Shape shifting alloy antennas promise new applications
By Darren Quick
December 1, 2009
The shift to wireless communication using ever-smaller devices has necessitated the need for smaller and smaller antennas. Thankfully, the days of extendable antennas on mobile phones are a thing of the past with manufacturers now able conceal them inside the casing. Now scientists have created shape-shifting antennas that, while not likely to appear in consumer devices like mobile phones any time soon, could open the door to a host of uses in fields ranging from bridge safety monitoring to military deployment.
Modern antennas are made from copper or other metals, but there are limitations to how far they can be bent – and how often – before they break completely. Now scientists at North Carolina State University have created antennas using an alloy that can be bent, stretched, cut and twisted – and return to its original shape.
The researchers make the new antennas 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. The channels are hollow, like a straw, with openings at either end – but can be any shape. 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.
“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,” says Dr. Michael Dickey, assistant professor of chemical and biomolecular engineering at NC State and co-author of the research.
While the alloy makes an effective antenna that could be used in a variety of existing electronic devices, its durability and flexibility also open the door to a host of new applications. For example, an antenna in a flexible silicone shell could be used to monitor civil construction, such as bridges. 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 thinks these new applications are the most likely uses for the new antennas, since the alloy is more expensive than the copper typically used in most consumer electronics that contain antennas, such as mobile phones, radios and GPS devices.
The research, “Reversibly Deformable and Mechanically Tunable Fluidic Antennas,” is published in Advanced Functional Materials.