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Innovations:
Cutting-edge research from Berkeley Engineering
Innovations features brief updates on the pioneering research done by Berkeley Engineering faculty and students. See more at www.coe.berkeley.edu/newsroom.
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Artist’s impression of a beam of intense radiation (from upper left) striking a solar cell and imaging a cluster of iron impurities in the silicon.
TONIO BUONASSISI/UC BERKELEY PHOTO
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“Dirty” silicon could reduce cost of manufacturing solar cells
An inexpensive new technique that rearranges rather than eliminates metal defects in low-grade silicon could reduce the cost of manufacturing solar cells, says a Berkeley-led team of engineers in the August 14 issue of Nature Materials.
Most solar, or photovoltaic, cells use a highly refined form of silicon, the same expensive material used to make integrated circuits. A cheaper form of silicon is available, but it is laden with metal impurities and performs poorly in photovoltaic cells. Techniques to remove the impurities are prohibitively expensive.
The researchers first analyzed how the impurities responded to alterations in processing techniques. They found that slowing down the cooling rate during manufacturing caused the impurities to group in clusters rather than in a scattered distribution, improving performance by a factor of four.
The researchers, including principal investigator and MSE professor Eicke Weber and Applied Science and Technology graduate student Tonio Buonassisi, believe that other simple alterations in manufacturing could enhance the efficiency of dirty silicon and drive down the cost of making solar cells.
When is a needle not a needle?
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The MicroJet won’t entirely replace the hypodermic needle (foreground), but its comparative precision could facilitate its use in microsurgery and in delivering arthritis drugs into joint areas too shallow for a needle to penetrate.
MARCIO VON MUHLEN PHOTO, UC BERKELEY
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Three Berkeley bioengineering undergrads are developing a new MicroJet injector to facilitate needleless drug delivery and reduce the pain, the potential for contamination, and the disposal problems associated with hypodermic needles.
The device uses a tiny piezoelectric actuator, which expands or contracts in response to an applied voltage, to propel liquids at speeds of 140 meters per second, about 315 miles per hour, through a patient’s skin. Unlike similar devices now in use that operate with compressed air or mechanical springs, the MicroJet’s electrical power source gives it greater control over delivery volume and speed, useful in tailoring injections to children and adults as well as to different areas of the body.
“The diameter of the nozzle is only 70 micrometers, which is nearly three times smaller than the thinnest conventional hypodermic needles,” says Marcio von Muhlen, one of the students doing research under the guidance of BioE assistant professor Dan Fletcher. The other students include Laleh Jalilian and now alum Menzies Chen (B.S.’04 BioE).
Superlens first to achieve nanoscale optical imaging
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The word NANO, recorded onto an organic polymer, appears sharper in the image created with the silver superlens (top) than that created with a conventional lens (bottom). The scale bar represents 2 micrometers.
IMAGE COURTESY OF UC BERKELEY |
Berkeley engineers have developed a silver “superlens” used in conjunction with ultraviolet light to capture images at a higher resolution than ever before possible.
The research could lead to such advances as optical microscopes capable of capturing never-before-seen biomedical details in real time, like individual protein movements within a living cell, which could help in the development of new drugs.
“The field of optics is involved in much of today’s technology, including imaging and photolithography, which is used to make semiconductors and integrated circuits,” says ME professor Xiang Zhang, principal investigator of the study. Beyond imaging, the work has longer-term implications for higher density electronic circuitry and faster fiber optic communications, such as a computer processor that could quickly search through the entire Library of Congress or other huge volume of data.
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