Rod-like colloids in external electric fields

Electric fields can induce interactions between charged colloids that lead to the formation of new phases and dynamical states. In this presentation, the phase/state behavior of very long and thin, highly charged rod-like colloids (fd-virus particles) under oscillating external electric fields is discussed. Fd-virus suspensions exhibit an isotropic-nematic phase transition. For concentrations of fd-virus particles within the two-phase isotropic-nematic coexistence region, various field-induced phase transitions and dynamical states are observed, depending on the field-amplitude and frequency. A non-chiral nematic, a chiral nematic, a homeotropically aligned homogeneous phase, and a dynamical state where non-chiral nematic domains persistently melt and form are observed. The molecular origin of the various phases is discussed, and a semi-quantitative theory is presented for the dynamical state