Follow Slashdot blog updates by subscribing to our blog RSS feed

 


Forgot your password?
Close
typodupeerror
×
Biotech Science

Weighing An Attogram 42

Posted by timothy from the more-than-a-soul dept.
Roland Piquepaille writes "Researchers at Cornell University have reached a new level of precision by measuring objects with a mass of less than an attogram (10^-18 gram). They used a silicon cantilever oscillator to measure small dots of gold. But their real goal is to detect and identify viruses. The team also wants to reduce the size of the cantilever, extending the sensitivity well into the zeptogram (10^-21 gram) range. This summary contains more details and an image of a small gold dot resting on the silicon cantilever they used to achieve this breakthrough."
This discussion has been archived. No new comments can be posted.

Weighing An Attogram More

Weighing An Attogram

Comments Filter:

  • New tests for gravity. (Score:5, Interesting)

    by G4from128k ( 686170 ) on Wednesday February 25, 2004 @01:29PM (#8388035)
    If they can use this to measure very small forces on very small objects, they might be able to construct some interesting tests of gravitational fields or of quintessence [physicsweb.org]. We all think gravity changes with 1/r^2 and is irrespective of material composition, but do we really know that this rule works for ALL ranges of mass, distance, and material?

    Inquiring physicists want to know and this innovation could help them know it.

    • Tests will be difficult (Score:5, Insightful)

      by Spamalamadingdong ( 323207 ) on Wednesday February 25, 2004 @02:04PM (#8388569) Homepage Journal
      At that scale, influences like Van der Waals forces become far more powerful than gravity. Reading the pull of gravity with all the EM-related forces at work seems like a very, very difficult job.

    • Re:New tests for gravity. (Score:5, Informative)

      by marcus ( 1916 ) on Wednesday February 25, 2004 @03:48PM (#8389881) Journal
      Your question reveals some confusion, perhaps produced by the wording of the article.

      They are not "weighing" anything. They are measuring the mass of the gold. These are two different things. Gravity is not involved in the latter.
      • I think his experiment was in regards to interact between 'particles' on that small of a scale, now that we have a better means of 'seeing' them, but not necessarily how very small objects are affected by planetary forces.

    • Re:New tests for gravity. (Score:5, Informative)

      by QuantumFTL ( 197300 ) * on Wednesday February 25, 2004 @06:03PM (#8391495)
      If they can use this to measure very small forces on very small objects, they might be able to construct some interesting tests of gravitational fields or of quintessence.

      I don't really think that this technology in its current form can measure the forces on a particle that size. If you read the article, it is measuring the mass by measuring the resonant frequency, not measuring the forces present on the object.

      Yes I know that external forces can shift the frequency (due to nonlinearity) however I do not think that the precision of the device allows for measurement of such a weak effect.

      This has little to do, as another poster metioned, with other forces masking things at this small scale, but rather with the fundamental nature of the measuring device.

      Disclaimer: I'm a semester away from my BS in physics.

      Cheers,
      Justin

  • How many... (Score:3, Interesting)

    by dnahelix ( 598670 ) <slashdotispieceofshit@shithome.com> on Wednesday February 25, 2004 @01:49PM (#8388349)
    How many atoms of gold is that?
    Very fascinating! I love the picture.

    • Re:How many... (Score:5, Informative)

      by Patrik_AKA_RedX ( 624423 ) on Wednesday February 25, 2004 @01:57PM (#8388473) Journal
      Au: 197g/mol
      10E-18 / 197 = 5.076x10E-21 mol
      5.076x10E-21 x 6.022x10E23 = 3056.8 gold atoms.

      • Re:How many... (Score:2, Funny)

        by Anonymous Coward
        I was going to make a joke about atoms being atomic... ahh forget it.
      • that's cool. I'm guessing it should be rounded to an integer.

        Next question:
        How much is one gold atom worth?
        • If you could isolate exactly one gold atom. I would say quite a lot.
          Really pure metals are quite expensive, and these are usualy only 99.9999% pure (give or take a nine). These are only used in labs, more common materials have a purity near 99% or worse.

        • Re:How many... (Score:2, Insightful)

          by Anonymous Coward
          that's cool. I'm guessing it should be rounded to an integer.

          Actually... with his calculations it should be rounded to 3060 because there are only three significant figures in 197g/mol

          Obviously it gets the point across either way though.
      • 3056.8 gold atoms

        So that's what? 3056 gold atoms and a europium atom?
        • It means one atom is for only 80% part of the attogram. The other 20% is part of the attogram next to it.

          Or: 3056 gold atoms and a Gd atom (157.3ame ~80% of 197.0ame).

          Or: I broke one of the gold atoms, there quite fragile, you know.

      • Re:How many... (Score:4, Interesting)

        by Beryllium Sphere(tm) ( 193358 ) on Wednesday February 25, 2004 @04:46PM (#8390543) Journal
        Nostalgia department: there was one Asimov novel where a character is walking through a lab, and to convey a sense of wonder Asimov says the lab has a scale capable of weighing a billion atoms.

