A Nanoscopic Thermometer

A nanoscopic thermometer, consisting of a magnesium oxide nanotube filled with gallium metal, may dramatically increase the temperature range of tiny thermometers. Researchers at the National Institute for Materials Sciences (contact: Prof. Yoshio Bando, phone number +81-29-860-4426; bando.yoshio@nims.go.jp) announced the creation of a carbon nanotube thermometer last year, but the device had at least one shortcoming: nanoscopic carbon tubes rapidly degrade in air at temperatures of 600-700 degrees Celsius. The new nanotubes are made of magnesium oxide cylinders with inner diameters of 20-60 nanometers, or about a thousandth the thickness of a human hair. Magnesium oxide nanotubes, in contrast to carbon versions, can withstand high temperatures. Often, there is a gap in a nanotube's gallium filling, and because gallium expands as it's heated, the temperature of the thermometer is read out by measuring changes in the gap between the two portions of the metal. The tiny thermometers are expected to function well up to about 1000 degrees Celsius. Eventually, miniature thermometers such as these could be important for measuring temperature in the vicinity of nanoscopic motors and other tiny devices. (Y.B. Li, Y. Bando, D. Golberg, and Z.W. Liu, Applied Physics Letters, 4 August 2003)