  We study the behaviour of confined cubic blue phases under shear flow via
lattice Boltzmann simulations. We focus on the two experimentally observed
phases, blue phase I and blue phase II. The disinclination network of blue
phase II continuously breaks and reforms under shear, leading to an oscillatory
stress response in time. The oscillations are only regular for very thin
samples. For thicker samples, the shear leads to a "stick-slip" motion of part
of the network along the vorticity direction. Blue phase I responds very
differently: its defect network undergoes seemingly chaotic rearrangements
under shear, irrespective of system size.
