Lamella

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Diagram of lamellar layers.
At high concentration, surfactants can form lamellar layers.
Image of droplets forming at water-oil interface.
Edge of a water drop that has been placed in dodecane containing 0.25 mg/mL POPC. Here one can see a droplet with a multilamellar interface forming at the surface between dodecane and water.

A lamella is a two-dimensional structure typically formed by surfactants or micelles in high concentration. When micelles align in parallel layers in order to minimize free energy, these layers are called lamellae and they typically have fluid in between them. Lamellae more generally refer to fine sheets of material parallel to each other with liquid between them. Because they are an arrangement of liquid particles with a high degree of order but not rigid alignment, lamellae are a type of liquid crystal.

Other geometries

Pautot et al and other researchers recently investigated the spontaneous formation of lipid structures at oil/water/lipid interfaces. When they placed droplets of water in dodecane prepared with phospholipid surfactant, they observed the formation of onion-like structures consisting of multiple lamellar layers. This was not the first time that this "onion" lamellar structure was observed, but it was the first time it was found that it could form from water in oil, rather than from oil in water.

They concluded that lipid concentration in dodecane and temperature had the greatest effects on whether and how the spherical multilamellar structures formed. Using coherent anti-Stokes Raman scattering (CARS) microscopy, they demonstrated that the shell of the structure consisted of partially hydrated concentric bilayers, while lipids, water, and dodecane comprised the core.