Robust accurate fatigue assessment enabled by an ultrasoft and super-adhesive low-impedance conducting polymer hydrogel

Abstract

The evaluation of muscle fatigue is vital for the prevention and diagnosis of diseases, medical treatment planning, and tracking rehabilitation outcomes. Surface electromyography (sEMG) signals, which mirror the activity of muscles, are commonly captured using skin-mounted electrodes to assess fatigue levels. Nevertheless, conventional epidermal electrodes usually fall short in terms of adhesion and compliance, impairing their capacity to seamlessly conform to the skin and accommodate its dynamic movements, thereby compromising the precision of muscle fatigue assessments. Herein, we introduce a plasticized template and synergistic doping strategy to fabricate the PAA/PEDOT:PSS/LS (PAPL) hydrogel, where a polyacrylic acid (PAA) network serves as a dynamic scaffold for PEDOT:PSS and sodium lignosulfonate (LS) as a plasticizer and secondary dopant. The PAPL hydrogel, characterized by its ultrasoft nature (Young’s modulus ≈ 0.76 kPa), high conductivity (5.52 S m⁻¹), strong adhesion (171 kPa on PET), and ultralow interface impedance (<1 kΩ) ensuring robust, seamless conformal adhesion along with reliable sEMG signals (SNR ≈ 30 dB) during movements. Furthermore, the PAPL hydrogel exhibits outstanding self-healing capabilities, remarkable ultraviolet resistance, and potent antibacterial properties, enabling it to fulfill diverse functional requirements in real-world applications. PAPL hydrogel is capable of monitoring muscle activity and providing accurate fatigue assessment, with performance markedly superior to that of commercial electrodes, demonstrating its application potential in personalized medicine and future healthcare systems