Tropes

www.sci-news.com 2015 00509.txt.txt

#Scientists Create Liquid Metal Antenna By placing an electrical potential across the interface between liquid eutectic gallium and indium and an electrolyte, Dr Adams and his colleagues found that they could cause the metals to spread by applying a positive voltage or to contract by applying a negative voltage. sing a liquid metal that can change its shape allows us to modify antenna properties more dramatically than is possible with a fixed conductor, said Dr Adams, senior author on the study published in the Journal of Applied Physics. The scientists created the tunable antenna by using electrochemical reactions to shorten and elongate a filament of liquid metal and change the antenna 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. he 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. These differences in surface tension dictate which direction the metal will flow, Dr Adams explained. his advance makes it possible to remove or regenerate enough of the xide skinwith an applied voltage to make the liquid metal flow into or out of the capillary. We call this lectrochemically controlled capillarity, which is much like an electrochemical pump for the liquid metal. Although antenna properties can be reconfigured to some extent by using solid conductors with electronic switches the liquid metal approach greatly increases the range over which the antenna operating frequency can be tuned. or eutectic gallium-indium monopoles with lengths between 75m and 4m, the measured resonance frequency tunes from 0. 66 GHZ to 3. 4hz for a tuning ratio to 5. 2: 1, which is beyond the ratio obtained by switch or varactor-based antennas. urthermore, the measured total efficiency ranges from 41%to 70, %which, while lower than a conventional monopole, presents a tradeoff between efficiency and versatility that is evident in most tunable systems. ur antenna prototype using liquid metal can tune over a range of at least two times greater than systems using electronic switches, Dr Adams said. Myriads of potential applications await within the realm of mobile devices. obile device sizes are continuing to shrink and the burgeoning Internet of things will likely create an enormous demand for small wireless systems, Dr Adams said. nd as the number of services that a device must be capable of supporting grows, so too will the number of frequency bands over which the antenna and RF (reconfigurable radiofrequency) front-end must operate. his combination will create a real antenna design challenge for mobile systems because antenna size and operating bandwidth tend to be conflicting tradeoffs. e

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