Interfacial Polarization Locked Flexible β-Phase Glycine/Nb₂CT_x Piezoelectric Nanofibers

Biomolecular piezoelectric materials show great potential in the field of wearable and implantable biomedical devices. Here, a self-assemble approach is developed to fabricating flexible β-glycine piezoelectric nanofibers with interfacial polarization locked aligned crystal domains induced by Nb₂CT_x nanosheets. Acted as an effective nucleating agent, Nb₂CT_x nanosheets can induce glycine to crystallize from edges toward flat surfaces on its 2D crystal plane and form a distinctive eutectic structure within the nanoconfined space. The interfacial polarization locking formed between O atom on glycine and Nb atom on Nb₂CT_x is essential to align the β-glycine crystal domains with (001) crystal plane intensity extremely improved. This β-phase glycine/Nb₂CT_x nanofibers (Gly-Nb₂C-NFs) exhibit fabulous mechanical flexibility with Young's modulus of 10 MPa, and an enhanced piezoelectric coefficient of 5.0 pC N^-1 or piezoelectric voltage coefficient of 129 × 10^-3Vm N^-1. The interface polarization locking greatly improves the thermostability of β-glycine before melting (≈210°C). A piezoelectric sensor based on this Gly-Nb₂C-NFs is used for micro-vibration sensing in vivo in mice and exhibits excellent sensing ability. This strategy provides an effective approach for the regular crystallization modulation for glycine crystals, opening a new avenue toward the design of piezoelectric biomolecular materials induced by 2D materials.