Yielding Mechanisms in Dense Colloidal Suspensions: The Role of Interparticle Forces

Dense colloidal suspensions are essential to a wide range of scientific and industrial applications. Under external shear, these materials exhibit a solid-fluid yielding transition when applied stress and deformation surpass a critical threshold. This transition is often accompanied by structural reorganization, leading to complex rheological phenomena such as shear banding and resolidification. Understanding these behaviors is crucial for the design and optimization of advanced materials used in applications like coatings, additive manufacturing, and solid-state batteries.

In this work, we explore the influence of interparticle forces on the yielding behavior of dense colloidal suspensions through Fast Lubrication Dynamics (FLD) simulations. Our suspension model comprises spherical colloids with a narrow size distribution at a volume fraction of 48%. When the interparticle forces are repulsive, the suspension remains homogeneous and exhibits only Andrade creep. Conversely, attractive interparticle forces induce delayed yielding and resolidification. This shift in rheological behavior results from the arrested phase separation of colloids under attractive interactions. Under constant external shear stress, deformation localizes within the low-density interfacial regions between denser phases, leading to significant dynamical heterogeneity and interfacial instability, which drives the delayed yielding and resolidification. Our simulation results align well with Rheo-XPCS experiment observations, corroborating both the macroscopic rheological response and the two-time scattering intensity autocorrelation function, which characterizes the non-equilibrium microscopic dynamics. Verified by the experiments, our simulations provide a microscopic picture of the yielding mechanism in dense colloidal suspensions.