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Deliverable D2.4: Status of Dry Electrode Development Activity

Author: Mihajlovic, V. · Garcia Molina, G.
Publisher: Philips Research
Institution: Philips Research
Identifier: TN-2010/00289
Keywords: biomedical electrodes · biosensors · eeg · wearable sensors
Rights: (c) 2010 Koninklijke Philips Electronics N.V.


The goal of dry electrode development activity within the WP2 is tobuild a dry electrode prototype for brain wave sensing that is comfortable for the user and provides sufficient signal quality. The electrodes are to be utilized in BCI applications, namely Steady-StateVisually Evoked Potential (SSVEP),Event Related Synchronization andDe-synchronization (ERD/ERS),and P300 based BCIs. Due to the statusof the dry electrode technology and our non-encouraging results onthe evaluation of the contactless dry sensors we re-focused our efforts in developing an EEG system using dry electrodes that have galvanic contact to the human scalp. The first goal we set is to reliably detect the alpha brain rhythm (brain waves in the range from 8 to12Hz) as these brain waves are the most prominent ones in the EEG spectrum.The outcome of the evaluation presented here is that the signal quality of dry electrodes is sufficient to reliably measure alpha brainactivity. This is con-firmed through user studies with the medicallycertified amplifier - Mobi from TMSi. However, due to the skin contact problems and high input impedance, reported in the deliverable,robustness of dry-electrode (in combination with the amplifier) hasto be further improved. In particular, the dry electrode design andamplifier front end have to be further optimized.The robustness of the dry electrode-amplifier combination has to befurther improved to achieve a stable signal and reliable performancewhen measuring brain waves of people with long and thick hair. Thefollowing directions for further developments are envisioned:- Optimization of dry electrode design, focusing on- electrode material, i.e., using “bio-approved” materials such asgold and silver/silver-chloride used in this deliverable that willenable low impedance to the skin- number of pins to achieve good contact and increase the comfort- Optimization of amplifier front-end to cope with variation in input impedance- Optimize existing amplifier technology for usage with the developed dry electrodes.

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