Design of a lipid bilayer electrical device. Strong chemical structure dependence and molecular mechanisms on the phase transition-dependent electrical impedance responses of the device in air

This paper describes the design and fabrication of a lipid film-modified electrical device and the relation between the chemical structure of the lipids and the impedance responses of the device in air. Eight different synthetic poly(ion-complexed) lipids including quaternary ammonium lipids, glutamic acid (Glu)-based lipids with a short or a long methylene spacer chain, and diethanolamine-based quaternary ammonium lipids with a long or a short spacer chain were synthesized. Transparent multibilayer films with crystalline-to-liquid crystalline phase transition were formed, and impedance responses for interdigitated array electrodes coated with cast films of these lipids were examined. Complex plane plot analyses together with quartz crystal microbalance and FTIR experiments have revealed molecular mechanisms for the unique impedance responses which could be classified as the following three types. Type I is the phase transition-dependent impedance responses, where the impedance changes dramatically near t...