A bluetooth-enabled, light weight, flexible epidermal electronic system for ECG monitoring

Abstract

With 17.9 million deaths annually, cardiovascular diseases (CVDs) have become the leading cause of mortality worldwide. This increased death rate creates a significant need for long-term ambulatory ECG monitoring for early diagnosis and treatment. Commercially existing ECG monitors use rigid materials, aggressive adhesives, and lack mechanical compliance with skin. Here, a wireless, Bluetooth-enabled, flexible, low-profile epidermal ECG monitoring device is presented with high-quality ECG signals. Electrode placements with different distances are investigated to find the optimal placement position of the electrode on the chest for identical readings with traditional ECG lead I and II. Afterward, the dry electrode and circuit are microfabricated using 2 $\mu{m}$-thick copper foil. The functionality of the electrode is demonstrated with stretchability, contact impedance, and EMG SNR measurement. The device's functionality is presented with a flexibility test, antenna performance test, RSSI measurement, and ECG signal collection. Contact impedance values for gel and dry electrodes are comparable, which are 3.94 and 3.96, respectively. Also, EMG SNR values are comparable for gel and dry electrodes, with 18.12 dB and 17.84 dB, respectively. Mechanical and electrical experiments suggest a 2 mm radius of curvature at 180° bending as the maximum flexibility of the device and a 30m long working distance for constant wireless communication between the device and a portable device. The morphology and quality of ECG signals acquired from human subjects during different activities demonstrate the device's potential for ambulatory monitoring. Overall, our findings prove the device is flexible, Bluetooth enabled, and can provide conformal contact with skin to achieve ECG monitoring in real-time effortlessly. Future work should include validating the device's functionality with data collection during different activities of the human subject.