Complex electric double layers in charged topological colloids

TL;DR

This paper demonstrates that electric double layers with complex topologies such as tori and knots can be engineered around charged colloids, with their geometry and topology controllable via medium properties and particle shape, opening new avenues in material design.

Contribution

It introduces the concept of topologically complex electric double layers in charged colloids, using numerical modeling to explore their design and tunability.

Findings

Double layers with non-trivial topology can be realized around colloids.

The complexity of double layers can be tuned by medium screening length.

Topology influences the properties and potential applications of colloidal systems.

Abstract

Charged surfaces in contact with liquids containing ions are accompanied in equilibrium by an electric double layer consisting of a layer of electric charge on the surface that is screened by a diffuse ion cloud in the bulk fluid. This screening cloud determines not only the interactions between charged colloidal particles or polyelectrolytes and their self-assembly into ordered structures, but it is also pivotal in understanding energy storage devices, such as electrochemical cells and supercapacitors. However, little is known to what spatial complexity the electric double layers can be designed. Here, we show that electric double layers of non-trivial topology and geometry -including tori, multi-tori and knots- can be realised in charged topological colloidal particles, using numerical modelling within a mean-field Poisson-Boltzmann theory. We show that the complexity of double layers -including geometry and topology- can be tuned by changing the Debye screening length of the medium, or by changing the shape and topology of the (colloidal) particle. More generally, this work is an attempt to introduce concepts of topology in the field of charged colloids, which could lead to novel exciting material design paradigms.