A noval active pin–shaped dry EEG electrode designed in accordance with surface Laplacian structure

Currently, scalp electroencephalography (EEG) is limited by its low spatial resolution, insufficient spatial localization capability for neuronal activities in the brain, and susceptibility to myogenic signal interference. The primary reasons for these limitations are the volume conductor effect and interference from other signal noises. To address these issues, this study proposes a Laplacian dry electrode. In terms of the electrode's structure, we designed a quasi-bipolar concentric ring composed of 15 flexible Ag/AgCl dry electrodes, enabling it to penetrate hair for EEG signal acquisition. Additionally, this structure accurately estimates the Laplacian potential at the center point by weighting the potential values of surrounding points. By applying the Laplacian potential estimation method, we can reduce interference signals introduced by surrounding electrodes and enhance the spatial resolution of EEG signals. Furthermore, a front-end amplification circuit, consisting of three modules—gain buffer circuit, amplification circuit, and AC coupling circuit—is designed to be as close as possible to the flexible Ag/AgCl dry electrodes. This circuit amplifies the EEG signals during acquisition, improves the common-mode rejection ratio, and reduces noise interference. Experimental results demonstrate that the overall root mean square noise of the electrode is 0.2199 µV, with a contact impedance of 34.37 kΩ. Finally, to validate the performance of the Laplacian dry electrode, BCI experiments including spontaneous and evoked EEG were conducted. The results indicate that the quality of EEG signals acquired by this electrode is comparable to that of wet electrodes, demonstrating that the Laplacian dry electrode can acquire high-quality EEG signals.