Nanotechnology: It’s a Small World After All
February 11, 2011
If you go back and watch the earliest science fiction movies, one of the things you will notice they never got right was miniaturization (except maybe for “ray guns”). Of course, transistors and microchips hadn’t been invented and it was difficult for people to imagine a world without vacuum tubes. We no longer suffer mental barrier. Over the past couple of months, Gizmag has published a number of articles dealing with breakthroughs in nanotechnology and those articles provide an eye-opening view of how nanotechnology could change the way we live. Let’s start with a story in which nanotechnology has obvious practical applications.
Over the holidays and through early January, snow reportedly covered 70 percent of the United States. Lives were disrupted as travelers were stranded in airports and flights were delayed. One of the reasons that flights can be delayed during bad weather is that a de-icing solution needs to be applied to aircraft fuselages and wings. According to Ben Coxworth, having to de-ice an aircraft before takeoff could become a thing of the past thanks to nanotechnology [“Nanostructured materials to put an end to icy airplanes and roads,” 15 November 2010]. Coxworth reports:
“Much to the chagrin of those of us in the Northern Hemisphere, winter … means a return to icy roads, sidewalks, power lines and even airplane wings. Traditionally, the main methods of getting rid of this ice – or at least, keeping it under control – involve the use of salt and/or de-icing chemicals. Both of these are labor-intensive, environmentally-unfriendly, plus the salt kills grass and causes cars to rust. Now, however, researchers from Harvard University are developing nanostructured materials that could keep ice from ever forming on surfaces in the first place. Like the superhydrophobic coating developed by a University of Pittsburgh-led team that mimics the rutted surface of lotus leaves to reduce the surface area to which water can adhere, the Harvard team got their inspiration from natural models. Although the principle is the same, instead of the lotus leaf the Harvard team turned to the eyes of mosquitoes and the legs of water striders for their inspiration. In both cases, the insects are able to keep these body parts dry due to an array of tiny bristles that repel droplets of water by minimizing the available surface area.”
In a couple of past posts, I’ve noted that more and more scientists and engineers are turning to nature for inspiration and obtaining startling results. Who knew that the pesky mosquito could actually benefit mankind? Coxworth continues:
“The researchers proceeded to create silicon surfaces incorporating various nanoscale shapes, patterns and geometries, such as bristles, blades, honeycombs and bricks. When they watched slow-motion videos of supercooled droplets hitting some of these surfaces, they saw that that the droplets would initially spread out, but then retract back into a sphere and bounce off before they could freeze. The surfaces with interconnected patterns were particularly effective. On regular smooth surfaces, by contrast, the droplets would simply spread out and freeze. The nanostructured materials were shown to prevent the formation of ice down to a temperature of -30C (-22F). Even below that, what ice did form wasn’t able to adhere well, so would be relatively easy to remove.”
At this point it is hard to imagine road systems in northern climes being paved with material featuring these nanoscale properties (states and cities can’t even afford to fix potholes!); but it doesn’t stretch the imagination to picture future aircraft being built with such material — in fact, the sooner the better.
About three years ago, I wrote a post entitled A New Form of Data Storage. The data storage method under discussion was called racetrack memory and the post discussed work being done by IBM. Coxworth provides an update on racetrack memory being done by IBM as well as other organizations [“‘Racetrack memory’ could be 100,000 times faster than hard drives,” 15 November 2010]. Coxworth reports:
“Racetrack Memory … is a proposed new shock-proof system that is said to be 100,000 times faster than current hard drives, while also being 300 times more energy-efficient. Although it incorporates cutting-edge nanotechnology, it’s based on the same principles as the humble VHS videotape. IBM has been working on developing Racetrack Memory for a couple of years, after Stuart Parkin of IBM’s Almaden Research Center came up with the concept of spintroncs-based memory that has no moving parts, but in which the information moves. Prof. Mathias Kläui of Switzerland’s Ecole Polytechnique Federale de Lausanne (EPFL) decided to pursue it after he got tired of waiting the two to three minutes for his computer to boot up. Like a videocassette, Racetrack Memory would store data magnetically. Instead of on a moving tape, however, it would be stored on a tiny unmoving nickel-iron nanowire. The bits of information, which are stored in the wire using the spin of electrons rather than an electronic charge, would be moved around at several hundred meters per second, using a spin polarized current. Adjacent bits would be delineated from one another via domain walls with magnetic vortices.”
Admit it, “spin polarized current” and “magnetic vortices” are not phrases tossed about in normal conversation. They sound a lot like something that would be said during a conversation between characters on an episode of Star Trek. Welcome to the future. Coxworth continues:
“EPFL says that accessing one of these nanowires would be like reading an entire VHS tape in less than a second, and the plan is for millions or even billions of these wires to be embedded on one chip. Perhaps you start to get the idea of just how speedy this thing could be. Kläui says that, not only would Racetrack Memory-equipped computers boot up instantly, they could also access information 100,000 times more rapidly than a traditional HDD. Additionally, because there are no moving parts, there is nothing to wear out, and unlike flash SSDs, it can be rewritten to endlessly.”
