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Carbon Nanotube Thread


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#31 Reno

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Posted 23 June 2010 - 07:04 PM

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A new type of high-power battery may help make larger hybrid vehicles a reality, according to a research paper published this week. A group of scientists at MIT have found a way to use carbon nanotubes to create a device that combines the strengths of batteries and capacitors, resulting in a battery than can both store a large amount of energy and put out a high rate of power. The ability to provide a better combination of high power and rapid discharge may help engineers tailor the batteries to a broader range of vehicles.

Batteries and capacitors have long occupied independent niches when it comes to storing electricity. Lithium batteries can store a significant amount of energy using chemical processes, but can only supply a low rate of power; capacitors can deliver a lot of power at once by eliminating the difference between two oppositely charged plates, but have low total energy storage.

Researchers have been trying to mitigate the shortcomings of both devices for some time, by either forcing higher rates of output from batteries or more storage from capacitors. They've achieved some success in increasing the rate of discharge from lithium batteries by shortening the distance that the ions diffuse to a few nanometers, but the output remained too low for many high-power applications. Similar efforts to adapt capacitors have yielded limited successes.

To get the functionality they were looking for, researchers needed a material that could quickly shuffle ions around the battery, but would also bond strongly to them, ensuring a higher release of energy when the ions are released. As is often the case in materials science, they needed to look no further than carbon nanotubes.

To construct an electrode for their new battery, the researchers created alternating layers of carbon nanotube sheets coated with carboxylic acid and amine functional groups—these can undergo charge transfer reactions with lithium ion charge carriers. Their addition also seems to roughen up the surface of the nanotubes, increasing the surface area available for reactions.

The researchers tested a battery that used the layered carbon nanotube electrode on the positive end, and a lithium electrode on the negative end. The power output of the batteries declined as the nanotube electrode's thickness increased, placing a ceiling on its numbers. But an electrode three micrometers thick could still deliver energies of 200 watt-hours per kilogram (a bit better than current-generation lithium batteries), and a power of 100 kilowatts per kilogram. They were able to match the energy of lithium ion batteries at lower power outputs, and at high power had better energy delivery than the nanoscale-diffusion lithium batteries.

While these numbers were impressive, batteries with pure lithium electrodes are not the norm. For a more realistic setup, researchers tried instead using a composite electrode made of lithium titanium oxide along with the carbon nanotube electrode. They found that these batteries had lower energy and power, but at 30 watt-hours per kilogram and 5 kilowatts per kilogram, their performance is several times better than the current generation of capacitors. The battery was also very resilient, showing no drop in performance even after 2,500 cycles.

The new battery doesn't best either capacitors or batteries at their respective strengths— it stores energy only about as well as any lithium ion battery, and supplies rushes of power as well as a capacitor. However, it may find use as a versatile middle-of-the-road device that has high storage and can supply bursts of power if needed.

Researchers hope that this new style of battery will eventually allow for larger hybrid vehicles that are less reliant on their gas engines to sustain a high power draw. Potential benefactors of the technology might include tractor trailers and buses.

The authors indicate that they plan to continue by verifying how the electrodes behave on larger scales, where "larger" means tens and hundred of micrometers. They also hope to develop ways to prevent some of the energy loss during charging and discharging. The new battery may also benefit from a new method of assembling multiwalled carbon nanotubes by spraying them on layer by layer, which may allow fine tuning of the voltage differences needed during charge and discharge.


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I'm looking forward to those purely CNT based batteries they were talking about a few months ago. It'll be exciting to see batteries made purely from renewable resources, no expiration date, high rate of energy storage and discharge.

Edited by Reno, 23 June 2010 - 07:07 PM.


#32 Reno

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Posted 15 July 2010 - 02:48 AM

Nanotubes pass acid test

Rice University scientists have found the "ultimate" solvent for all kinds of carbon nanotubes (CNTs), a breakthrough that brings the creation of a highly conductive quantum nanowire ever closer.

