Advanced Technique for EEG and HRV Measurement Using Around-Ear Capacitive Electrodes

Long-term electroencephalogram (EEG) monitoring requires devices that are unobtrusive, comfortable, and user-friendly. Capacitive electrodes, unlike gel or dry electrodes, do not require direct galvanic skin contact, making them ideal for extended use. This paper investigates the efficacy of capacitive electrodes for recording four biopotential channels from around-ear areas. A printed circuit board was developed and assessed through an alpha-block experiment. The posterior-ear capacitive EEG achieved a statistically significant power gain (APSD) of 2.77 dB in the alpha band and 5.84 dB at 10 Hz. Additionally, a mean absolute error (MAE) of 8.9 milliseconds was observed between heart rate variability (HRV) measurements from a capacitive superior-ear electrode and shoulder ECG. These results indicate that around-ear capacitive electrodes are suitable for multimodal biopotential applications, offering a promising solution for long-term EEG monitoring.