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Voltage-controlled liquid metal antenna expands IoT use cases

Posted: 21 May 2015 ?? ?Print Version ?Bookmark and Share

Keywords:North Carolina State University? liquid metal? antenna?

Liquid metal electronics does offer its own brand of advantages to the industry, however, it also has its own share of downsides. The devices tend to require external pumps that can't be easily integrated into electronic systems, consequently slowing the advance of such device. As such, using electrochemistry, researchers from the North Carolina State University have developed a reconfigurable, voltage-controlled liquid metal antenna that may play a huge role in future mobile devices and the coming Internet of Things (IoT).

The team's work was inspired by a phenomenon recently observed during studies of liquid metal by co-author professor Michael Dickey's group within the department of chemical and biomolecular engineering at NCSU. By placing an electrical potential across the interface between the liquid metal and an electrolyte, they found that they could cause the liquid metal to spread by applying a positive voltage, or to contract by applying a negative voltage.

Antenna, feed and reservoir

This image shows the antenna, feed and reservoir. (Image courtesy of Jacob Adams)

The shape and length of the conducting paths that form an antenna determine its critical properties such as operating frequency and radiation pattern. "Using a liquid metal, such as eutectic gallium and indium, that can change its shape allows us to modify antenna properties more dramatically than is possible with a fixed conductor," explained Jacob Adams, co-author and an assistant professor in the department of electrical and computer engineering at NCSU.

The team created the tunable antenna controlled by voltage only by using electrochemical reactions to shorten and elongate a filament of liquid metal and change the antenna's operating frequency. Applying a small positive voltage causes the metal to flow into a capillary, while applying a small negative voltage makes the metal withdraw from the capillary.

The positive voltage "electrochemically deposits an oxide on the surface of the metal that lowers the surface tension, while a negative potential removes the oxide to increase the surface tension," Adams said. These differences in surface tension dictate which direction the metal will flow.

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