  Employing video microscopy, we explore the cage dynamics for colloidal
particles confined in quasi-two dimensions (q2D). Our experiments reveal that
while ensemble-averaged dynamics of cages are isotropic in the laboratory
frame, its evolution in the displacement frame of the caged particle is
anisotropic and asymmetric. In turn, this leads to particles in specific
regions of the cage contributing either to cage persistence or breaking,
influencing the structural relaxation of the fluid. Our findings, thus, provide
microscopic insights into cage evolution and dynamics for colloidal fluids in
q2D, with direct potential implications for the flow of complex fluids,
structural relaxation in dense suspensions, and collective motion in active
matter in confined geometries.
