Only a new president can rescue the field from this funding mess.
It's unclear if a new technique to generate embryonic stem cells without destroying the embryos from which they were derived will be eligible for federal funding, according to news reports last week. Some seem to think the new method satisifies restrictions that prohibit federal funding for research that harms embryos. Others disagree. This latest debate only serves to highlight the need for a new administration and new funding policies to rescue the field from an ethical logjam.
Scientists have jumped through a series of hoops trying to find ways around Bush's 2001 restrictions. (Up until now, derivation of new stem-cell lines required that donor embryos be destroyed.) In the new method,a single cell is removed from an embryo in a procedure similar to that performed by fertility clinics.
This approach, developed by scientists at Advanced Cell Technologies, seems more sensible than previous efforts. (See "Stem Cells from Embryos--without Destroying Them.") For example, last year, scientists created genetically modified embryos that could not develop past a certain point, thereby preventing the destruction of viable embryos. This satisfied some ethicists, but others countered that the method merely generated crippled embryos.
Now an NIH official says that while the method appears to satisfy federal funding rule, the only way to prove it would be to perform an experiment that no one would deem ethically acceptable: implanting embryos used in the experiment into a woman's uterus to see if they can develop normally.
According to the Washington Post,
... the new work shows for the first time that healthy, normal embryonic stem cells can be cultivated directly from embryos without destroying them.
That means the work should be eligible for federal financing under President Bush's six-year-old policy of funding only stem cell research that does not harm embryos, said study leader Robert Lanza, chief scientific officer at Advanced Cell Technology in Worcester.
But that is not likely, said Story Landis, who heads the National Institutes of Health Stem Cell Task Force, which oversees grants for studies on the medically promising cells.
The embryos Lanza used, which were donated for research, appear not to have been damaged, Landis acknowledged. However, she said, "it is impossible to know definitively" that the embryos were not in some subtle way harmed by the experiment. And "no harm" is the basis of the Bush policy, she said.
Landis said the only way to prove that the technique does not harm embryos would be to transfer many of them to women's wombs and see whether the resulting babies were normal. But it would be unethical to do that experiment, she said, so the question cannot be answered.
The only solution to the quagmire? A new president who would support new federal funding guidelines already approved in Congress.
http://www.technologyreview.com/blog/editors/22003/
Wednesday, January 16, 2008
Unclear if New Stem Cells Eligible for Federal Funding
Expandable Silicon
A new design for silicon-based chips makes it possible to mechanically stretch them out to cover large areas. These expanded chips, which could be thousands of times the size of the original, could be used to make cheaper solar panels, sensor networks, and flat-screen TVs.
The chips, built by researchers at Stanford University, consist of free-floating islands of silicon surrounded by coils of silicon wire. Each island can be processed to include transistors, sensors, or materials for tiny solar cells. When the corners of the chip are pulled on, the coils around the silicon islands unwind. As they do, the islands, which start out nearly touching each other, spread apart. The end result is a netlike array of silicon devices.
So far the researchers have demonstrated arrays that are 50 times larger than the original chip, but they've been limited by the size of their laboratory equipment. Peter Peumans, the professor of electrical engineering at Stanford who led the work, says that the chips could be made to expand thousands, or even tens of thousands, of times. Peumans's work was presented this week at the International Electron Devices meeting in Washington, DC.
Silicon nets: Using conventional silicon-processing techniques, researchers at Stanford University have built chips that consist of islands of silicon surrounded by silicon coils. The top-left image shows one such silicon island, and the bottom-left image shows the entire chip composed of an array of these islands. When the corners of the chip are pulled, the coils unwind, and the islands spread apart. The finished network is shown at the bottom right. The top-right image shows the coils completely unwound.
The work is "taking the integrated circuit concept that has been so successful in microelectronics and adapting it to large-area applications," says Marc Baldo, a professor of electrical engineering at MIT. The semiconductor industry has excelled at packing more high-performance transistors into a given space, driving down the cost per transistor in the process. But many applications require that transistors and other silicon-based devices be more distributed.
For example, flat-screen TVs need millions of transistors spread out to control each pixel. For LCD TVs, it's been possible to use relatively low-performance transistors, which can be made by depositing amorphous silicon onto large pieces of glass. But the next generation of brighter, more colorful, and more energy-efficient displays, such as organic LED displays, require much higher performance transistors created from higher-grade silicon, which can be extremely expensive, making it impractical to coat an entire display with it. With Peumans's method, it could be possible to use only a small amount of high-grade silicon, thereby cutting costs. What's more, the devices are already wired together. That's an important advantage over some other methods for making large-area electronics since "wiring up large-area electronics can be very expensive," Baldo says.
The ability to use less silicon, and to form orderly arrays of prewired silicon devices, could also be useful for making cheaper solar panels. In conventional solar panels, light is absorbed because the entire panel is coated with high-grade silicon. Now a number of companies are reducing the amount of silicon needed by concentrating sunlight onto smaller silicon chips. For example, one company makes an array of small lenses that focus light onto even smaller silicon solar cells. Peumans says that his method offers a cheaper way of making such solar-cell arrays. Earlier this year, he founded a company called NetCrystal, based in Mountainview, CA, to make such panels, which he expects can be created for a third of the cost of today's panels.
