Purdue University: Nanowire Implants offer Remote-Controlled Drug Delivery: Applications: Spinal Cord Injuries; Chemotherapy


Purdue-signatureA team of researchers has created a new implantable drug-delivery system using nanowires that can be wirelessly controlled.

The nanowires respond to an electromagnetic field generated by a separate device, which can be used to control the release of a preloaded drug. The system eliminates tubes and wires required by other implantable devices that can lead to infection and other complications, said team leader Richard Borgens, Purdue University’s Mari Hulman George Professor of Applied Neuroscience and director of Purdue’s Center for Paralysis Research.

“This tool allows us to apply drugs as needed directly to the site of injury, which could have broad medical applications,” Borgens said. “The technology is in the early stages of testing, but it is our hope that this could one day be used to deliver drugs directly to spinal cord injuries, ulcerations, deep bone injuries or tumors, and avoid the terrible side effects of systemic treatment with steroids or chemotherapy.”

The team tested the drug-delivery system in mice with compression injuries to their spinal cords and administered the corticosteroid dexamethasone. The study measured a molecular marker of inflammation and scar formation in the central nervous system and found that it was reduced after one week of treatment. A paper detailing the results will be published in an upcoming issue of the Journal of Controlled Release and is currently available online.

Purdue U Nano Wire 94283_web

IMAGE: An image of a field of polypyrrole nanowires captured by a scanning electron microscope is shown. A team of Purdue University researchers developed a new implantable drug-delivery system using the… view more

Credit: (Purdue University image/courtesy of Richard Borgens)

The nanowires are made of polypyrrole, a conductive polymer material that responds to electromagnetic fields. Wen Gao, a postdoctoral researcher in the Center for Paralysis Research who worked on the project with Borgens, grew the nanowires vertically over a thin gold base, like tiny fibers making up a piece of shag carpet hundreds of times smaller than a human cell. The nanowires can be loaded with a drug and, when the correct electromagnetic field is applied, the nanowires release small amounts of the payload. This process can be started and stopped at will, like flipping a switch, by using the corresponding electromagnetic field stimulating device, Borgens said.

The researchers captured and transported a patch of the nanowire carpet on water droplets that were used used to deliver it to the site of injury. The nanowire patches adhere to the site of injury through surface tension, Gao said.

The magnitude and wave form of the electromagnetic field must be tuned to obtain the optimum release of the drug, and the precise mechanisms that release the drug are not yet well understood, she said. The team is investigating the release process.

The electromagnetic field is likely affecting the interaction between the nanomaterial and the drug molecules, Borgens said.

“We think it is a combination of charge effects and the shape change of the polymer that allows it to store and release drugs,” he said. “It is a reversible process. Once the electromagnetic field is removed, the polymer snaps back to the initial architecture and retains the remaining drug molecules.”

For each different drug the team would need to find the corresponding optimal electromagnetic field for its release, Gao said.

This study builds on previous work by Borgens and Gao. Gao first had to figure out how to grow polypyrrole in a long vertical architecture, which allows it to hold larger amounts of a drug and extends the potential treatment period. The team then demonstrated it could be manipulated to release dexamethasone on demand. A paper detailing the work, titled “Action at a Distance: Functional Drug Delivery Using Electromagnetic-Field-Responsive Polypyrrole Nanowires,” was published in the journal Langmuir.

Other team members involved in the research include John Cirillo, who designed and constructed the electromagnetic field stimulating system; Youngnam Cho, a former faculty member at Purdue’s Center for Paralysis Research; and Jianming Li, a research assistant professor at the center.

For the most recent study the team used mice that had been genetically modified such that the protein Glial Fibrillary Acidic Protein, or GFAP, is luminescent. GFAP is expressed in cells called astrocytes that gather in high numbers at central nervous system injuries. Astrocytes are a part of the inflammatory process and form a scar tissue, Borgens said.

A 1-2 millimeter patch of the nanowires doped with dexamethasone was placed onto spinal cord lesions that had been surgically exposed, Borgens said. The lesions were then closed and an electromagnetic field was applied for two hours a day for one week. By the end of the week the treated mice had a weaker GFAP signal than the control groups, which included mice that were not treated and those that received a nanowire patch but were not exposed to the electromagnetic field. In some cases, treated mice had no detectable GFAP signal.

