Japanese researchers, Yihau Gao and Yoshio Bando at the National Institute for Materials Science in Tsukuba, have developed a nanothermometer made from a liquid gallium filled carbon nanotube.
Last year they found that a column of liquid gallium in a sheet of graphite rolled into a cylinder - a nanotube - varies linearly with temperature, just as mercury does in a normal thermometer. Their nanothermometer, however, is less than 150 nanometres in diameter and is read using an electron microscope. It only worked in a vacuum. Their latest development is a nanothermometer that works in air and at temperatures between 323 and 823 kelvin.
If the nanotube is left open at one end the thermometer will operate in air. A thin oxide layer of gallium will form on the walls of the nanotube at high temperatures. The oxide layer corresponds to the height of the gallium meniscus and remains in place after cooling. It therefore marks the maximum temperature reached.