Fluid Imaging
Troubleshooting
Rev. D
Dimension 3100 Manual
173
10.6 Troubleshooting
10.6.1
Cantilever Tune Plot Looks Poor
Become familiar with the characteristics of the Cantilever Tune plot when you successfully obtain
good images. You may use the Cantilever Tune plot as a diagnostic tool. If the plot looks
substantially different from previous successful experiments, there may be a problem with the fluid
cell or the cantilever may be loose in its holder. Ensure there is good physical coupling between the
probe and the fluid cell, and that the laser is positioned correctly at the free end of the cantilever.
10.6.2
Laser Sum Signal Absent or Weak
Remove all air bubbles from the cantilever. Bubbles may attach themselves to the cantilever,
causing the laser beam to diffract. Remove bubbles by gently squirting the tip and sample with a
stream of fluid, taking care not to squirt or splash fluid into spaces above the protective skirt.
10.6.3
Poor Image Quality
Some types of samples may adhere to the cantilever and tip (e.g., certain proteins). If you suspect
tip contamination, you must protect the tip against contamination using either of the following
methods:
•
If the tip adheres to a sample surface through diffusion (e.g., diffusion of protein onto
mica), first diffuse the sample substance into the substrate, then flush away stray
substance using a straight fluid media. Lower the tip into a fluid containing little or no
stray substances that may adhere to the tip.
•
If the sample is short-lived and must be imaged quickly, mask the tip against
contamination by bringing the tip into gentle contact with an uncontaminated substrate
surface. Set the Dimension 3100 in Contact Mode by switching the
AFM mode
parameter on the
Other Controls
panel to
Contact
. Engage the substrate surface using
a zero scan size. While keeping the tip gently in contact with the substrate surface, add
the sample substance to be imaged to the petri dish and allow the sample substance to
settle onto the substrate. Once diffusion is reached, quickly lift the tip from the substrate
surface. Switch to
TappingMode
and image the sample.
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