Tunable Liquid Metal Antennas

Using electrochemistry, North Carolina State University researchers have created a reconfigurable, voltage-controlled liquid metal antenna that may play a huge role in future mobile devices and the coming Internet of Things

In the long term, Adams and colleagues hope to gain greater control of the shape of the liquid metal — not only in one-dimensional capillaries but perhaps even two-dimensional surfaces to obtain nearly any desired antenna shape. “This would enable enormous flexibility in the electromagnetic properties of the antenna and allow a single adaptive antenna to perform many functions,” he added.

Researchers have held tremendous interest in liquid metal electronics for many years, but a significant and unfortunate drawback slowing the advance of such devices is that they tend to require external pumps that can’t be easily integrated into electronic systems.

So a team of North Carolina State University (NCSU) researchers set out to create a reconfigurable liquid metal antenna controlled by voltage only, which they describe in the Journal of Applied Physics, from AIP Publishing.

The team’s work was inspired by a phenomenon recently observed during studies of liquid metal by coauthor 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.

For a bit of background, 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, coauthor and an assistant professor in the Department of Electrical and Computer Engineering at NCSU.

How did the team create 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.

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