The name is absent

1.6 Electrostatic double layer force and charge regulation

The electrostatic double-layer force arises because of surface charges at interfaces. Water
in particular has a high dielectric constant. Thus, surface charges dissociation into the
water is very common. The surface charge is balanced by dissolved counterions which
are attracted back towards the surface by the electric field. These are not reabsorbed but,
instead, form a diffuse cloud close to the surface. Taken together the ions and charged
surface are known as the electric double layer. When another surface approaches, the
double layer is perturbed, and the results in a force known as the double-layer force.
When the approaching surface charges have the same sign, the concentration of ions
between the surfaces always increases. This results in a repulsive force [21]. The
electrostatic double-layer force can be calculated using continuum theory based on work
by Gouy, Chapman, Debye, and Huckel for electric double layers.

Figure 1.10: Schematic of the diffuse electric double layer formed over a negatively
charged surface. The red dots represent positive counterions. The density of the
counterions close to the surface is higher than in the bulk. This cloud of positive
counterions is the diffuse electric double layer.

AFM tips made of silicon nitride are commonly used in studies of biological samples in
fluid and we have used such tips in our work. The surface chemistry of silicon nitride is

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