Active doping controls the mode of failure in dense colloidal gels

Area of Science:

• Soft Matter Physics
• Materials Science
• Statistical Mechanics

Background:

• Mechanical properties of disordered materials depend on their free energy landscape.
• Active particles introduce nonequilibrium internal fields, influencing material behavior.

Purpose of the Study:

• Investigate how active particle activity modifies the mechanical response of colloidal gels.
• Determine the role of active particle "swim force" in mechanical failure modes.

Main Methods:

• Computer simulations of deeply annealed polydisperse colloidal gels.
• Analysis of mechanical properties, gel porosity, and structural disorder.

Main Results:

• A critical swim force was identified, causing an abrupt decrease in mechanical properties.
• Below critical force: enhanced ductility via increased structural disorder.
• Above critical force: heterogeneous structure, dynamical heterogeneities control response.

Conclusions:

• Active particle swim force dictates brittle vs. ductile failure in colloidal gels.
• Modulation of gel porosity and inter-particle forces alters mechanical response.
• Complex interplay between gel energy landscape and embedded activity observed.