Eur. Phys. J. E (2006) 19: 5-15
https://doi.org/10.1140/epje/e2006-00002-y

Regular Articles

Screened electrostatics of charged particles on a water droplet

CPMOH, CNRS-Université Bordeaux 1, 351 cours de la Libération, 33405, Talence, France

^* e-mail: a.wuerger@cpmoh.u-bordeaux1.fr

Received: 30 August 2005
Published online: 17 January 2006

Abstract

We study the electrostatic properties of charged particles trapped at an interface in a water-in-oil microemulsion. The electrostatic potential and the counterion distribution in the water droplet are given in terms of the ratio of the Debye screening length κ^-1 and the droplet radius R. In the limit R→∞ we recover the well-known results for a flat interface. Finite-size corrections are obtained in terms of the small parameter 1/κR. Part of the counterions spread along the interface and form a charged layer of one Debye length thickness. In particular, there is a uniform surface charge contribution. We derive explicit expressions for the electric field, the mobile charge density, and the charge-induced pressure on the interface.