Whether the reduction in astrocytes had any significant impact on spinal cord healing or functional outcomes was not studied. In addition, the concentration of drug maintained during treatment is not known because it is below the limits of systemic detection, Borgens said.

“This method allows a very, very small dose of a drug to effectively serve as a big dose right where you need it,” Borgens said. “By the time the drug diffuses from the site out into the rest of the body it is in amounts that are undetectable in the usual tests to monitor the concentration of drugs in the bloodstream.”

Polypyrrole is an inert and biocompatable material, but the team is working to create a biodegradeable form that would dissolve after the treatment period ended, he said.

The team also is trying to increase the depth at which the drug delivery device will work. The current system appears to be limited to a depth in tissue of less than 3 centimeters, Gao said.


Story Source:

The above post is reprinted from materials provided by Purdue University. The original item was written by Elizabeth K. Gardner. Note: Materials may be edited for content and length.


Journal Reference:

  1. Wen Gao, Richard Ben Borgens. Remote-controlled eradication of astrogliosis in spinal cord injury via electromagnetically-induced dexamethasone release from “smart” nanowires. Journal of Controlled Release, 2015; 211: 22 DOI: 10.1016/j.jconrel.2015.05.266
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Novel superconducting hybrid crystals developed


Copper Nanowire id35309A new type of nanowire crystals that fuses semiconducting and metallic materials on the atomic scale could lay the foundation for future semiconducting electronics. Researchers at the Univ. of Copenhagen are behind the breakthrough, which has great potential.

The development and quality of extremely small electronic circuits are critical to how and how well future computers and other electronic devices will function. The new material, comprised of both a semiconductor and metal, has a special superconducting property at very low temperatures and could play a central role in the development of future electronics.

“Our new material was born as a hybrid between a semiconducting nanowire and its electronic contact. Thus we have invented a way to make a perfect transition between the nanowire and a superconductor. The superconductor in this case is aluminium,” says Assoc. Prof. Thomas Sand Jespersen. “There is great potential in this.” Jespersen has worked in the field for more than 10 years, ever since research into nanowire crystals has existed at the Nano-Science Center at the Niels Bohr Institute.

Nanowire and contact formed at the same time
Nanowires are extremely thin nanocrystal threads used in the development of new electronic components, like transistors and solar cells. Part of the challenge of working with nanowires is creating a good transition between these nanowires and an electrical contact to the outside world. Up until now, researchers, not just at the Niels Bohr Institute, but from all over the world, have cultured nanowires and the contact separately. However, with the new approach, both the quality and the reproducibility of the contact have improved considerably.

“The atoms sit in a perfectly ordered lattice in the nanowire crystal, not only in the semiconductor and the metal, but also in the transition between the two very different components, which is significant in itself. You could say that it is the ultimate limit to how perfect a transition one could imagine between a nanowire crystal and a contact. Of course this opens many opportunities to make new types of electronic components on the nanoscale and in particular, this means that we can study the electrical properties with much greater precision than before,” explains Asst. Prof. Peter Krogstrup, who has worked hard in the laboratory to develop the contact.

Chips with billions of nanowire hybrids
In their publication in Nature Materials, the research group has demonstrated this perfect contact and its properties and has also shown that they can make a chip with billions of identical semiconductor-metal nanowire hybrids.

“We think that this new approach could ultimately form the basis for future superconducting electronics, and that is why the research into nanowires is interesting for the largest electronics companies,” says Jespersen.

Source: Univ. of Copenhagen

‘Forests’ of carbon nanotubes grown on 3-D substrates


NAno Antennas 140714122817-largeSource: AVS: Science & Technology of Materials, Interfaces, and Processing
Summary:
Researchers are growing vertically aligned “forests” of carbon nanotubes on three-dimensional (3-D) conductive substrates to explore their potential use as a cathode in next-gen lithium batteries.

