Exact expressions for the mobility and electrophoretic mobility of a weakly charged sphere in a simple electrolyte
Abstract
We present (asymptotically) exact expressions for the mobility and electrophoretic mobility of a weakly charged spherical particle in a 1 : 1 electrolyte solution. This is done by analytically solving the electro and hydrodynamic equations governing the electric potential and fluid flow with respect to an electric field and a nonelectric force. The resulting formulae are cumbersome, but fully explicit and trivial for computation. In the case of a very small particle compared to the Debye screening length (R \ll r_D) our results reproduce proper limits of the classical Debye and Onsager theories, while in the case of a very large particle (R \gg r_D) we recover, both, the nonmonotonous charge dependence discovered by Levich (1958) as well as the scaling estimate given by Long, Viovy, and Ajdari (1996), while adding the previously unknown coefficients and corrections. The main applicability condition of our solution is charge smallness in the sense that screening remains linear.
 Publication:

EPL (Europhysics Letters)
 Pub Date:
 December 2013
 DOI:
 10.1209/02955075/104/68004
 arXiv:
 arXiv:1305.4060
 Bibcode:
 2013EL....10468004L
 Keywords:

 Condensed Matter  Soft Condensed Matter
 EPrint:
 6 pages, 1 figure