New dry electrodes based on iridium oxide (IrO) for non-invasive biopotential recordings and stimulation

Abstract

This paper presents a new type of dry electrodes for acquisition of biopotentials and stimulation. These dry electrodes are composed by 16 microtip structures (by forming an array of 4 × 4 microtips), which were fabricated through bulk micromachining of a 1 0 0 -type silicon substrate in a potassium hydroxide (KOH) solution. The fabrication process was trimmed in a way that each microtip presents solid angles of 54.7 • , a width in the range 150-200 m, a height of 100-200 m, and an inter-microtip spacing of 2 mm. The electrodes have a thin layer (obtained by reactive DC-sputtering) of iridium oxide (IrO) to improve the contact with the skin. These dry electrodes penetrate the outer skin layer (i.e. stratum corneum that is 10 m thick) to allow a direct contact with the electrolyte fluids of the inner skin layers. The new electrode avoid the use of conductive gels and reduce the skin preparation time in EEG experiments, which may take about 45 min for a set of 32 standard silver/silver chloride (Ag/AgCl) electrodes. The electrode-electrolyte impedance spectrometry (IS) of the IrO thin-films was performed in a saline solution, 0.9% concentration by weight, to mimic the electrode-tissue interface. The IS measured results for the IrO coatings were comparable to the results observed for the standard Ag/AgCl electrodes. The new dry microtips array constitutes an inexpensive, low resistance and mechanically robust alternative electrode for non-invasive biopotential recording/stimulation with fast application on skin.

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

“…Two recently proposed solutions of the skin invasive category use microtip electrodes, coated with iridium oxide [8] and carbon nanotubes [9] ("Enobio"). As one may expect, both methods lead to high signal quality and are from this perspective well suited for EEG recording.…”

“…As one may expect, both methods lead to high signal quality and are from this perspective well suited for EEG recording. However, the possibility of the microtips breaking off while partly still inside the skin cannot be completely ruled out [8]. For the case of carbon nanotubes, the authors also mention these safety concerns, for which reason they have performed only limited tests with a single subject [9].…”

Affective signal processing (ASP) : unraveling the mystery of emotions

“…Such actuators can directly communicate with our body, either physical [160,265] or chemically [159,451]. Alternatively, actuators can communicate indirectly and influence our environment as we sense it either consciously or unconsciously; for instance, a song can be played or lighting can be activated to create a certain ambiance.…”

TO WHAT EXTENT CAN DRY AND WATER-BASED EEG ELECTRODES REPLACE CONDUCTIVE GEL ONES? - A Steady State Visual Evoked Potential Brain-computer Interface Case Study

“…The approaches range from developing hydrogel-based electrode (Alba et al, 2010) to numerous versions of dry electrodes. Dry electrode solutions include electrodes that are integrated into the wearable material (contactless electrodes) or affixed on top of the scalp (insulated electrodes) (Alizadeh- Taheri et al, 1996;Harland et al, 2002;von Ellenreider et al, 2006;Sullivan et al, 2007;Fonseca et al, 2007;Chi et al, 2009), electrodes that penetrate the outer layer of the skin (Ruffini et al, 2006;Ruffini et al, 2008;Griss et al, 2002;Gramatica et al, 2006;Chiou et al, 2006;Matteucci et al, 2007;Lin et al, 2008;Chang and Chiou, 2009;Ng et al, 2009;Dias et al, 2010), and dry contact electrodes that exhibit galvanic contact to the skin without the usage of additional electrolyte (Taheri et al, 1994;Matthews et al, 2007;Gargiulo et al, 2010). Due to skin damage they can cause, users might be exposed to a higher risk of infection and skin irritation (Ferree et al, 2001) for all dry electrode types except the last one -dry contact electrodes.…”