Large-area kinetic stabilization of metastable R-glycine via meniscus-driven self-assembly with anisotropic piezoelectricity

Abstract

The development of natural piezoelectric biomaterials with tunable structure and functionality is crucial for advancing sustainable and biocompatible technologies in energy harvesting, implantable electronics, and biomedical systems. Glycine, the simplest amino acid classified into alpha, R, and gamma polymorphs, exhibits inherent substantial piezoelectricity at the R-phase structure. However, achieving controllable and scalable R-phase formation remains a key challenge due to its thermodynamic instability. Here, we present a scalable meniscus-guided self-assembly strategy for the large-area fabrication of uniform R-glycine crystals. Precise balancing of solvent evaporation and crystal growth kinetics enables direct crystallization and selective stabilization of the R-phase. This approach further induces pronounced crystallographic alignment, producing highly oriented R-glycine domains. The non-centrosymmetric structure and electromechanical functionality of the aligned crystals are verified by piezoresponse force microscopy (PFM) and second harmonic generation (SHG) analysis. The resulting assemblies demonstrate piezoelectric energy harvesting capability, confirming the potential of R-glycine as a functional piezoelectric material. This work offers a promising step toward enhancing the piezoelectric performance of natural biomaterials with potential implications for future self-powered biomedical applications.