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и
Figure 3.3: Fluid AFM topographical image of a 1:9, DMPChDMPS lipid patch. We are
able to identify the lipid bilayer patch from its cross-sectional height which is 5 nm.
The scan size is Ixl μm.
3.2.3 Computational analysis
Van der Waals forces between the tip and the sample were calculated using a custom-
written MatLab routine. Tip-induced charge regulation was modeled as follows. We first
created a finite element simulation domain of the tip and the lipid sample using the
general methods described in Section 2.2 of this thesis. We then visually chose the D
value, which we will call Do, at which the Chapter 2 model starts deviating significantly
from the data. For the sample data in Figure 3.2, Do = 11 nm (see Figure 3.5). For Do and
lower, we include the tip-induced perturbations of the lipid surface into our finite element
calculation in the form of a variable surface charge density boundary condition (see
Figure 3.4).
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