Antifouling All-Polymeric Microneedle Array for Long-Term Wearable ECG Monitoring

Cardiovascular disease demands reliable long-term monitoring for early and accurate diagnosis. While conventional gel electrodes are commonly utilized for monitoring electrocardiogram (ECG) signals, they have limitations, such as dehydration-induced signal degradation and motion artifacts, hindering their effectiveness for continuous long-term use. To address these issues, this study develops a biocompatible and all-polymeric microneedle electrode (MNE) optimized for stable ECG monitoring over extended periods. The MNE surface is sequentially coated with poly(3,4-ethylenedioxythiophene):tosylate (PEDOT:Tos) to reduce the interfacial impedance (0.63 kΩ∙cm² at 10 Hz), followed by zwitterionic sulfobetaine methacrylate (SBMA) to prevent nonspecific protein adsorption and cellular adhesion (84.2% and 98.6% reduction in E. coli and BSA, respectively). Moreover, the SBMA-coated MNE demonstrates excellent mechanical strength, allowing it to penetrate human skin without deformation, as verified by optical coherence tomography and insertion-force assessments. In practical applications using a wireless wearable ECG monitoring system, the SBMA-coated MNE consistently captures high-quality ECG signals over a 14-day period, significantly outperforming gel electrodes under dynamic movement conditions.