Development of strong intermittency in densely packed soft particles under shearing

We study experimentally the dynamics of centimeter-sized fully-immersed PDMS particles that are densely packed and are subject to smooth constant-speed shearing. In addition to previously reported internal imaging, we further characterize the development of intermittency by measuring the fluctuations of boundary force simultaneously. Fluctuation measurements allow us to identify the development of intermittency (with driving rates) and the role of interparticle frictions, which can otherwise be missed in the conventional time-averaged rheology. By varying the compostion of particles, we also vary their elasticity and find a non-trivial dependence of intermittency, suggesting a rich dynamics behind these soft contacts.