A team of University of Maryland researchers is growing vertically aligned “forests” of carbon nanotubes on three-dimensional (3-D) conductive substrates to explore their potential use as a cathode in next-gen lithium batteries.

During the AVS 61st International Symposium & Exhibition, being held November 9-14, 2014, in Baltimore, Md., the team will describe their process for creating lithium-oxygen (Li-O2) battery cells.

Carbon nanotubes are typically grown on two-dimensional or planar substrates, but the structure developed by the team is considered “3-D” because the carbon nanotubes are grown on a porous, “sponge-like” foam structure made of nickel coated with aluminum oxide ceramic.

Batteries usually consist of an anode, cathode and electrolyte; the researchers’ 3-D structure forms the “cathode” part of the battery.

“Our team developed self-standing, catalyst-decorated carbon nanotube cathodes for Li-O2 batteries using atomic layer deposition (ALD) and electrochemical deposition methods,” said Marshall Schroeder, a member of the Rubloff Research Group in Materials Science and Engineering at the University of Maryland. “And we also have unique capabilities for in situ characterization via scanning electron microscopy and X-ray photoelectron spectroscopy for elemental analysis of pristine electrodes and at different points during cycling.”Nano Wires 2147496528_220x220

How does the team build their battery cathode? First, they use a nickel foam current collector to deposit a thin layer (~5nm) of aluminum oxide using ALD. This is chased by a layer of iron, sputtered as a growth catalyst for chemical vapor deposition (CVD) of carbon.

The ALD layer “acts as a diffusion barrier to keep the growth catalyst from diffusing into the nickel foam during the high-temperature carbon growth process,” Schroeder explained. “The type of carbon growth is heavily dependent on the CVD process parameters — catalyst ripening temperature/time, growth time/temperature, precursor type, and flow rate, etc. — so optimization of the growth process was required to achieve a vertically aligned carbon nanotube architecture.”

These structures were put to the test as cathodes in lithium oxygen cells, and the team discovered that the optimized growth process resulted in a hierarchical pore structure featuring dense carpets of vertically aligned carbon nanotubes on a 3-D current collector scaffold.

Preliminary studies of this cathode structure show promising results for oxygen reduction reaction (ORR) performance, according Schroeder. “For the oxygen evolution reaction (OER), continued studies will focus on optimization of the electrode performance via decoration with ALD-deposited catalysts,” he adds. “We’ve also started studying the catalyst performance on other carbon nanotube substrates and now have a preliminary fundamental understanding of the catalyst chemistries developed by our team.”

The team’s work shows that combining their ALD capabilities with the unique structure of the 3-D cathode may “significantly improve the performance of one of the most promising next-generation lithium battery technologies,” Schroeder noted.


Story Source:

The above story is based on materials provided by AVS: Science & Technology of Materials, Interfaces, and Processing. Note: Materials may be edited for content and length.

New research points to graphene as a flexible, low-cost touchscreen solution


Nano Wires 2147496528_220x220New research published today in the journal Advanced Functional Materials suggests that could soon replace current touchscreen technology, significantly reducing production costs and allowing for more affordable, flexible displays.

The majority of today’s touchscreen devices, such as tablets and smartphones are made using (ITO) which is both expensive and inflexible. Researchers from the University of Surrey and AMBER, the materials science centre based at Trinity College Dublin have now demonstrated how graphene-treated nanowires can be used to produce flexible touchscreens at a fraction of the current cost.

Using a simple, scalable and inexpensive method the researchers produced hybrid electrodes, the building blocks of touchscreen technology, from and graphene.

Nano Wires 2147496528_220x220

Dr Alan Dalton from the University of Surrey said, “The growing market in devices such as wearable technology and bendable smart displays poses a challenge to manufacturers. They want to offer consumers flexible, touchscreen technology but at an affordable and realistic price. At the moment, this market is severely limited in the materials to hand, which are both very expensive to make and designed for rigid, flat devices.”

Lead author, Dr Izabela Jurewicz from the University of Surrey commented, “Our work has cut the amount of expensive nanowires required to build such touchscreens by more than fifty times as well as simplifying the production process. We achieved this using graphene, a material that can conduct electricity and interpret touch commands whilst still being transparent.”