Nanotubes have the frustrating habit of bundling, making them less useful than when they're separated in a solution. Rice scientists led by Matteo Pasquali, a professor in chemical and biomolecular engineering and in chemistry, have been trying to untangle them for years as they look for scalable methods to make exceptionally strong, ultralight, highly conductive materials that could revolutionize power distribution, such as the armchair quantum wire.

The armchair quantum wire -- a macroscopic cable of well-aligned metallic nanotubes -- was envisioned by the late Richard Smalley, a Rice chemist who shared the Nobel Prize for his part in discovering the the family of molecules that includes the carbon nanotube. Rice is celebrating the 25th anniversary of that discovery this year.

Pasquali, primary author Nicholas Parra-Vasquez and their colleagues reported this month in the online journal ACS Nano ("Spontaneous Dissolution of Ultralong Single- and Multiwalled Carbon Nanotubes") that chlorosulfonic acid can dissolve half-millimeter-long nanotubes in solution, a critical step in spinning fibers from ultralong nanotubes.

Current methods to dissolve carbon nanotubes, which include surrounding the tubes with soap-like surfactants, doping them with alkali metals or attaching small chemical groups to the sidewalls, disperse nanotubes at relatively low concentrations. These techniques are not ideal for fiber spinning because they damage the properties of the nanotubes, either by attaching small molecules to their surfaces or by shortening them.

A few years ago, the Rice researchers discovered that chlorosulfonic acid, a "superacid," adds positive charges to the surface of the nanotubes without damaging them. This causes the nanotubes to spontaneously separate from each other in their natural bundled form.

This method is ideal for making nanotube solutions for fiber spinning because it produces fluid dopes that closely resemble those used in industrial spinning of high-performance fibers. Until recently, the researchers thought this dissolution method would be effective only for short single-walled nanotubes.

In the new paper, the Rice team reported that the acid dissolution method also works with any type of carbon nanotube, irrespective of length and type, as long as the nanotubes are relatively free of defects.

Parra-Vasquez described the process as "very easy."

"Just adding the nanotubes to chlorosulfonic acid results in dissolution, without even mixing," he said.

While earlier research had focused on single-walled carbon nanotubes, the team discovered chlorosulfonic acid is also adept at dissolving multiwalled nanotubes (MWNTs). "There are many processes that make multiwalled nanotubes at a cheaper cost, and there's a lot of research with them," said Parra-Vasquez, who earned his Rice doctorate last year. "We hope this will open up new areas of research."

They also observed for the first time that long SWNTs dispersed by superacid form liquid crystals. "We already knew that with shorter nanotubes, the liquid-crystalline phase is very different from traditional liquid crystals, so liquid crystals formed from ultralong nanotubes should be interesting to study," he said.

Parra-Vasquez, now a postdoctoral researcher at Centre de Physique Moleculaire Optique et Hertzienne, Universite' de Bordeaux, Talence, France, came to Rice in 2002 for graduate studies with Pasquali and Smalley.

Study co-author Micah Green, assistant professor of chemical engineering at Texas Tech and a former postdoctoral fellow in Pasquali's research group, said working with long nanotubes is key to attaining exceptional properties in fibers because both the mechanical and electrical properties depend on the length of the constituent nanotubes. Pasquali said that using long nanotubes in the fibers should improve their properties on the order of one to two magnitudes, and that similar enhanced properties are also expected in thin films of carbon nanotubes being investigated for flexible electronics applications.

An immediate goal for researchers, Parra-Vasquez said, will be to find "large quantities of ultralong single-walled nanotubes with low defects -- and then making that fiber we have been dreaming of making since I arrived at Rice, a dream that Rick Smalley had and that we have all shared since."


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#33 Reno

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Posted 27 July 2010 - 03:35 PM

This is cool.


