Figure 8 (a) Holographic propagation imaging of a so-called black lipid membrane (BLM), i.e. lipid membranes spanned over an aperture between two aqueous compartments in a Teflon
chamber with polyimide windows for X-ray transmission. Since the lipids system is
prepared by `painting' a solution of lipids in decane, the bilayer is still swollen
with decane. The exact thickness of the BLM can be determined by analysis of the Fresnel
finges. Following Beerlink et al. (2009 ), we can model the density profile (or equivalently phase profile) and use Fresnel
propagation for least-square fitting of the radial intensity profiles (b, c, d). The experimental profiles are shown as a function of radial distance r from the center of a circle describing the averaging over a range of azimuthal angles,
as indicated in (a), to increase the signal-to-noise ratio. Here, the BLM thickness d was ranged between 50 nm and 70 nm, but this depends on the configuration, and in
particular on the solvent outflow (BLM thinning). |