Integration of flexible, recyclable, and transient gelatin hydrogels toward multifunctional electronics

Facing the challenges posed by exponentially increasing e-waste, the development of recyclable and transient electronics has paved the way to an environmentally-friendly progression strategy, where electronics can disintegrate and/or degrade into eco-friendly end products in a controlled way. Natural polymers possess cost and energy efficiency, easy modification, and fast degradation, all of which are ideal properties for transient electronics. Gelatin is especially attractive due to its unique thermoreversible gelation processes, yet its huge potential as a multifunctional electronic material has not been well-researched due to its limited mechanical strength and low conductivity. Herein, we explored versatile applications of gelatin-based hydrogels through the assistance of multifunctional additives like carbon nanotubes to enhance their electromechanical performances. The optimized gelatin hydrogel displays not only a high conductivity of 0.93 S/m, electromagnetic shielding effectiveness of 39.6 dB, and tensile stress tolerance of 263 kPa, but also shows a negative permittivity phenomenon, which may find versatile applications in novel electronics. As a proof of concept, hydrogels were assembled as wearable sensors to sensitively detect static and dynamic pressures and strains generated by solids, liquids, and airflow, as well as diverse body movements. Furthermore, the recyclability, biocompatibility, and degradability of gelatin-based hydrogels were well studied and analyzed. This work outlines a facile method to design multifunctional transient materials for wearable, sustainable, and eco-friendly electronics.