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 method for the self-shaping of liquid crystal (LC) droplets into anisotropic and three-dimensional 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 and 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 microdroplets 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 biomembranes 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.
Highlights
Interfacial tension plays a central role in the phase separation of binary mixtures into superstructures, such as droplet emulsions, filaments, and more complex objects
We show the self-shaping of smectic vesicle structures and monodispersed droplet formation at the nematic–smectic transition, utilizing the Liquid crystal (LC) bulk elasticity
We explore the interplay between the orientational elasticity of LCs and the surfactantaffected interfacial tension that leads to the shape transformation of a spherical LC droplet into single and branched fibers of uniform thickness
Summary
Interfacial tension plays a central role in the phase separation of binary mixtures into superstructures, such as droplet emulsions, filaments, and more complex objects. Spontaneous filament formation was reported in a number of partially ordered liquids, in binary mixtures of thermotropic LCs, which form the SmA phase while cooling from the isotropic phase or through the coexistence region of two phases [30,31,32,33,34]. In these cases, the volume of the filaments is not conserved, which contrasts with our experiments, in which the volume of the LC is conserved and only a shape transformation takes place. We show how different life-like vesicles are spontaneously self-shaped from a single droplet in the SmA* phase and the tranformation of nonchiral SmC droplet into a helical fiber
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