Tuning colloidal gel mechanics by active doping.

The mechanical behaviors of disordered colloidal gels are intimately connected with their complex energy landscape and inherent structures. By embedding a small fraction of active particles into the gel, we demonstrate the ability to quickly and precisely control the gel pore structure and mechanics. Using Brownian dynamics simulations, we show that varying the dynamical properties of the active particles can fine-tune the pore-size distribution and gel connectivity, as well as the mechanical response under external loading. More dramatic changes of the gel ductility and local crystalline order can be induced by a high-activity (swim speed) treatment for a finite time period. The non-equilibrium energy source from the active particles assists the gel in overcoming kinetic barriers without thermal annealing. Our results pave the way to design principles for adaptive colloidal gels.