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Contactless magnetic gears open up new use cases

Posted: 19 Feb 2016 ?? ?Print Version ?Bookmark and Share

Keywords:Okinawa Institute of Science and Technology? coupling? magnetic gear? nanosystem?

Magnetic gears, which transmit rotary motion such as mechanical gears but instead of teeth use magnetic attraction and repulsion between rotating magnets, may be found in common appliances of today, such as the milk frother you are using to prepare your cappuccino.

Johannes Schonke, a post-doctoral scholar at the Okinawa Institute of Science and Technology Graduate University (OIST), has published in Physical Review Applied a theory that extends the possibilities and applications for smooth magnetic couplings, which can produce an even motion without any counterforce. This research has several potential applications in nanotechnology, microfluidics and robotics.

Magnetic gears have several advantages over mechanical gears. The main one is the absence of direct contact between the parts. While mechanical gears, such as the meshing gears inside a watch, transmit the motion through the contact between moving teeth, magnetic gears are contactless. Magnetic gears require less maintenance, no lubrication, they have also better reliability and efficiency, and they produce lower vibration and noise. Magnetic gears are often based on an alloy of iron, boron and neodymium, which creates the strongest permanent magnets known to date.

Interacting rotating magnets

Figure 1: Illustrative example of a paddle boat using three interacting rotating magnets (red arrows) as a drive. Two magnets are connected to the paddles and one to the driver. If the driver magnet is rotated, the paddles move accordingly (yellow arrows).

Some of our food mixers in the kitchen, magnetic stirrers in a chemistry lab or other industrial magnetic couplings are based on the idea that the two magnets rotate around the same axis. "I wanted to explore the possibility of positioning the input and output axes at any desired inclination angle," explained Schonke. "Furthermore, there are certain configurations of the two magnets that allow the addition of a third magnet at a specific position and still maintain a smooth coupling."

Mechanical gear system

Figure 2: Analogy between the quadrupole-dipole interaction and a mechanical gear system. The quadrupole (left) is symbolised with four dipoles, two of them point in and two point out in an antiparallel way. In this example the rotation axes (grey) are perpendicular. In both, the magnetic and the mechanical case, the left gear has twice as many teeth as the right gear, so a full cycle of the right gear corresponds to half a cycle of the left gear.

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