Lactadherin binds convex ridges of supported membranes and annexin A5 binds concave valleys. We fabricated chemically etched silica nano-ridge/-trough substrates as described in “Materials and methods.” (A) Color-coded AFM topographic image of a representative substrate containing ridges (yellow) and troughs (orange/brown) with radii of curvature of +10 and −300 nm, respectively. Insets i and ii: schematics of the expected positively and negatively curved lipid bilayers formed on the ridges and troughs, respectively. (B) A high-resolution scanning electron microscopy side-view image of the substrate. (C) Top-down phase images of the substrate showing brightly reflective ridges and dark troughs. (D) Substrates were overlaid with lipid bilayers containing 4% PS, 20% PE, and 76% PC followed by incubation with 10 nM lactadherin-alexa-647 (blue pseudocolor) and 10 nM annexin A5-FITC (green) in the presence of calcium and imaged by serial-section confocal microscopy. Compressed z stacks are represented as a maximum-intensity projection image. (E) Fluorescence intensity profiles corresponding to the white line in panel D. Lactadherin preferentially bound to the positively curved ridges, whereas annexin A5 selectively bound to the negatively curved troughs (dashed lines). Additional quantitative evaluation displayed in supplemental Figure 1.