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DY: Fachverband Dynamik und Statistische Physik

DY 43: Poster: Statistical Physics

DY 43.18: Poster

Mittwoch, 11. März 2026, 15:00–18:00, P5

Localized Driving of the Jamming Transition in a Quasi-2D Colloidal Platform — •Jordan D. Groh, Timo Betz, and Bart Vos — Drittes Physikalisches Institut, Göttingen, Deutschland

The jamming transition marks the abrupt emergence of rigidity when a dense assembly of particles is compressed beyond a critical packing fraction. Decades of experiments and simulations have identified its static signatures, a sharp rise of the shear modulus and contact-network percolation, for globally driven systems. What remains largely unexplored is how a jammed material reacts to localized perturbations and whether they can steer the system into new metastable states.

We therefore construct a reproducible quasi-2D colloidal chamber that confines a binary mixture of polyacrylamide hydrogel beads (elastic stress sensors) and polystyrene beads (optically addressable active centres). A small fraction of temperature-responsive pNIPAm beads allows us to tune the effective packing fraction; cooling below the LCST swells them, thereby raising the global packing fraction with high precision. High-speed confocal microscopy provides particle trajectories, from which we locate the jamming point and perform contact-network analysis.

The platform enables calibrated optical forces on single beads and local heating-induced volume changes, yielding full spatiotemporal maps of displacement and stress fields. This testbed will allow us to map a local-driving jamming phase diagram, study force-propagation lengths, and ultimately design amorphous metamaterials with programmable mechanical heterogeneity.

Keywords: Jamming