Janus Tough Adhesive Ionotronics for High‐Fidelity Biomechanical and Electrophysiological Signal Recording

ABSTRACT Wearable bioelectronics require soft materials that combine robust skin interfacing, mechanical resilience, and stable signal transduction under dynamic conditions. However, conventional ionogels suffer from electrolyte leakage, interfacial instability, and susceptibility to external disturbances, leading to compromised sensing fidelity. Herein, a Janus‐adhesive ionogel is engineered via a stepwise polymerization strategy to integrate asymmetric adhesion with stable ionic conduction. The adhesive layer ensures conformal and durable skin‐electrode coupling through cation‐π interactions and hydrogen bonding, while the non‐adhesive layer provides mechanical protection and environmental insulation, enabling functional decoupling. The ionogel exhibits excellent mechanical performance (fracture energy of 17.70 kJ m −2 and toughness of 6.39 MJ m −3 ), stable ionic conductivity (0.55 mS cm −1 ), and durable adhesion. Benefiting from its asymmetric architecture, the device achieves low interfacial impedance and suppresses motion artifacts and interference. It enables high‐fidelity acquisition of electrophysiological signals (sEMG, ECG) with enhanced signal‐to‐noise ratios compared to commercial electrodes, as well as precise detection of subtle biomechanical motions. The results establish a generalizable strategy for improving interfacial stability and signal fidelity in wearable ionotronics.