ABSTRACT
Charged materials are ubiquitous in nature due to the high permit-
tivity of water that favors ionic dissociation. The strong electrostatic
attraction favors electroneutrality. However, ion entropy due to their
dissociation in water allows for local charges. The Bjerrum length,
lB, the distance beyond which the thermal energy dominates the electrostatic interaction between unit charges, is only of lB ∼ 7 A˚ for water at room temperature. The competition between entropy and
electrostatics results in a distribution of ions around a given charge
over distances of the order of the Debye length, κ−1, a characteristic of the screening of electrostatic interactions by the ionic atmosphere
(in the nanometer range for usual conditions) [Hunter (2001)].
Hence, the dynamics of charged fluids poses a number of challenges
because one needs to capture the behavior from themolecular scales
(ion size and solvation), to the micron scale of colloids without
overlooking the collective ion distribution and response, which
evolves naturally on the nanometer and nanosecond scales.
