A Xerotic Skin‐Compatible Neuromotor Electrode Interface for Non‐Invasive Muscle Weakness Evaluation in Dermatomyositis

Dermatomyositis creates a clinical demand for non-invasive, quantitative muscle weakness assessment, which can be achieved by decomposing neuromotor information from surface electromyography (sEMG). However, the absence of a stable electrode interface compatible with pathologically xerotic skin has hindered this approach. Here, we develop a conformable neuromotor electrode interface that overcomes this via molecular engineering, exhibiting an ultrasoft modulus (∼ 2.13 kPa), low impedance (∼ 0.9 kΩ at 1 kHz), and stable electrical retention over 7 days. This interface enables the acquisition of high-fidelity sEMG from dermatomyositis patients with low baseline noise (< 2 µV root mean square) and high inter-channel signal correlation, allowing robust decomposition of neuromotor biomarkers including motor unit count, action potential amplitude, and firing rate. Clinically, our multi-biomarker quantification strategy shows strong agreement with gold standard assessments. Moreover, our approach can detect subtle interpatient variations like early recruitment patterns, enabling personalized treatment beyond the clinical gold standard. This work establishes a transformative platform for precise muscle weakness evaluation, overcoming the limitations of needle electromyography and subjective clinical scales.