Novel flexible dry PU/TiN-multipin electrodes: First application in EEG measurements

Abstract

Dry biosignal electrodes for electro-encephalography (EEG) are an essential step for realization of ubiquitous EEG monitoring and brain computer interface technologies. We propose a novel electrode design with a specific shape for hair layer interfusion and reliable skin contact. An electrically conductive Titanium-Nitride (TiN) thin layer is deposited on a polyurethane substrate using a multiphase DC magnetron sputtering technique. In the current paper we describe the development and manufacturing of the electrode. Furthermore, we perform comparative EEG measurements with conventional Ag/AgCl electrodes in a 6-channel setup. Our results are promising, as the primary shape of the EEG is preserved in the signals of both electrodes sets, according to recordings of spontaneous EEG and visual evoked potentials. The variance of both signals is in the same order of magnitude. The Wilcoxon-Mann-Whitney two-sample rank-sum test revealed no significant differences for 25 of the 28 compared signal episodes. Hence, our novel electrodes show equivalent signal quality compared to conventional Ag/AgCl electrodes.

Ag:TiN‐Coated Polyurethane for Dry Biopotential Electrodes: From Polymer Plasma Interface Activation to the First EEG Measurements

“…The power increases for lower frequencies for all electrodes. For frequencies below 3 Hz, an increase toward higher values is perceivable in the plasma treated dry MP electrodes, which should be attributed to slightly increased drift behavior, which was already observed in previous studies …”

“…Moreover, incorrect and/or uncomfortable skin contact may arise due to the stiff nature of some of the proposed base materials (aluminium, [3] steel, [11,12] silicon, [13,14] titanium, [15] and polycarbonate [16] ), and designspecific conceptual problems (micro-needle electrodes [13,14] and rigid planar plates/disks unable to interfuse the hair layer [15,16] ). Hence, in order to reduce some of the referred drawbacks, several authors focused not only on the development of new electrode designs, which allow an effective hair interfusion, [17][18][19][20] but also on the use of more compliant base materials, such as textiles [21] and, above all, flexible polymers. [22][23][24][25] Thermoplastic polyurethanes (TPU) have been extensively applied in several fields that range from technical coatings to biomedical applications, [26][27][28] due to their excellent balance between mechanical properties (high flexibility, dependent on the composition), chemical barrier behavior, soft tact, and biocompatibility, [29,30] thus being appropriate to be used as biopotential electrode base material.…”

Electrochemical and structural characterization of nanocomposite Agy:TiNx thin films for dry bioelectrodes: the effect of the N/Ti ratio and Ag content

“…), the authors recently explored the sputtering viability of Ag x :TiN coatings (with close-stoichiometric TiN) by optimizing their deposition parameters and properties [22,23], architecture [24] and electrochemical behaviour [25] on classic substrates (glass and silicon), so that they can be later sputtered onto flexible polymer-based substrates. Preliminary investigations by the authors demonstrated that the use of flexible polymer electrodes with nanocoatings of electrically conductive TiN x allowed for comfortable dry EEG recording, providing signal quality comparable to conventional Ag/AgCl wet electrodes [26], although the coatings displayed a low mechanical stability. Silver was then added to TiN in order to tailor several properties of the matrix (e.g.…”

Novel flexible Dry multipin electrodes for EEG: Signal quality and interfacial impedance of Ti and TiN coatings

“…The specific shape is capable of interfusing the hair layer and enabling stable contact with the scalp. In a preliminary test on a single volunteer a titanium nitride (TiN) coated MP electrode proved to provide Ag/AgCl-comparable signal quality [10]. In the current paper a further comparison of two different titanium (Ti) and TiN coated MP electrodes as well as a conventional Ag/AgCl reference electrode is performed in terms of electrode-skin interfacial impedance and EEG signal quality in of a multi-volunteer study.…”