Ion-Driven Interfacial Engineering of MXene-Polyacrylamide Hydrogels for Advanced Wearable Electrocardiography and...

MXene (Ti₃C₂T _x )-based hydrogels hold great promise for wearable bioelectronics but are limited by unstable interlayer spacing, poor mechanical resilience, and inadequate skin compatibility. An ion-driven interfacial engineering strategy is introduced that stabilizes Ti₃C₂T _x nanosheets via Ca²⁺ intercalation and Cl^- electrostatic screening, expanding interlayer spacing and enabling ultrafast gelation (<5 min). The resulting Ti₃C₂T _x -polyacrylamide hydrogel exhibits ultrastretchability (2920%), high conductivity (0.39 s m^-1), and ≈99% cell viability, surpassing existing MXene and commercial hydrogels in terms of cytocompatibility, durability, and skin adherence. Molecular dynamics simulations reveal dynamic interlayer adaptability (6.2-8.2 Å) and ion transport mechanisms that underpin strain-adaptive sensing and stability across a temperature range of -20 to 40 °C. Integrated into wearable electrodes, the hydrogel enables high-quality electrocardiography (ECG) acquisition across diverse skin types, achieving signal-to-noise ratios of up to 27.2 dB without the need for auxiliary treatments. Coupled with a convolutional neural network-bidirectional gated recurrent unit model trained on ECG data from 17 subjects, the system delivers real-time, cuffless blood pressure estimation with MAE ± SD of 2.91 ± 3.03 mmHg (systolic blood pressure) and 2.36 ± 2.33 mmHg (diastolic blood pressure), meeting Association for the Advancement of Medical Instrumentation and British Hypertension Society standards. This synergistic material and AI framework establishes a new paradigm for smart, long-term cardiovascular monitoring.