Antennas are used in everything from cell phones to GPS devices. Traditionally, the devices are made from copper or other metals, but there are limitations on how far they can be bent before they break.
Engineers at North Carolina State University have created shape-shifting antennas that open the door to many new applications in fields ranging from public safety to military deployment. The antennas are made from an alloy that can be bent, stretched, cut and twisted, but will return to its original shape. The antennas can be deformed (twisted and bent), because the mechanical properties are dictated by the elastomer and not the metal.
The antennas are made by injecting an alloy made up of the metals gallium and indium, which remains in liquid form at room temperature, into very small channels the width of a human hair. For example, the alloy can be injected into elastic silicone channels, creating wirelike antennas that can be manipulated into a variety of shapes.
The channels are hollow, like a straw, with openings at either end. Once the alloy has filled the channel, the surface of the alloy oxidizes, creating a “skin” that holds the alloy in place while allowing it to retain its liquid properties.
“Because the alloy remains a liquid, it takes on the mechanical properties of the material encasing it,” says Michael Dickey, an assistant professor of chemical and biomolecular engineering at North Carolina State. “This flexibility is particularly attractive for antennas because the frequency of an antenna is determined by its shape. So, you can tune these antennas by stretching them.”
While the alloy can be used in existing electronic devices, its durability and flexibility opens the door to a wide array of new applications. “For example, an antenna in a flexible silicone shell could be used to monitor civil construction, such as bridges,” Dickey points out. “As the bridge expands and contracts, it would stretch the antenna, changing the frequency of the antenna, and providing civil engineers information wirelessly about the condition of the bridge.”
Flexibility and durability are also ideal characteristics for military equipment, since the antenna could be folded or rolled up into a small package for deployment and then unfolded again without any impact on its function. Dickey believes these new applications are the most likely uses for the new antennas, since the alloy is more expensive than copper, which is typically used in most consumer electronic devices.