Liquid metal could be used to create morphing electronics24/09/2014 03:13
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Who could forget the scene in Terminator 2: Judgement Day where the shape-shifting T-1000 reassembles itself from thousands of blobs of molten metal? Researchers from North Carolina State University (NCSU) have taken the first steps to such science fiction becoming reality by developing a way to control the surface tension of liquid metals with the application of very low voltages. This may offer opportunities in a new field of morphing electronic circuits, self-healing electronics, or – one day – maybe even self-assembling terminator-style robots.
The liquid metal used by the researchers was an alloy of gallium and indium. Gallium is liquid just above room temperature at about 29° C (84° F), while Indium has a much higher melting point at around 156° C (312° F), yet when mixed together, they form an alloy that is liquid at room temperature. In other words, a eutectic alloy – one that is composed of metals with disparate melting points that, when combined, melt as a whole at a specific temperature.
Another important aspect of this eutectic alloy, and one that the researchers sought to exploit in their experiments, is its exceptionally high surface tension of approximately 500 millinewtons per meter (mN/m). The consequence of this is that a blob of this alloy resting on a surface will tend to form an almost spherical ball and hold its shape if undisturbed.
Researchers found that if they applied a small voltage (less than one volt) in water to such a blob of the alloy, they were able reduce the surface tension significantly, resulting in the molten metal spreading and flattening out. When the voltage was removed, the high surface tension returned, and the blob once more took on its spherical shape.
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