Co-author, Professor Jonathan Coleman, AMBER, added, “This is a real alternative to ITO displays and could replace existing touchscreen technologies in electronic devices. Even though this material is cheaper and easier to produce, it does not compromise on performance.”

“We are currently working with industrial partners to implement this research into future devices and it is clear that the benefits will soon be felt by manufacturers and consumers alike.”

Explore further: Conductive nanofiber networks for flexible, unbreakable, and transparent electrodes

Researchers’ at Rice University Find Acid-Free Approach Leads to Strong Conductive Carbon Threads


Rice Carbon Threads 25-researchersaThe very idea of fibers made of carbon nanotubes is neat, but Rice University scientists are making them neat—literally.

Why It Matters: To create strong, conductive fibers needed for projects ranging from nanoscale electronics to macro-scale power grids.

The single-walled carbon in new fibers created at Rice line up like a fistful of uncooked spaghetti through a process designed by chemist Angel Martí and his colleagues.

The tricky bit, according to Martí, whose lab reported its results this month in the journal ACS Nano, is keeping the densely packed nanotubes apart before they’re drawn together into a fiber.

Rice Carbon Threads 25-researchersa

Rice University scientists are making carbon nanotube solutions that act as liquid crystals as a precursor to pulling them into strong, conductive fibers. Credit: Martí Group 

Left to their own devices, carbon nanotubes form clumps that are perfectly wrong for turning into the kind of strong, conductive fibers needed for projects ranging from nanoscale electronics to macro-scale power grids.

Earlier research at Rice by chemist and chemical engineer Matteo Pasquali, a co-author on the new paper, used an acid dissolution process to keep the nanotubes separated until they could be spun into fibers. Now Martí, Pasquali and their colleagues are producing “neat” fibers with the same mechanical process, but they’re starting with a different kind of feedstock.

“Matteo’s group used chlorosulfonic acid to protonate the surface of the nanotubes,” Martí said. “That would give them a positively charged surface so they would repel each other in solution. The technique we use is exactly the opposite.”

Researchers’ acid-free approach leads to strong conductive carbon threads
Fiber of pure carbon nanotubes has potential for use in small-scale electronics and large scale power applications. Credit: Jeff Fitlow

A process revealed last year by Martí and lead authors Chengmin Jiang, a graduate student, and Avishek Saha, a Rice alumnus, starts with negatively charging carbon nanotubes by infusing them with potassium, a metal, and turning them into a kind of salt known as a polyelectrolyte. They then employ cage-like crown ethers to capture the potassium ions that would otherwise dampen the nanotubes’ ability to repel one another.

Put enough nanotubes into such a solution and they’re caught between the repellant forces and an inability to move in a crowded environment, Martí said. They’re forced to align—a defining property of liquid crystals—and this makes them more manageable.

The tubes are ultimately forced together into fibers when they are extruded through the tip of a needle. At that point, the strong van der Waals force takes over and tightly binds the nanotubes together, Martí said.

But to make macroscopic materials, the Martí team needed to pack many more nanotubes into the solution than in previous experiments. “As you start increasing the concentration, the number of nanotubes in the liquid crystalline phase becomes more abundant than those in the isotropic (disordered) phase, and that’s exactly what we needed,” Martí said.

The researchers discovered that 40 milligrams of nanotubes per milliliter gave them a thick gel after mixing at high speed and filtering out whatever large clumps remained. “It’s like a centrifuge together with a rotary drum,” Martí said of the mixing gear. “It produces unconventional forces in the solution.”

Carbon nanotubes extruded into a pure fiber are the product of an acid-free process invented at Rice University. Credit: Martí Group

Feeding this dense nanotube gel through a narrow needle-like opening produced continuous fiber on the Pasquali lab’s equipment. The strength and stiffness of the neat fibers also approached that of the fibers previously produced with Pasquali’s acid-based process. “We didn’t make any modifications to his system and it worked perfectly,” Martí said.

