Formation of suspended bilayer lipid membrane between electrowetting-driven encapsulated droplets

Using limited lipid molecules held by two water-core/oil-shell encapsulated droplets, we formed an optically observable bilayer lipid membrane (BLM) across a microfabricated aperture whose dimension was precisely determined and easily scalable. For the minute volume of a 0.1 μL oil (n-decane) shell encapsulating a 1.5 μL water core droplet, only 0.2 to 2.8 nmol or 0.17 to 2.4 μg lipid was required. Microscopes and electrophysiological measurements were performed on the parallel-plate device with three major steps demonstrated: (1) manipulating self-assembled lipid monolayers at the water-oil interface of the encapsulated droplets by electrowetting-on-dielectric (EWOD), (2) forming a BLM by bringing two lipid monolayers towards the aperture and thinning down the oil film between them by Young-Laplace pressure, and (3) incorporating membrane-bound nanopores, α-hemolysin (αHL), on the BLM. This study shows the influence of the lipid concentration to the interfacial tension and EWOD. Plateau-Gibbs border and black membrane area of the BLM were optically observed, while trans-membrane electrophysiological signals were electrically recorded from a pair of Ag/AgCl electrodes.