National Physical Laboratory

Scanning Probe Metrology - Nanomaterials

Scanning probe metrology (SPM) is a powerful technique, which allows imaging of non-conducting surfaces down to the sub-nanometer level without the need for any additional sample preparation. An ultra sharp tip probes a surface and the force between the two is measured via the deflection of a cantilever.

Mode of operation of AFM showing deflection of a cantilever due to surface interaction
Mode of operation of AFM showing deflection of a cantilever due to surface interaction


Force Spectroscopy

Goes beyond imaging by detecting adhesion between tip and sample. By modifying the tip with a specific molecule single molecule sensitivity can be found. Attaching an avidin molecule to the tip allows the detection, and measurement of specific biotin-avidin interactions.

Magnetic Spectroscopy

The tip is magnetised, so scanning across the sample elucidates the magnetic structure of the surface

Force Modulation Microscopy (FMM)

A combination of contact and non-contact modes. The tip is vibrated whilst in contact with the surface, measuring changes in surface hardness.

Parameters of the Atomic Force Microscpe (AFM)

Energies
      KBT = 4pNnm
      ATP Hydrolysis: 12-21 KBT
      H-Bond: 4-18 KBT
      Covalent Bond: 100 – 200  KBT
      Protein Stability: 6-20  KBT
 
Forces
      Covalent Bonds: 2-5 nN
      Unzipping DNA: 20 pN (GC)/10 pN (AT)
      1mW of light reflecting off a surface: 7 pN

Last Updated: 7 Nov 2016
Created: 30 Jul 2007

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