Peumans is also working with Boeing to develop sensor networks for airplanes. The goal is to distribute high-performance, silicon-based sensors between layers of the composite materials that make up the wings and other parts of new aircraft, such as the Boeing 787. These sensors would be used to determine if the materials are cracking or delaminating. The sensors could decrease downtime for inspections and help maintenance crew spot problems earlier, Peumans says.
Peumans's technology is not the first attempt to make large-area electronics. Other approaches, however, tend to produce devices that fall considerably short of the performance of chip-grade, single-crystalline silicon. Some researchers, for example, are developing inexpensive methods that use commercial printing techniques to deposit inorganic or organic semiconductor "inks." But the best inorganic ink-based devices perform about an order of magnitude worse than single-crystalline silicon, whereas organic ink-based transistors are a thousand times worse.
The biggest hurdle in developing Peumans's approach was showing that the coils around the silicon islands would be strong enough not to break as they unwind, but he demonstrated a way to treat the coils to make them stronger. The next step is to demonstrate functioning devices. He has already developed prototype solar cells and is working on partnerships to develop other applications.
http://www.technologyreview.com/Nanotech/19901/page2/
Nanogenerator Fueled by Vibrations
An array of zinc-oxide nanowires that generates current when vibrated with ultrasonic waves could provide a new way to power biological sensors and nanodevices.
Using ultrasonic waves to vibrate an array of zinc-oxide nanowires, researchers at Georgia Tech have made a tiny generator that can produce direct current. By taking advantage of the fact that zinc-oxide nanowires are piezoelectric--they can convert mechanical energy into electricity--and by finding a way to collect electricity from multiple nanowires, the researchers have taken a big step toward a practical nanoscale power generator.
"We can make each and every wire simultaneously and continuously produce electricity," says Zhong Lin Wang, a professor of materials science at Georgia Tech, who led the work. In a Science paper published this week, Wang and his colleagues demonstrate a prototype device, about two millimeters square, that generates around 0.5 nanoamperes of current for more than an hour.
"The technique essentially provides a new method of power generation," says Pulickel Ajayan, a materials engineering professor at Rennselaer Polytechnic Institute. He says that the generator could be coupled with devices that are difficult or inefficient to power using conventional means.
One important application is powering implantable biological sensors. According to Thomas Thundat, who researches nanoscale biological sensors at Oak Ridge National Laboratory, current battery technology limits the use of microelectromechanical sensors that measure cancer biomarkers, blood pH, and glucose. These sensors are getting smaller and smaller, but conventional chemical batteries can't keep up. "[The batteries] are huge and they run out of power...most of the time it's the battery that's big compared to the sensing part," Thundat says. "We have always been looking for very small power sources that don't need refilling." The new nanowire generator looks like a promising answer, he says. It could be implanted in the body, and, driven by muscle contractions, blood flow, or external vibrations transmitted through tissue, it could power the sensors.
The generator could also drive nanodevices. Wang's research group has previously made nanowire pressure sensors that can detect extremely small piconewton forces as well as nanowire gas sensors. (See "A Nano Pressure Sensor.") Instead of an external battery, these devices could run on wind or water flow using the new generator.
A key innovation that has led to the nanowire generator is a new electrode design. The surface of the platinum-coated electrode has a zigzag shape like the teeth of a saw: it has alternating parallel peaks and trenches. This zigzag electrode goes on top of an array of upright zinc-oxide nanowires, and its teeth can push many nanowires at the same time if it moves up and down.
To vibrate the electrode, the researchers package the device, put it in water, and expose it to ultrasonic waves. As the zigzag electrode moves up and down, its peaks push and bend the nanowires, which generate electric current that the electrode collects simultaneously. "The wires can be compressed, can be vibrated left or right--it doesn't matter: all the current adds up in the same direction," Wang says.
This is the first demonstration of a direct current output from nanowires that are driven by mechanical energy, says Charles Lieber, a chemistry professor at Harvard University. The new development is a "key step towards novel, cost-effective, adaptable, and mobile applications of nanogenerators in nanotechnology," he says.
For real-world applications, the current generated by the nanogenerator would need to be higher and more stable. Wang's research group is working on improvements toward that goal. Right now, the nanowires are grown randomly, and the researchers estimate that anywhere between 250 and 1,000 nanowires contribute to the current. This is less than 1 percent of all the wires in the array, Wang says. An important next step is to grow a more regular array of nanowires that are uniform in size and height. Matching the nanowire pattern with the pattern on the electrode would utilize all the nanowires, increasing the current output and making it more stable, he says.
The research team also needs to increase the generator's lifetime. It runs for a little more than an hour right now, and Wang says the researchers are not sure why it dies after that time. As a proof of concept, though, Thundat says that this work is a "major advancement in the power-generation area."
http://www.technologyreview.com/Nanotech/18496/