Bead-on-string Ag/AgCl heterostructures enable nonpolarizable stretchable dry electrodes for long-term, high-fidelity electrophysiological interfaces

Wearable electrophysiological interfaces demand bioelectrodes that combine low-impedance, stable ion-electron transduction with high mechanical deformability, yet these requirements remain fundamentally incompatible in existing systems. Here, we present a nonpolarizable stretchable dry electrode based on a bead-on-string Ag/AgCl heterostructure, in which AgCl nanoparticles (NPs) are selectively assembled along percolated silver nanowire networks embedded within an elastomer matrix. This architecture spatially decouples Faradaic reaction sites from conductive pathways, constructing abundant, mechanically robust Ag/AgCl heterointerfaces for efficient ion-electron transduction while preserving continuous electron transport under large deformation. By systematically tuning the size of AgCl NPs (50-800 nm), the spatial distribution and interfacial length scale of Faradaic domains are optimized to maximize electrochemical performance. The resulting electrode achieves ultralow interfacial impedance (49 kΩ, 10 Hz), stable electrode potentials, and tolerance to severe mechanical deformation (ε > 370%), with minimal degradation over 500 stretch cycles. It enables low-noise, high-fidelity signal acquisition in the low-frequency regime, effectively suppressing motion artifacts and maintaining stable operation over 120 days of storage in air. When integrated with a spatiotemporal neural network for electrooculography decoding, the system achieves 98% accuracy in hands-free game control, demonstrating a robust paradigm for next-generation wearable bioelectronics.