Vapor-phase self-assembly of orientation-controlled amino acid nanorod arrays for energy harvesting

Biomolecules can form micro- and nanoscale structures with unique physicochemical properties. These structures tend to grow randomly in solution or on a substrate, and the lack of orientation control stems from a limited understanding of the self-assembly process, hindering their applications. Here, we achieve aligned, uniform nanorod arrays of aromatic amino acids via an electric-field-assisted physical vapor deposition process. The electric driving force and non-covalent intermolecular interactions work synergistically in biomolecular self-assembly. The vapor-deposition angle controls the stacking direction of tyrosine, phenylalanine, and levodopa, and a dynamic transition from vertical columnar crystals to horizontal needle-like epitaxial growth is observed. The good mechanical properties and piezoelectric response enable the fabrication of piezoelectric nanogenerators for environmental energy harvesting. The present work provides a new direction for the controlled growth of smart biomaterials and promotes their practical applications.