Figure 1.

Vesicle electrodeformation reveals differences in membrane viscosity. (A) A uniform electric field deforms a GUV into a prolate ellipsoid by pulling out area stored in suboptical thermally excited membrane undulations. Snapshots of the vesicle during the experiment. Imaging with phase contrast microscopy. Scale bar, 15 μm. (B) Prolate deformation of a POPC GUV in an electric field with amplitude E₀ = 10 kV/m and frequency of 1 kHz. Time zero in all graphs corresponds to turning the field on. The inset shows that repeated deformation does not alter the initial slope of the deformation curve. Because of the applied field forcing, deformation while the electric field is on is much faster than the relaxation driven by the membrane tension; the characteristic timescale of electrodeformation, $\eta /\epsilon E_0^2$, is much shorter than the relaxation timescale, ηR/σ. (C) Vesicles made of lipids (DOPC, POPC) and the diblock copolymer PBD₂₂PEO₁₄ deform at a different rate indicating different membrane viscosity. The field strength and frequency are 8 kV/m and 1 kHz. The solid lines correspond to the theoretical fit with Eq. 2. To see this figure in color, go online.