        I think it was one of the Caves of Steel series.

        Not only can we weigh things, we can identify them at infinitesimal quantities. There was a fact article in Analog about analytical chemistry. There are sensors today that can match the sensitivity of a dog's nose. That field has been advancing at the same explosive rate as computer performance has.

        • Great (Score:2, Funny)

          by BoomerSooner ( 308737 )
          Now I can figure out what smells so good in my crotch. Maybe I can get it in a bottle, make it stronger and spray it all over.

          I can see it now: Crotch in a Bottle, by Calvin Klein

      • So can I have all of those extra fractional gold atoms? No one will miss 0.8 atoms out of 3056. I'll deposit them into my Swiss bank account, a la "Office Space".

  • Ah, finally... (Score:3, Funny)

    by blate ( 532322 ) on Wednesday February 25, 2004 @02:25PM (#8388855)
    ...finally a way to weigh my post-dot-com crash paycheck. :D

  • Weight Via Chaos Theory (Score:3, Interesting)

    by Doug Dante ( 22218 ) on Wednesday February 25, 2004 @02:38PM (#8389021)
    I had this idea, which I've never implemented, of weighing items with extreme precision using a chaotic system. Since the chaotic system is sensitively dependent upon initial conditions, it should be possible to take measurements over a short period of time and work backwards mathematically to one of several possible initial weights. Eliminate those values that are not possible via other means (negative weights, far too heavy, far too light), and you should end up with an extremely accurate initial weight.

    I'm not sure that it would really work in practice, but I just thought it was a neat idea, and vaguely related to the authors' use of an oscilator.

    Perhaps if they were able to make the position of the oscilator at any time sensitively dependent on initial conditions, they could invent such a measurment tool (e.g. swing another weight in and out based on the position of the oscilator to slightly modify the local gravity in a nonmodal fashion that would make the oscilator sensitively dependent upon its weight and its inital position)

    My differential equations work is so far gone, I couldn't even begin to measure this mathematically anymore.
    • Isn't the whole point of a chaotic system that you *can't* work it backwards like that, because it's all too complicated?

      • Re:Weight Via Chaos Theory (Score:5, Interesting)

        by Baron_Yam ( 643147 ) on Wednesday February 25, 2004 @03:41PM (#8389795)
        Actually, this has already been done... though with optics. You take large numbers of measurements of 'nothing' and note the random static produced by the sensor. You can then subtract the average noise from the average of a large number of measurements of something and get an accuracy level theoretically beyond the ability of your instrument.
        • But isn't random noise random, as the name suggests? (or at least chaotic, but without more information than it is realistically possible to get, it's as good as random) Minusing a random number will get you a random number. You can try and find some sort of systematic error and minus that, but pretending random error is systematic is going to cause problems, no?
          • The idea is to average the noise over a large number of samplings, and subtract that from the average of a large number of samplings of whatever you are measuring.

            You don't subtract a single noise measurement from a single final measurement, which would double your error margin (you could have a perfect cancellation, or perfect addition).

        • A technique like the one you mention is very common in many measuring applications: it's called oversampling [earlevel.com] followed by lowpass filtering.

          Essentially, you're trading bandwidth for accuracy: the lower you make your lowpass bandwidth, the more you "average out" the noise, and the more accurate your measurement can become. However, the downside is that your bandwidth is very small, which causes your measuring time to be very large (you'll have to wait for your lowpass filter to complete at least a reasonabl

    • Re:Weight Via Chaos Theory (Score:3, Informative)

      by PD ( 9577 )
      The problem with this is that your system is chaotic. If you measure it one way, you can't tell how it's going to turn out. If you measure it the other way, you also can't tell how it began.

      And, the number of possibilities you have for a starting state would probably depend on just how sensitive your system is. If there's not many possibilities to choose from, then your system is probably insensitive enough to get an accurate measurement right up front.

      But it's a cool idea that would probably make a good
  • But their real goal is to detect and identify viruses.

    A virus is what we doctors call very very small. So small in fact it could not possible have made off with an entire leg.

  • Zeptogram? (Score:3, Funny)

    by whistler36 ( 189652 ) * on Wednesday February 25, 2004 @11:34PM (#8394145)
    The zeptogram was never as popular as the grouchogram. People only use it because it's better looking.
  • Damn little bastards will become weight concious and go on a diet just to elude detection.
  • But their real goal is to detect and identify viruses.

    Maybe they should license this technology to Microsoft?
  • Let me tell you, I'm very impressed. I tried doing this and I could never pull it off. No matter how many diets I tried and how many hours I spent on the treadmill, I could never get down to one attogram. So, to you dedicated researchers who managed to weigh an attogram... congratulations, and good luck in your modeling career.

Slashdot Top Deals

Intel CPUs are not defective, they just act that way. -- Henry Spencer

Close