Biomimetic bone hydrogel enables a seamless interface for aqueous battery and human/machine interaction†

Abstract

Hydrogels offer promising avenues for developing advanced aqueous battery technology for sustainable energy storage and wearable electronic devices in future human/machine interactions. However, an excessively large liquid-phase region in the hydrogel often results in parasitic reactions, modulus mismatch, and low strength. Therefore, it is crucial to develop a new hydrogel system with denser structures that enable reduced water content and better-matched modulus. Herein, inspired by the bionic principles of mammalian joint structures, an ultra-dense (3.26% of porosity) and highly robust (30.82 MPa of tensile strength) biomimetic bone hydrogel (BBH) system was designed through a biomimetic densification process. Notably, the robust ‘bone/collagen’ and flexible ‘collagen/synovial fluid’-like interactions not only ensure excellent mechanical properties but also disrupted the strong crystallization tendency to realize a seamless and fast ion transfer process. BBH displayed an expanded electrochemical window of 3.26 V and superior cycling in aqueous batteries with a practical cathode loading of 33.8 mg cm⁻² (N/P = 2.46), indicating its suitability for application as an electrode/electrolyte interface. Moreover, its application as a seamless human/machine interface for on-skin physiological monitoring with high fidelity was demonstrated. Overall, this biomimetic densification design provides a new direction for the development of advanced hydrogels for next-generation energy storage and interactive devices.