What’s the News: In traditional solar cells, sunlight is absorbed by the cell (made from silicon or titanium dioxide), freeing electrons, which travel across the cell to an electron collector, or electrode. A problem with solar cells is that many electrons don’t find their way to the electrode; carbon nanotubes can be used as bridges between the loosened electrons and the electrode, but nanotubes tend to bunch up, decreasing the efficiency and causing short circuits. Researchers have now created genetically engineered viruses can be used to keep the nanotubes in place, increasing energy conversion by nearly one-third. “A little biology goes a long way,” research group leader Angela Belcher told MIT News, noting that the entire virus-nanotube bridging layer represents only 0.1% of the finished cell’s weight.
Posts Tagged ‘nanotechnology’
Materials Scientists’ Solar Cell Has a Virus—and That’s a Good Thing
IBM Creates Nanoparticles That Burst Superbugs Like Popped Balloons
What’s the News: Scientists are using nanoparticles to develop ways to fight bacteria that are resistant to conventional antibiotics. These tiny drugs physically punch holes through bacteria instead of killing them chemically, which means that they could be especially effective on antibiotic-resistant bacteria strains like the dangerous methicillin-resistant Staphylococcus aureus (MRSA). “The applications are going to be very diverse, whether we’re talking about wound healing or dressing, skin infection, and quite possibly injections into the bloodstream,” James Hedrick, master inventor at IBM Almaden Research Center in San Jose, California, told Popular Science.
Carbon-Nanotube Cancer Detector Can Catch Even a Single Marauding, Malignant Cell
What’s the News: Scientists have developed a new carbon nanotube device (pictured above) that’s capable of detecting single cancer cells. Once implemented in hospitals, this microfluidic device could let doctors more efficiently detect the spread of cancer, especially in developing countries that don’t have the money for more sophisticated diagnostic equipment. Any improvement in detecting cancer’s spread is important, says MIT associate professor of aeronautics and astronautics Brian Wardle, because “of all deaths from cancer, 90 percent are … from tumors that spread from the original site.”
What’s the Context:
- The researchers’ original microfluidic device from four years ago featured tens of thousands of microscopic silicon posts coated with tumor-sticking antibodies: when cancer cells bumped into the posts, they’d stick. But if cancer cells didn’t bump into a silicon post, they’d go undetected. The group says their new version is eight times better.
- When cancer cells migrate, there are “usually only several [cancer] cells per 1-milliliter sample of blood” containing billions of other cells, making cancer exceedingly difficult to detect.
- This new dime-sized microfluidic machine works in the same way, but the solid silicon tubes were switched out for highly porous carbon nanotubes. This allows the blood to actually flow through the tubes instead of just around them, increasing the likelihood of catching a cancer cell.
- In other cancer detection news, some are using dogs to sniff out cancer and others use genetic tests to figure out cancer risks.
- Combating cancer ranges from new cancer-fighting drugs to just ignoring cancer (sometimes).
Not So Fast: The process of commercializing a technology like this takes quite a while; the previous version from four years ago is being tested in hospitals now and is may be commercially available “within the next few years.”
Next Up: The scientists are currently tweaking the device to try to catch HIV.
Reference: Grace D. Chen et al. “Nanoporous Elements in Microfluidics for Multiscale Manipulation of Bioparticles.” Small. DOI: 10.1002/smll.201002076
Image: Brian Wardle/MIT
Harvard Engineers Build Tiny Processors out of Nanowires
Today in the journal Nature, researchers led by Charles Lieber report a big step forward in the field of tiny computing: the creation of linked-up logic circuits made of nanowires, which could be used to build itty-bitty processors.
The devices described in the paper layer additional wires across the germanium-silicon ones; charges can be trapped in these wires, influencing the behavior of the underlying nanowires. This charge trapping is nonvolatile but reversible; in other words, you can switch one of the nanowires on or off by altering the charge stored in its neighborhood. This makes it possible to turn the nanowires into a standard field-effect transistor (the authors term them NWFETs for “nanowire field-effect transistors”). [Ars Technica]
Lieber had been able to create simple versions of those NWFETs before, but those were difficult to build on a large enough scale to create logic circuits.