Nanotechnology Delivers Revolutionary Pumpless Water Cooling

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Purdue has implemented and tested the nanotech cooler and expects to bring it to market with a few years. (Source: Purdue University School of Mechanical Engineering)

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It essentially offers a pumpless liquid cooler, which can dissipate massive amounts of heat by boiling the cooling fluid -- water -- in microchannels. (Source: School of Mechanical Engineering, Purdue University)

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The new cooler design uses copper-coated carbon nanotubes. (Source: Wikimedia Commons)

Forget traditional metal block coolers a nanowick could remove 10 times the heat of current chip designs

A collaboration of university researchers and top industry experts has created a pumpless liquid cooling system that uses nanotechnology to push the limits of past designs.

One fundamental computing problem is that there are only two ways to increase computing power -- increase the speed or add more processing circuits. Adding more circuits requires advanced chip designs like 3D chips or, more traditionally, die shrinks that are approaching the limits of the laws of physics as applied to current manufacturing approaches. Meanwhile, speedups are constrained by the fact that increasing chip frequency increases power consumption and heat, as evidence by the gigahertz war that peaked in the Pentium 4 era.

A team led by Suresh V. Garimella, the R. Eugene and Susie E. Goodson Distinguished Professor of Mechanical Engineering at Purdue University, may have a solution to cooling higher frequency chips and power electronics. His team cooked up a bleeding edged cooler consisting of tiny copper spheres and carbon nanotubes, which wick coolant passively towards hot electronics.

The coolant used is everyday water, which is transferred to an ultrathin "thermal ground plane" -- a flat hollow plate.

The new design can handle an estimated 10 times the heat of current computer chip designs. That opens the door to higher frequency CPUs and GPUs, but also more efficient electronics in military and electric vehicle applications.

The new design can wick an incredible 550 watts per square centimeter. Mark North, an engineer with Thermacore comments, "We know the wicking part of the system is working well, so we now need to make sure the rest of the system works."

The design was first verified with computer models made by Gamirella, Jayathi Y. Murthy, a Purdue professor of mechanical engineering, and doctoral student Ram Ranjan. Purdue mechanical engineering professor Timothy Fisher's team then produced physical nanotubes to implement the cooler and test it in an advanced simulated electronic chamber.

Garimella describes this fused approach of using computer modeling and experimentation hand in hand, stating, "We have validated the models against experiments, and we are conducting further experiments to more fully explore the results of simulations."

Essentially the breakthrough offers pumpless water-cooling, as the design naturally propels the water. It also uses microfluidics and advanced microchannel research to allow the fluid to fully boil, wicking away far more heat than similar past designs.

This is enabled by smaller pore size than previous sintered designs. Sintering is fusing together tiny copper spheres to form a cooling surface. Garimella comments, "For high drawing power, you need small pores. The problem is that if you make the pores very fine and densely spaced, the liquid faces a lot of frictional resistance and doesn't want to flow. So the permeability of the wick is also important."

To further improve the design and make the pores even smaller the team used 50-nm copper coated carbon nanotubes.

The research was published in this month's edition of the peer-reviewed journal International Journal of Heat and Mass Transfer.

Raytheon Co. is helping design the new cooler. Besides Purdue, Thermacore Inc. and Georgia Tech Research Institute are also aiding the research, which is funded by a Defense Advanced Research Projects Agency (DARPA) grant. The team says they expect commercial coolers utilizing the tech to hit the market within a few years. Given that commercial cooling companies (Thermacore, Raytheon) were involved, there's credibility in that estimate.


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#34 Reno

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Posted 10 September 2010 - 04:19 AM

Your looking at the beginning of comprehensive tools to research in intense detail the interactions of molecules. There is already so much data coming out of such research that it's becoming difficult for scientists to analyze it all. I see a day coming soon where this type of research is completely automated.

Scientists observe single ions moving through tiny carbon-nanotube channel

For the first time, a team of MIT chemical engineers has observed single ions marching through a tiny carbon-nanotube channel. Such channels could be used as extremely sensitive detectors or as part of a new water-desalination system. They could also allow scientists to study chemical reactions at the single-molecule level.

