Mechanical and Rheological Properties of Lipid Bilayers

The physical properhes of hpid bilayers are those that define their response to external perturbations. Knowing the mechanical and rheological characteristics of hpid membranes will prepare us to tackle problems related to stress induced in bilayers by electric fields and the phenomena that it triggers, for example, dynamics of vesicle and cell deformahon, bilayer instability, electroporation, and electrofusion. 

As a simple depiction of a hpid bilayer, one can consider it as a film or a slab, which may be curved, compressed or dilated, and sheared. At physiological temperatures most natural hpid membranes are fluid. Therefore, within this slab, the hpid molecules are free to move. Below the hpid phase transition temperature, single-component membranes crystalhze. In this so called gel phase, the relative mohon of hpids and membrane inclusions is principally hindered. The fluidity of the membrane and resistance to shear in the plane of the film are characterized by the shear viscosity, % (or the diffusion coefficient of the hpids). Typical values 

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