Scalable Fabrication of All-Biopolymer-Derived Conductive Hydrogels for Flexible Mechanosensors and Zinc-Ion Hybrid Supercapacitors

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Traditional synthetic hydrogels for flexible electronic devices are mostly derived from nonsustainable polymers, resulting in environmental pollution. Herein, scalable, moldable, and stretchable ionic hydrogels are synthesized utilizing two model biopolymers, κ-carrageenan (κ-CG) and amylopectin (Amy). In such hydrogels, physically cross-linked κ-CG networks work as a relatively rigid component to maintain the shape of hydrogels, Amy networks cross-linked by borate/cis-diol dynamic covalent bonds help to improve the stretchability, and ZnSO 4 is introduced as an ionic conductive component. The hydrogels, denoted as κ-CG/Amy/Zn 2+ hydrogels, exhibit acceptable stretchability (>100%) because of the special cross-linking structure and ionic conductivity (2.9 S·m –1 ) due to the existence of various ions. Flexible mechanosensors (resistive strain sensors and capacitive pressure sensors) are demonstrated utilizing κ-CG/Amy/Zn 2+ hydrogels, and high gauge factors (0.76 for strain sensors and 0.77 kPa –1 for pressure sensors) are achieved. Interestingly, κ-CG/Amy/Zn 2+ hydrogels also work as quasi-solid-state electrolytes in zinc-ion hybrid supercapacitors, which exhibit an initial specific capacity of 47.4 mAh·g –1 at a current density of 3 A·g –1 and stable charge/discharge ability in more than 42,000 cycles. The sustainable biopolymer hydrogels may provide promising eco-friendly materials for future wearable devices and energy storage systems.