Interface-induced high piezoelectric γ-glycine-based flexible biodegradable films

Flexible biodegradable piezoelectric composite films prepared by combining water-soluble rigid piezoelectric crystals with flexible polymers have immense potential in the fields of wearable and implantable bioelectronics due to their self-powered, biocompatible, and biodegradable properties. However, comprehensive research on maintaining a high piezoelectric coefficient during fabrication of a flexible film is still lacking. In this work, based on γ-glycine, a simplest natural biodegradable piezoelectric crystal, we investigated the effects of different water-soluble biodegradable polymers and film-forming interfaces on the crystal type, arrangement, structure, and piezoelectric properties. The glycine-PEO composite film prepared using the co-dissolution-evaporation method on the more hydrophobic PTFE interface exhibits a higher out-of-plane piezoelectric coefficient (d33) of ~8.2 pC/N, which is very close to the theoretical d33 (10.4 pC/N) of the γ-glycine crystal. This study establishes that interface-induced effects have significant impacts on the crystal arrangement and piezoelectricity of composite films. This study provides important guidance for future research on flexible preparation of other flexible piezoelectric materials.