Klaseboer Evert, Chan Derek Y C
Institute of High Performance Computing, 1 Fusionopolis Way, Singapore 138632, Singapore.
School of Mathematics and Statistics, University of Melbourne, Parkville, VIC 3010 Australia; Department of Mathematics, Swinburne University of Technology, Hawthorn, VIC 3121 Australia.
J Colloid Interface Sci. 2020 May 15;568:176-184. doi: 10.1016/j.jcis.2020.02.032. Epub 2020 Feb 14.
One of the most enduring, broadly applicable and widely used theoretical results of electrokinetic theory is the Smoluchowski expression for the electrophoretic mobility. It is a limiting form that holds for any solid particle of arbitrary shape in an electrolyte of any composition provided the thickness of the electrical double layer is "infinitely" thin compared to the particle size and the particle has uniform surface potential. The familiar derivation of this result that is a simplified version of the original Smoluchowski analysis in 1903, considers the motion of the electrolyte adjacent to a planar surface. The theory is deceptively simple but as a result much of the interesting physics and characteristic hydrodynamic behavior around the particle have been obscured, leading to a significantly incorrect picture of the fluid velocity profile near the particle surface. This paper provides a derivation of this key theoretical result by starting from Smoluchowski's original 1903 analysis but brings out overlooked details of the hydrodynamic features near and far from the particle that have not been canvassed in detail. The objective is to draw together all the key physical features of the electrophoretic problem in the thin double layer regime to provide an accessible and complete exposition of this important result in colloid science.
