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Comfortable Consumer EEG Headset Shown by Imec and Holst Centre

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By Ed Korczynski, Sr. Technical Editor

A new wireless electroencephalogram (EEG) headset that is comfortable while providing medical-grade data acquisition has been shown by the partnership of imec, the Holst Centre, and the Industrial Design Engineering (IDE) department of TU Delft. The 3D-printed low-volume product enables early research and self-monitoring of emotions and mood in daily life situations using a smartphone application. Consumer applications include games that monitor relaxation and/or concentration, and medical applications that help with sleep disorders and treatment of Attention Deficit Hyperactivity Disorder (ADHD).

Figure 1 shows the new headset with novel elastic electrode arrays in an elegant uni-body assembly to optimize both comfort and signal quality. The electronics package in the middle of the headset fits on the back of the user’s neck. Each electrode is a small array of elastic polymer fingers which allow for dry contact—without needing a conductive liquid or gel—to skin for long-term comfortable use.

Figure1: Comfortable EEG headset developed by imec and Holst Centre and TU Delft in 2015, providing medical-quality data tracing of emotions and mood in daily life situations using a smartphone application. (Source: imec)

“Leveraging imec’s strong background in EEG sensing, dry polymer and active electrodes, miniaturized and low-power data acquisition, and low-power wireless interfaces to smartphones, we were able to focus on the ergonomics of this project. In doing so, we have successfully realized this unique combination of comfort and effectiveness at the lowest possible cost to the future user,” stated Bernard Grundlehner, EEG system architect at imec.

In 2011, imec and Holst Centre created an 8-channel ultra-low-power analog readout application-specific integrated circuit (ASIC) that consumes only 200µW and features high common mode rejection ratio (CMRR) of 120dB and signal to noise ratio of 25dB on real EEG signals. This ASIC is tuned to high input impedance (1GΩ) for compatibility with the use of dry electrodes. That system—including ASIC, radio, and controller chips— could be integrated in a package of 25mmx35mmx5mm dimensions for easy of integration in headsets, helmets, or other accessories. That system consumes only 3.3mW for continuous recording and wireless transmission of 1 channel—9.2mW for 8 channels—allowing for 1.5 to 4 days of functionality when powered by a 100mAh Li-ion battery.

In 2009, imec and Holst Centre showed off a rough mobile EEG prototype to partners and journalists at the yearly imec Technology Forum. Figure 2 shows that the prototype was bulky and a bit awkward to wear, while the figure does not show that sintered silver/silver-chloride electrodes are very hard such that dry contact to the human scalp tends to be uncomfortable.

Figure2: Ed Korczynski tests an imec EEG headset rough prototype, using uncomfortable hard silver/silver-chloride electrodes, at the 2009 Imec Technology Forum. (Source: Ed Korczynski)

The 2015 model uses new flexible electrodes arrays which are inherently more comfortable than hard silver/silver-chloride electrodes. A team of six master students from IDE of TU Delft led the design optimization of the 3D unibody for the new headset using 3D printing for short-loop prototyping and testing of different shapes for stability and comfort. Iterative tests with users for multiple applications led to this design which is intended for long-term comfortable use by consumers outside of a controlled research environment.

The new EEG headset is manufactured in one piece using 3-D printing, after which the electronic components are placed, connected, and covered by a 3-D-printed rubber inlay. The EEG electrodes are situated at the front of the headset for optimal acquisition of signals related to emotion and mood variations. A mobile app can then tie the user’s emotional state to environmental information such as location, time, agenda, and social context to track possible unconscious effects.

—E.K.



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