If you want to design really tiny mechanical devices, like robots or something similar, first you have to locate or create microscopic motors. Traditional electromagnetic motors, driven by coils and magnets, suffer from significant physical limitations that makes it difficult to create motors under 1 mm in diameter.
Ultrasonic motors are a more viable alternative, but until recently it has been extremely difficult to create under 1 mm diameter motors using existing ultrasonic motor technology. All that appears to be changing since earlier this week Seiko Instruments, headquartered in Chiba, Japan, announced a breakthrough motor design with a diameter of only 0.95 mm (0.037 inches).
The tiny new motor was developed by SII and the Furukawa Lab at Tokyo University of Agriculture and Technology (TUAT). Drawing on work done by Professor EmeritusTadashi Moriya (Tokyo Metropolitan University) and Professor Yuji Furukawa (TUAT), production of the new motor was made possible by application of manufacturing and processing technologies developed by SII through decades of precision watch manufacturing.
How does it work?
Departing from conventional motor design, the new motor uses an external ultrasonic oscillator and a 50 μm diameter wire used as a waveguide. This causes ultrasonic waves to propagate affecting a coiled stator at the tip of the motor which causes the cylindrical motor rotor to rotate at surprisingly high speed.
One real advantage of this design is that its simplicity will help facilitate further motor size reductions. The current design is only 0.95 mm in diameter and 3.6 mm long. It can achieve rotational speeds of between 2,000 to 4,000 rpm. And, as you might expect, the torque it produces is very low - 0.2 μNm.
We're not going to hold our breath waiting for an engineer to create a fully functional robot using this unique technology. And certainly tiny humanoid robots with articulated joints are even further off in the distance. Nevertheless, there are numerous applications for the microscopic motors,
SII Press Release - 0.95 mm Motor (Japanese)