Micro-Corrugated Hydrogel Electrodes for High-Performance Biofuel Cells via Capillary Force and Ligand...

Biocompatible enzyme-based biofuel cells (EBFCs) with enzymatic electrodes show great potential as power sources for wearable and implantable biomedical devices. However, their practical application has been limited by poor electron transfer efficiency and insufficient operational stability. In this study, we present a mediator-free, hydrogel-based EBFC that addresses these challenges through the integration of capillary force-assisted assembly and hydrophobic metal nanoparticle (NP) deposition. The resulting highly conductive hydrogel electrode enables enhanced power output and long-term stability. To achieve this goal, the hydrogel, composed of poly(ethylene imine) functionalized with amine (-NH₂) groups, was immersed in a solution of tetra(octylammonium) (TOA)-stabilized Au NPs. This process induced ligand exchange reaction and room-temperature NP fusion at the interface between the NH₂-functionalized hydrogel and the hydrophobic Au NPs, along with capillary-force-driven self-assembly, thereby converting the initially insulating hydrogel into a highly conductive hydrogel with micro-corrugated structure. Subsequently, glucose oxidase and TOA-Au NPs were deposited onto the conductive, micro-corrugated hydrogel to construct the anode, while a platinum (Pt)-modified hydrogel served as the cathode. This EBFC achieved a high-power output of ∼3.7 mW cm^-2 and maintained ∼80% of initial power after 30 days of continuous operation, representing a significant advancement toward hydrogel-based EBFC.