January/February 2010

Bend, twist, fold: Antenna won't break

Engineers at North Carolina State University have created a highly efficient, flexible, and self-healing antenna using a metal alloy that is a liquid at room temperature.

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A flexible antenna consists of liquid metal injected into microchannels in a stretchy polymer.
Source: North Carolina State University

The new liquid-metal antenna could make it easier to send and receive data from flexible electronics, reported Technology Review. Possible uses include sensors incorporated into clothing or other textiles, pliant electronic paper, or implantable biomedical devices.

Michael Dickey, an assistant professor of chemical and biomolecular engineering at NC State, was working with a gallium-indium alloy, which is liquid at room temperature, researching how it behaves in microchannels with a view to electronics fabrication applications. Hunting for other possible uses, he hit on the idea of making a flexible antenna. In collaboration with electrical engineer Gianluca Lazzi-then at NC State, now chair of the department of electrical and computer engineering at the University of Utah-Dickey and his students used the alloy and a common flexible polymer called polydimethylsiloxane (PDMS) to make a simple dipole antenna-essentially a straight rod, like the old-fashioned "bunny ear" antennas used for analog TV.

The researchers poured liquid PDMS into a mold that left it with a single internal channel once cured. They then injected the liquid gallium-indium mixture into the channel and sealed it.

Researchers at Lazzi's lab tested the antenna's performance and found they could create an electrical contact with the device simply by jabbing a wire into the liquid, eliminating the need for solder. In the lab, the antenna radiated over a broad frequency range at about 90% efficiency. The antenna also remained functional while the engineers bent, twisted, and folded it in half; they even stretched it an additional 40% beyond its normal length. When the stress was released, the PDMS snapped back to its original shape.