The hair-width fibers can be woven into thicker cables, and the team is investigating ways to improve their electrical properties through doping the nanotubes with iodide. “The research is basically analogous to what Matteo does,” Martí said. “We used his tools but gave the process a spin with a different preparation, so now we’re the first to make neat of pure electrolytes. That’s very cool.”

Pasquali said that the spinning system worked with little need for adaptation because the setup is sealed. “The nanotube electrolyte solution could be protected from oxygen and water, which would have caused precipitation of the nanotubes,” he said.

“It turns out that this is not a showstopper, because we want the nanotubes to precipitate and stick to each other as soon as they exit the sealed system through the needle. The process was not hard to control, adapt and scale up once we figured out the basic science.”

Explore further: Carbon nanotube fibers outperform copper

Provided by Rice University search and more info website

Silicene research challenges the limitations of nanotechnology


As computer chips continue to get smaller and more powerful, the field of electronics is approaching some severe limits. “Once a device becomes too small it falls prey to the strange laws of the quantum world,” says University of Saskatchewan researcher Neil Johnson, who is using the Canadian Light Source synchrotron to help develop the next generation of computer materials. Johnson is a member of Canada Research Chair Alexander Moewes’ group of graduate students studying the nature of materials using synchrotron radiation.

Siliscene id37277Researcher Neil Johnson during Theory @ CLS day.

His work focuses on silicene, a recent and exciting addition to the class of two-dimensional materials. Silicene is made up of an almost flat hexagonal pattern of silicon atoms. Every second atom in each hexagonal ring is slightly lifted, resulting in a buckled sheet that looks the same from the top or the bottom. In 2012, mere months before Johnson began to study silicene, it was discovered and first created by the research group of Prof. Guy Le Lay of Aix-Marseille University, using silver as a base for the thin film.

The Le Lay group is the world-leader in silicene growth, and taught Johnson and his colleagues how to make it at the CLS themselves. “I read the paper when the Le Lay announced they had made silicene, and within three or four months, Alex had arranged for us to travel down to the Advanced Light Source with these people who had made it for the first time,” says Johnson. It was an exciting collaboration for the young physicist. “This paper had already been cited over a hundred times in a matter of months. It was a major paper, and we were going to measure this new material that no one had really started doing experiments on yet.” The most pressing question facing silicene research was its potential as a semiconductor.

Today, most electronics use silicon as a switch, and researchers looking for new materials to manage quantum effects in computing could easily use the 2-D version if it was also semiconducting. Calculations had shown that because of the special buckling of silicene, it would have what’s called a Dirac cone – a special electronic structure that could allow researchers to tune the band gap, or the energy space between electron levels. The band gap is what makes a semiconductor: if the space is too small, the material is simply a conductor. Too large, and there is no conduction at all. Since silicene has only ever been made on a silver base, the materials community also wondered if silicene would maintain its semiconducting properties in this condition. Though its atomic structure is slightly different than freestanding silicene, it was still predicted to have a band gap.

However, silver is a metal, which may make the silicene act as a metal as well. No one really knew how silicene would behave on its silver base. To adapt the Le Lay group’s silicene-growing process to the equipment at the CLS took several days of work. Though their team had succeeded in silicene synthesis at the Advanced Light Source at Berkeley lab, they had no way to keep those samples under vacuum to prevent them from oxygen damage. Thanks to the work of fellow beamteam members Drs. David Muir and Israel Perez, samples grown at the CLS could be produced, transported and measured in a matter of hours without ever leaving a vacuum chamber.

Johnson grew the silicene sheets at the Resonant Elastic and Inelastic X-ray Scattering (REIXS), beamline, then transferred them in a vacuum to the XAS/XES endstation for analysis. Finally, Johnson could find the answer to the silicene question.
“I didn’t really know what to expect until I saw the XAS and XES on the same energy scale, and I thought to myself, that looks like a metal,” says Johnson.
And while that result is unfortunate for those searching for a new computing wonder material, it does provide some vital information to that search.
“Our result does help to guide the hunt for 2-D silicon in the future, suggesting that metallic substrates should be avoided at all costs,” Johnson explains. “We’re hopeful that we can grow a similar structure on other substrates, ideally ones that leave the semiconducting nature of silicene intact.”
That work is already in process, with Johnson and his colleagues planning to explore three other growing bases this summer, along with multilayers and nanoribbons of silicene.
Source: Canadian Light Source

Nano-storage wires


(QDOTS imagesCAKXSY1K 8Nanowerk Spotlight) Nanowires are considered a major  building block for future nanotechnology devices, with great potential for  applications in transistors, solar cells, lasers, sensors, etc. (see for instance: “Nanowires  for the electronics and optoelectronics of the future” and “Nanotechnology explained:  Nanowires and nanotubes”).

