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Hydrodynamic simulations of charge-regulation effects in colloidal suspensions

Abstract

Self-organization of charged soft matter is of crucial importance in biology. However, it is an extremely complex phenomenon due to dynamical couplings between hydrodynamic flow, ions, and charges of soft matter. For colloidal suspensions, the coupling between the former two has already been studied by numerical simulations while the colloid surface charge being fixed. However, the self-organization of colloids and/or the application of an external electric field make the electrostatic environment of each colloid inhomogeneous in both space and time. Thus, this leads to inhomogenisation of the surface charge of each colloid under the ionisation equilibrium condition. This effect is known as ``charge regulation'' and of great importance in various electrostatic and electrokinetics phenomena in not only in colloid suspensions but also in solutions of biomolecules. However, there have so far been no success in taking the charge regulation effect into account in numerical simulations of colloidal electrokinetics. Here we extend the fluid particle dynamics (FPD) method to incorporate the charge regulation effect. We present a theoretical formulation of the method and its application to two types of problems, where charge regulation plays an important role: (i) cluster formation of colloid particles and (ii) a single colloid particle under an external field. By these examples, we show not only the importance of considering charge-regulation effects in self-organization of charged systems but also the applicability of our simulation method to more complex problems of charged soft matter systems.

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Publication details

The article was received on 20 Mar 2018, accepted on 09 May 2018 and first published on 11 May 2018


Article type: Paper
DOI: 10.1039/C8SM00579F
Citation: Soft Matter, 2018, Accepted Manuscript
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    Hydrodynamic simulations of charge-regulation effects in colloidal suspensions

    K. Takae and H. Tanaka, Soft Matter, 2018, Accepted Manuscript , DOI: 10.1039/C8SM00579F

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