Imaging Modes - JPK instruments nanowizard afm Handbook

5.3 Imaging modes

The two main modes used to image cells are contact mode and intermittent contact
mode. The choice of mode will depend, in part, on user preference, but there are
some indicators for which will be the best choice.
Contact mode
Pros
Enhances visualization of subsurface cytoskeletal
structures in both living and fixed cells
Better suited for the imaging of cells with steep
edges, i.e. high cell body or dendrites
Allows faster scan speeds on flatter cells
Cons
Flexible objects will move laterally, in the scan
direction (this will happen in all imaging modes
but is exacerbated in contact mode)
The user must monitor the scan closely to ensure
that the imaging conditions remain optimal and
the applied force does not increase too much due
to deflection drift
Comments
In contact mode the applied force is directly
related to the spring constant of the cantilever and
the deflection setpoint. A softer cantilever (lower
spring constant) and a lower setpoint value will
apply a lower force and should therefore in
general give better imaging, particularly for living
cells
JPK Instruments NanoWizard
Intermittent contact mode
Less lateral disruption during the scanning
process
Less predominance
structure (for imaging of features other than
subsurface cytoskeleton)
Phase images showing material properties
available
The amplitude may remain quite constant even if
the cantilever bends somewhat due to material
adsorbing, for example.
force offset in contact mode, but not immediately
in IC mode.
Responds less well to steep height changes -
such as sides of dendrites or the side of the cell
body, which can complicate imaging whole cells
More susceptible to complications due to a sticky
sample or substrate
For soft cantilevers
frequencies, the scan speeds may be rather
limited, since the data collection rate can be in
the range of the oscillation frequency for soft
cantilevers. The feedback system will require
several oscillation cycles to accurately determine
the amplitude of the oscillation.
In intermittent contact mode, the applied force is
not so directly related to the spring constant of
the cantilever, since the imaging sensitivity
depends on the resonance properties of the
cantilever. A slightly stiffer cantilever may have
a better resonant behavior and hence give more
sensitive imaging.
frequency will also enable faster imaging.
®
Handbook Version 2.2a
of submembranous
This would cause a
with low resonant
A higher resonance
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