3D-printed, directly conductive and flexible electrodes for personalized electroencephalography

Electroencephalography (EEG) is a widely used non-invasive brain monitoring technique that records the electrical signals generated within the brain, with applications ranging from epilepsy to Brain-Computer Interfaces (BCI). The electrode connecting the EEG instrumentation to the user’s scalp is a key part of this system which determines the overall performance. Traditionally, disc electrodes, or fingered electrodes to pass through hair, have been used, but with a very limited number of sizes and shapes available which do not reflect all users and head-hair types. Recently, 3D-printed electrodes have been proposed for allowing personalized manufacturing and more inclusive EEG. Current 3D- printed electrodes can be physically flexible for comfort, and allow recording without a conductive gel being added. However, they are formed by printing a base structure which is then coated with Silver/Silver-Chloride to make it suitable for non-invasive brain recording. This paper presents novel 3D-printed EEG electrodes with that can be made using a directly conductive flexible filament. The resulting electrodes are gel free, coating free, can be personalized, have reduced manufacturing time, and cost less compared to previous electrodes. Our electrodes are characterized in terms of contact impedance, contact noise, on-phantom signal recording, mechanical strength, and the recording of Steady-State Visual Evoked Potentials (SSVEPs) from volunteers. They have much higher contact impedance present compared to Silver/Silver-Chloride coated electrodes, resulting in higher contact noise and more susceptibility to motion artifacts, but offer a wide range of benefits for low cost personalized electroencephalography.