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May The Force Be With You (Thermophoretic Force)

02/17/2017 9:26 AM

Take what you thought you knew about levitation, gravity, and so forth then toss a wrench into it. While It's not the holy grail of hollywood levitation it's pretty far out.

Take a look at what these guys at the University of Chicago have done and try to explain it in layman's terms.

Levitating lint!? Ice.. seeds.. .. what's next? A sugarcube?

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#1

Re: May The Force Be With You. (Thermophoretic Force)

02/17/2017 10:43 AM

Thermally induced air currents.

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#3
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Re: May The Force Be With You. (Thermophoretic Force)

02/17/2017 10:45 AM

In vacuum?

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#5
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Re: May The Force Be With You. (Thermophoretic Force)

02/17/2017 1:05 PM

There seem to be inconsistencies in the report that confused me when I read it. It says it's in a vacuum chamber but talks about air currents maintaining stability.

"Third-year Frankie Fung and fourth-year Mykhaylo Usatyuk led a team of UChicago researchers who demonstrated how to levitate a variety of objects—ceramic and polyethylene spheres, glass bubbles, ice particles, lint strands and thistle seeds—between a warm plate and a cold plate in a vacuum chamber."

"The key to obtaining high levitation stability is the geometrical design of the two plates. A proper ratio of their sizes and vertical spacing allows the warm air to flow around and efficiently capture the levitated objects when they drift away from the center. Another sensitivity factor is that the thermal gradient needs to be pointing upward—even a misalignment of one degree will greatly reduce the levitation stability."

https://news.uchicago.edu/article/2017/02/14/new-method-uses-heat-flow-levitate-variety-objects

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#6
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Re: May The Force Be With You. (Thermophoretic Force)

02/17/2017 1:39 PM

B-

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#11
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Re: May The Force Be With You. (Thermophoretic Force)

02/18/2017 1:08 AM

I too saw those inconsistencies. They did say that the pressure was one of the important factors. Apparently, the vacuum chamber allows them to adjust the amount of gas in the chamber. So it is in a vacuum chamber, but not in a vacuum.

So are the items being levitated by radiated heat, or by air flow, or some combination of the two?

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#12
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Re: May The Force Be With You. (Thermophoretic Force)

02/18/2017 12:44 PM

These things work because there is a tiny bit of air left inside. A slight warming of the black side of the vanes compared with the white when they are illuminated causes it to turn as, one theory proposes, molecules rebound off the black sides more energetically than off the white sides.

https://en.wikipedia.org/wiki/Crookes_radiometer

In the experiment, my guess is that molecules rebounding from the lower hot plate are more energetic than those rebounding from the upper cold plate, and this is what is causing the lift as they strike the levitated object.

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#14
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Re: May The Force Be With You. (Thermophoretic Force)

02/18/2017 7:36 PM

GA! I suspect you are correct. It's not radiation, but gas molecules doing the lifting.

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#2

Re: May The Force Be With You. (Thermophoretic Force)

02/17/2017 10:44 AM

Must be based on radiation pressure.

In this case heat radiation.

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#4

Re: May The Force Be With You. (Thermophoretic Force)

02/17/2017 10:58 AM

Wouldn't radiant heat be considered an electromagnetic wave?

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#10
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Re: May The Force Be With You. (Thermophoretic Force)

02/17/2017 5:10 PM
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#7

Re: May The Force Be With You. (Thermophoretic Force)

02/17/2017 1:47 PM

What really impresses me is how young these guys are!

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#8

Re: May The Force Be With You (Thermophoretic Force)

02/17/2017 4:40 PM

Could it be thermo-electronic pressure counteracting gravity on the lint?

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#9
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Re: May The Force Be With You (Thermophoretic Force)

02/17/2017 5:04 PM

I dunno? It acts like it's floating in a fluid.

The focus seems to be keeping it perfectly level like a fluid as well.

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#13

Re: May The Force Be With You (Thermophoretic Force)

02/18/2017 7:12 PM

I'm still not sure I have a deep understanding of what's going on.. I'll just have to pop over to the lab.

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