Construction of cholesteric liquid crystal microlens array at air/CLC/air and water/CLC/air interfaces

Abstract

This study addressed the limitations of cholesteric liquid crystal (CLC) based microlens arrays, which required submersion of the CLC in water for their formation. We successfully constructed microlens arrays at both the air/CLC/air and water/CLC/air interfaces by doping E7, a nematic host, with a strong chiral dopant, (S)− 1-Phenylethane-1, 2-diyl bis(4-(trans-4-pentyl cyclohexyl) benzoate) (S1011) at different concentrations (0.3, 0.5, and 1 wt%). By spreading the mixture on transmission electron microscopy square-geometry grids, we observed that the lenses thickened at the water/CLC/air interface and thinned at the air/CLC/air interface with increasing dopant concentrations. A non-inverted image on the same side as the object was analyzed, created from the inverted virtual image of the object on the opposite side of the lens. The non-inverted image's focal length ranged from 6–6.24 mm for air/CLC/air and 4.8–3.6 mm for water/CLC/air, corresponding at 0.3, 0.5, and 1 wt% of S1011. Furthermore, the effect of interfacial tension on focal length was also observed by replacing water with sodium dodecyl sulfate (SDS) solution, and it was found that the focal length increased by 60 µm with increasing SDS from 0.1 to 1 mM. These findings suggest that the S1011 doped E7 microlens array can be easily constructed and potentially used in optical technologies.