Development of Low-Contact-Impedance Dry Electrodes for Electroencephalogram Signal Acquisition

Abstract

Dry electroencephalogram (EEG) systems have a short set-up time and require limited skin preparation. However, they tend to require strong electrode-to-skin contact. In this study, dry EEG electrodes with low contact impedance (<150 kΩ) were fabricated by partially embedding a polyimide flexible printed circuit board (FPCB) in polydimethylsiloxane and then casting them in a sensor mold with six symmetrical legs or bumps. Silver–silver chloride paste was used at the exposed tip of each leg or bump that must touch the skin. The use of an FPCB enabled the fabricated electrodes to maintain steady impedance. Two types of dry electrodes were fabricated: flat-disk electrodes for skin with limited hair and multilegged electrodes for common use and for areas with thick hair. Impedance testing was conducted with and without a custom head cap according to the standard 10–20 electrode arrangement. The experimental results indicated that the fabricated electrodes exhibited impedance values between 65 and 120 kΩ. The brain wave patterns acquired with these electrodes were comparable to those acquired using conventional wet electrodes. The fabricated EEG electrodes passed the primary skin irritation tests based on the ISO 10993-10:2010 protocol and the cytotoxicity tests based on the ISO 10993-5:2009 protocol.

High‐Resolution Recording of Neural Activity in Epilepsy Using Flexible Neural Probes

“…[49] Traditional brain-computer interface systems for diagnosing and treating epilepsy rely largely on implantable rigid electrodes, which have several limitations, including limited electrode detection points, high power consumption, and a high risk of post-implantation inflammatory reactions. [20][21][22] With advancements in bio-affinity materials, micro-nano-scale processing technologies, and semiconductor micro-system integration, the development of brain-computer interfaces is shifting towards miniaturization, low power consumption, ultra-flexibility, high throughput, and high resolution. [31] In this study, we successfully established mouse epilepsy models and recorded neural neurophysiological signals using highchannel and high-density flexible neural electrodes.…”

“…[14][15][16][17][18] First, most SEEG and micro-wire probes possess only 8-32 recording sites with few exceptions, leading to constrained spatial resolution and coverage with few exceptions. [19][20][21][22] Furthermore, these probes are often fabricated from rigid materials like silicon or tungsten, which can induce inflammation and glial cells accumulation due to the mechanical mismatch between the probes and brain tissue. [23,24] This, in turn, results in the gradual deterioration of signal quality over time.…”

State-of-the-Art on Brain-Computer Interface Technology

“…Recent advances in EEG sensor technology have made them smaller, lighter, and cheaper than ever before while still providing high levels of accuracy and reliability when compared to traditional systems [25,26,42]. Moreover, newer systems often make use of dry electrode designs, which eliminate the need for conductive gels that were previously required for proper functioning [43][44][45][46][47]. Furthermore, many new portable devices exist now that allow users to easily record their own EEG signals without having to visit a clinic [9,[48][49][50][51].…”

A Film Electrode upon Nanoarchitectonics of Bacterial Cellulose and Conductive Fabric for Forehead Electroencephalogram Measurement

“…These reasons make gel electrodes unsuitable for long-term, repeated use. Nowadays, many wearable dry electrodes have been researched [ 12 , 13 , 14 , 15 ]. The main research content is to record EEG in a hairy area [ 16 , 17 , 18 ].…”