Tuning the rheology and microstructure of colloidal gels via electric field*

Colloidal gels are complex soft materials characterized by a disordered network of short-range attractive particles suspended in a fluid. Owing to their widespread applications in industry and nature, the ability to effectively control their properties is crucial. In this study, we use large-scale Stokesian dynamics simulations to investigate the impacts of an electric field on colloidal gels. Similar to electrorheological (ER) fluids, the application of an electric field causes dipolar interactions, resulting in the formation of chain-like structures along the field direction. As opposed to repulsive suspensions, where viscosity increases with the field magnitude (positive ER effect), the viscosity of colloidal gels can be reduced by increasing the field magnitude (negative ER effect) depending on the ratio of electric and attractive forces. Furthermore, we observe the emergence of cluster rotations due to the competition between dipolar and attractive interactions, which also contributes to the decrease in viscosity. A detailed analysis on microstructure will be given to elucidate the viscosity decrease. In addition, the recovery process after the electric field is off will be explored.