Abstract
For electroencephalography (EEG) in haired regions of the head, finger-based electrodes have been proposed in order to part the hair and make a direct contact with the scalp. Previous work has demonstrated 3D-printed fingered electrodes to allow personalisation and different configurations of electrodes to be used for different people or for different parts of the head. This paper presents flexible 3D-printed EEG electrodes for the first time. A flexible 3D printing element is now used, with three different base mechanical structures giving differently-shaped electrodes. To obtain improved sensing performance, the silver coatings used previously have been replaced with a silver/silver-chloride coating. This results in reduced electrode contact impedance and reduced contact noise. Detailed electro-mechanical testing is presented to demonstrate the performance of the operation of the new electrodes, particularly with regards to changes in conductivity under compression, together with on-person tests to demonstrate the recording of EEG signals.
Highlights
EEG is a widely-used tool for the non-invasive monitoring of electrical signals in the brain and is used in applications from epilepsy diagnosis to brain–computer interfaces [1]
Connections to the phantom head did not have hair and similar application obstacles, and so, the contact impedances were generally low; lower than those with our previous dry 3D-printed electrodes, which were in the range of 5–10 kΩ [6] and below the 10 kΩ limit typically used for passive electrode
The spiny electrode had the lowest contact impedance, it was similar in magnitude to the spider electrode
Summary
EEG is a widely-used tool for the non-invasive monitoring of electrical signals in the brain and is used in applications from epilepsy diagnosis to brain–computer interfaces [1]. A wide range of electrode materials [2] are possible, with sintered silver/silver-chloride (Ag/AgCl) being the most widely used due to its biocompatibility, non-polarising nature and low contact noise and baseline drift [3] The work in [6] used a desktop-grade 3D printer (0.5-mm resolution head used) to produce fingered 3D-printed electrodes similar in shape to that, which were coated in silver These electrodes were printed using a standard PLA plastic and so were rigid. The new electrodes have been coated in silver/silver-chloride to obtain better sensing performance compared to the earlier 3D-printed designs, which used silver to make the electrode conductive. Data availability details are given at the end of the paper
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