Strong coupling electrostatics for randomly charged surfaces: antifragility and effective interactions

Area of Science:

• Colloid and Interface Science
• Statistical Mechanics
• Electrostatics

Background:

• Understanding interactions between charged surfaces in ionic fluids is crucial for nanotechnology and biological systems.
• Surface charge disorder and strong electrostatic coupling with multivalent ions significantly influence interfacial phenomena.
• Dielectric properties and salt effects modify ion distributions and effective forces.

Purpose of the Study:

• To investigate the effective interaction between dielectric surfaces with quenched random charges in Coulomb fluids.
• To analyze the role of surface charge disorder, dielectric effects, and multivalent counterions on ion distribution and interaction pressure.
• To explore the phenomenon of antifragility arising from disorder-induced potentials.

Main Methods:

• Theoretical analysis of electrostatic interactions in a system with quenched random surface charges.
• Modeling of Coulomb fluids with multivalent counterions and asymmetric ionic mixtures.
• Calculation of ion density profiles and effective interaction pressure between surfaces.

Main Results:

• A disorder-induced potential attracts multivalent counterions, leading to a singular density profile at surfaces in homogeneous systems.
• Interfacial dielectric discontinuities alter but do not eliminate the strong accumulation of counterions near disordered surfaces.
• A non-monotonic interaction pressure with significant attraction at small-to-intermediate separations is observed, driven by charge disorder and multivalent ion coupling.
• This disorder-induced attraction can dominate surface repulsion and van der Waals forces, especially at nanometer separations.

Conclusions:

• Surface charge disorder, coupled with multivalent ions, generates a strong attractive force between dielectric surfaces.
• The system exhibits antifragility, transitioning to a state of lower thermal disorder.
• The findings are relevant for designing nanomaterials and understanding biological interfaces where charge disorder is prevalent.