25
continuously tap on the body of Pavone to induce one circle of noise and press the
“calibrate” button on the interferometer, 2) go in contact with the sample and press
calibrate from the “Initialize” menu, do not save calibration factor. However, if the
signal is not just slightly displaced from the demodulation circle but rather became
very small, it means that the cantilever got stuck to the fiber. To fix it, you can try one
of these methods: 1) lift the probe up out of the well, prewet the probe and move
down, 2) perform cleaning procedure, 3) dry the probe with the tissue, 4) get the
cantilever unstuck by gently touching it from below with the tissue.
14.
Finally, calibration can be verified by performing an indentation directly after the calibration. Load
or make an experiment file
(“Config.experiment”)
, using the default displacement mode settings
and changing to a calibration distance to displace the probe again on the stiff substrate. When
‘Run experiment’, check the demodulation circle in the interferometer window.
The white signal
should be on top of the red circle during indentation. The results
in ‘Time data’
should show that
the piezo displacement (blue line) is equal to the cantilever bending (green line) because the
indentation starts in contact and no material deformation is expected (see
-f). If both
lines do not superimpose, check the reasons above for failed calibration.
Figure 18:
a) Cantilever stuck to fiber. b) Releasing cantilever with the tissue. c) Drying the probe with the tissue. d) Air bubble stuck
to cantilever.
a)
b)
c)
d)
