Electrocardiography (ECG) is a primary tool for diagnosis of various types of disease and disorders such as arrhythmias, coronary heart disease, heart attack, mental disorders, etc. Reliable wearable ECG devices can be a valuable tool in early diagnosis and effective treatment of such disease and disorders. Convention wearable ECG sensor-systems are rigid, bulky, expensive, and the recorded ECG signals using these wearable devices lack required accuracy for medical diagnosis mainly due to motion artifacts that is originated from slippage of sensors on skin and/or instable interface between the soft sensor and the rigid electronic circuits.

Here, we report a low-modulus, soft and stretchable wearable electrocardiography (ECG) sensor-system patch which enables continuous and long-term recording of ECG signals with minimal motion artifacts. This system consists of two reusable, detachable-attachable patches: sensor patch and circuit patch, as shown in Figure 1a. The reusable multi-wall carbon nanotube (MWCNT) based sensor patch is fabricated on stretchable elastomer substrate by our developed cost and time-effective method. Reusable, front-end and wireless circuit patch is made by integration of the off-the-shelf integrated circuit components with three-dimensional (3D) stretchable-deformable interconnects (SDI). SDIs are 3D springs of liquid metal (EGaIn). Unlike other reported liquid metal based interconnects, SDI has been designed in 3D form to increase the stretchability and make it low-modulus and robust to deformations in all directions. The stretchability of SDI structure is beyond 500% (the limit of our measurement system) without any negligible change in electrical resistivity of the interconnects. With less than 1% change in the resistance of SDIs after 50,000 cycles of applied tensile strain of 200%, the SDI structure ensures reliable stretchability and durability of the circuit patch for long-term electrocardiography.

The sensor patch is soft, stretchable and it is fabricated using a low-cost scalable method. This soft and stretchable ECG sensor-system shows comparable performance with respect to medical grade Ag/AgCl wet gel electrodes. Our CNT-PDMS sensors shows low electrode-skin interface impedance and low susceptibility to motion artifact which similar of it in medical grade Ag/AgCl wet gel sensors (Fig. 1b). Further, it is waterproof, reusable and comfortable to wear.

The circuit patch includes a rechargeable battery and ECG signals is wirelessly sent to a personal device such as cellphone, tablet and laptop through Bluetooth low energy (BLE) and it is displayed in real-time (Fig. 1c) Our developed sensor-system is a multi-use platform which can be applied for the detection of EMG, EEG or EOG signals.