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A thermometer with the diameter of a blood globule

A tiny carbon tube thermometer is developed in Japan * The measurement ranges are huge: between 30 and 1,000 degrees Celsius

Dr. Noah Brosh

Direct link to this page: https://www.hayadan.org.il/nanothermometer.html

Japanese researchers reported that they managed to build a tiny thermometer that can measure temperatures in a huge range: between 30 and 1,000 degrees Celsius.

The Japanese thermometer is made of a carbon tube, which has a diameter of 75 thousandths of a millimeter and a length of 0.8 thousandths of a mm - that is, a little more
of the diameter of a human red blood cell. As in the normal thermometer, here too the tiny tube contains a liquid, whose height inside the tube indicates the degree of heat. In this case liquid gallium was used, which allows the thermometer to measure extremely high temperatures.

The rise of the liquid gallium inside the tube occurs due to the expansion of the liquid metal with the heat, just as mercury - another liquid metal - expands in the glass tubes in the usual thermometers.
However, unlike the normal thermometer, in the Japanese thermometer it is not possible to read the temperature indication by eye. For this purpose, a microscope must be equipped
Electron scanner, which magnifies the image 200 thousand times. An electron beam scans the tube, and part of it even penetrates inside and is reflected back from the gallium.

The researchers thought of two more phenomena that should be taken into account: First, the heating also causes the carbon tube to expand. This should be taken into account when calibrating the thermometer. Second, certain liquids wet the walls of the tubes in which they are located, and an increase in the liquid is caused due to the capillary phenomenon. Gallium was chosen to be used in the thermometer also because it does not wet the inside of the carbon tube and its level inside the thermometer remains
flat. Despite this, the heating effect of the electron beam that scans the thermometer and reads the temperature - remains. In the future, the Japanese researchers hope to take this into account as well, and get a very reliable thermometer.

Published in Maariv, 17/8/03
The science of nanotechnology

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