Optical Control Of Mass Ejection From Ferroelectric Liquid Droplets: A Possible Tool For The Actuation Of Complex Fluids

We report on the optical control of the recently observed electromechanical instability of ferroelectric liquid droplets exposed to the photovoltaic field of a lithium niobate ferroelectric crystal substrate. The ferroelectric liquid is a nematic liquid crystal in which almost complete polar ordering of the molecular dipoles generates an internal macroscopic polarization locally collinear to the mean molecular long axis. Upon entering the ferroelectric phase, droplets irradiated by unfocused beam undergo an electromechanical instability and disintegrate by the explosive emission of fluid jets. We show here that the regions of jets emission can be controlled by focusing the light beam in areas close to the droplet's edge. Once emitted, the fluid jets can be walked by moving the beam up to millimeter distance from the mother droplet. Reverting the lithium niobate substrate, jets become thinner and show the tendency of being repelled by the beam instead of being attracted, thus offering an additional tool for their optical manipulation. These observations may pave the way to intriguing applications of ferroelectric nematic fluids related to manipulation, actuation, and control of soft, flexible materials.Comment: 11 pages, 5 figure

Elasticity and Viscosity of DNA Liquid Crystals

Concentrated solutions of blunt-ended DNA oligomer duplexes self-assemble in living polymers and order into lyotropic nematic liquid crystal phase. Using the optical torque provided by three distinct illumination geometries, we induce independent splay, twist, and bend deformations of the DNA nematic and measure the corresponding elastic coefficient

Colossal optical nonlinearity in dye-doped liquid crystals

We report the experimental evidence of a nonlinear optical response among the highest ever observed. A nonlinear refractive index on the order of 103 cm2/W (that is 108 times higher than in Giant Optical Nonlinearity) has been obtained in randomly oriented thin liquid crystal cells. This result shows the fundamental role played by the surface in the nonlinear optical response of dye-doped liquid crystals

Enhanced optoelastic interaction range in liquid crystals with negative dielectric anisotropy

International audienceWe demonstrate that the long-range interaction between surface-functionalized microparticles immersed a nematic liquid crystal--a "nematic colloid"--and a laser-induced "ghost colloid" can be enhanced by a low-voltage quasistatic electric field when the nematic mesophase has a negative dielectric anisotropy. The optoelastic trapping distance is shown to be enhanced by a factor up to 2.5 in presence of an electric field. Experimental data are quantitatively described with a theoretical model accounting for the spatial overlap between the orientational distortions around the microparticle and those induced by the trapping light beam itself