Hair-compatible sponge electrodes integrated on VR headset for electroencephalography

Virtual reality (VR) technology has emerged as a promising tool for brain-computer interaction and neuroscience research due to its ability to provide immersive and interactive experiences for its users. As a powerful tool to noninvasively monitor the cortex, electroencephalography (EEG) combined with VR represents an exciting opportunity for the measurement of brain activity during these experiences, providing insight into cognitive and neural processes. However, traditional gel-based EEG sensors are not compatible with VR headsets, and most emerging VR-EEG headsets utilizing rigid comb electrodes are uncomfortable after prolonged wear. To address this limitation, we created soft, porous, and hair-compatible sponge electrodes based on conductive poly(3,4-ethylenedioxythiophene) polystyrene sulfonate/melamine (PMA) and integrated them onto a VR headset through a customized, flexible circuit for multichannel EEG during VR task performing. Our PMA sponge electrodes can deform to make contact with the scalp skin through hairs under the pressure naturally applied by the strap of the VR headset. The specific contact impedance was consistently below 80 kΩ·cm2, even at hairy sites. We demonstrated the capability of our VR-EEG headset by recording alpha rhythms during eye closure at both hairless and hairy sites. In another demonstration, we developed a VR task to evoke the contingent negative variation potential and achieved a classification accuracy of 0.66 ± 0.07, represented by the cross-validated area under the receiver operating characteristic curve. Our sponge-electrode-integrated VR headset is user-friendly and easy to set up, marking a step toward future reliable, comfortable, and reusable VR-EEG technology.