Pictured: A Patchwork Quilt of Graphene’s Atoms
This picture may look like an exuberant patchwork quilt, or a stretch of really interesting farmland as seen from an airplane. In fact, what you’re looking at is sheet of graphene–a one-atom-thick layer of carbon, measuring about 100,000 atoms across.
The image, produced by an electron microscope, reveals that the honeycomb-like lattice of carbon atoms that forms a sheet of graphene is full of irregularities. Each sheet is composed of patches of atoms, and each patch has a slightly different rotation than that of its neighbors. By firing electrons at a sheet and using different colors to identify the angles at which the electrons bounced back, researchers made this rainbow image of a graphene sheet with the patch boundaries clearly shown.
Lead researcher David Muller says this is an easy and efficient way to understand a graphene sheet’s properties.
“You don’t want to look at the whole quilt by counting each thread. You want to stand back and see what it looks like on the bed. And so we developed a method that filters out the crystal information in a way that you don’t have to count every atom,” said David Muller, professor of applied and engineering physics and co-director of the Kavli Institute at Cornell for Nanoscale Science. [press release]
The research, which was published in Nature, will be useful as nanotechnologists continue to investigate graphene’s exciting electrical properties. Researchers had previously thought that larger patches would improve the electrical conductivity of graphene, but Muller’s experiments suggest that theory is wrong. Rather, it’s impurities in graphene sheets that interfere with their conductivity, he argues.
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Image: Cornell University/ P.Y. Huang / D. A. Muller
Super Rubber Made of Nanotubes Stretches Like Elastic, Oozes Like Honey
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]
Nanogenerator Takes Us One Step Closer to Power-Generating Clothing
Devices that use the wasted mechanical energy from clothing movements or even a heartbeat seem far out, if not just a bit creepy, but new advances in nanogenerators are making such energy-scavenging electronics possible.
Now researchers at Georgia Tech have made the first nanowire-based generators that can harvest sufficient mechanical energy to power small devices, including light-emitting diodes and a liquid-crystal display. [Technology Review]
The new generators use materials that have a particularly odd property: They collect a charge and drive a current when flexed (this is called piezoelectricity). The problem in using these materials for energy-harvesting applications has been that the materials that were sufficiently efficient at driving a current were too rigid, and those that were flexible enough weren’t very efficient.
Scientists Create “Artificial Electronic Skin” From Nanowire Mesh
From “When the Robots Sing ‘Touch-A, Touch-A, Touch-Me,’ the E-Skin Is Working,” on the DISCOVER blog Science Not Fiction:
That’s right, e-skin. A group of scientists at UC-Berkeley devised a flexible mesh using nanowires to create a substance that reacts to pressure, and, as their paper in Nature Materials said, “effectively functions as an artificial electronic skin.” In the same issue, a team from Stanford University announced it had devised a kind of skin so sensitive, it can detect the weight of a bluebottle fly. All of which means for one shining issue, a scientific journal was a skin mag.
Read the rest of this post (with video).
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Image: UC Berkeley
Self-Assembling, Self-Repairing Solar Cells Pass Endurance Test
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]
Nanowire-Coated Cotton Cleans Water by Zapping Bacteria to Death
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.
MIT Invents a Swarm of Sea-Skimming, Oil-Collecting Robots
Earlier this week, DISCOVER brought you oil-cleaning bacteria. Today, we bring you oil-cleaning bots.
This weekend in watery Venice, Italy, MIT scientists will demonstrate a creation called Seaswarm, a fleet of autonomous swimming bots intended to skim the water’s surface; each bot would drag a sort of mesh net to collect the crude sitting there. According to their creators, the machines will be able to find oil on their own and talk to one another to compute the most efficient way to tidy it up.
The Seaswarm robots, which were developed by a team from MIT’s Senseable City Lab, look like a treadmill conveyor belt that’s been attached to an ice cooler. The conveyor belt piece of the system floats on the surface of the ocean. As it turns, the belt propels the robot forward and lifts oil off the water with the help of a nanomaterial that’s engineered to attract oil and repel water [CNN].
