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OpenEarable ExG: Open-Source Hardware for Ear-Based Biopotential Sensing Applications

Philipp Lepold, Tobias Röddiger, Tobias King, Kai Kunze, Christoph Maurer, Michael Beigl

TL;DR

OpenEarable ExG is an open-source hardware platform designed to measure biopotentials in and around the ears, and demonstrates the successful detection of smooth pursuit eye movements via Electrooculography, alpha brain activity via Electroencephalography (EEG), and jaw clenching via Electromyography (EMG).

Abstract

While traditional earphones primarily offer private audio spaces, so-called "earables" emerged to offer a variety of sensing capabilities. Pioneering platforms like OpenEarable have introduced novel sensing platforms targeted at the ears, incorporating various sensors. The proximity of the ears to the eyes, brain, and facial muscles has also sparked investigation into sensing biopotentials. However, currently there is no platform available that is targeted at the ears to sense biopotentials. To address this gap, we introduce OpenEarable ExG - an open-source hardware platform designed to measure biopotentials in and around the ears. OpenEarable ExG can be freely configured and has up to 7 sensing channels. We initially validate OpenEarable ExG in a study with a left-right in-ear dual-electrode montage setup with 3 participants. Our results demonstrate the successful detection of smooth pursuit eye movements via Electrooculography (EOG), alpha brain activity via Electroencephalography (EEG), and jaw clenching via Electromyography (EMG). OpenEarable ExG is part of the OpenEarable initiative and is fully open-source under MIT license.

OpenEarable ExG: Open-Source Hardware for Ear-Based Biopotential Sensing Applications

TL;DR

OpenEarable ExG is an open-source hardware platform designed to measure biopotentials in and around the ears, and demonstrates the successful detection of smooth pursuit eye movements via Electrooculography, alpha brain activity via Electroencephalography (EEG), and jaw clenching via Electromyography (EMG).

Abstract

While traditional earphones primarily offer private audio spaces, so-called "earables" emerged to offer a variety of sensing capabilities. Pioneering platforms like OpenEarable have introduced novel sensing platforms targeted at the ears, incorporating various sensors. The proximity of the ears to the eyes, brain, and facial muscles has also sparked investigation into sensing biopotentials. However, currently there is no platform available that is targeted at the ears to sense biopotentials. To address this gap, we introduce OpenEarable ExG - an open-source hardware platform designed to measure biopotentials in and around the ears. OpenEarable ExG can be freely configured and has up to 7 sensing channels. We initially validate OpenEarable ExG in a study with a left-right in-ear dual-electrode montage setup with 3 participants. Our results demonstrate the successful detection of smooth pursuit eye movements via Electrooculography (EOG), alpha brain activity via Electroencephalography (EEG), and jaw clenching via Electromyography (EMG). OpenEarable ExG is part of the OpenEarable initiative and is fully open-source under MIT license.

Paper Structure

This paper contains 17 sections, 3 figures.

Table of Contents

  1. Introduction and Related Work
  2. Design Principles
  3. Hard- and Software
  4. OpenEarable Core
  5. ExG Hardware
  6. Analog-to-Digital Converter
  7. Instrumentation and Operational Amplifier
  8. Driven-Right-Leg Active Ground
  9. Pin-Assignment
  10. Earpiece and Mechanical Design
  11. Extensibility
  12. Software
  13. Applications
  14. EEG: Brain Activity Sensing
  15. EMG: Jaw Clenching
  16. ...and 2 more sections

Figures (3)

  • Figure 1: An overview of the system architecture of OpenEarable ExG which builds upon OpenEarable v1.3 roddiger2022openearable.
  • Figure 2: (A) PCB and components of OpenEarable ExG; (B) 3D-printed in-ear plugs based on Dätwyler SoftPulse in-ear electrodes datwyler_softpulse_products (C) assembled device with 3D-printed housing and custom in-ear electrodes; (D) user wearing OpenEarable ExG.
  • Figure 3: (1.A) - (1.F) display brain activity measured via ear EEG for three participants, with eyes open and closed, revealing increased alpha activity when eyes are closed. (2.A) - (2.F) illustrate the rise in signal amplitude measured by ear EMG during jaw muscle clenching for the same participants. (3.A) - (3.E) present smooth pursuit signals measured via ear EOG, showing signal deflection in opposite directions based on the participants' gaze direction.