Work performed during the project TCDL is concerned with the development of an underlying theory to describe ionic charges (salt) around complex-shaped topological charged particles and/or in nematic liquid crystals. The main results include the calculation of charge distributions around complex-shaped particles and liquid crystal topological defects (as found in, for example, liquid crystal displays, LCDs). But also, we highlighted the influence of external liquid flow. These theoretical findings are expected to lead to new, exciting experiments. More precisely, we made the following discoveries:
We showed how ions distributions can be tuned when coupled to the underlying particle shape topology and geometry, altering their interaction and perhaps also transport properties (see accompanying figure below).
[see: J. C. Everts and M. Ravnik, Complex electric double layers in charged topological colloids, Sci. Rep. 8, 14119 (2018)].
Ion distributions in a nematic host can significantly alter the surface align of liquid-crystalline molecules along an external wall, which might be useful to tune particle self-assembly.
[see: J. C. Everts and M. Ravnik, Charge-, salt- and flexoelectricity-driven anchoring control in nematics, submitted. Preprint at: arXiv:2003.02914 (2020)].
External flow can induce an inhomogenous surface charge distribution in a flat plate, leading to possible new microfluidic applications.
[see B. L. Werkhoven, J. C. Everts, S. Samin, and R. van Roij, Flow-induced surface charge heterogeneity in electrokinetics due to Stern-layer conductance coupled to reaction kinetics, Phys. Rev. Lett. 120, 264502 (2018)].
Charged colloidal spheres in a nematic electrolyte interact with each other not only with an anisotropic elastic interaction, but the dielectric anisotropy also makes the screened electrostatic interaction anisotropic even for isotropic particle shapes.
[see: J. C. Everts, B. Senyuk, H. Mundoor, M. Ravnik, I. I. Smalyukh, Anisotropic electrostatic and elastic interactions in charged colloid spheres (working title), in preparation]
Ions in nematic hosts can be captured by topological defects due to selective solvation, whereas flexoelectricity can lead to ionic charge separation around the defect core.
[see: J. C. Everts and M. Ravnik, Ionically-charged topological defects in nematic fluids (working title), in preparation].
Using the geometry of the double layer, one can map any charged particle to a singular charge distribution, making it possible for an analytical formulation of the electrostatic potential and effective pair interaction for a wide range of complex-shaped particles
[see: J. C. Everts, Effective charge models for screened electrostatic interactions (working title), in preparation].
Topological defects can be used to manipulate surface charge distributions on charge-regulating or conducting flat plates,
[see: M. Ravnik and J. C. Everts, Topological-defect induced surface-charge heterogeneities in nematic electrolytes, submitted].