Now, for the first time, nanotechnology researchers have  utilized nanowires as a ‘storage’ device for biochemical species such as ATP.   Led by Seunghun Hong, a professor of physics, biophysics and chemical  biology at Seoul National University, the team developed a new nanowire  structure – which they named ‘nano-storage wire’ – which can store and release  biomolecules.

Reporting their findings in the July 16, 2013 online edition of  ACS Nano (“Nano-Storage Wires”), Hong’s group demonstrated  that their nano-storage wire structure can be deposited onto virtually any  substrate to build nanostorage devices for the real-time controlled release of  biochemical molecules upon the application of electrical stimuli.

“Our nano-storage wires are multisegmented nanowires comprised  of three segments and each segment plays a role in extending the applications of  the nanowire,” Hong explains to Nanowerk: “1) the conducting polymer segment  stores biomolecules; 2) the nickel segment allows the utilization of magnetic  fields to drive the nanowires and place them onto a specific location for device  applications; and 3) the gold segment enables a good electrical contact between the deposited nano-storage  wires and the electrodes. The polymer segment is utilized for the controlled  release of ATP molecules. The nickel segment enables the magnetic localization  of nano-storage wires, while the gold segment provides a good electrical contact with electrodes.”

nano-storage wire Left:  Schematics of a nano-storage wire. Right: SEM image of a single nano-storage  wire. The dark, intermediate, and bright regions represent PPy-ATP (conducting  polymer with ATP molecules), nickel, and gold segments, respectively. (Images:  Dr. Seunghun Hong, Seoul National University)    The released biomolecules from such a nanowire-storage system  can be used for instance to control the activity of biosystems. As a proof of concept, the researchers stored  ATP in their nano-storage wires and released it by electrical stimuli, which  activated the motion of motor protein systems. The team also demonstrated flexible nanostorage devices. Here, nano-storage wires were driven by magnetic  fields and deposited onto nickel/gold films on a transparent and flexible  polyimide film. The device  transmitted some light, and it can be easily bent. They also showed that the nanowires could be deposited onto  curved surfaces such as the sharp end of a micropipet.       

     nano-storage wires deposited on tip of a micropipette

SEM  image of nano-storage wires deposited on a micropipet. (Reprinted with  permission from American Chemical Society)   

“Such probe-shaped storage devices can be used for the delivery  of chemicals to individual cells through a direct injection,” says Hong.  “Basically, our results show that nano-storage wires are quite versatile  structures and we  can deposit them onto virtually any structure to create nanoscale devices for  the controlled release of biochemical materials.”

“Nano-storage wires will allow the fabrication of advanced  biochips which can activate or deactivate the activities of biosystems in real  time,” Hong points out. “The activation and deactivation of biosystems such as  biomotors, are controlled by specific biomolecules. In our method, we can  selectively control the biomolecular activities related with ATP or any released  chemical species while leaving other biomolecular activities unaltered.”

Having demonstrated the storage of ATP, the team is now planning  to store other  biomolecules in our nano-storage wires. Examples are drugs to control the  activity of cells and tissues, enzymes to activate specific signal pathways in  biosystems etc. “Eventually, we would like to build an advanced biochip which  can be utilized to control the activities of desired biosystems in real-time,” says Hong.

