Branched fatty acids, such as those found on the surface of hair and wool, have recently been shown to form novel 3D self-assembly curvature structures at the air–water interface—nanocaps. On the hair surface, the branched fatty acid 18-methyleicosanoic acid (18-MEA) is expressed together with shorter, unbranched, straight chain fatty acids to form a protective palisade layer. The biological function of the chain length differences was hitherto unknown. Using a combination of atomic force microscopy and Langmuir isotherms, a safe, versatile route for tuneable nanopatterning of solid surfaces is demonstrated, via fatty acid interfacial nanocap deposition from biomimetic mixtures. Further, it is shown that chain length dependence of the interaction with the branched chain is exquisitely sensitive, leading to profoundly different morphologies in the self-assembly structures. The vastly enhanced properties of the mixed films compared to the individual components alone reveals the biological origin of the hair surface composition.