The functionalities of peptide microstructures and nanostructures can be enhanced by controlling their crystallinity. Gaining control over the crystallinity within the desired structure, however, remains a challenge. We have developed a three-dimensional (3D) printing method that enables spatioselective programming of the crystallinity of diphenylalanine (FF) dipeptide microarchitectures. A femtoliter ink meniscus is used to spatially control reprecipitation self-assembly, enabling the printing of a freestanding FF microstructure with programmed shape and crystallinity. The self-assembly crystallization of FF can be switched on and off at will by controlling the evaporation of the binary solvent. The evaporation-dependent crystallization was theoretically studied by the numerical simulation of supersaturation fields in the meniscus. We found that a 3D-printed FF microarchitecture with spatially programmed crystallinity can carry a 3D digital optical anisotropy pattern, applicable to generating polarization-encoded anticounterfeiting labels. This crystallinity-controlled additive manufacturing will pave the new way for facilitating the creation of peptide-based devices.
Keywords: 3D Printing; Anticounterfeiting; Crystallinity; Dipeptides; Self-Assembly.