By Michael Berger. Copyright © Nanowerk

Read more: http://www.nanowerk.com/spotlight/spotid=31619.php#ixzz2buibAVQY

Guided growth of nanowires leads to self-integrated nanoelectronics circuits


QDOTS imagesCAKXSY1K 8(Nanowerk News) Researchers working with tiny  components in nanoelectronics face a challenge similar to that of parents of  small children: teaching them to manage on their own. The nano-components are so  small that arranging them with external tools is impossible. The only solution  is to create conditions in which they can be “trusted” to assemble themselves.
Much effort has gone into facilitating the self-assembly of  semiconductors, the basic building blocks of electronics, but until recently,  success has been limited. Scientists had developed methods for growing  semiconductor nanowires vertically on a surface, but the resultant structures  were short and disorganized. After growing, such nanowires need to be  “harvested” and aligned horizontally; since such placement is random, scientists  need to determine their location and only then integrate them into electric  circuits.
A team led by Prof. Ernesto Joselevich of the Weizmann  Institute’s Materials and Interfaces Department has managed to overcome these  limitations. For the first time, the scientists have created self-integrating  nanowires whose position, length and direction can be fully controlled.
This is a SEM image of a logic circuit based on 14 nanowires
This  is a SEM image of a logic circuit based on 14 nanowires.
The achievement, reported today in the Proceedings of the  National Academy of Sciences (“Self-integration of nanowires into circuits via  guided growth”), was based on a method developed by Joselevich two years ago  for growing nanowires horizontally in an orderly manner. In the present study —  conducted by Joselevich with Dr. Mark Schvartzman and David Tsivion of his lab,  and Olga Raslin and Dr. Diana Mahalu of the Physics of Condensed Matter  Department — the scientists went further, creating self-integrated electronic  circuits from the nanowires.
First, the scientists prepared a surface with tiny, atom-sized  grooves and then added to the middle of the grooves catalyst particles that  served as nuclei for the growth of nanowires. This setup defined the position,  length and direction of the nanowires. They then succeeded in creating a  transistor from each nanowire on the surface, producing hundreds of such  transistors simultaneously. The nanowires were also used to create a more  complex electronic component — a functioning logic circuit called an Address  Decoder, an essential constituent of computers. These ideas and findings have  earned Joselevich a prestigious European Research Council Advanced Grant.
“Our method makes it possible, for the first time, to determine  the arrangement of the nanowires in advance to suit the desired electronic  circuit,” Joselevich explains. The ability to efficiently produce circuits from  self-integrating semiconductors opens the door to a variety of technological  applications, including the development of improved LED devices, lasers and  solar cells.
Source: Weizmann Institute of Science 

Read more: http://www.nanowerk.com/news2/newsid=31631.php#ixzz2at9wQ1GV

Nanowires: Major Building-block for Nanotechnology Devices: Transistors, Solar Cells, Lasers and More


By Michael Berger. Copyright © Nanowerk

201306047919620(Nanowerk Spotlight) Nanowires are considered a major  building block for future nanotechnology devices, with great potential for  applications in transistors, solar cells, lasers, sensors, etc.

 

*** Read articles explaining how ‘nanowires and nanotubes’ differ from other quantum materials, such as quantum dots, and their potential applications here:

http://www.nanowerk.com/news2/newsid=29945.php

http://www.nanowerk.com/news/newsid=16857.php

 

Now, for the first time, nanotechnology researchers have  utilized nanowires as a ‘storage’ device for biochemical species such as ATP.   Led by Seunghun Hong, a professor of physics, biophysics and chemical  biology at Seoul National University, the team developed a new nanowire  structure – which they named ‘nano-storage wire’ – which can store and release  biomolecules.

Reporting their findings in the July 16, 2013 online edition of  ACS Nano (“Nano-Storage Wires”), Hong’s group demonstrated  that their nano-storage wire structure can be deposited onto virtually any  substrate to build nanostorage devices for the real-time controlled release of  biochemical molecules upon the application of electrical stimuli.

