Parylene-based flexible dry electrode for bioptential recording

The conventional wet silver/silver chloride (Ag/AgCl) electrode is used to record biopotential mostly due to its potential reproducibility, excellent signal to noise ratio (SNR), reliability and biocompatibility. However, this type of electrode only works with conductive gel, and the conductive gel would result in irritation and injury of the skin. Furthermore, the conductive gel would dehydrate over time and thus the quality of biopotential signal degrades. In this paper, a new novel flexible dry electrode with thousands of AgCl micro-pads is proposed for biopotential recording. As the radius of AgCl pad was only 50 μm, the moisture of the skin could be used as the electrolyte of the flexible dry electrode during the biopotentail recording. The fabricated electrode was thin and flexible, so that it attached conformably onto the skin. As a consequence, the contact impedance of electrode-skin interface was relatively stable. The experimental results indicated that the SNR (23.8 dB) of the fabricated electrode was higher than that of conventional dry Ag electrode (20.6 dB). The flexible dry electrode was suitable for long-term biopotential recording and further used in wearable systems for human health monitoring.