Dynamic Electrophoretic Mobility of a Cylindrical Colloidal Particle

Area of Science:

• Colloid Science
• Electrokinetics
• Computational Physics

Background:

• Understanding colloidal particle behavior in electric fields is crucial for applications.
• Dynamic electrophoretic mobility governs particle motion under time-varying fields.
• Cylindrical particles present unique electrokinetic challenges compared to spheres.

Purpose of the Study:

• Derive accurate approximate formulas for the dynamic electrophoretic mobility of cylindrical hard colloidal particles.
• Investigate mobility in both transverse and tangential oscillating electric fields.
• Analyze the dependence of mobility on the Debye-Huckel parameter (kappa) and particle radius (a).

Main Methods:

• Developed approximate formulas using Hankel and modified Bessel functions.
• Formulas are valid for all kappa*a (Debye-Huckel parameter times particle radius).
• Considered cases with zero particle permittivity and low zeta potentials.

Main Results:

• Obtained accurate formulas for dynamic electrophoretic mobility in transverse and tangential fields.
• Demonstrated that tangential field mobility depends on kappa*a, unlike the static case.
• Averaged dynamic mobility for randomly oriented cylinders approximates that of a sphere with 1.5x radius.

Conclusions:

• The derived formulas provide a valuable tool for numerical calculations of dynamic electrophoretic mobility.
• The kappa*a dependence in tangential fields highlights dynamic effects in cylindrical colloids.
• Randomly oriented cylindrical particle mobility can be approximated by a larger spherical particle.