Rapid Formation of Supported Lipid Bilayers on Unfavorable Surfaces under AC-Electric Fields

Lipid vesicles and supported bilayers have been studied as model systems to understand the structures, transport and biological function of cell membranes. In this work, we investigate the AC-electric field induced instability and supported bilayer formation of lipid vesicles on unfavorable solid surfaces by fluorescence microscopy. We have designed a microchannel fluid cell with embedded asymmetric electrode surfaces to apply non-uniform AC-electric fields across lipid vesicle thin films and control the formation of supported lipid bilayers of mixed egg PC/1,2-dioleoyl-3-trimethylammonium-propane(DOTAP) on solid substrates. In the absence of applied AC-fields, we observe no formation of supported lipid bilayers of egg PC/DOTAP on a quartz surface coated with a monolayer of 11-Mercaptoundecanoic acid. In contrast, we observe the rapid spreading of egg PC/DOTAP lipids from the edge of the gold electrode to the thiol-treated quartz surface to form lipid bilayers of varied morphology under applied AC-fields of varied frequency from 1-100 kHz. A strong dependence of AC-field frequency and strength on the lipid spreading velocity and resulting morphology of lipid bilayers is quantified. The mechanism involving AC- induced counterion redistribution and lipid segregation is also experimentally explored.