5. Single-Phase Velocity Profile Comparison between H-H and P-H
Pores
This section focuses on the effect of the electric field single-phase
velocities for different pore sizes for a fixed acceleration of 0.002
nm/ps2 in P-H and H-H pores. The results are shown in
Fig. 14 indicating that the P-H nanopore exhibits flatter flow profiles
at the pore center due to the presence of the electric field as shown in
Fig.5.
Normally, adsorption is the result of van der Waals forces, covalent
bonding and electrostatic attraction101. In this work,
we do not consider covalent bonding102. Therefore, in
our study, adsorption is solely due to the van der Waals force and
electrostatic attraction. Adjacent to the surface, these forces impact
fluid transport. However, van der Waals force quickly diminish for
increasing distances from the pore surface 103, while
the long-range electrostatic interaction can extend tens of
nanometers32.
Therefore, in the P-H pore, fluid transport is controlled by the
electric field and imposed acceleration, leading to a flat pattern as
shown in Figs.14a-b. Increasing pore sizes for P-H pores increases the
width of flat pattern as shown in Figs.14c-d because of the increase in
the width of the zone dominated by the electric field. However, in H-H
nanopore, there is a negligible electric field at the nanopore center.
Therefore, classical parabolic shaped patterns are observed in H-H
nanopores as shown in Fig.14.