Carbon nanotubes — tiny, hollow cylinders whose walls are lattices of carbon atoms — are about 10,000 times thinner than a human hair. Since their discovery nearly 20 years ago, researchers have experimented with them as batteries, transistors, sensors and solar cells, among other applications.

In the Sept. 10 issue of Science ("Coherence Resonance in a Single-Walled Carbon Nanotube Ion Channel"), MIT researchers report that charged molecules, such as the sodium and chloride ions that form when salt is dissolved in water, can not only flow rapidly through carbon nanotubes, but also can, under some conditions, do so one at a time, like people taking turns crossing a bridge. The research was led by associate professor Michael Strano.

The new system allows passage of much smaller molecules, over greater distances (up to half a millimeter), than any existing nanochannel. Currently, the most commonly studied nanochannel is a silicon nanopore, made by drilling a hole through a silicon membrane. However, these channels are much shorter than the new nanotube channels (the nanotubes are about 20,000 times longer), so they only permit passage of large molecules such as DNA or polymers — anything smaller would move too quickly to be detected.

Strano and his co-authors — recent PhD recipient Chang Young Lee, graduate student Wonjoon Choi and postdoctoral associate Jae-Hee Han — built their new nanochannel by growing a nanotube across a one-centimeter-by-one-centimeter plate, connecting two water reservoirs. Each reservoir contains an electrode, one positive and one negative. Because electricity can flow only if protons — positively charged hydrogen ions, which make up the electric current — can travel from one electrode to the other, the researchers can easily determine whether ions are traveling through the nanotube.
They found that protons do flow steadily across the nanotube, carrying an electric current. Protons flow easily through the nanochannel because they are so small, but the researchers observed that other positively charged ions, such as sodium, can also get through but only if enough electric field is applied. Sodium ions are much larger than protons, so they take longer to cross once they enter. While they travel across the channel, they block protons from flowing, leading to a brief disruption in current known as the Coulter effect.

Strano believes that the channels allow only positively charged ions to flow through them because the ends of the tubes contain negative charges, which attract positive ions. However, he plans to build channels that attract negative ions by adding positive charges to the tube.

Once the researchers have these two types of channels, they hope to embed them in a membrane that could also be used for water desalination. More than 97 percent of Earth's water is in the oceans, but that vast reservoir is undrinkable unless the salt is removed. The current desalination methods, distillation and reverse osmosis, are expensive and require lots of energy. So a nanotube membrane that allows both sodium and chloride ions (which are negatively charged) to flow out of seawater could become a cheaper way to desalinate water.

This study marks the first time that individual ions dissolved in water have been observed at room temperature. This means the nanochannels could also detect impurities, such as arsenic or mercury, in drinking water. (Ions can be identified by how long it takes them to cross the channel, which depends on their size). "If a single arsenic ion is floating in solution, you could detect it," says Strano.


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Edited by Reno, 10 September 2010 - 04:20 AM.


#35 Reno

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Posted 13 September 2010 - 02:02 AM

"Those were the years when the icecaps melted due to the greenhouse gases and the oceans had risen and drowned so many cities along all the shorelines of the world. Amsterdam, Venice, New York forever lost. Millions of people were displaced. Climate became chaotic. Hundreds of millions of people starved in poorer countries. Elsewhere a high degree of prosperity survived when most governments in the developed world introduced legal sanctions to license pregnancies. Which was why robots, who were never hungry and did not consume resources beyond those of their first manufacture were so essential an economic link in the chain mail society." -- Artificial Intelligence

Engineers at the University of California, Berkeley, have developed a pressure-sensitive electronic material from semiconductor nanowires that could one day give new meaning to the term "thin-skinned."

"The idea is to have a material that functions like the human skin, which means incorporating the ability to feel and touch objects," said Ali Javey, associate professor of electrical engineering and computer sciences and head of the UC Berkeley research team developing the artificial skin.

