medium, can be applied to lipid membranes to describe effective surface potentials at
long range and can be further augmented by charge regulation mechanisms (Section 1.6
below) to accurately model experimental measurements of the lipid membrane surface
potential [9].
1.4 Atomic Force Microscopy
The Atomic Force Microscope (AFM) [10], is a microscope with an imaging resolution
which can approach fractions of a nanometer. It is a member of the family of instruments
known as the scanning probe microscopes. They all operate by scanning a sharpened tip
across the sample and obtaining surface information from the interaction between the
sample and the surface. The AFM in particular, is able to operate in both fluid and has
been of great utility in biology. In addition to imaging, the AFM is also able to measure
forces with resolution approaching a few piconewtons. The AFM measures topography
by raster scanning a very sharp tip along the surface being imaged.
Figure 1.5: Schematic of typical AFM tip-cantilever assemblies.
