The phrase “liquid metal” readily evokes images of toxic mercury, mad hatters, and the menacing villain from the movie Terminator 2. (Incidentally, the villain’s computer rendering was based on mercury.) Suffice it to say, the phrase often carries negative connotations.
However, there is hope for liquid metals: Gallium has a melting point near room temperature and doesn’t share Hg’s toxicity. When Ga was discovered in 1875, Hg had already been known for more than 1000 years and was being used in thermometers, electrochemical reactions, and dental fillings. But because Ga reacts readily with oxygen to form a thin oxide crust on its surface, it could not readily replace toxic Hg.

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