Weak Anchoring and Surface Elasticity Effects in Electroosmotic Flow of Nematic Liquid Crystals Through Narrow Confinements

摘要

Advent of nematic liquid crystals flows have attracted renewed attention inview of microfluidic transport phenomena. Among various transport processes,electroosmosis stands as one of the efficient flow actuation method throughnarrow confinement. In the present study, we explore the electrically actuatedflow of a nematic fluid with ionic inclusions taking into account theinfluences from surface induced elastic and electrical double layer phenomena.Influence of surface effects on the flow characteristics is known to getaugmented in micro-confined environment and must be properly addressed. Towardsthis, we devise the coupled flow governing equations from fundamental freeenergy analysis considering the contributions from first and second-orderelastic, dielectric, flexoelectric, ionic and entropic energies. We havefurther considered weak anchoring surface conditions with second orderelasticity which helps us to more accurately capture the director deformationsalong the boundaries. The present study focuses on the influence of surfacecharge and elasticity effects in the resulting linear electroosmosis through aslit-type microchannel whose surface are considered to be chemically treated inorder to display a homeotropic-type weak anchoring state. An optical periodicstripe configuration of the nematic director has been observed especially forhigher electric fields wherein the Ericksen number for the dynamic study isrestricted to the order of unity.