A Closed-Loop Ear-Worn Wearable EEG System with Real-Time Passive Electrode Skin Impedance Measurement for Early Autism Detection †
<p>(<b>a</b>) Conventional Autism Diagnostic Observation Schedule (ADOS-2) for ASD diagnosis along with (<b>b</b>) proposed ASD prediction system.</p> "> Figure 2
<p>Proposed ear-worn EEG acquisition, ASD prediction, and real-time ESI monitoring system.</p> "> Figure 3
<p>AFE schematic along with electrode placement and ESI circuit.</p> "> Figure 4
<p>ASD classification processor block diagram.</p> "> Figure 5
<p>Feature calculation unit’s hardware implementation.</p> "> Figure 6
<p>SNN unit’s hardware implementation.</p> "> Figure 7
<p>Skin layers and respective equivalent Webster ESI model for wet and dry electrodes under different conditions (no sweating and sweating conditions).</p> "> Figure 8
<p>Configuration schematics and measuring model for approximate ESI.</p> "> Figure 9
<p>AFE power profile details.</p> "> Figure 10
<p>(<b>a</b>) Fabricated PCB. (<b>b</b>) Completely assembled device. (<b>c</b>) Mobile application for real-time EEG, ESI measurement, and ASD classification.</p> "> Figure 11
<p>EEG acquisition (Fp1 and Fp2) for various conditions including (<b>a</b>) closed eyes, (<b>c</b>) open eyes, and (<b>e</b>) blinking eyes along with the respective signal spectrograms (<b>b</b>,<b>d</b>,<b>f</b>) for 1 min using wet pre-gelled Ag/AgCl electrodes.</p> "> Figure 12
<p>(<b>a</b>) Raw and (<b>b</b>) filtered EEG signal acquired using the developed device for a window of five seconds using dry electrodes.</p> "> Figure 13
<p>EEG AFE characteristic measurements results for (<b>a</b>) CMRR, (<b>b</b>) input referred noise, and (<b>c</b>) AFE variable gain.</p> "> Figure 14
<p>(<b>a</b>) Various types of electrodes along with the effective asking contact area (SCA *). The 7.2 mm diameter dry electrodes, (<b>b</b>) 8 mm diameter wet electrodes, (<b>c</b>) 10 mm diameter wet electrodes, and (<b>d</b>) conductive paste.</p> "> Figure 15
<p>(<b>A</b>) Effect of pressure on ESI with the wet disposable pre-gelled Ag/AgCl electrodes and (<b>B</b>) dry reusable Ag/AgCl electrodes.</p> "> Figure 16
<p>Effect of skin preparation on dry Ag/AgCl electrodes for ESI.</p> "> Figure 17
<p>(<b>a</b>) Effect of skin locations on the electrodes. (<b>b</b>) Wet electrode ESI measurement on forehead. (<b>c</b>) Dry electrode ESI measurement on forearm. (<b>d</b>) Dry electrode ESI measurement under pressure.</p> "> Figure 18
<p>SNN processor die photo and performance summary.</p> "> Figure 19
<p>ASD detection processor measurement results.</p> ">
Abstract
:1. Introduction
2. Proposed Ear-Worn EEG Acquisition System For ASD Detection
2.1. Analog Front End Design
2.1.1. Low-Noise Amplifier
2.1.2. Programmable Gain Amplifier
2.2. Back-End Micro Controller
2.2.1. Digitization, Storage, and Transmission
2.2.2. Approximate ESI Calculation
2.3. Shallow Neural Network ASD Prediction Processor
2.3.1. ASD Prediction Data Set
2.3.2. Feature Set and Feature Calculation Unit
2.3.3. Shallow Neural Network Classification Unit
2.4. Electrode–Skin Impedance Unit
3. Device Power Profile and Prototype
4. Measurements and Results
4.1. Electroencephalogram Measurement
4.2. Analog Front End Measurement
4.3. Electrode Skin Interface Impedance Measurement
4.3.1. Types of Electrodes
4.3.2. Electrode Skin Interface Impedance Measurement Test
- Effect of Pressure:The effect of the pressure on ESI was observed using both dry reusable Ag/AgCl electrodes and wet disposable Ag/AgCL electrodes. Figure 15 shows the effect of pressure on ESI measurement. Electrodes were placed at the Fp1 and Fp2 locations on the forehead. It was observed that there was no significant effect of pressure on the wet Ag/AgCl electrodes for ESI as depicted in Figure 15A. However, for dry electrodes, a significant decrease in ESI was observed until a specific minimum point was reached at which the electrodes were firmly in contact with the skin [9,46,47,48]. Figure 15B shows the effect of pressure on ESI measurement using dry Ag/AgCl electrodes. A pressure of 15 mm Hg was applied using an elastic headband for trials no 2, 4, 6, 8, and 10. This experiment was repeated five times. This analysis suggests that the electrodes should be in firm contact with the skin to ensure a small ESI value for dry electrodes.Multiple ESI measurements with the designed device were obtained using different dry and pre-gelled Ag/AgCl electrodes of variable diameter (8 mm, 10 mm, and 7.2 mm, 10 mm). Figure 15 shows the ESI measurements of two different sizes of pre-gelled Ag/AgCl electrodes at various time stamps. Time Stamp number 4 shows the ESI when adequate pressure was applied to the measuring electrodes. It can be observed that the ESI decreases when sufficient pressure is applied [29,30] for both wet and dry electrodes as shown in Figure 15A and Figure 15B, respectively.
- Effect of Skin Preparation on Dry Electrodes:The effect of skin preparation was also observed for the dry reusable Ag/AgCl electrodes. Skin preparation was performed by cleaning the forehead with an alcohol pad and then applying Ten20 conductive electrode paste. Figure 16 shows the effect of skin preparation on the ESI of the dry AG/AgCl electrodes. A slight decrease in ESI for skin preparation as compared to unprepared skin can be observed.
- Skin Locations:To verify the design device and validity of ESI measurement, the electrodes were placed at different body locations including the forehead and forearm with a distance of 30 cm between the electrodes. The effect of skin location on the ESI is shown in Figure 17. The nature and composition of the skin at various body locations are different due to stratum corneum thickness, sweat glands, hairs, etc.Maximum ESI was observed on the forearms while minimum ESI was observed on the forehead for both the wet and dry electrodes as shown in Figure 17a. Figure 17b and Figure 17c show the wet electrode ESI measurement and dry electrode ESI measurement setup respectively. Figure 17d shows the dry electrode ESI measurement setup with pressure using an elastic band.
4.4. SNN-Based ASD Prediction Processor
5. Conclusions
Author Contributions
Funding
Data Availability Statement
Conflicts of Interest
Abbreviations
ASD | Autism Spectrum Disorder |
ML | Machine Learning |
ESI | Electrode–Skin Interface Impedance |
EEG | Electroencephalogram |
AFE | Analog Front End |
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Sheeraz, M.; