Microstructure and rheology of Janus particle suspensions

Abstract

The aggregate sizes and morphologies formed with colloidal particles have important consequences on the rheological behavior of colloidal suspensions. Self- and directed-assembly are the most used phenomena to produce aggregates with controllable size and structure. On the other hand, the challenges focusing the actual technology requires better control and deep understanding of the aggregation phenomena at equilibrium and beyond it. Therefore, the design of colloidal particle interacting with anisotropic potentials—often known as Janus particles—arise as ideal candidates to advance in this direction. This dissertation sheds some light on the self- and directed-assembly of Janus particles suspensions with an introduction to the study of rheological properties of such systems through Brownian dynamics simulation. The colloidal particles are designed with amphiphilic, magnetic or catalytic Janus features subjected to a simple shear flow, a magnetic field, or to a single force (self-propulsion). Results show a richness structural behavior of Janus colloidal systems not observed with their isotropic counterparts. The different aggregate sizes and morphologies predicted as a function of interaction range, Janus patch size, interaction strength (i.e. Van Der Waals or magnetic interaction), shear rate, and self-propulsion strengths open new actuation routes for reconfigurable materials and applications.