Smart shell membrane prepared by microfluidics with reactive nematic liquid crystal mixture

Smart, uniform-sized, solid-state nematic liquid crystal (NLC) (NLC_solid) shell membranes were successfully fabricated from a reactive mesogen mixture (RMM727) and 4-cyano-4′-pentylbiphenyl (5CB) using a microfluidic method that combines flow-focusing and co-flow glass capillary geometries after UV curing and 5CB extraction. The NLC shells having planar anchoring with poly(vinyl alcohol) (NLC_p shells) showed unavoidable defects as per the Poincaré theorem, with a total of +2 defect strengths on the top of the shell (often the weakest point of the shell), and were usually ripped during UV curing. The NLC shells having homeotropic anchoring with sodium dodecyl sulfate/polysorbate 80 (1/1, w/w) (NLC_h shells) had a defect-free structure and could be formed into NLC_solid shells without ripping when the density of the RMM727/5CB mixture matched that of the aqueous medium in the microfluidic channel (controlled using a glycerol/water mixture). The thin part of the NLC_h shell was easily ripped during UV curing without density matching. The thus-produced NLC_solid shells exhibited good swelling/shrinkage properties depending on the solvent quality and temperature, which could be further utilized for encapsulating/releasing Rhodamine 6G in/from the core of the NLC_solid shell. The pores in the NLC_solid shell (the size of which was controlled by the 5CB content of the RMM727/5CB mixture) were completely closed in a poor solvent and open in a good solvent. The encapsulation/release properties were studied based on the fluorescence intensity of encapsulated Rhodamine 6G. This study provides a method for preparing uniform-sized and robust NLC_solid shell membranes that can be used for several applications, such as in smart actuators, sensors, and parts of microelectromechanical systems.