Self-shaping liquid crystal droplets by balancing bulk elasticity and interfacial tension

Significance Liquid crystal (LC) research is rapidly expanding to include studies of curved and topologically non-trivial structures, exploring the interplay between elasticity and topology. Here, we explore the role of the bulk LC elasticity and interfacial energy as variable parameters under weak thermal stimuli to achieve structural transformations in LC emulsions using two different surfactants: one in the dispersed and the other in the continuous-aqueous phase. Our method is universal and could be used for any LC material or phase. A theoretical model for transforming LC emulsions into uniform fibers and vice versa is presented. We also show the self-shaping of smectic vesicle structures and monodispersed droplet formation at the nematic-smectic transition, utilizing the LC bulk elasticity. This work opens a new area in LC research, where a controllable shape transformation for a constant volume of different LCs and other soft materials could be used to obtain complex curved structures. Abstract The shape diversity and controlled reconfigurability of closed surfaces and filamentous structures, universally found in cellular colonies and living tissues, are challenging to reproduce. Here, we demonstrate a novel method for the self-shaping of liquid-crystal (LC) droplets into anisotropic and 3D superstructures, such as LC fibers, LC helices, and differently shaped LC vesicles. The method is based on two surfactants: one dissolved in the LC dispersed phase, the other in the aqueous continuous phase. We use thermal stimuli to tune the bulk LC elasticity and interfacial energy, thereby transforming an emulsion of polydispersed, spherical nematic droplets into numerous, uniform-diameter fibers with multiple branches and vice versa. Furthermore, when the nematic LC is cooled to the smectic A LC phase, we produce monodispersed micro-droplets with a tunable diameter dictated by the cooling rate. Utilizing this temperature-controlled self-shaping of LCs, we demonstrate life-like smectic LC vesicle structures analogous to the bio-membranes in living systems. Our experimental findings are supported by a theoretical model of equilibrium interface shapes. The shape transformation is induced by negative interfacial energy, which promotes a spontaneous increase of the interfacial area at a fixed LC volume. The method was successfully applied to many different LC materials and phases, demonstrating a universal mechanism for shape transformation in complex fluids.Corresponding author: Venkata. S. R. Jampani (softmatter@vsrjampani.com