Self Organization of Binary Colloidal Mixtures via Diffusiophoresis

Abstract

Catalytic activity of the colloids and chemotactic response to gradients of the chemicals in the solution leads to effective interaction between catalytic colloids. In this paper, we simulate mixtures of active and passive colloids via a Brownian dynamics algorithm. These particles interact via phoretic interactions, which are determined by two independent parameters, surface activity and surface mobility. We find rich dynamic structures by tuning passive colloids’ surface mobility, size, and area fractions, which include schools of active colloids with exclusion zone, yolk/shell cluster, and stable active–passive alloys to motile clusters. Dynamical cluster can also be formed due to the nonreciprocity of the phoretic interaction. Increasing the size ratio of passive colloids to active colloids favors the phase separation of active and passive colloids, resulting in yolk/shell structure. Increasing the area fraction of active colloids tends to transfer from dynamical clusters into stable alloys. The simulated binary active colloid systems exhibit intriguing nonequilibrium phenomena that mimic the dynamic organizations of active/passive systems.

Estimating the velocity of chemically-driven Janus colloids considering the anisotropic concentration field

“…Although non-spherical shapes can be found in a variety of experimental systems (Brooks et al (2019); Baker et al (2019); Gibbs (2020); Sun et al (2020); Shah et al (2020); Zhu et al (2021); Sun et al (2022)), the spherical approximation based on the Legendre expansion method is still widely applied in theoretical studies (Golestanian et al (2007); Bianchi et al (2013); Papavassiliou and Alexander (2017); Campbell et al (2019);De Corato et al (2020)) due to the lower computational cost compared to resolving the shape using techniques such as the finite element method (FEM) (Lyu et al (2021); Zhou et al (2021)) or the boundary-element method (Varma et al (2018); Baker et al (2019)). Far-field approximation is also employed to further improve calculation efficiency, especially when adapting to simulate a large number of colloids (Soto and Golestanian (2014); Lei et al (2022)). However, the quantitative validation, even for the nearlyspherical colloids, is still lacking.…”