The artificial skin, dubbed "e-skin" by the UC Berkeley researchers, is described in a Sept. 12 paper in the advanced online publication of the journal Nature Materials. It is the first such material made out of inorganic single crystalline semiconductors.

A touch-sensitive artificial skin would help overcome a key challenge in robotics: adapting the amount of force needed to hold and manipulate a wide range of objects.

"Humans generally know how to hold a fragile egg without breaking it," said Javey, who is also a member of the Berkeley Sensor and Actuator Center and a faculty scientist at the Lawrence Berkeley National Laboratory Materials Sciences Division. "If we ever wanted a robot that could unload the dishes, for instance, we'd want to make sure it doesn't break the wine glasses in the process. But we'd also want the robot to be able to grip a stock pot without dropping it."
A longer term goal would be to use the e-skin to restore the sense of touch to patients with prosthetic limbs, which would require significant advances in the integration of electronic sensors with the human nervous system.

Previous attempts to develop an artificial skin relied upon organic materials because they are flexible and easier to process.

"The problem is that organic materials are poor semiconductors, which means electronic devices made out of them would often require high voltages to operate the circuitry," said Javey. "Inorganic materials, such as crystalline silicon, on the other hand, have excellent electrical properties and can operate on low power. They are also more chemically stable. But historically, they have been inflexible and easy to crack. In this regard, works by various groups, including ours, have recently shown that miniaturized strips or wires of inorganics can be made highly flexible – ideal for high performance, mechanically bendable electronics and sensors."

artificial e-skin with nanowire active matrix circuitry covering a hand
An artist's illustration of an artificial e-skin with nanowire active matrix circuitry covering a hand. The fragile egg illustrates the functionality of the e-skin device for prosthetic and robotic applications.

The UC Berkeley engineers utilized an innovative fabrication technique that works somewhat like a lint roller in reverse. Instead of picking up fibers, nanowire "hairs" are deposited.

The researchers started by growing the germanium/silicon nanowires on a cylindrical drum, which was then rolled onto a sticky substrate. The substrate used was a polyimide film, but the researchers said the technique can work with a variety of materials, including other plastics, paper or glass. As the drum rolled, the nanowires were deposited, or "printed," onto the substrate in an orderly fashion, forming the basis from which thin, flexible sheets of electronic materials could be built.

In another complementary approach utilized by the researchers, the nanowires were first grown on a flat source substrate, and then transferred to the polyimide film by a direction-rubbing process.

For the e-skin, the engineers printed the nanowires onto an 18-by-19 pixel square matrix measuring 7 centimeters on each side. Each pixel contained a transistor made up of hundreds of semiconductor nanowires. Nanowire transistors were then integrated with a pressure sensitive rubber on top to provide the sensing functionality. The matrix required less than 5 volts of power to operate and maintained its robustness after being subjected to more than 2,000 bending cycles.
The researchers demonstrated the ability of the e-skin to detect pressure from 0 to 15 kilopascals, a range comparable to the force used for such daily activities as typing on a keyboard or holding an object. In a nod to their home institution, the researchers successfully mapped out the letter C in Cal.

"This is the first truly macroscale integration of ordered nanowire materials for a functional system – in this case, an electronic skin," said study lead author Kuniharu Takei, post-doctoral fellow in electrical engineering and computer sciences. "It's a technique that can be potentially scaled up. The limit now to the size of the e-skin we developed is the size of the processing tools we are using."

Other UC Berkeley co-authors of the paper are Ron Fearing, professor of electrical engineering and computer sciences; Toshitake Takahashi, graduate student in electrical engineering and computer sciences; Johnny C. Ho, graduate student in materials science and engineering; Hyunhyub Ko and Paul Leu, post-doctoral researchers in electrical engineering and computer sciences; and Andrew G. Gillies, graduate student in mechanical engineering.


