Analysis of bilayer contact angles using a microfluidics setup. (A) Schematic overview of the chip geometries used. Both the devices have a cross-geometry and the lipid monolayers meet at the intersection of the channels forming the bilayer. In subpanel a, fluorescence microscopy micrographs show how the chip was first filled by injection from one of the two inlets with a lipid solution in squalene stained with Rhodamine-labeled PE and then with a buffer phase using hydrostatic pressure. This setup allowed for the lipids to decorate the oil-buffer interface. In subpanel b, the chip was also filled with membrane lipids (inlet 2) as part of a squalene solution containing Rhodamine-labeled PE. Afterwards, the two buffer fingers were introduced from opposite sides (inlets 1) resulting in membrane lipid decoration of the two interfaces. After generating a close contact through hydrostatic pressure manipulation, the membrane lipids formed a bilayer as shown in the optical micrographs. The geometry of the chip in subpanel was found to form more stable bilayers due to a better control of hydrostatic pressure. The scale bar is 75 µm. (B) Optical micrographs of the bilayer contact angles for artificial membranes with different cholesterol contents increasing from top to bottom (scale bar = 50 µm).