Intermetallic-anchored epidermal EGaIn patch with analog constriction gates for cardiorespiratory monitoring

Chronic respiratory diseases lack accessible tools for continuous, at-home monitoring, as wearable strain sensors struggle to combine accuracy, linearity, and stability. Here, we present HELP (heteromodal epidermal liquid-metal patch), a materials-and-structure co-designed wearable to overcome these limitations. Indium-driven alloying of silver nanowires anchors liquid metal to eliminate drift, while graded hemispherical bulges acting as progressive analog strain gates yield R² = 0.998 linearity, <0.4% hysteresis, detection to 0.01% strain, and durability over 500,000 cycles via simple stencil brushing. Its dual channel allows simultaneous strain-insensitive electrocardiogram and ultrasensitive respiratory sensing. In pilot studies, HELP captured thoracoabdominal effort, heart rate, posture, and oxygenation, enabling obstructive sleep apnea detection with high polysomnography agreement, objective tracking of bronchodilator response in asthma, and unmasking of nocturnal hypoxemia hidden by wakeful compensation in chronic obstructive pulmonary disease. By integrating respiratory mechanics and autonomic phenotyping, this self-applied epidermal device establishes a promising platform for future decentralized cardiorespiratory monitoring.