Frustrating colloidal rods

The free diffusion of rod-like particles is strongly frustrated by the presence of other rods. This frustration underlies a plethora of phase transitions with increasing concentration of colloidal rods, going from a completely disordered phase (isotropic) to orientational ordering (nematic phase), and to 1-D (smectic phase) and 2-D (columnar phase) positional ordering. We will monitor the dynamic behaviour of the rods throughout this sequence of phase transitions on a single particle level, using fluorescence microscopy. We show how dynamics subtly depends on the specific features of the rods thus elucidating the nature of the complex phase behaviour. Rods can also be frustrated on a more coarse level, as we will see by confining the nematic phase in a range of different geometries. The competition between the elasticity of the nematic phase, wall anchoring and confinement leads to programmable director structures, from which information on the nematic phase can be obtained