PHYSICISTS have set a new record for detecting tiny forces by recording a
鈥渘udge鈥� of only 2 attonewtons鈥�2 billionths of a billionth of a newton. 鈥淎n
attonewton is to the weight of a feather as the weight of a feather is to the
weight of the Hoover dam,鈥� says John Mamin of IBM鈥檚 Almaden Research Center in
California.
The advance takes researchers a step closer to the goal of detecting
individual protons and electrons using magnetic resonance imaging.
MRI can detect different substances inside the human body, for example, by
applying varying magnetic fields and detecting oscillations in the protons of
certain types of nuclei.
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Physicists would like to detect a single proton within a nucleus or a single
electron from the way they oscillate. Such sensitivity would open new horizons
for material scientists, says Chris Hammel of Los Alamos National Laboratory in
New Mexico. 鈥淵ou can tell someone what a molecule looks like by telling them
where each proton is.鈥�
Researchers hope to exploit the fact that a proton or electron will
experience a slightly different force depending on whether its own magnetic
field points into or out of an applied uneven magnetic field. Now Mamin and his
colleague Dan Rugar have a device that could measure that force.
The researchers built a silicon post 260 micrometres tall and 0.3 micrometres
thick that was fixed at its base. They shook the post with a force of 2
attonewtons and found that they could detect a wobble in the post of less than
one 10-billionth of a metre, by reflecting laser light off its tip into a
detector.
Hammel says the work shows that the tiny device, with the addition of a
magnet on its tip, should be sensitive enough to detect a single proton or
electron using MRI. But Mamin notes that they still have to figure out how to
hold the electron or proton steady. 鈥淲e have to make it do what we want it to do
long enough to detect it.鈥