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#36 Reno

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Posted 14 November 2010 - 06:39 AM

New patent describes carbon nanotube binding peptides

Four scientists have invented carbon nanotube binding peptides. The U.S. Patent was issued on Nov. 9 (No. 7,829,504). The co-inventors are Siqun Wang, Wilmington, Del.; Anand Jagota, Bethlehem, Pa.; Hong Wang, Kennett Square, Pa.; and Steven Raymond Lustig, Landenberg, Pa.

An abstract of the invention, published by the U.S. Patent and Trademark Office, states: "Peptides have been generated that have binding affinity to carbon nanostructures and particularly carbon nanotubes. Peptides of or the invention are generally about twelve amino acids in length. Methods for generating carbon nanotube binding peptides are also disclosed."
The patent was assigned to E.I. du Pont de Nemours & Co., Wilmington, Del. The application was filed on Feb. 13, 2006 (No. 11/352,582), and the document is available here.


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#37 Reno

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Posted 18 December 2010 - 09:59 PM

Innovative method to fabricate complex 3D microstructures


(Nanowerk News) Researchers from imec and the University of Michigan have reported a new technology to fabricate complex three-dimensional microstructures, with intricate bends, twists, and multidirectional textures, starting from vertically aligned carbon nanotubes (CNT) ("Diverse 3D Microarchitectures Made by Capillary Forming of Carbon Nanotubes"). The resulting assemblies have a mechanical stiffness exceeding that of microfabrication polymers, and can be used as molds for the mass production of 3D polymer structures. The method is straightforward, in that it requires only standard two-dimensional patterning and thermal processing at ambient pressure.

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Illustration of CNT forest growth and capillary forming sequence.

Complex surfaces with precisely fabricated nanosized features are needed in, for example, metamaterials, substrates for cell culture and tissue engineering, smart active surfaces, and lab-on-a-chip systems. But existing methods of fabricating 3D microstructures all have their drawbacks, requiring tradeoffs in feature geometry, heterogeneity, resolution, and throughput. This new method, which the researchers have termed 'capillary forming', promises a path to robust, deterministic fabrication of intricate structures with high mechanical stiffness.

The approach to capillary forming of CNTs starts with patterning a catalyst layer on a silicon wafer, using optical lithography. Second, that layer is used to grow microstructures made of vertically aligned CNTs – CNT forests – through thermal chemical vapor deposition (CVD) at atmospheric pressure. Next, a solvent such as acetone is condensed on the substrate. This is done by positioning the substrate, with the CNT patterns facing downward, over a container with the boiling solvent. The solvent vapor rises through the container and condenses on the substrate. Due to capillary rise, the solvent is drawn into each CNT microstructure independently. After the substrate has been exposed to the vapor for the desired duration, it is removed from the container. As a result of the process of infiltration and evaporation of the solvent liquid, capillary forces will bundle the CNTs, resulting in a transformation of the initial 2D geometries into intricate 3D structures.

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SEM image of CNT forests before (A) and after (B) capillary forming, as well as more complex arrangements of microstructures (C,D).

With this method, it is possible to construct robust 3D assemblies of filamentary nanostructures. The researchers have demonstrated this method through the fabrication of a library of diverse CNT microarchitectures. A bending motion, for example, can be combined into twisting and bridge-shaped architectures which cannot be made using standard lithography. This new approach to manipulate nanoscale filaments using local mechanical deformations makes it easier to deterministically design and fabricate 3D microarchitectures with complex geometries as well as nanotextured surfaces. Yet it only requires a standard patterning and thermal processing at ambient pressure.

This work received the Robert M. Caddell award for outstanding research in materials and manufacturing.

Source: imec
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Edited by Reno, 18 December 2010 - 10:00 PM.


#38 Elus

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Posted 27 December 2010 - 06:01 AM

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I'm impressed with the precision of the structures. They are all nearly identical, and a 10-50um scale is nothing to scoff at. If I understand their technique correctly, they have systematically caused a solvent to evaporate from a CNT forest, leaving behind these intact structures that are bound together in unique ways by the evaporating solvent molecules. Very neat.

Edited by Elus, 27 December 2010 - 06:01 AM.





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