Electrostatic attraction between overall neutral surfaces

Ram M. Adar, David Andelman, and Haim Diamant
Phys. Rev. E 94, 022803 – Published 24 August 2016

Abstract

Two overall neutral surfaces with positively and negatively charged domains (“patches”) have been shown in recent experiments to exhibit long-range attraction when immersed in an ionic solution. Motivated by the experiments, we calculate analytically the osmotic pressure between such surfaces within the Poisson-Boltzmann framework, using a variational principle for the surface-averaged free energy. The electrostatic potential, calculated beyond the linear Debye-Hückel theory, yields an overall attraction at large intersurface separations, over a wide range of the system's controlled length scales. In particular, the attraction is stronger and occurs at smaller separations for surface patches of larger size and charge density. In this large patch limit, we find that the attraction-repulsion crossover separation is inversely proportional to the square of the patch-charge density and to the Debye screening length.

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  • Received 6 April 2016

DOI:https://doi.org/10.1103/PhysRevE.94.022803

©2016 American Physical Society

Physics Subject Headings (PhySH)

Polymers & Soft Matter

Authors & Affiliations

Ram M. Adar and David Andelman*

  • Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel

Haim Diamant

  • Raymond and Beverly Sackler School of Chemistry, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel

  • *andelman@post.tau.ac.il

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Issue

Vol. 94, Iss. 2 — August 2016

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