Force Spectroscopy

The cantilevers used for the experiment are made of silicon.Their geometrical dimensions are characterized by :

l : the length of the beam
w : the width of the beam and
t : the thickness of the beam.

When the beam is anchored regidly on one of its sides and a force is acting on the front end its other side, the beam bends downwards according to its mechanical properties. the total deflection of the beam at its final end is :

Z = – (L^3) F/3EL

Here, E is the modules of elasticity and I is the moment of inertia given by the cross section of the beam :

l = ∫A dz 2 dA (dZ = distance from neutral axis)

The force constant of the cantilevers used in the experiment is provided by the producer in the data sheet.

Force Spectroscopy Atomic Force Microscopy mode Force Spectroscopy Atomic Force Microscopy mode
There are many parameters regarding spectroscopy that can be changed in Ara – AFM software as shown in the figure.
Force Spectroscopy Atomic Force Microscopy mode
If the tip is sharp and surface of the sample is not sticky, it might be o.k. to retract the tip between 100 nm and 200nm, only.Then, the force-distance curve might look like this :
Force Spectroscopy Atomic Force Microscopy
If the tip is blunt and/or is sticky, it is possible that the tip remains in contact with the sample.
Force Spectroscopy Atomic Force Microscopy mode