospital (MGH) have created a polymer gel that overcomes this safety concern
and could allow for the development of long-acting devices that reside in the stomach, including orally delivered capsules that can release drugs over a number of days, weeks,
or potentially months following a single administration. Shiyi Zhang, a postdoc at the Koch Institute and the papers lead author, holds a ring-shaped device prototype (left),
Image courtesy of the researchers) This polymer is ph-responsive: It is stable in the acidic stomach environment
but dissolves in the small intestines near-neutral ph, allowing for safe passage through the remainder of the gastrointestinal (GI TRACT.
The material is also elastic, allowing for the compression and folding of devices into easily ingestible capsules meaning this polymer can be used to create safe devices designed for extremely prolonged residence in the stomach.
One of the issues with any device in the GI TRACT is that theres the potential for an obstruction,
which is a medical emergency potentially requiring surgical intervention, says Koch Institute research affiliate Giovanni Traverso,
also a gastroenterologist at MGH and an instructor at Harvard Medical school. A material like this represents a real advance
because it is both safe and stable in the stomach environment. Traverso and Robert Langer, the David H. Koch Institute Professor at MIT and a member of the Koch Institute, are the senior authors of a paper in the July 27 issue of Nature Materials("A ph
-responsive supramolecular polymer gel as an enteric elastomer for use in gastric devices")that describes the application of this new polymer gel for creating gastric devices.
Shiyi Zhang, a postdoc at the Koch Institute is the papers lead author. Safely stretching Designing devices for the stomach is complicated a matter of sizes and shapes.
the researchers were interested in developing a polymer with elastic properties. An elastic device can be folded into something small
But the size and shape of existing devices with elastic polymers have been limited by safety concerns,
as there is a greater risk for fracture if a device is too large or too complex.
Because of this, the researchers wanted their polymer to also be enteric or have a mechanism that would enable it to pass through the stomach unaltered before disintegrating in the intestines.
The proposed supramolecular polymer gel network. Structures in yellow are synthesized polymer; structures in purple are linear polymer;
and the red structures are inter-polymer hydrogen bonds. Image courtesy of the researchers) To lower any possible risk of obstruction,
we wanted a material that could dissolve in the intestines, thereby dissociating the device, and safely pass out of the body,
Zhang says. To create this new material, the researchers synthesized an elastic polymer and combined it in solution with a clinically utilized enteric polymer.
Adding hydrochloric acid and centrifuging the solution resulted in a flexible, yet resilient, polymer gel that exhibits both elastic and enteric properties.
The researchers used the gel polycaprolactone (PCL), a nontoxic, degradable polyester, to construct several device prototypes.
They first created ring-shaped devices by using the gel to link arcs of PCL in a circular mold.
These elastic devices had a diameter of 3 centimeters wider than the pylorus before they were folded into orally ingestible capsules.
In testing the capsules in pigs, the researchers found that the rings expanded into their original shape within 15 minutes of ingestion
the polymer gel dissolved, allowing for the safe passage of the small PCL pieces without obstruction.
and delivered through the esophagus with the assistance of an endoscope. These devices remained in the stomach for up to five days
Improving adherence The combined enteric and elastic properties of this polymer gel could significantly improve the design and adoption of gastric-resident devices.
ingestible electronics, which can diagnose and monitor a variety of conditions in the GI TRACT; or extended-release drug-delivery systems that could last for weeks or months after a single administration.
a professor of medical science and engineering at Brown University who was not involved with this study.
With further work in adjusting the polymer composition or the design of the system they say that they could tailor devices to release drugs over a specific timeframe of up to weeks or months at a time.
MIT is negotiating an exclusive license agreement with Lyndra, an early-stage biotechnology company developing novel oral drug-delivery systems, for this and other related technologies.
patients adherence to long-term therapies for chronic illnesses is only 50 percent in developed countries, with lower rates of adherence in developing nations.
Medication nonadherence costs the U s. an estimated $100 billion every year, the bulk of which comes in the form of unnecessary hospitalizations.
The researchers also say that single-administration delivery systems for the radical treatment of malaria
and other infections could significantly benefit from these technologies. In a March 2015 commentary piece in Nature("Perspective:
Special delivery for the gut"),Traverso and Langer wrote that the GI TRACT is an area rife with opportunity for prolonged drug delivery in tackling this global health problem.
they envision an emerging field of orally delivered devices that can maximize adherence and therapeutic efficacy y
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