  We show that geometric confinement dramatically affects the shear-induced
configurations of dense mono-disperse colloidal suspensions; a new structure
emerges, where layers of particles buckle to stack in a more efficient packing.
The volume fraction in the shear zone is controlled by a balance between the
viscous stresses and the osmotic pressure of a contacting reservoir of
unsheared particles. We present a model that accounts for our observations and
helps elucidate the complex interplay between particle packing and shear stress
for confined suspensions.
