The force-separation profile measured between a hydrophilic tip and a hydrophilic glass surface in NaCl. The separation between the surfaces was determined by conventional AFM techniques (blue crosses), and by using Eq. (2) to determine the separation from the scattering of the AFM tip (red circles). Scattering and deflection data were collected simultaneously.
Profiles measured for a tip and a glass solid in DDAB. (a) Scattering intensity as a function of piezo displacement. The profile shows hysteresis due to the adhesion of the tip to the glass. (b) Force as a function of separation measured by conventional AFM analysis (blue circles) and EW-AFM (red circles). The inset shows scattering data only on an expanded scale. The black line is running average of 10 points.
(a) Raw scattering intensity. The intensity is greater at the start of the withdrawal because the tip is in contact with glass on withdrawal. (b) Force-separation profile measured using Eq. (4) for the separation. The red curve (A) is the film thickness using the contact method to determine the tip position on approach. The blue curve (A1) would be the separation if the reference method is used to determine separation. (c) AFM tip deflection captured simultaneously to scattering data in (a). (d) The force-separation profile determined using the AFM deflection data. The withdrawal (W) and approach (A) are coincident using conventional AFM analysis. The green curve (A2) would be the apparent film thickness if we assumed the displacement between approach and withdrawal runs is due to the thickness of the film. The blue curve (A3) would be film thickness if the piezo position prior to the addition of polymer was used to determine the tip position on approach.
Force-separation profiles determined using Eq. (4) in polymer-salt solution. The first withdrawal (1) and approach (2) are re-plotted from Fig. 3(a) approach-withdrawal collected after a equilibration time with the tip away from the surface. (b) The tip was left in contact with the polymer surface for , withdrawn (3), and then immediately brought back into contact (4). All data shown are the average of 10 measured points.
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