When I see the term liquid metal I think of the sporting goods manufacturer spun out of CalTech who makes amorphous metal golf clubs, tennis rackets and other high performance products. But a team at North Carolina State University has a new meaning for the phrase, or maybe a more appropriate use. The product is quite literally a metal alloy that is a liquid at room temperature. In this case the alloy is a mix of gallium and indium, elements chosen for their electrical conductivity and suitability to act as an antenna. As an interesting article in the Economist details the object of their research was to produce an antenna that would achieve all of the transmission and reception properties of a copper antenna without the tendency to break under harsh use specifically by the military.
Antennas transmit signals by using an oscillating electrical current in a length of conductive material to generate electromagnetic radiation, such as radio waves. When receiving they do the opposite, transforming electromagnetic radiation passing through the conductive material into electrical current. So an antenna subjected to a radio beam will create an electrical impulse making it an effective sensor when scanned by radio waves.
Source: The Economist, Ju-Hee So, North Carolina State University
Being liquid the alloy has to be encased in something but that allows the technology to be used in various different applications. For example encased in a rigid container the antenna could be well protected but encased in rubber it becomes flexible and even stretchy. Lengthening or shortening an antenna changes the wavelength that it transmits so an application for micro antenna attached to dams, buildings or bridges could be used to remotely monitor movement, expansion, contraction, etc.
Unlike copper, which once it breaks it stays broken, liquid metals have the ability to self heal or reform in their original shape making them as durable as their casing. The possibilities for this technology are only just being explored, expect more ideas to be reported in the years ahead as more exotic alloys are found or new applications for existing ones developed.