Oxidized Liquid Metal‐Based Stretchable Patch for Wearable Health Monitoring

Traditional electronic devices are significantly constrained by their intrinsic rigidity, which restricts their application in stretchable and wearable electronics. To address these challenges, this study presents a cost‐effective and accessible approach to fabricate stretchable electronic circuits using liquid metal (EGaIn) and stencil printing technique with a laser‐engraved mask. The liquid metal ink, synthesized through overoxidation process, exhibits high conductivity, printability, and exceptional strain insensitivity ( R / R ₀  < 2.5 under 400% strain), enabling high‐resolution patterning with a minimum feature size of 50 μm. The liquid metal‐based circuits demonstrate stable electrical performance under significant deformations and reliable integration with commercial rigid electronic components. By leveraging this method, we successfully transformed a commercial photoplethysmography (PPG) sensor into a stretchable device and integrated it with an electrocardiogram (ECG) sensor to construct a wearable cardiovascular monitoring system. The results showed the system can obtain a comparable ECG, PPG signals, and systolic blood pressure with those obtained from a commercial instrument, which was further used for continual HR, SpO2, and blood pressure monitoring with excellent stability. This work provides a transformative platform for the low‐cost and simple manufacturing of stretchable electronic devices, with broad potential applications in wearable health monitoring.