Electro-osmosis and flexo-electricity in the dowser texture

Area of Science:

• Liquid crystal physics
• Soft matter science
• Materials science

Background:

• The dowser texture, a pseudo-planar liquid crystal phase, possesses spontaneous flexoelectric polarization.
• This texture's degeneracy allows alignment via electric fields and fluid flows.
• Electro-osmotic flows can generate hydrodynamic torques comparable to electric torques.

Purpose of the Study:

• To investigate the influence of electro-osmotic flows on the alignment of the dowser texture.
• To analyze the impact of hydrodynamic torques on flexoelectric polarization measurements.
• To understand the interplay between electrical and fluidic forces in liquid crystal alignment.

Main Methods:

• Theoretical analysis of torques acting on the dowser texture.
• Experimental investigation using 5CB liquid crystal.
• Measurement of flexoelectric polarization under varying flow conditions.

Main Results:

• Flexoelectric polarization in the dowser texture is confirmed.
• Alignment of the dowser texture by electric fields and Poiseuille flows driven by electro-osmosis is demonstrated.
• Hydrodynamic torques from electro-osmotic flows are shown to be linear with the electric field, similar to electrical torques.
• Electro-osmotic flows were found to alter the measurement of flexoelectric polarization in 5CB.

Conclusions:

• Electro-osmotic flows present a significant factor that can affect the accurate measurement of flexoelectric polarization in liquid crystal systems like 5CB.
• The alignment mechanisms of the dowser texture are complex, involving both electrical and hydrodynamic contributions.
• Further research is needed to decouple these effects for precise material characterization.