Scanning force microscopy (SFM)

SFM technology's ancestor, STM (Scanning Tunneling Microscopy), was invented in 1981 by Gerd Binnig and Heinrich Rohrer at the IBM in Zurich, Switzerland. They went on to win the Nobel Prize in physics for their discovery. Their work has formed the basis for all serious scanning probe microscopy research worldwide ever since.

A scanning force microscope basically works like an old fashioned record player, where the movement of the needle sends the recorded impulse through the amplifier and on to the speakers to produce music. Unlike to the record player a SFM detects the movement of the needle through a laser beam, which is reflected from the top of a cantilever to a photodiode. The bending of the cantilever can be measured by using a four-quadrant photodiode. The strength of the cantilever deflection is allocated to a colour scale and the data is used to generate a map of the surface topography.

Topography map: Superhelical plasmid DNA with one nucleosome

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