Researchers at North Carolina State University have finally discovered how to control the liquid metal inside antennas, without using an external pump for moving the metal to different bandwidth lengths.
The results were published in the Journal of Applied Physics, and show that by applying negative voltage to the metal, it contracts, and that the opposite thing happened when applying positive voltage, where the liquid metal would spread. The liquid metal used could be eutectic gallium or indium. This was the initial discovery, made by a group led by coauthor Professor Michael Dickey at NCSU, within the Department of Chemical and Biomolecular Engineering. They could achieve the different voltages by placing an electrical potential across the interface between the liquid metal and an electrolyte.
The how part of this is explained by Jacob Adams, assistant professor in the Department of Electrical and Computer Engineering at NCSU, and also coauthor. When applying positive voltage, it “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.”
With the ability to switch the antenna off and on from different wavelengths with the electrochemical signals, antennas can now provide devices such as mobile phones, or the increasing number of things in our homes and everyday lives that are controlled via Internet, with more than two times the range than what the previous system with electronic switches has been capable of.
Looking for even more ways to expand the usability of this novel control technique, the research team now investigates ways to control the liquid metal in more than one direction. The first goal is to not only move the metal upwards and downwards, but also sideways, creating more and more advanced two-dimensional shapes, allowing for a wide range of flexibility for numerous functions.
The problem with the present antennas are that they can’t go under a certain length and size, since the antenna contains fixed conductors that can only be switched on and off between conductors of different lengths. Odd things happening, such as the so called “death grip” on iPhone 4 will now be history, where covering over the bottom of your phone no longer will have an impact on the much shorter and more capable antenna inside.
Image: Patrick Hoesly