Science Scoops: The World's Tiniest Thermometer
by Stephen James O'Meara
Yup, scientists have done it. They've taken tiny cylinders of pure carbon and turned them into thermometers, each measuring just 10 micrometers long—one-tenth the width of a human hair, or the size of two spores kissing. Instead of filling the carbon nanotubes (less than 150 nanometers in diameter) with mercury, Yihua Gao and Yoshio Bando (National Institute for Materials Science in Ibaraki, Japan) used liquid gallium.
Like mercury, liquid gallium's behavior within the tube changes predictably with temperature. And, as with the mercury in a conventional thermometer, a minuscule meniscus in the nanodevice moves up and down as the liquid gallium expands and contracts in response to temperature. The nanodevice can measure temperatures between 50 and 500 degrees Celsius. The temperatures can be read when the thermometer is viewed through a high-powered electron microscope.
The researchers say that the device “should be suitable for use in a wide variety of microenvironments.” For instance, it can measure the temperature change that occurs when small groups of molecules react with one another, and can help scientists learn more about how lasers burn through materials such as skin and other body tissues.
- The curved upper surface of a nonturbulent liquid in a container.
- Very small; tiny.
- How does a gallium thermometer work?
[anno: The gallium thermometer works in the same way a mercury thermometer does. The gallium contained in a tube expands or contracts depending on the temperature of the substance surrounding the thermometer.]
- Look at a Periodic Table and find the symbols for gallium and for mercury. What are the symbols for each element? Why do you think scientists are using gallium in this thermometer instead of mercury?
[anno: The symbol for gallium is Ga. The symbol for mercury is Hg. Answers may vary but could include that gallium is more sensitive to temperature than mercury, making it a better material for detecting small temperature changes. Students may also suggest that since mercury is about three times as heavy as gallium, more gallium than mercury will fit into a small thermometer, making it passible to produce more accurate readings.]
- Imagine that you wake up one morning with a fever. Could you use a gallium thermometer to measure your body's temperature? Why or why not?
[anno: You could not use a gallium thermometer to measure your body's temperature because a gallium thermometer works only from 50 to 500 degrees Celsius, and the human body's temperature is much lower than 50 degrees Celsius.]
- Do you think it would take more force to move the same volume of mercury or gallium?
[anno: Answers may vary but could include that it probably takes more force to move a column of mercury, as it is heavier than gallium.]