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Myelin Figures-- the Instability of Soap

myelins.jpgMyelin figures are long thin cylindrical structures that grow when water is added to the concentrated lamellar phase of certain surfactants such as soap. The Sidney Nagel and Tom Witten groups at the University of Chicago developed a method to produce isolated myelin figures, based on previous investigations of ring stain formation pioneered at the MRSEC. This allowed them to study their growth and stability in detail.

They discovered that myelin figures grow at exposed edges of bilayer stacks of the concentrated surfactant and require the presence of a driving stress to form and grow; when this stress is removed, myelins retract. [1,2]

[1] "Stability and Control of Single Myelin Figures," Ling-Nan Zou and Sidney R. Nagel, Phys. Rev. Lett., 96, 13801 (2006).

[2] "Theory of Myelin Coiling," Jung-ren Huang, Eur. Phys. J. E, 19, 4, 399-412 (2006).