Unlocking Piezoelectric Potential in Collagen: Intrafibrillar Mineralization Matters

Mineralized collagen fibrils in bone display piezoelectricity under external mechanical loads, although the contribution of intrafibrillar mineralization to this effect is not fully understood. Furthermore, the limited piezoelectric performance of collagen biomaterials constrains their use in bioelectronic devices. This study reveals that the intrafibrillar crystallization of hydroxyapatite within collagen fibrils markedly enhances collagen's piezoelectric properties, expanding their bioelectronic applications. In this work, the intrafibrillar mineralized collagen (imCol) is prepared via the coassembly of collagen fibrils with citrate-stabilized calcium phosphate precursors. The obtained imCol exhibits superior piezoelectricity compared with native collagen, which is attributed to changes in collagen conformation and the unique twisted asymmetrical structure of hydroxyapatite crystallization. The imCol films produced by simple evaporation demonstrate high sensitivity to mechanical stimuli, achieving a maximum open-circuit voltage of 83.32 V under 75 N compression. Due to its excellent biocompatibility and biodegradability, the piezoelectric imCol film is a promising candidate for electrical biomaterials and transient components in bioelectronic devices.