Tailored Construction of Piezoelectricity in Amino Acid Assemblies through Molecular Engineering.

Amino acid assemblies are a promising smart biomaterial for wearable and implantable bioelectronics due to their intriguing physical properties, inherent biocompatibility, and adaptability to functionalization. However, the impact of metal ions on the favorable packing and physical properties of amino acid crystals remains unclear. Herein, we introduce metal ions into the precursor solution to obtain glycine-based crystals and investigate the effect of metal ions on their physical properties. The polarity of solutions modified with different metal ions can promote the conformation of glycine-based crystals, transforming them from two-dimensional layered structures to three-dimensional network structures. The supramolecular arrangements, characterized by distinct intermolecular interactions, can influence thermal, mechanical, and piezoelectric properties. The weak intermolecular interactions between H and O atoms cause a low modulus that favors the piezoelectric response. As a result, the glycine-Cu crystals achieve a surprisingly high piezoelectric constant of 151.78 pm/V. The glycine-Cu-based piezoelectric nanogenerators produce an output voltage of 2.13 V, which is higher than that of reported nanogenerators based on amino acids and peptides. Our work provides insight into developing functional biomaterials from simple building blocks through the manipulation of solvents.