Highly conformable stretchable dry electrodes based on inexpensive flex substrate for long-term biopotential (EMG/ECG) monitoring

Abstract

The comfortable, long-term, accurate, and continuous biopotential monitoring is of paramount importance for biomedical applications. In this respect, dry electrodes are the way forward for the next generation of wearable health monitoring devices. However, it is still challenging to record the bioelectrical signals, i.e., electroencephalogram (EEG), electromyogram (EMG), electrocardiogram (ECG), of patients during their everyday life. It is mainly because, soft skin-like, at the same time, electrically conducting and biocompatible materials have to be integrated with electrical circuits. Dry electrodes have the potential to be integrated in this manner into a variety of wearable form factors. However, most dry electrodes are fabricated on rigid substrates, which do not possess sufficient flexibility and conformability to human skin. Novel flexible/stretchable substrates are a topic of research in the state-of-the-art literature for dry electrodes in pursuit of the wearable biopotential electrodes.In this work, a novel flexible and wearable dry electrode technology based on polydimethylsiloxane (PDMS) is presented. It has been tested for EMG and ECG signal acquisition as the proof of principle. The performance of the fabricated dry electrodes is investigated by measuring the contact impedance between the skin and the electrode. The impedance is compared with the commercially available wet Ag/AgCl electrodes. Overall the contact impedance of the dry electrodes is comparable compared to the wet Ag/AgCl in the frequency range of interest for biopotential electrodes. Experimentally received signal quality of EMG/ECG with the dry electrode is comparable to the wet electrode as well. The dry electrodes do not require any skin preparation nor conductive gels. Thanks to the extreme flexibility of our electrode, it provides more robust contact as well as less skin irritation. The provided results suggest that the presented electrodes/technology have the potential to be used in clinical health-care applications. To support this claim, long term EMG/ECG results are also provided in the manuscript.