This talk was part of the Thematic Programme on "Non-equilibrium Processes in Physics and Biology" held at the ESI August 19 -- October 11, 2024.

Soft glassy materials formed by suspensions of charged vesicles in salty water are widespread in nature and industrial production. Those suspensions, in fact, can form Wigner glasses at progressively smaller vesicle volume fraction as the strength and range of the electrostatic repulsion increase (by decreasing the salt concentration) [1]. Amorphous solids can alternatively be obtained by adding polymers to promote depletion interaction and gel formation.

In this talk, I will discuss yielding and rheology of one such system by means of experimental and numerical results, including flow curves, oscillatory shear analysis (amplitude and frequency sweeps) and creep tests [2]. Our Brownian dynamics simulations (inspired by a recent work [3]) properly reproduces experimental data and can thus be exploited to understand the macroscopic rheology on a microstructural ground.

If time permits, I will also show some ongoing analysis on aging and dynamics of the investigated system, including DDM analysis [4].

Overall, our study may help understanding soft glassy materials with competing attractive and repulsive interactions.

References
G. Porpora, F. Rusciano, V. Guida, F. Greco, and R. Pastore, “Understanding charged vesicle suspensions as Wigner glasses: Dynamical aspects,” J. Phys.: Condens. Matter 33, 104001 (2020).
N. Kolezakis, R. Pastore, F. Rusciano, G. D’Avino, P. L. Maffettone, V. Guida, in preparation.
R.N. Zia, B.J. Landrum, and W.B. Russel, “A micro-mechanical study of coarsening and rheology of colloidal gels: Cage building, cage hopping, and Smoluchowski’s ratchet”, Journal of Rheology 58, 1121 (2014).
R. Cerbino and V. Trappe, “Differential dynamic microscopy: Probing wave vector dependent dynamics with a microscope,” Phys. Rev. Lett. 100, 188102 (2008).