PARTICLES IN LCs

Drag On Particles In A Nematic Suspension By A Moving Nematic-Isotropic Interface

We demonstrated moving colloidal particles by a moving nematic-isotropic interface.

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We have also determined the factors such as particle size, anchoring energy and speed of moving front, that control the particle movement. By controlling these factors we can control the morphology of the colloid and its physical properties (See figures below). Such control is necessary to develop and optimize these colloids for specific applications.

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Suspension Of Alkali Halide Particles In Nematic Liquid Crystal

We propose a new composite system consisting of micro-crystals of alkali halides dispersed in nematic LC. We studied NaCl-particles dispersed in pentyl-cyanobiphenyl. The doping of the LC with NaCl-particles does not change the macroscopic properties of LC. Strong interaction between LC molecules and the surface of the micro-crystals results in a strong light scattering by the suspension. Application of an electric field switches the material to a light transparent state due to director reorientation and matching of the refractive indexes of the LC domains and micro-crystals. The initial state recovers very quickly (< 1 ms) on removing the field. We consider alkali halide suspensions very promising for IR applications since they are highly transparent in this spectral region.

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Magnetically-Induced Alignment Of Ferro-Nematic Suspension

In this work we report the observation of magnetically controlled LC anchoring of ferro-nematic suspension. We found that application of a weak magnetic field to the cell with the ferro-suspension induces an easy orientation axis with a weak anchoring energy on glass surface. Varying the direction of the magnetic field can change the easy axis orientation. We believe that the magnetically-induced alignment of the ferro-LC suspension is caused by adsorption of the ferro-particles on the test surface and their manipulation with magnetic fields. The developed system is very promising for ultra-sensitive magnetically controlled LC devices for information processing and storage.

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