The name is absent

As shown in Figure 3.2, the results obtained from the model given in Chapter 2 start
deviating from the AFM data at short tip-sample separations (11 nm and less in the figure
below).

450

400

350

300

(a) S²⁵⁰

200

150

100

50

°    5    10    15   20   25   30   35    40

Tip-sample separation D (nm)

Figure 3.2: (a) The fixed charged density model is a good fit for the data for D > 11 nm.
(b) A closer view of the same data shown in (a) reveals that the simulation deviates from
the data when D < 11 nm. The data is for a 1:5, DOPC:DOPS mixture.

The fixed surface charge density model of Chapter 2 consistently over-estimates the force
in the short-range. Thus, we reason that the short-range correction must be due to a
lessening in repulsion between the tip and the lipid. We will first show that the van der
Waals interaction between the tip and the sample does not account for the observed short
ranged deviation. Next, we will demonstrate that the AFM tip-induced counterion

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