Sound too good to be true? You may be right. Coxworth explains:
“There are hurdles to be overcome before we start seeing Ractrack Memory appearing in consumer devices. … Experiments by researchers at the University of Hamburg showed that microscopic imperfections in the crystal structure of the wires, which led to the magnetic domains becoming ‘stuck,’ resulted in performance roughly equal to traditional HDDs. If these and other problems can be overcome, we can look forward to instant-on computers that are ready to go when we are.”
Memory storage isn’t the only kind of future hoping to benefit from breakthroughs in nanotechnology.
Energy storage is another area [“Graphene-based supercapacitor hits new energy storage high,” by Grant Banks, Gizmag, 7 December 2010]. Banks reports:
“A breakthrough in supercapacitor performance has been achieved with the development of a device that can store as much energy as a battery while recharging in seconds. The graphene-based supercapacitor being developed in the U.S. by researchers at Nanotek Instruments can store as much energy per unit mass as nickel metal hydride batteries and could one day be used to help deliver almost instant charging to recharge mobile phones, digital cameras or micro electric vehicles.”
If nothing else, the promise of “almost instant charging” should have caught your attention. Such promises are what make scientific research so interesting to follow. Banks continues:
“With the high surface area of their electrodes and an extremely narrow gap between the electrodes, supercapacitors, also known as electric double-layer capacitors or electrochemical capacitors, can store a large amount of electrical charge in a tiny volume.”
Banks goes on to explain how the device is made (beginning with a graphene-based slurry) and the energy density it can achieve (the best values for electric double layer supercapacitors based on carbon nanomaterials recorded to date).
It’s a bird … it’s a plane … it’s a carbon-nanotube material
The more you read about nanotechnology the more you hear terms like nano-wires, nano-fibers, and nano-tubes. These are the basic building blocks for practical, real-world applications — like bulletproof vests [“Engineers create new nano-fiber tougher than Kevlar,” by Grant Banks, 7 December 2010]. Banks reports:
“A new high performance fiber that is better at absorbing energy without breaking than Kevlar has been created by the U.S. Department of Defence. While still under development, the material could be used in bulletproof vests, parachutes, or in composite materials for vehicles, airplanes and satellites in the future. The fiber has been engineered from carbon nanotubes spun into a yarn and held together using a polymer. The resultant material is tough and strong while still remaining flexible.”
Banks notes that most fibers are either strong or ductile. The new material, being developed Northwestern University’s McCormick School of Engineering and Applied Science appears to be both very strong and very ductile. Banks continues:
“To create the new fiber, researchers began with carbon nanotubes. These cylindrical-shaped carbon molecules are known to individually have one of the highest strengths of any material in nature. Previously the largest issue facing materials researchers has been that when nanotubes are bundled together they lose strength because of lateral slippage. To solve this problem a polymer was added to bind them together, and then the resulting material was spun into yarns. … The result is a material that has a higher ability to absorb energy without breaking than Kevlar, though Kevlar still has a higher resistance to failure. The next step is to study how to engineer the interactions between carbon nanotube bundles and the nanotubes within the bundle itself to increase the strength of the material.”
Before you get too excited about the strength of nanotubes, the material used to make nanotubes (graphene) has been found to have some flaws [“Columbia researchers find graphene can’t cope with stress,” by Dario Borghino, 6 December 2010]. Borghino reports:
“Graphene, a one-atom-thick layer of carbon, is considered the strongest material known to mankind. It has found countless applications in the field of nanotechnology, including the manufacturing of stronger-than-steel-by-a-hundredfold nanotubes. However, Assistant Professor Chris Marianetti at Columbia University has exposed a fundamental structural weakness of graphene that leads to its possible mechanical failure under strain, and could change the way we use this and other materials to build nanotech devices. Using quantum theory and aided by supercomputers, Marianetti has discovered that when pure graphene is subject to equal strain in all directions, it morphs into a new structure that is mechanically unstable – the honeycomb arrangement of carbon atoms in the graphene sheet transforms into a series of isolated hexagonal rings that is structurally weaker, causing a mechanical failure of the material. At any temperature above absolute zero, all the atoms in a crystal vibrate with a certain intensity – the higher the temperature, the stronger the vibrations. The team led by Marianetti found that under isotropic stress, a phonon (the collective vibrational mode of atoms within a crystal) is altered and becomes ‘soft.’ The system then distorts its atoms along the vibrational mode and transitions to a new arrangement that is structurally weaker. This is the first time a soft optical phonon has been linked to mechanical failure, and opens the way to further research that should ascertain whether, as the team suspects, this failure mechanism is present in other very thin materials as well. Strains may even be a means to engineer the properties of graphene, so understanding its limits is critical.”
I suspect that for many applications this graphene “flaw” will simply never come into play. Nevertheless, I’m glad someone is researching the topic.
