Bristle-sensors—low-cost flexible passive dry EEG electrodes for neurofeedback and BCI applications

Abstract

In this paper we present a new low-cost dry electrode for EEG, that is made of flexible metal-coated polymer bristles. We examine various standard EEG paradigms, such as capturing occipital alpha rhythms, testing for event related potentials in an auditory oddball paradigm and perform a sensory motor rhythm-based event-related (de-) synchronization paradigm to validate the performance of the novel electrodes in terms of signal quality. Our findings suggest, that the dry electrodes we developed result in high quality EEG recordings and are thus suitable for a wide range of EEG studies and BCI applications. Furthermore, due to the flexibility of the novel electrodes a higher comfort is achieved in some subjects, this being essential for long-term use. Background and ObjectiveWhile there has been a recent surge in dry electrode technology with many groups starting research in this domain [1,2,3], dry electrodes have already been proposed since the early 90's [4,5], early pioneering work of capacitive electrodes had already begun in the early 70's [6]. The miniaturization of EEG equipment [7] as well as the wearability and convenience of novel EEG systems will be a vital factor in determining whether EEG-based related BCI technology will be accepted by the wider community and thus gain wide-spread use. Being able to measure high-quality EEG signals through hair, while at the same time not posing any health risks is also very important.Classic gel-based electrodes present a number of inconveniences that have prevented this spread so far. For one there is the time-consuming setup of an EEG cap, but also the gel is wet, it may dry up and requires washing of the hair after use. In addition the drying up gel can lead to varying impedances and the need of periodical recalibration, making long-term monitoring more difficult.

Soft, curved electrode systems capable of integration on the auricle as a persistent brain–computer interface

“…This arrangement causes skin irritation (erythema) and leads to electrical degradation for periods of use that extend more than a few hours, typically caused by drying of the electrolyte gel (6). Recent technologies replace the gel (7,8) with needles (8,9), contact probes (10,11), capacitive disks (12,13), conductive composites (14,15), or nanowires (16). Such dry electrodes have some promise, but they require multistep preparations, obtrusive wiring interfaces, and/or cumbersome mechanical fixtures.…”

Active Electrodes for Wearable EEG Acquisition: Review and Electronics Design Methodology

“…Silver-coated polymer bristles [14], dry foam electrodes [15], polymer electrodes made of polydimethylsiloxane (PDMS) [16] or polyurethane [17], and comb-shaped polymer electrodes [18] can provide soft contact to the skin while still providing low electrode impedance in the order of 20kΩ to 500kΩ, being promising alternatives for wearable EEG applications.…”

Impedance analysis of ZnO nanowire coated dry EEG electrodes

“…In recent years, different types of dry electrodes, such as polymer foam electrode, solid-gel electrode, textile electrode, pin-shaped metallic electrode have been developed. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] To evaluate the performance of these electrodes, comparing the spontaneous EEG signals (e.g., the alpha wave) or the evoked potential acquired by the dry electrodes and conventional Ag/AgCl electrodes qualitatively or quantitatively is a common approach. [2][3][4][11][12][13] However, the signal quality is not only affected by the electrode itself, but also the acquisition components of the EEG system.…”

“…[15][16][17] Electrodes made of silver-coated polymer bristles have been proposed and shown to be more conductive, flexible and comfortable. [7] Our group has developed a novel dry EEG * Correspondence: Wenyan Jia; Email: wej6@pitt.edu; Address: Department of Neurosurgery, University of Pittsburgh, PA, USA.…”