Microscopic characterisation of self-assembled colloidal particles in electrohydrodynamic convection of a low-birefringence nematic liquid crystal

ABSTRACT

Electrokinetics of small particles immersed in anisotropic fluids is attracting attention in recent years. Here we focus on microscopic appearance of single as well as self-assembled particles moving in the electrohydrodynamic convection (EHC) of a nematic liquid crystal with low birefringence. Characterisation of the birefringent properties is made by polarised light microscopy under different illumination conditions. Because of the small optical anisotropy, the director distortion around the particles clearly exhibits distinctive colours on both sides depending on the height in the cell. The observation can be explained as the change in the net phase retardation of the light. It is also found that a caterpillar-like motion is possible by tuning temperature, although the horizontal size of the EHC rolls is relatively narrow.

GRAPHICAL ABSTRACT

KEYWORDS:

• Nematic liquid crystals
• electrohydrodynamic convection
• liquid-crystal colloids
• electrokinetics

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplemental data

Supplemental data for this article can be accessed here. Movie 1 (0.1 × speed) shows an elastic dipole moving in EHC under cross-polarised condition with the insertion of a λ-plate. Movie 2 (1x speed) shows a chain in EHC under plane polarised condition.

Additional information

Funding

This work was partly supported by a Grant-in-Aid for Scientific Research on Innovative Areas ‘Fluctuation and Structure’ [grant number 25103006] from the Ministry of Education, Culture, Sports, Science, and Technology of Japan.