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. 2011 May 17;2:312. doi: 10.1038/ncomms1321

Figure 2. History-dependent linear viscoelasticity.

Figure 2

(a) Linear viscoelasticity of as-prepared liquid-condensed dipalmitoylphosphatidylcholine (LC-DPPC) monolayers at air/water interfaces (Π=9±1 mN m−1). Surface shear moduli indicate a dominant low-frequency elastic response, G′s(ω)>G′′s(ω) down to 0.1 Hz, crossing over to a primarily viscous response, G′′s(ω)>G′s(ω) above 5 Hz. (b) Direct visualization of the DPPC monolayer reveals the elastic response to result from a network of interlocked LC domains that cannot deform without deforming neighbouring domains. (c) After forcing a large-amplitude microbutton rotation, LC-DPPC appears viscous G′′s(ω)>G′s(ω) at all frequencies. (d) Visualization reveals the creation of a 'slip line' (white arrow) within the monolayer, which enables non-cooperative deformation under shear (scale bar, 20 μm).