Nematic-liquid-crystal-air interface in a radial Hele-Shaw cell: electric field effects

The influence of an external electric field (applied to the nematic liquid crystal layer) on the morphology of the nematic-liquid-crystal-air interface has been studied experimentally in radial Hele-Shaw geometry. The effective viscosity mu(eff) of the nematic has been tuned by the electric field E and by the flow. At low excess pressure p(e) (where the growth of the interface is controlled mainly by the surface tension sigma), the applied E has no significant influence on the morphology of the interface, but decreases its normal velocity due to the increase of mu(eff). At higher p(e) (where the growth is not only controlled by sigma, but also by the kinetic term that depends on the effective viscosity) a significant difference in the morphology has been observed as a function of E. Experiments have shown that the influence of the electric field on the pattern morphology increases with the driving force (pressure gradient).