Biomedical Engineering Reference
In-Depth Information
lateral periodicity of stripes and channels depends on the parameters used during the
preparation of the sample.
We imaged the sample using the oscillation amplitude as a feedback signal in the
FM-mode using CE before we recorded 50 spectroscopy curves along a predefined
direction marked in Figure 2.14a. All data sets were than transformed into tip-sample
potential curves using the mathematical method described in Section 2.4.5. Finally,
we computed the corresponding contour map as shown in Figure 2.14. The complete
procedure was done by a computer script using IGOR Pro software (Wavemetrics
Inc.).
The resulting color-coded image reveals the different tip-sample interaction on
the stripes (LC-phase) and in the channels (LE-phase). The potential is significantly
larger above the stripes (
≈−
100 eV) compared with the channels (
≈−
150 eV), as
it can be seen by the color coding in Figure 2.14.
(a)
(b)
12
0
10
8
-50
6
-100
4
-150
2
0
(c)
-4
-5
-6
-7
-8
-9
LC phase
LE phase
02468 0 2
14
Scan position (
μ
m)
14 μm
2
) of the topog-
raphy of the L-α-dipalmitoyl-phosphatidycholine (DPPC) film prepared by the Langmuir-
Blogdett technique. The monolayer shows alternating stripes and channels that consists of
DPPC adsorbed in the liquid condensed and liquid expanded phase, respectively. The white
line marks the position where we recorded the frequency shift and amplitude versus distance
curves for the construction of the contour map of the tip-sample interaction potential shown in
(b). The graph in (c) displays the corresponding adhesion force obtained from the data shown
in (b). The parameters of the cantilever were
f
0
FIGURE 2.14
(
See color insert.)
(a) Surface plot (scan size: 14
×
=
,
=
.
=
170
460 Hz,
k
cant
39
6N/m,and
Q
492.
Search WWH ::
Custom Search