A Nano-Wiretap: Scientists Use Nanowires to Spy on a Cell’s Inner Life
Meet the cyborg cell. By attaching probes with nano-hairpin connectors to living cells, researchers have measured electrical currents from inside. They hope the probes will provide a useful way to monitor cells’ health.
A team at Harvard University conducted the study, which appears in Science. Though other probes can measure the currents in electrical impulse-producing cells–such as beating heart cells–none have given researchers the precision of measuring from inside. The probes designed in this study allowed researchers to successfully measure the electric pulses from cultured chicken heart cells’ beating.
One of the team’s challenges was getting the wires to kink into the hairpin shape–a difficult maneuver using traditional nanowire-making techniques. They noted if they stopped the wire as it formed, they could force it to bend.
Spitzer Telescope Finds Buckyballs… in Spaaace!
Looking at a planetary nebula 6,500 light years away, scientists recognized an old friend: the buckyball. The large, soccer ball-shaped molecule–made from bonding 60 carbon atoms together–was first seen in a lab in 1985. In a paper published today in Science, scientists confirm the first known extraterrestrial existence of the rare carbon balls.
The buckyballs’ planetary nebula, called TC 1, surrounds a white dwarf star. Using NASA’s Spitzer Space Telescope, a team led by Jan Cami of the University of Western Ontario observed traces of the the 60-atom balls and their 70-atom cousins while looking at light coming from the white dwarf.
When light hits molecules and atoms, they will vibrate in specific, measurable ways–a field of science known as spectroscopy. One of Cami’s colleagues, who was studying Tc 1, found some unfamiliar fingerprints in the nebula’s infrared light. Cami recognized them as carbon’s 60-atom configuration and its favored 70-atom carbon partner. [Discovery News]
Making Super-Powered Solar Panels Via Quantum Dots
A new type of solar cell using “quantum dots” may double the theoretical efficiency of current solar cells–allowing a panel to convert around 60 percent of the sun’s energy that it laps up into electricity. The research on these new cells appeared Friday in Science.
Current silicon-based solar cells lose about 80 percent of the sun’s energy they take in. It’s an inherent flaw: even working at their theoretical ideal, these cells would still lose 70 percent.
We can blame the sun’s diversely energized photons for this inefficiency. Silicon cells can only purposefully harvest photons with just the right amount energy. When they strike the cell, photons with just enough juice will prod an electron into motion (and create an electric current). An overly energized photon will excite the electrons to no purpose; the electrons will just quickly give off that photon’s energy as heat.
In two steps, this project, funded in part by the Department of Energy, salvages these “hot electrons.”
“There are a few steps needed to create what I call this ‘ultimate solar cell,’” says [Xiaoyang] Zhu, professor of chemistry and director of the Center for Materials Chemistry. “First, the cooling rate of hot electrons needs to be slowed down. Second, we need to be able to grab those hot electrons and use them quickly before they lose all of their energy.” [University of Texas at Austin]
Huge Mirrors, DNA Robots, & Brain Communication Win 2010 Kavli Prizes
Show them the money: The winners of the Kavli Prizes have been announced, and the eight scientists will split a total of $3 million in prize money.
No, these aren’t the Nobels. The Kavlis are a relatively new award created to award scientists whose fields don’t get much recognition in Stockholm:
These are only the second ever recipients of Kavli Prizes, the biennial awards launched in 2008 by Fred Kavli. Recipients in the fields of astrophysics, neuroscience and nanoscience each receive a scroll, a gold medal and (perhaps most importantly) a share of the $1 million pot for each discipline [Nature].
1. Astrophysics
The prize recognized three men—Jerry Nelson, Roger Angel, and Raymond Wilson—not for finding new phenomena deep in the cosmos, but for engineering the telescopes to make those searches possible. Nelson and Angel are renowned for their prowess in casting the mirrors for the largest telescopes on Earth; Nelson’s work will go into the Thirty Meter Telescope, for which Mauna Kea in Hawaii was just chosen as the preferred location.
Dr. Wilson pioneered the use of a technology known as active optics, in which computer-controlled supports correct the shapes of telescope mirrors to cancel the distortions caused by gravity, wind and temperature, allowing astronomers to build mirrors that are thinner and lighter [The New York Times].
