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The smallest engine in the world

At the University of Berkeley in California, they developed for the first time an engine 300 times smaller than the thickness of a human hair

Alex Doron

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15 years ago scientists at the University of California at Berkeley built the world's first motor in micron dimensions. The world's first micromotor was made of silicon, and was 100 microns long - roughly the thickness of a human hair. Now the world's first nano engine (billionth of a meter) has been built there. It is a gold rotor, or propeller, placed on a carbon nanotube shaft, and it could even be installed on a virus. The tiny motor is about 500 nanometers wide - 300 times smaller than the thickness of a human hair.

Prof. Alex Zettl, a physicist at the University of Berkeley who led the development team, said that "this is the smallest synthetic engine ever built."
He pointed out that in nature there are biological engines of similar or even smaller dimensions, "and now we are getting closer to them".

In a report to the scientific journal Nature, the development team emphasized that the construction of the electrostatic motor is an important milestone in the development of nanotechnology. The scientific achievement demonstrates how nanotubes and other structures on this tiny scale can be manipulated and assembled into real devices.

Prof. Zettel's team previously assembled transistors from nanotubes, but the current development is different and much more complex: "This is the first device to which you can add external wiring, turn it on an axis or sideways and control its movement - which makes it a motor
For everything'', emphasized the American scientist. The motor was operated with direct current of 50 volts.

The team believes that the tiny engine can be used in cellular communication devices and computers, in an optical circuit for the direction of light (to create an optical switch), as a microwave oscillator or as a liquid mixer, and in tiny devices where there is a flow of microfluids.

The micromotors developed 15 years ago use microelectromechanical systems (MEMS), such as the airbags in cars, pacemakers and tiny mirror mechanisms. At the time, the micro-engines were built for demonstration of capabilities and design only. The nanomotor is much more advanced: its construction proves that devices can be controlled
The sophisticated also in these dimensions - which of course opens a new and exciting era in future technology.

Among the problems that have not yet been solved is the measurement of the speed of the tiny motor: using a scanning electron microscope, the speed of movement was photographed at a rate of 33 thousandths of a second, but this threshold cannot be exceeded. Therefore, it is not yet clear whether the speed of the axial rotation of the propeller is higher than 30 revolutions per second. ''We assume that a much higher speed can be developed, up to the speed of the microwave frequency, but we cannot track it yet. In principle, the engine speed should be much higher than the current one,'' explains Prof. Zettel.

The development team stated that they intend to try and reduce the dimensions of the engine they built by 5 times, and measure it according to the world of quantum, subatomic concepts.

They know nano technology
For information on the Berkeley University website

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