Engineered gelatin-based conductive hydrogels for flexible wearable electronic devices: Fundamentals and recent advances

With the fast and ever-growing development of multifunctional wearable intelligent electronic devices (WEDs), the ideal building block materials for the fabrication of WEDs should be naturally abundant with characteristics such as green and non-toxic, excellent biocompatibility, biodegradability, and sanitation property. Gelatin is denatured collagen from natural connective tissue that mimics components of the native extracellular matrix regarding its biomimetic primary structure and chemical composition. Recently, gelatin-based conductive hydrogels (GC-Gels) are considered promising materials for developing flexible wearable sensors due to their unique porous structure and excellent application performances. This review first provides a comprehensive overview of the preparation, composition, structure, and properties of gelatin, followed by the current development status and progress of GC-Gels as well as GC-Gels-based flexible wearable devices with different structures and functions. Finally, the possible challenges and suggestions for the future development of GC-Gels-based flexible wearable devices are provided. This review is expected to promote and inspire the emerging applications of gelatin, its derivatives, and even other natural raw materials as sustainable advanced materials for WEDs.