Boffins have made a liquid metal device which can alter its shape through voltage alone, removing the need for clunky external pumps previously used to arrange such material.
In a breakthrough which brings humanity much too close to the development of functioning T-1000s, boffins from North Carolina State University (NCSU) have demonstrated a reconfigurable liquid-metal prototype in the Journal of Applied Physics.
The paper, titled A reconfigurable liquid metal antenna driven by electrochemically controlled capillarity describes "a new electrochemical method for reversible, pump-free control of liquid eutectic gallium and indium (EGaIn) in a capillary."
Antennas are interesting as the shape and length of the conducting paths which form them determine their operating frequencies and radiation patterns.
"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 of the paper and an assistant professor in the Department of Electrical and Computer Engineering at NCSU, in a press release by the American Institute of Physics.
The team exploited electrochemical reactions to shorten and elongate a filament of liquid metal to alter the antenna's operating frequency. The simplicity of applying a small positive voltage to cause the metal to flow into a capillary, and a small negative voltage to make it withdraw again, obviously takes place on a much smaller scale than the mimetic poly-alloy which makes up the Terminator, but the NCSU boffins are making progress across the board in liquid metals research.
Among previous developments have been a way to print liquid metals into 3D structures at room temperature, those structures being "stabilized by a thin oxide 'skin' that forms on the liquid metal. The approaches shown [in the video below] represent new ways to direct write metals in 3D. In addition, the resulting components can, in principle, self-heal and be ultra-stretchable."
While the critical properties of solid conductor antennas may be reconfigured by switched circuit elements (e.g., diodes and varactors) at a few locations to modify the current distribution on the device, the use of liquid metal greatly increases the range over which the antenna's operating frequency can be tuned.
"Our antenna prototype using liquid metal can tune over a range of at least two times greater than systems using electronic switches," said Adams.
"Mobile device sizes are continuing to shrink and the burgeoning Internet of Things will likely create an enormous demand for small wireless systems," Adams added, noting more applications for his work. "And 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 [radiofrequency] front-end must operate. This combination will create a real antenna design challenge for mobile systems because antenna size and operating bandwidth tend to be conflicting tradeoffs."
The ability to miniaturise and adapt tunable antennas may make them highly desirable, especially if they can correct for near-field loading problems such as the iPhone Death Grip effect. Liquid metal systems "yield a larger range of tuning than conventional reconfigurable antennas, and the same approach can be applied to other components such as tunable filters," Adams said.
The researchers have apparently already begun to explore the fundamental and applied elements of tunable liquid metals.
"There's still much to learn about the behavior of the surface oxides and their effect on the surface tension of the metal," Adams told AIP. "And we're studying ways to further improve the efficiency and speed of reconfiguration."
In the long term, Adams and colleagues hope to be able to manipulate the shape of the liquid metal to an ever greater degree, moving away from one-dimensional capillaries towards two-dimensional surfaces which would allow the metals 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. ®