High-Performance Polyacrylamide Hydrogel-Based Wearable Sensors for Electrocardiography Monitoring and Motion Sensing

Conductive hydrogels have gained significant attention due to their remarkable properties, including stretchability, self-adhesiveness, deformability, and cost-effectiveness. However, existing hydrogel-based sensors often suffer from limited biocompatibility, poor mechanical strength, and inadequate adhesion, limiting their suitability for wearable electronics. Herein, we report a highly conductive, skin-friendly hydrogel electrode for real-time electrocardiography (ECG) and motion monitoring. The hydrogel is based on a polyacrylamide (PAM) network incorporated with the conductive polymer poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS). The PAM-PEDOT:PSS hydrogel exhibited exceptional mechanical properties, with tensile strengths of 5-68 kPa at corresponding strains of 142 to 646%. It also demonstrated excellent biocompatibility, gentle skin adhesion, and optimized mechanical performance by tailoring the cross-linker concentration (N,N-methylene Bis(acrylamide)) in the PAM matrix. Notably, the hydrogel exhibited low hysteresis (<3%) under stress-strain cycling, ensuring reliable performance during repeated deformation. Wearable hydrogel electrode testing showed a strong correlation (99.6%) between recorded ECG signals and those from commercial electrodes. Additionally, the fabricated strain sensors exhibited high sensitivity, an extensive sensing range (0-646% strain), rapid response, and outstanding stability. These features enable precise monitoring of diverse physical signals, from large-scale joint movements to subtle muscle contractions. This work presents a promising approach for developing flexible strain sensors and electronic skins, advancing next-generation wearable devices.