Remarkably, the interfacial freezing also dramatically decreases the surface energy. Liquid droplet of oil in water, with tail-like protrusions emanating from two of its vertices. 1), with the 12 five-fold defects as vertices.įig. The droplet reduces the lattice stretching energy associated with these defects by distorting its shape into an icosahedron (Fig. To minimize the lattice distortion, the defects are maximally separated on the droplet’s surface. In the frozen monolayer at our droplet’s surface such pentagonal inclusions, called “five-fold defects”, stretch and distort the lattice.
#Droplet transition principle app full#
Put differently, hexagonal tiles can never fully cover a spherical surface: at least 12 pentagonal tiles are also required for full coverage, as demonstrated by a common soccer ball, where 12 pentagonal patches are required to complement the hexagonal ones. The latter introduces an important topological factor into the game: hexagonal packing is incompatible with a spherical surface. The former renders the surface-frozen layer’s elasticity dominate over the surface tension. The shape transition is driven by two effects: the reduction of the droplet’s surface tension to near-zero values by the interfacial freezing, and the interfacially-frozen monolayer’s hexagonal molecular packing. Amazingly, the elasticity of this one-molecule-thick crystalline monolayer, fully controls the shape of the liquid droplet, comprising ~10 15 identical molecules. For certain combinations of oil and surfactant molecules, a single layer of molecules residing at the surface of the oil droplets freezes forming a hexagonally-packed crystalline monolayer, only 2nm thick. These fascinating shape transitions are driven by a recently-discovered phenomenon, called “interfacial freezing”. 1), tetrahedra, and hexagrams, forms in a different temperature range, enabling mass-production of micron-sized faceted building blocks for future nanotechnology-based materials. Moreover, each of the different droplet shapes: icosahedra (Fig. This faceting of liquid droplets, never reported before, is temperature-controlled: the droplets turn faceted upon cooling, but regain a spherical shape upon re-heating. In an apparent contradiction with this general principle, we have recently demonstrated that liquid oil droplets, suspended in dilute water solutions of soap molecules (known as “surfactants”), spontaneously undergo a unique shape transition: the droplets adopt polyhedral shapes, while still remaining liquid. Liquid droplet of oil in water spontaneously adopting an icosahedral shape (optical microscopy image).
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