Electrical conductance across self-assembled lipid bilayers
This study investigates electrical conduction across lipid bilayers that self-assemble in oil between a water drop and a hafnium oxide surface. Morphology and electrical properties of two bilayers formed from equal molar concentrations of sorbitan monooleate (Span 80) and sorbitan trioleate (Span 85) in dodecane are quantified and compared. The molecular structures of the two surfactants are quite similar, except that sorbitan monooleate contains one unsaturated lipid tail per molecule, whereas sorbitan trioleate contains three. We find that the leakage current density across both bilayers increases exponentially with electric field. The relative leakage current densities across the two bilayers scale with the packing density of lipid tails in the bilayers. This correlation provides evidence that the lipid tail interactions through thermal fluctuations provide a pathway of electrical conduction across the membrane.