Finite particle size drives defect-mediated domain structures in strongly confined colloidal liquid crystals

When liquid crystals are confined to finite volumes, the competition between the surface
anchoring imposed by the boundaries and the intrinsic orientational symmetry-breaking of
these materials gives rise to a host of intriguing phenomena involving topological defect
structures. For synthetic molecular mesogens, like the ones used in liquid-crystal displays,
these defect structures are independent of the size of the molecules and well described by
continuum theories. In contrast, colloidal systems such as carbon nanotubes and biopolymers
have micron-sized lengths, so continuum descriptions are expected to break down under
strong confinement conditions. Here, we show, by a combination of computer simulations
and experiments with virus particles in tailor-made disk- and annulus-shaped microchambers,
that strong confinement of colloidal liquid crystals leads to novel defect-stabilized symme-
trical domain structures. These finite-size effects point to a potential for designing optically
active microstructures, exploiting the as yet unexplored regime of highly confined liquid
crystals.