Granular and Colloids Lab

Amorphous materials like foams, emulsions, colloidal suspensions, metallic glass and granular media can jam into a rigid, disordered state with finite yield stress. Rigidity transition of different amorphous materials is qualitatively understood in terms of a universal jamming picture. Jamming transition i.e. transition from the freely flowing state to the jammed state can easily be made by tuning various control parameters like temperature, density and stress applied to the sample.

Examples include the transition of a colloidal dispersion to colloidal glasses with increase in density, flowing foams become static when shear stress is decreased below the yield stress, and super-cooled liquids forming glasses when the temperature is reduced below the glass transition temperature (See below Figures). The jamming transition has apparently no structural signature i.e. the structure remains the same in the jammed state as was before in the unjammed state. One of the most challenging tasks is to provide better understanding of the onset of the jamming transition in soft amorphous materials. We employ simulations, theory as well as experiments to unravel the physics of these soft materials. The overall goal of the research is to search for the universality across diverse non-equilibrium materials and formulate an equation of state if possible.