Stories
Slash Boxes
Comments

SoylentNews is people

posted by charon on Thursday February 16, @12:15AM   Printer-friendly
from the more-trouble-than-it's-worth dept.

Although scientists have been able to levitate specific types of material, a pair of UChicago undergraduate physics students helped take the science to a new level.

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.
...
In the experiment, the bottom copper plate was kept at room temperature while a stainless steel cylinder filled with liquid nitrogen kept at negative 300 degrees Fahrenheit served as the top plate. The upward flow of heat from the warm to the cold plate kept the particles suspended indefinitely.

"The large temperature gradient leads to a force that balances gravity and results in stable levitation," said Fung, the study's lead author. "We managed to quantify the thermophoretic force and found reasonable agreement with what is predicted by theory. This will allow us to explore the possibilities of levitating different types of objects." (Thermophoresis refers to the movement of particles by means of a temperature gradient.)


Original Submission

This discussion has been archived. No new comments can be posted.
Display Options Threshold/Breakthrough

Mark All as Read

The Fine Print: The following comments are owned by whoever posted them. We are not responsible for them in any way.
  • (Score: 5, Informative) by butthurt on Thursday February 16, @12:31AM

    by butthurt (6141) on Thursday February 16, @12:31AM (#467672) Journal

    The phys.org page says the experiment was done in a vacuum chamber and that "[l]evitation of macroscopic particles in a vacuum is of particular interest" which is misleading because the Knudsen Compressor effect causing the levitation requires a gas. The pressures used were "between 1 and 10 Torr" according to the journal article, which says

    [...] air molecules coming from the hotter side transfer on average a larger momentum to the particle than those from the colder side. A net momentum transfer due to collisions with molecules overcomes gravity [...]

    -- http://aip.scitation.org/doi/10.1063/1.4974489 [scitation.org]

    • (Score: 5, Informative) by butthurt on Thursday February 16, @12:42AM

      by butthurt (6141) on Thursday February 16, @12:42AM (#467677) Journal

      more titbits that came up when I searched for information about the Knudsen Compressor effect:

      An earlier experiment of this sort was done on a rocket following a parabolic trajectory (sothat the effect of gravity was easier to overcome).

      http://eea.spaceflight.esa.int/portal/exp/?id=9352 [esa.int]

      The University of Chicago researchers have an alternate abstract on their site:

      We demonstrate levitation of micron-sized ice, ceramic, glass and polyethylene particles at low pressure (1-10 Torr) in the presence of a temperature gradient. Under thermophoresis, collisions with more energetic gas molecules from below provide a net upward momentum transfer. Particles initially levitate a few millimeters above a cold plate due to the Knudsen Compressor effect. Particles are then accelerated upwards by the thermophoretic force in the direction from hot to cold in the rarefied gas. In the appropriate pressure regime this allows for stable levitation for up to two hours. Lately we have also succeeded in levitating other materials, including thistle seeds and lint. Our future goals are to levitate water droplets, push levitated particles with a laser, and examine the dynamics behind multi-particle levitation.

      -- https://web.archive.org/web/20161206234058/http://ultracold.uchicago.edu/ [archive.org]

  • (Score: 2) by bob_super on Thursday February 16, @01:04AM

    by bob_super (1357) on Thursday February 16, @01:04AM (#467681)

    The other night, I made some dark multi-millimeter particles levitate in an upwards flow of molecules which were rising from a hot source towards a cold one.
    Macroscopic. Normal pressure. Highly reproducible. Sub-dollar costs.
    Should I publish?

    • (Score: 0) by Anonymous Coward on Thursday February 16, @01:56AM

      by Anonymous Coward on Thursday February 16, @01:56AM (#467689)

      Only if you want that sweet grant money.

      • (Score: 2) by bob_super on Thursday February 16, @05:17PM

        by bob_super (1357) on Thursday February 16, @05:17PM (#467881)

        Patent of the Month: Bob_super is granted exclusive rights to fire!

    • (Score: 2) by Bogsnoticus on Thursday February 16, @05:42AM

      by Bogsnoticus (3982) on Thursday February 16, @05:42AM (#467725)

      Let me guess.
      Laying face down in bed after a Taco Bell daily special?

      --
      Genius by birth. Evil by choice.
  • (Score: 0) by Anonymous Coward on Thursday February 16, @01:33AM

    by Anonymous Coward on Thursday February 16, @01:33AM (#467685)

    Isn't that how a sterling engine works?

    • (Score: 0) by Anonymous Coward on Thursday February 16, @03:01AM

      by Anonymous Coward on Thursday February 16, @03:01AM (#467697)

      Yes, the pound has been floating since 1971. [investopedia.com]

  • (Score: 2) by Rivenaleem on Thursday February 16, @08:51PM

    by Rivenaleem (3400) on Thursday February 16, @08:51PM (#467954)

    This would be great to see applied to lifting space ships into orbit. They could be designed to expel vast amounts of heat downward countering the effect of gravity to produce upward motion.