“Our nano-storage wires are multisegmented nanowires comprised  of three segments and each segment plays a role in extending the applications of  the nanowire,” Hong explains to Nanowerk: “1) the conducting polymer segment  stores biomolecules; 2) the nickel segment allows the utilization of magnetic  fields to drive the nanowires and place them onto a specific location for device  applications; and 3) the gold segment enables a good electrical contact between  the deposited nano-storage wires and the electrodes. The polymer segment is  utilized for the controlled release of ATP molecules. The nickel segment enables  the magnetic localization of nano-storage wires, while the gold segment provides  a good electrical contact with electrodes.”

  nano-storage wire Left:  Schematics of a nano-storage wire. Right: SEM image of a single nano-storage  wire. The dark, intermediate, and bright regions represent PPy-ATP (conducting  polymer with ATP molecules), nickel, and gold segments, respectively. (Images:  Dr. Seunghun Hong, Seoul National University)   

The released biomolecules from such a nanowire-storage system  can be used for instance to control the activity of biosystems. As a proof of  concept, the researchers stored ATP in their nano-storage wires and released it  by electrical stimuli, which activated the motion of motor protein systems.   The team also demonstrated flexible nanostorage devices. Here,  nano-storage wires were driven by magnetic fields and deposited onto nickel/gold  films on a transparent and flexible polyimide film. The device transmitted some  light, and it can be easily bent.   They also showed that the nanowires could be deposited onto  curved surfaces such as the sharp end of a micropipet.

nano-storage wires deposited on tip of a micropipette

SEM  image of nano-storage wires deposited on a micropipet. (Reprinted with  permission from American Chemical Society)   

“Such probe-shaped storage devices can be used for the delivery  of chemicals to individual cells through a direct injection,” says Hong.  “Basically, our results show that nano-storage wires are quite versatile  structures and we can deposit them onto virtually any structure to create  nanoscale devices for the controlled release of biochemical materials.”   “Nano-storage wires will allow the fabrication of advanced  biochips which can activate or deactivate the activities of biosystems in real  time,” Hong points out. “The activation and deactivation of biosystems such as  biomotors, are controlled by specific biomolecules.

In our method, we can  selectively control the biomolecular activities related with ATP or any released  chemical species while leaving other biomolecular activities unaltered.”   Having demonstrated the storage of ATP, the team is now planning  to store other biomolecules in our nano-storage wires. Examples are drugs to  control the activity of cells and tissues, enzymes to activate specific signal  pathways in biosystems etc.   “Eventually, we would like to build an advanced biochip which  can be utilized to control the activities of desired biosystems in real-time,”  says Hong.

By Michael Berger. Copyright © Nanowerk

Read more: http://www.nanowerk.com/spotlight/spotid=31619.php#ixzz2apWtDi34

 

Elastic conductors for new sensing applications


201306047919620Researchers from North Carolina State University have developed elastic conductors made from silver nanowires, as the basis of stretchable electronic devices.

The silver nanowires can be printed to fabricate patterned stretchable conductorsStretchable circuitry could be used, for example, to create tactile, strain and motion sensors in wearable or conformable applications.

Dr Yong Zhu, an assistant professor of mechanical and aerospace engineering at NC State, and Feng Xu, a PhD student in Zhu’s lab have developed elastic conductors using silver nanowires. Silver has very high electric conductivity. The technique developed at NC State embeds silver nanowires in a polymer that can withstand significant stretching without adversely affecting the material’s conductivity. This makes it attractive as a component for use in stretchable electronic devices.

Simple fabrication

Silver nanowires are placed on a silicon plate and a liquid polymer is poured over the silicon substrate, which flows around the silver nanowires. High heat turns the polymer from a liquid into an elastic solid, trapping the nanowires in the polymer. The polymer is peeled off the silicon plate.

Zhu says the elastic conductor technology could be commercially viable within five years. Fabrication is simple and is compatible with printing and patterning techniques, including screen and inkjet. Zhu’s team has made some prototypes, filed for patents and discussions about next steps towards commercialisation are taking place. When the polymer is stretched and relaxed, the surface containing nanowires buckles, creating a composite that is wavy on the side that contains silver nanowires and flat on the other.

After the nanowire-embedded surface has buckled, the material can be stretched up to 50% of its elongation, or tensile strain, without affecting the conductivity of the silver nanowires, because the buckled shape of the material allows the nanowires to stay in a fixed position in relation to each other, as the polymer is being stretched.

The research was supported by the National Science Foundation.