Ultrasoft eutectogel electrodes for non-invasive face nerve monitoring

Abstract

Facial nerve injury arising from diseases or clinical interventions can cause significant physiological and psychological harm. Continuous monitoring of facial muscle electrophysiology can mitigate these risks by informing surgical procedures and guiding postoperative rehabilitation. However, conventional electrodes are predominantly invasive and fabricated from mechanically stiff metals that mismatch soft tissues, often leading to secondary injury and discomfort. Here, we develop an ultrasoft eutectogel and employ it as a non-invasive electrode material for a surface electromyography (sEMG) monitoring array. The eutectogel is synthesized by random copolymerization of acrylic acid (AA) and the zwitterionic monomer 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonio]propane-1-sulfonate (SBMA) in a deep eutectic solvent (DES), yielding an electrode that integrates ultra-low modulus, strong adhesion, ionic conductivity, and environmental tolerance. The ultra-low modulus and adhesiveness facilitate conformal, dynamic coupling with epidermal tissues, providing an ideal material platform for non-invasive high-quality acquisition of physiological electrical signals, including facial nerve-related activity. We further validate the feasibility of predicting facial nerve functional integrity using this platform. The eutectogel and the flexible multi-electrode array provide a promising strategy for clinical protection and monitoring of facial nerve function.