The smallest named unit in the metric system is the yoctogram, equal to 0.000000000000000000000001 grams. (Yes, that’s 24 zeros.) For a scale that can measure differences in mass as small as a yoctogram, which is on the order of the mass of a proton, physicists writing in Nature Nanotechnology turned to the wunderkind of nanotechnology: carbon nanotubes.
Now and then we stop to marvel at the feats of carbon nanotube researchers, who use these infinitesimal tubes to build materials of adamantine strength and impressive electrical conductivity. But what if you could marry the robustness of nanotubes to the stretchiness of viscous liquids? You’d be Xu Ming and his fellow Japan-based scientists, who have creating a super rubber that—unlike normal rubber—does not crack and fall apart at extreme temperatures.
Xu’s team outlines its creation in a study for this week’s edition of the journal Science.
Made entirely of carbon, it can flow and stretch slowly like thick honey and spring back to its original form, said [Xu].”It looks like a metal sponge that is porous, it is made from trillions of entangled carbon nanotubes,” she said in a telephone interview. “When you stretch and release it, it can come back slowly (to its original shape).” [ABC News]
The material’s litany of talents—especially its ability to keep its shape up to temperatures of 1000 degrees C (1832 Fahrenheit) and down to -196 C (-321 F)—inspires visions of using it in all kinds of extreme conditions.
That huge range of temperatures means the new material could be used in everything from spacecraft to car shock absorbers, said Roderic Lakes, a scientist at the University of Wisconsin who studies viscoelastic materials. Spacecraft equipped with this material could withstand the intense cold of [Saturn]’s largest moon, Titan, said Gogotsi, or the heat of the sun in space, said Lakes. [Discovery News]
Faced with the sun’s damaging rays, new biological solar cells can repair themselves, regaining their maximum efficiency when some competitors might fade. In their current form these biological solar cells, made with a bacterium’s photosynthesis hub and carbon nanotubes, only reach a small fraction of the efficiency seen in the best traditional solar cells. But their ability to reinvent themselves by shedding damaged proteins and reassembling to regain their maximum efficiency could be a useful feature for future solar cells.
The researchers, who published their work in Nature Chemistry, used a bacterium’s natural light collection center to generate solar power, used proteins and lipids to make supporting disc forms, and employed conducting carbon nanotubes to channel away electric current. This set of materials chemically clumps together, making the cells self-assembling.
The spontaneous assembly occurs thanks to the chemical properties of the ingredients and their tendency to combine in the most energetically comfortable positions. The scaffolding protein wraps around the lipid, forming a little disc with the photosynthetic reaction center perched on top. These discs line up along the carbon nanotube, which has pores that electrons from the reaction center can pass through. [Science News]
Illness-inducing bacteria, meet nano-engineered cotton–and a quick death. Researchers have created a new “filter” that zaps bacteria with electric fields to clean drinking water. They say their system may find use in developing countries since it requires only a small amount of voltage (a couple of car batteries, a stationary bike, or a solar panel could do the job) and cleans water an estimated 80,000 times faster than traditional devices.
Instead of trapping bacteria in small pores like many slow-going traditional filters, the cotton and silver nanowire combo uses small electric currents running through the nanowires to kill the bacteria outright. In a paper to appear in the journal Nano Letters researchers say that 20 volts and 2.5 inches worth of the material killed 98 percent of Escherichia coli in the water they tested in their lab setup.
The structure of Aleksandr Noy’s new transistor is unimpressively simple: just a carbon nanotube connecting two metal electrodes. But what makes it special is what he and his team use to control it: adenosine triphosphate (ATP), the fuel from our own cells. The project, published in a study in Nano Letters, achieves a key step in unifying man and machine.
The way it works: An insulator coats the ends of the nanotube, but not the middle—it’s left exposed.
The entire device is then coated again, this time with a lipid bi-layer similar to those that form the membranes surrounding our body’s cells [New Scientist].
Finally, the team poured a solution of ATP plus potassium and sodium across the transistor. That created an electric current, one that was stronger the more ATP they poured.
The magic is in the lipid bi-layer, which contains an ATP-sensitive protein that serves as a kind of ion pump when ATP is present. The lipid hydrolyses ATP molecules, with each occurence causing three sodium ions to move one way through the lipid and two potassium ions to move the other way, netting one charge across the bi-layer to the nanotube [Popular Science].
Noy claims to have created “the first example of a truly integrated bioelectronic system,” New Scientist says. And as simple as the transistor is, the idea behind it—harnessing the energy already in our bodies to power electronics—will be one of the keys to creating battery-free devices that monitor our cells, connect to our brains, or do things we won’t think of until we’ve (finally!) got nanodevices hooked up to our brains.
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Image: Aleksandr Noy et. al.
So far in 2010 we’ve seen nanotubes that carry thermopower waves to create electricity, nanoparticles that latch onto only damaged cells to deliver drugs there, and more. Today there are a couple more clever uses for nanotechnology—taking the salt out of salt water, and nanobots that deliver gene therapy.
In Nature Nanotechnology, an MIT team showed they could use nanotech to desalinate water in a new way. At the moment, desalination plants employ reverse osmosis, in which pressure forces the salt ions through a membrane. But this process is an energy-gobbler and the membrane is prone to clogging, which means that de-sal plants are inevitably big, expensive, fixed pieces of kit [Sydney Morning Herald].
Carbon nanotubes have shown the potential to help us take better x-ray images, make cheaper hydrogen fuel cells, and replace silicon in computer chips. Add another possibility onto the pile: MIT researchers report this week in Nature Materials that they’ve used carbon nanotubes to create thermopower waves, a system they say could put out 100 times more energy than a lithium-ion battery.
Michael Strano’s team coated the tubes, which are only billionths of a meter across, with a fuel. This fuel was then ignited at one end of the nanotube using either a laser beam or a high-voltage spark, and the result was a fast-moving thermal wave traveling along the length of the carbon nanotube like a flame speeding along the length of a lit fuse [Environmental News Service]. That wave travels 10,000 times the typical speed of this chemical reaction, and the heat blasts electrons down the tubes. Voila, electric current.
This previously unknown phenomenon opens up an entirely new area of energy research, Strano says, and the technology’s potential applications are exciting. Strano envisions thermopower waves that could enable ultra-small electronic devices, no larger than a grain of rice, perhaps a sensor or treatment device that could be injected into the body. Or they might be used in “environmental sensors that could be scattered like dust in the air,” he says [Environmental News Service].
Stanford University researchers think they’ve stumbled upon a way to transform ordinary sheets of office paper into batteries and superconductors. By painting a carbon nanotube ink, which can collect electric charge, on plain copier paper, and then dipping the coated paper into a lithium ion solution and an electrolyte, they can create a current and store it within the paper battery.
The scientists had previously experimented with making batteries using a similar process of painting nanomaterial ink onto a thin layer of plastic. But in an unexpected twist, they found that pores in paper fibers make it hold the ink better than plastic, for a more durable battery [The New York Times]. The research team, led by Yi Cui, found that you can even crumple up the paper batteries or soak them in acid, and they’ll still work just fine. They hope their technology, which was reported in the journal Proceedings of the National Academy of Sciences, can usher in a new era of lightweight, low-cost batteries.