Moving atoms is easy, measuring the moves less so - February 22, 2008
Scientists have for the first time measured the force needed to move one individual atom.
In the latest issue of Science, researchers from IBM and the University of Regensburg in Germany detail how they used an atomic force microscope to measure the vertical and lateral forces exerted on individual atoms by the probe tip of the microscope probe (research paper, related perspective paper, IBM press release, Regensburg press release).
It seems to move a cobalt atom over a smooth platinum surface requires a force of 210 piconewtons. Moving a cobalt atom over a copper surface takes only 17 piconewtons. By contrast, IBM’s press release points out lifting a penny requires nearly 30 billion piconewtons.
These forces should have been fairly easy to predict: chemists have known for years the various bond strengths involved between adsorbed atoms and surfaces. However this new research “helps us to understand what is possible and what is not possible,” Andreas Heinrich, one of the new paper’s authors says (NY Times). “It’s a stepping stone for us, but it’s by no means the end goal.”
While moving the atom was easy, measuring the force was hard. The researchers swept a tiny piece of quartz at the end of their microscope across the surface on which they placed their atom to be moved. Eventually this quartz tip flipped the atom from one indentation in the surface to the next.
The quartz tip vibrates like a tuning fork until it comes into contact with the atom, when the frequency of the vibration changes. This change can be analysed to give the forced used to move the atom.
“From the surface science point of view you cannot measure much more than the force needed to move an atom,” Werner Hofer, a surface scientist at the University of Liverpool told Chemistry World. “We can now think about full control of chemical reactions, watching what happens when two molecules are pushed together to react to make another molecule.”
Video from IBM
Image: illustration of an Atomic Force Microscope (AFM) tip measuring the force it takes to move a cobalt atom on a crystalline surface / Jenny Hunter, IBM
Comments
Researchers and interested readers here could benefit immensely by accessing (1) for perusal. It is a one-page summary that would put also the atomic world in its true perspective.
If (1) does not seem nonsensical, then do check out also the 2½-page preprint in (2). The response from Physics World to the latter has since been negative, leaving the monetary offer therein for its refutation still open! Would one of your physics department heads kindly consider being the moderator and judge here (holding the minimum cash of US$25,000 in hand!)? Moderator's fee, too, will be paid by me in advance. No joke; no scam; just an earnest appeal here to mainstream peers in active research to resolve this matter for me early with your profound knowledge and expertise – not to my satisfaction but to that of your (or any) university physics department head alone. (The money offered is the least I could do in gratitude. It would be worth every penny for me considering the time I would otherwise be wasting in trying to flog a fundamentally flawed worldview.) Thank you.
(1) www.sittampalam.net/Summary.pdf
(2) www.sittampalam.net/LateralThoughts.pdf
Posted by: Eugene Sittampalam | February 27, 2008 05:47 PM