www.electrophoresis-journal.com Page 1 Electrophoresis Received: 27/08/2019; Revised: 21/11/2019; Accepted:14/12/2019 This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/elps.201900318. This article is protected by copyright. All rights reserved. The Effect of Finite-Size of ions and Debye Layer Overspill on the Screened Coulomb Interactions Between Charged Flat Plates Arghyadeep Paul 1 , Siddhartha Mukherjee 2 , Jayabrata Dhar 3 , Sandip Ghosal 4 and Suman Chakraborty 1,2* 1 Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, India 2 Advanced Technology Development Center, Indian Institute of Technology Kharagpur, Kharagpur 721302, India 3 Universit´e de Rennes 1, CNRS, G´eosciences Rennes UMR6118 - Rennes, France 4 Department of Mechanical Engineering & Engineering Sciences and Applied Mathematics, Northwestern University, Evanston, Illinois 60208, USA * Corresponding Author: Prof. Suman Chakraborty, E-mail: suman@mech.iitkgp.ac.in; https://orcid.org/0000-0002-5454-9766 KEYWORDS: EDL overspill, modified Poisson-Boltzmann equation, repulsion pressure, steric effect of ions. ABBREVIATIONS: DH: Debye-Hückel, DLVO: Derjaguin-Landau-Verwey-Overbeek, EDL: Electric Double Layer, mPB: modified Poisson-Boltzmann, PB: Poisson-Boltzmann. ABSTRACT: Screened repulsion between uniformly charged plates with an intervening electrolyte is analyzed for strongly overlapped electrical double layers (EDL), accounting for the steric effect of ions and their expulsion from EDL edges into the surrounding solution. As a generalization of a study by Philipse et. al. which does not account for these effects, an analytical expression is derived for the repulsion pressure in the limit of infinitely long plates with a zero-field assumption, which agrees closely with the corresponding numerical solution