(368d) Colloidal Depletion Gels, from Particle Bonds to Bulk Modulus

The rheology and stability of colloidal depletion gels affects the applications and shelf-life of materials and products ranging from paints, foods, and personal care products to pharmaceuticals and agrochemicals. Processes on multiple lengthscales contribute to the rheology of gels, including their elastic modulus and yield stress. These include the stretching and rupture of nanometer-scale colloidal interactions to the formation of micro-structures that percolate throughout the material. In this talk, I will discuss the direct measurement of the colloidal forces that constitute the rupturing of ”bonds" between particles in a gel. Thermal rupture force distributions are measured by averaging many approach and retraction bond rupturing cycles between pairs of particles. By connecting these bond-level mechanics to the bulk rheology to in a single model depletion gel material [1], we gain unique insight into the relationship between non-equilibrium gel states, the underlying phase behavior of colloidal suspensions, and the mesoscale mechanics that ultimately govern the elasticity of colloidal gels.

[1] Hsiao, L. C.; Solomon, M. J.; Whitaker, K. A.; Furst, E. M. A Model Colloidal Gel for Coordinated Measurements of Force, Structure, and Rheology. J. Rheology, 2014, 58, 1485–1504.