Moving back into the area of electronics, one of the promises of nanotechnology has been the creation of quantum computers. Nanowires play a vital role in the construction of quantum computers and other tiny electronic devices. The most recent breakthrough in nanowires is creating coils out of them [“Coiled nanowire key to stretchable electronics,” by Grant Banks, 12 January 2011]. Banks reports:
“Stretchability is not something you’d think of as synonymous with electronics. For this very reason the realm of wearable electronic devices has been limited to devices on clothes with rigid or at best semi-flexible circuit boards or solar panels and watches that can do just about everything except make a decent espresso. The game is about to change with the introduction of a silicon nanowire with elastic properties that could enable the incorporation of stretchable electronic devices into clothing, implantable health-monitoring devices, and a host of other applications. Researchers at North Carolina State University (NCSU) have created the first silicon nanowire coils that can be stretched to more than double their original length. Initial experimenting had been with folding electronic materials, which can stretch much like the bellows of an accordion, however this design was found to be flawed. Failures in the peaks and valleys of the waves were causing the entire structures to fail. Dr Yong Zhu, one of the researchers at NCSU then came across the idea of creating coiled structures to eliminate this problem.”
As interesting as devices using coiled nano-wires may be, electronics like quantum computers are able to use more traditional straight nano-wires. However, there are even breakthroughs being made with the traditional form of nano-wires [“Scientists successfully manipulate qubits with electrical fields,” by Darren Quick, 26 December 2010]. Quick reports:
“Until now, the common practice for manipulating the electron spin of quantum bits, or qubits, – the building blocks of future super-fast quantum computers – has been through the use of magnetic fields. Unfortunately, these magnetic fields are extremely difficult to generate on a chip, but now Dutch scientists have found a way to manipulate qubits with electrical rather than magnetic fields. The development marks yet another important development in the quest for future quantum computers, which would far outstrip current computers in terms of speed. Just like a normal computer bit, a qubit can adopt the states ‘0’ and ‘1’. One way to make a qubit is to trap a single electron in semiconductor material. It’s state can be set by using the spin of an electron, which is generated by spinning the electron on its axis. As it can spin in two directions, one direction represents the ‘0’ state, while the opposite direction represents the ‘1’ state. Until now, the spin of an electron has been controlled by magnetic fields but the scientists from the Kavli Institute of Nanoscience at Delft University of Technology and Eindhoven University of Technology have now succeeded in controlling the electron spin in a qubit with a charge or an electric field. According to Leo Kouwenhoven, scientist at the Kavli Institute of Nanoscience at TU Delft this form of control has major advantages. ‘These spin-orbit qubits combine the best of both worlds. They employ the advantages of both electronic control and information storage in the electron spin,’ he said. In another important quantum computing development, the scientists have also been able to embed these qubits into semiconductor nanowires. The scientists were able to embed two qubits in nanowires measuring just nanometers in diameter and micrometers in length made of indium arsenide. ‘These nanowires are being increasingly used as convenient building blocks in nanoelectronics. Nanowires are an excellent platform for quantum information processing, among other applications,’ said Kouwenhoven.”
The last nanotechnology story was about a really weird-looking substance called “frozen smoke” [“World’s lightest solid material, known as ‘frozen smoke’, gets even lighter,” by Grant Banks, 13 January 2011]. Banks reports:
“Researchers have created a new aerogel that boasts amazing strength and an incredibly large surface area. Nicknamed ‘frozen smoke’ due to its translucent appearance, aerogels are manufactured materials derived from a gel in which the liquid component of the gel has been replaced with a gas, resulting in a material renowned as the world’s lightest solid material. The new so-called ‘multiwalled carbon nanotube (MCNT) aerogel’ could be used in sensors to detect pollutants and toxic substances, chemical reactors, and electronics components. Although aerogels have been fabricated from silica, metal oxides, polymers, and carbon-based materials and are already used in thermal insulation in windows and buildings, tennis racquets, sponges to clean up oil spills, and other products, few scientists have succeeded in making aerogels from carbon nanotubes. The researchers were able to succeed where so many before them had failed using a wet gel of well-dispersed pristine MWCNTs. After removing the liquid component from the MWCNT wet gel, they were able to create the lightest ever free-standing MWCNT aerogel monolith with a density of 4 mg/cm3. MWCNT aerogels infused with a plastic material are flexible, like a spring that can be stretched thousands of times, and if the nanotubes in a one-ounce cube were unraveled and placed side-to-side and end-to-end, they would carpet three football fields. The MWCNT aerogels are also excellent conductors of electricity, which is what makes them ideal for sensing applications and offers great potential for their use in electronics components.”
Although frozen smoke has great thermal insulating properties, because of its excellent electrical conducting properties, I doubt you’ll see it used in winter clothing lines. I’d hate to be struck by lightning wearing a frozen smoke insulated jacket!
The world of nanotechnology appears to be as weird as it is wonderful. Walt Disney Company (and the Sherman brothers Robert and Richard) could have been thinking about the future of science when they came up with: It’s a small world after all.