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back to article Boffins use laser to move maglev disk

Readers may wish to skip to the video, below, if they’re too holidayed to want to read too many words. For the rest: a group of Aoyama Gakuin University researchers has demonstrated a magnetic-levitation disk that can be moved using lasers. The trick is in the materials: when the laser heats one part of the disk, the magnetic …

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Silver badge

Very interesting, but how much energy is required for the maglev itself? I rather suspect that it is several orders of magnitude greater than the energy harvested.

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Perhaps none.

It appears from the video that they're not using electromagetic levitation for the demonstration, but strong natural magnets.

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Anonymous Coward

Re: Perhaps none.

Yes, so the second question is, does it steal energy from the magnets? If it does not, it's rather useful. If it does, it's still useful, but less so for energy generation (as it eats at a "fuel" of magnets).

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Boffin

Re: Perhaps none.

You'd also need to factor in the energy costs of the laser, unless sufficiently focused sunlight might do the trick (i.e. similar to a magnifying glass). It also depends on the type of magnet being used as well. If it's one of those super-cooled magnets, the amount of energy required to reach the necessary temp might be prohibative.

One other thought is that although they can heat only a specific section of the magnet, what stops the heat spreading through the rest of it? If the magnet reaches it's Curie point, it'll lose its magnetism. (I learned about that from one of those "Choose Your Own Adventure" books! ^_^).

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Re: Perhaps none.

You might watch the video: you'll see it work with what looks like sunlight, but could have been artificial light. In any case, it was not laser light. The video clips also suggest that that the experiments were done at room temperature.

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Anonymous Coward

Re: Perhaps none.

I think the 'fuel' is the energy from the laser isn't it? Apologies if I'm wrong, it's new year's day and everything is a bit fuzzy still.

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Joke

Myself, I prefer..

moving discs by carefully balanced hydrophobes.

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Thumb Up

Re: Myself, I prefer..

Anything's better than exploding cabbages.

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pie in the sky

Sheer pie in the sky. Hysteresis losses in the disc from heating and cooling will far far greater than the energy converted to the dynamic. I've vague feeling that even the ancient greeks had bettered this. A long iron bar, alternately exposed and shaded from the sun would operate a ratchet with truly enormous forces. Even the shading function could be built in, and automatic. Wouldn't work in this country, mind. No sun.

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Thumb Up

The real question is why no one has "ever" thought of this before.

It's so simple

It's a graphite disk sitting on top of a stack of magnets and having laser shined on it.

No tricky materials, no exotic laser frequencies just a simple study of what happens if you try to do this.

Will the losses exceed the torque? Who knows. This is a demonstration not an engineered concept. But it is clever.

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Anonymous Coward

This could be fashioned into a little magneto to keep small lithium cells charged using focused sunlight. So could solar cells. But would a maglev last any longer or tolerate low level G forces.

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Silver badge

Indeed. I wonder if a focusing mirror would work instead of the laser?

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Anonymous Coward

It's heat not light that alters the magnetic properties of a magnet. A mirror may work but the light source would have to come from behind the magnet. Much like a feedhorn is located at the focal point on a radar dish.

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Bronze badge

Brilliant!

Patent it as a Moggie Amusement Device.

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Re: Brilliant!

Maybe as laser air hockey game.

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Bronze badge

Re: Brilliant!

Moggies are never amused. However, it could work as a Moggie Frustration Device.

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I wonder if this has the same properties as the coriolis effect (e.g. the direction of the water vortex down a plug hole north and south of the equator) when under sunlight, and that proximity to the equator will change it's behaviour.

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Happy

So, Gerry Anderson was right...

...those UFOs were obviously powered my magnets and light.

Shame he didn't get to see his ideas proved right.

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Anonymous Coward

Its certainly interesting

Have some PG and the required Holbach array (4 crossed pole magnets) to try this,

Its feasible to simply make a flat magnetic pad with crosspoints, an array of fluid lenses and PG disk above each crosspoint with mechanical limiters, then tap off energy with a large transparent coil made of ITO or graphene and apply offset voltages to track the Sun.

Literally energy for free, the energy needed to make pyrolytic graphite is considerable but this can be worked around by mass producing it on a silicon wafer then dicing it.

The magnets are the major sticking point as they are rare earth and neodymium is pretty expensive.

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Anonymous Coward

crookes radiometer

Reminds me of the Crookes Radiometer

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Re: crookes radiometer

Just what I was thinking. Thank you for reminding me of the name of the device that fascinated me as a child.

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Happy

Re: crookes radiometer

The Crookes radiometer looks very impressive. A windmill powered directly by sunlight!

In reality the force generated by photon pressure is tiny. I've seen a figure of 4.5 micro N/m^2.

What's really happening is differential absorption by the black sides of the vanes and local heating of the air near the surface of the vanes exerting a force to push on the vanes. This force is much bigger. A "real" Crookes radiometer could operate in a vacuum. The air pressure inside the globe is an integral part of the device.

I've sometimes wondered if such vanes, enclosed in a transparent slightly pressurised housing would make a good power generator on the Moon.

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Anonymous Coward

Hack *2

Use modified microwave oven with glass chamber, copper sheet and vacuum pump, backfill with low pressure helium and methane/argon although just helium and methane would probably work.

Homemade CVD system anyone?

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