Electric-field-induced domain movement in phospholipid monolayers

The motion of gel phase domains in inhomogeneous electric fields is observed by fluorescence microscopy with lipid monolayers at the air-water interface. Quantitative data analysis yields detailed information on the field geometry and the magnitude of the resulting forces. This knowledge then serves to derive information on monolayer dynamics, in particular on the surface viscosity η. The latter is measured as η = 0.015 P for the fluid phase of dipalmitoyl phosphatidyl choline, in order-of-magnitude agreement with published values on similar systems. Hence a technique is introduced to measure monolayer viscosities directly and microscopically.