Xerogel, Steps, and Ethanol Control Phase Behavior of Supported Lipid Bilayers

Lipid bilayers deposited onto nano-porous, microfabricated, or atomically flat substrates offer many advantages with respect to construction of devices and study of biological membrane processes. We demonstrate in three studies that the characteristics of these substrates (e.g. high curvature) can strongly influence the phase behavior of a mixed lipid bilayer offering some advantages and disadvantages that can be mitigated. First, we show that high curvature (r ~ 50 nm) in a silica xerogel layer can be used to induce lipid demixing or intrabilayer transport over large areas. Second, we use high curvature microfabricated steps (h ~ 20 nm) to align freely moving lipid domains in a multilayer system. Third, we develop an approach to counteract substrate-induced tension in mica-supported lipid bilayers. Consequently, we use AFM imaging to construct a lipid/sterol/ethanol phase diagram consistent with un-supported bilayers.