A Novel, Needle-Array Dry-Electrode With Stainless Steel Micro-Tips, for Electroencephalography Monitoring

Abstract

A novel, needle array dry electrode consisting of 10 × 10 array of stainless steel (SS) Microtips was developed for electroencephalography (EEG) monitoring. The developed dry electrode uses commercially available, inexpensive, SS acupuncture needles certified for invasive use, to collect the EEG signal. The microtips of the acupuncture needles project out of a flat Teflon base by approximately 150 μm. Mechanical failure analysis was carried out, with theoretical calculations for individual needles and experimental measurements with a universal testing machine (UTM). The theoretically calculated critical load for failure for individual needle was 0.88 N, while the UTM measurements show the failure occurring at 0.95 N; this difference is probably due to the simplified assumptions used in calculations. The UTM measurements of the individual needle applied against a Silicone elastomer reveal that the force required for the penetration of the needle of the electrode into skin maybe as low as 0.01 N. Needle array insertion into silicone elastomer sheet and its optical inspection was carried out to assess the ability of the microneedles to penetrate the skin. The impedance of the electrode, measured in three electrode configuration in 0.9% NaCl solution, was approximately 6.8KΩ at 20 Hz, which is sufficiently low to fulfill the requirements of biopotential measurement. The construction and characteristics of the developed needle array dry electrode show that they are suitable for penetrating the stratum corneum of the skin and acquire the EEG signal directly from the interstitial fluidic layer underneath. The construction of the electrode and its mechanical and electrical characteristics show that it is a promising dry electrode for long duration EEG Monitoring.

Nanomaterials-patterned flexible electrodes for wearable health monitoring: a review

“…EEG is a cheap, non-invasive method to record physiological electric signals generated due to the neural activity of the brain [ 290 – 292 ]. This signal can indicate the consciousness and alertness of the subject, sleep quality, and clinical applications for the diagnosis and treatment of brain dysfunctions and the onset of neuropsychological diseases [ 293 , 294 ]. EEG energy signal occurs due to five rhythms such as δ, θ, α, β, γ rhythm.…”

The Status of Textile-Based Dry EEG Electrodes

“…EEG is a classic example of a biopotential recording of the electrical signals produced by the activity of the brain [9][10][11]. It is useful for monitoring the quality and alertness of sleep, clinical applications, diagnosis and treatment of patients with epilepsy, Parkinson's disease and other neurological disorders, and continuous monitoring of fatigue/alertness of staff deployed in the field or under strain [12]. The EEG electrodes are placed on the scalp to monitor the activities in the brain (Figure 2).…”

“…Wang et al proposed a novel porous ceramic "semi-dry" electrode with a key feature that electrode tips can slowly and continuously release a small amount of electrolyte liquid into the scalp, providing an ionic conducting path for detecting neural signals that can effectively capture electrophysiological responses and is a viable alternative to conventional electrodes in brain-computer interface (BCI) applications [18]. Radhakrishnan et al developed a needle array dry electrode microstrip from stainless steel (SS) having an impedance about 6.8 kW at 20 Hz in a 0.9% NaCl solution, which is sufficiently low to fulfill the requirements of biopotential measurement and suitable for penetrating the stratum corneum of the skin and acquire the EEG signal directly from the interstitial fluidic layer underneath which could make it a promising dry electrode for long duration EEG monitoring [12]. In 2017, Kannan et al developed a wearable and less visible Ear-EEG recording device [19].…”

“…[11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] [44] [45] [46] [47]…”

Fructus Xanthii-Inspired Low Dynamic Noise Dry Bioelectrodes for Surface Monitoring of ECG

“…The surface microneedle array electrodes can avoid changes in skin potential due to skin stretching or electrode movement and can be divided into rigid microneedle array electrodes (RMAEs) and flexible microneedle array electrodes (FMAEs) . RMAEs can penetrate the high-impedance SC without skin pretreatment, thereby making direct contact with low-impedance living epidermal cells to eliminate the need for conductive gels. − However, there is a risk that such electrodes may break in practice, resulting in microneedle fractures entering the body. The main processing method for FMAEs is the processing of metallic patterns or conductive coatings on a flexible substrate, which makes them conductive and stretchable. − Compared to RMAEs, the flexible substrate of FMAEs naturally conforms to skin curves, with better adapting to the skin structure, curvature, and surface hair, resulting in more comfortable, stable, and lower impedance performance …”