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Building A Better "Eyelid" For Cameras


Developments to Watch

Building a Better "Eyelid" for Cameras

A Hostile laser attack can blind fighter pilots or the cameras and electronic sensors of a military satellite in the blink of an eye. To counter that threat, Paul H. Holloway and a team of engineers from the University of Florida in Gainesville have developed an "artificial eyelid" for lenses, a thin film that can "blink shut" in just one-10,000th of a second. Holloway unveiled a working prototype in early March at a conference of the International Society for Optical Engineering.

To build their high-tech eyelid, Holloway's team borrowed thin-film technology from the semiconductor industry. Six layers of polymers and conductive materials are laid down in patterns producing a protective coating that contains thousands of tiny apertures per square inch. When closed, the apertures are impervious to a broad swath of the light spectrum--from ultraviolet to infrared rays. When open, the apertures allow light to be easily transmitted through the glass wafer. A battery-operated sensor controls the apertures' openings and closings. When the sensor detects a laser beam, it generates a voltage signal that shuts the apertures.

While the primary application for Holloway's artificial lids is military, he sees a multitude of potential consumer uses. They range from better video camera lenses that could eliminate glare from the sun and bright lights to "smart" glasses that instantly adjust to changing light conditions.Edited by Ellen LickingReturn to top

A Nuclear Attack on Arthritic Pain

Millions of Americans suffer from rheumatoid arthritis, a potentially crippling disease caused by inflammation of the synovium, the membrane that surrounds knee, hip, and other joints. Drugs help check the inflammation, but in severe cases, the only way to slow the damage is to scrape out the synovium, an invasive procedure that scars the joints. But thanks to a new technique pioneered by Jacquelyn C. Yanch, a nuclear physicist at Massachusetts Institute of Technology, there may soon be a gentler way to ease the pain of rheumatoid arthritis.

Yanch's approach, called boron neutron capture synovectomy, may be difficult to say, but it is quite easy to do. A few drops of boron are injected into the arthritic joint, followed by exposure for several minutes to a beam of neutrons. Some of the neutrons will be "captured" by the boron molecules, making them radioactive. The radioactivity kills the inflamed tissue and then quickly decays away. Yanch says the procedure is very safe--the radioactive particles travel only a few millionths of meter before they decay, so they can kill only the cells that were injected with boron in the first place.

Preliminary studies in 36 arthritic rabbits support the claim. Yanch has shown that a 20-minute blast of neutrons of intermediate intensity kills all the damaged synovium but leaves the surrounding healthy cartilage unharmed. More animal tests must be done before the procedure is tried in humans. But Yanch believes the day will come when her technique, done as an outpatient procedure, will ease the pain of patients.Edited by Ellen LickingReturn to top

A New Way to Bring Color to LEDs?

Three years ago, Paul Alivisatos and a team of researchers from the University of California at Berkeley built a single-electron transistor using microscopic, chemically pure nanocrystals, dubbed "quantum dots." Because of their small size--about a billionth of a meter--the dots have an unusual property: When zapped by a laser, the crystals emit different colors depending on their size. A two-nanometer dot glows green, while a five-nanometer dot radiates red. The team envisioned using the dots in electronic devices such as light-emitting diodes (LEDs). There was just one snag: The light emitted from a single quantum dot is too dim to be seen.

Alivisatos may have a solution to that problem. In work published Mar. 2 in Nature, he describes how to grow nano-rods of precise lengths and diameters from his individual dots. With the right chemistry, these quantum rods line up in neat rows, generating different colors based on the width of the rods. Based on preliminary experiments, Alivisatos believes the rods should be 20 times more powerful than the dots. That probably isn't enough for use in LEDs, but "it's a step in the right direction," he says.Edited by Ellen LickingReturn to top


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