# Science Scoops: The World's Tiniest Thermometer

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.

## Vocabulary

meniscus:
The curved upper surface of a nonturbulent liquid in a container.

minuscule:
Very small; tiny.

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## Activity

1. 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.]
2. Design a machine that combines a simple machine, such as a lever, and an expanding column of liquid or air, as in a gallium thermometer. What produces pressure on the column of air or gas? How is the lever connected to the column? What does the lever do when a greater force acts on the column of liquid or air? What happens when the force on the column of liquid or air is reduced? What kind of work does your machine do? Draw a diagram of your machine. Then write a short paragraph describing how your machine works and what your machine does.
[anno: Answers will vary.]