Tuning in a Better Antenna

The light bulb flashed in Dr. Michael Dickey’s head within days of his arrival on the NC State campus. The assistant professor in the Department of Chemical and Biomolecular Engineering was going through his faculty orientation in August 2008 when he heard a professor in the Department of Electrical and Computer Engineering discuss his work on antennas. Dickey’s sudden inspiration was to make antennas out of gallium because of the metal’s unique characteristics. “I had a solution that was really just looking for a problem,” he now says. Dickey’s fascination with gallium started when he was a post-doctoral researcher at Harvard University. The chrome-colored metal melts at about room temperature, but exposure to air causes it to oxidize and form a thin membrane that sticks to surfaces. “It’s like a water bed,” he says. “It’s got this skin on the outside, while the liquid can still slosh around inside.” So, Dickey set out to study the interface between the liquid metal and its skin — and to learn how the skin changes gallium’s properties. “It’s really a composite system,” he says. “It doesn’t act like a normal fluid.”

As he was starting that research, however, inspiration struck like a lightning bolt hitting, well, an antenna. By injecting a mix of gallium and indium — the indium lowers the melting point to ensure the alloy remains a liquid at lower temperatures — into two microfluidic channels in piece of elastic silicone, Dickey’s research team created a dipole antenna. Because the shape of an antenna determines the frequency it picks up, stretching and twisting the flexible plastic allows the miniature “rabbit ears” inside to tune in different signals. “It worked the first time we tried it,” Dickey says. “I thought it would just be an academic curiosity, but antennas are in just about everything these days, so we’re getting a lot of interest.”

The business world is especially intrigued, Dickey says, from global-positioning system networks to wireless broadband providers to retailers who want to track inventory with radio-frequency tags. Some people also envision military applications or using the gallium antennas to monitor the stability of bridges. Dickey is using a three-year, $340,000 Recovery Act grant from the National Science Foundation to hire two Ph.D. candidates to help his research team continue studying the basic science of gallium and various antenna applications, including a coiled one that could be implanted next to a retina to help a visually impaired person see. “We’re exploring different uses of the metal while, at the same time, learning more about the fundamental properties of the material itself.”

 

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Dr. Michael Dickey’s flexible antenna, developed with gallium, has drawn interest from varied industries.