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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.
