Amino Acid-Based Piezoelectric Biocrystals for Bioelectronics: Material Design, Scalable Processing, and Biomedical Applications.

Amino acid (AA)-based biomolecular materials, including AAs, peptides, proteins, and their co-assembled systems, are emerging as an extraordinary material platform at the interface of materials science, biology, and electronics. As the molecular building blocks of life, these systems combine inherent biocompatibility and biodegradability with a remarkable ability to assemble into low-symmetry crystalline structures that can exhibit piezoelectricity and related electromechanical functionalities. Despite their low thermal stability and weak intermolecular interactions, emerging mild and sustainable processing approaches for AA-based biocrystals are opening transformative pathways toward bioelectronic devices that structurally, topologically, and mechanically mimic biological systems while enabling energy harvesting, sensing, electrostimulation, and other functional capabilities. In this review, we aim to provide an overview of arrays of AA-based biocrystals, their scalable processing approaches, and enabled mechanoresponsive devices for biomedical applications. We begin by comprehensively introducing AA-based materials and discussing their physicochemical properties. We then review the major approaches for large-scale processing of AA-based biocrystals, focusing on preserving crystal structures, controlling dipole alignment, as well as tailoring electromechanical properties. Representative biomedical devices and applications are discussed followingly. Finally, we identify the major challenges that remained in translating AA-based materials toward practical applications and highlight the potential solutions.