Neurobits:

Designing Microbeads wearable EEG Electrodes for Human-Computer Interfaces

Author

Elle Luo

Master's Thesis | Cornell University

Year

2021

Neurobits are wearable EEG electrodes that use silicone microbeads to attach to the hair while recording brain signals. The system was evaluated in a user study, examining signal quality and user experience in a natural environment.

See the full paper here.

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NeuroBits is a new type of comfortable microbead EEG electrode for monitoring brain signals. (a) Detail of the wearable EEG electrode and its parts. (b) NeuroBit electrodes are wired to a circuit board that hangs at the wearer’s back. (c) The small electrodes are attached to the user’s hair and may be nearly unnoticeable.

Overview

Conventional EEG devices are usually consist on a cap that with electrodes that measure electrical activity from the brain through either gel-based electrodes or spiky dry-electrodes. Due to the form factor and pressure from these devices, they may cause irritation on the scalp, hinder body movements, and can negatively impact the user’s comfort. This may limit the potential of neurotechnology for daily use in daily-life situations. We propose a head-conforming design of EEG-electrodes, NeuroBits, a system that incorporates EEG electrodes that attach to the hair, are seamless, lightweight, and tiny. These electrodes use silicone microbeads to attach to a strand of hair and blend in fluidly, while also having the capacity to continuously record brain activity inside and outside of the laboratory. The NeuroBits system was evaluated favorably in a user study of 14 participants, examining signal quality, user experience, and perceptions towards social acceptance in a natural environment, in comparison against the electrodes of a consumer available mobile-EEG device (OpenBCI). By integrating human-factors design into conventional neurotechnology, NeuroBits provides a novel wearable means of monitoring brain activity in real-world settings.

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Design Goals
  • Comfortable to wear

  • Lightweight

  • Fit into individual's size of head

  • Seamless & inconspicuous

  • Not covering the hair 

Prototype I: Temporary Tattoo-based PEDOT:PSS Electrode
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The initial idea of NeuroBit. (a) Design sketch, (b) first on-skin prototype using temporary tattoo substrate coated with PEDOT:PSS ink, (c) 3D design of the case that will contain the

electronics (back of the ear).

Prototype II: On-Skin Silver/Silver-Chloride Electrode
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The second iteration of NeuroBits. (a) On-skin prototype using silicone substrate coated with Ag/AgCl ink, (b) what the prototype looks like to be placed on the forehead, (c) compared signal patterns with a commercially available electrode and achieved similar quality.

Prototype III: On-Ear Electrode
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The third iteration of NeuroBits. (a) On-ear EEG prototype, (b) what the prototype looks like when being worn around the ear.

Prototype IV: Hairclip-Type Electrode
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The fourth and fifth iteration of NeuroBits. (a) The fourth iteration uses a hair extension clip to attach the electrode to the hair, (b) what the prototype looks like when being worn in the hair, (c) the fifth iteration uses a 3D designed hair clamp to attach to the hair, (d) what the prototype looks like when being attached to the hair.

Prototype V: Microbead-Type Electrode
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The final design of NeuroBits. (a) The full demonstration of a user wearing the final design of NeuroBit, (b) the closeup of what NeuroBits looks like when attached to the hair.

Devices Validation
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Raw EEG data comparison for one participant for NeuroBits vs. OpenBCI dry electrodes. The graphs show the data collected by both electrode types in four scalp locations during four different activities.

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Comparison of average band power dynamics across all participants for the four scalp locations during the “eyes closed” condition (Neurobits electrodes vs. wet and dry OpenBCI electrodes combined). Both EEG electrodes detect a clear Alpha rhythm peak at 8-13 Hz.

User Experience
Quantitative
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Results of the user experience questionnaire (e.g., Attrakdiff). (a) Mean values that participants gave to AttrakDiff positive/negative word pairs in relation to the two types of EEG devices. (b) Mean values for each of the four AttrakDiff survey dimensions. (c) User ratings of perceived social comfort while wearing the two types of EEG devices. The results from all parts of this questionnaire show a consistent preference for the NeuroBits over the OpenBCI products.

Qualitative

“[What did you like about wearing NeuroBits electrodes?] I think it is relatively comfortable. You don’t feel it once the device is on your head. “ – (P05)

“[What did you like about wearing NeuroBits electrodes?] . . . They were hidden very well. I think it is much more visually pleasant than a headset.” – (P01)

“The electrodes (NeuroBits) are very tiny. The wires are also pretty tiny. It is not chunky” – (P03)

“[What did you like about wearing NeuroBits electrodes?] It was very light. I did not feel any physical discomfort after 30 minutes of wearing them...” – (P01)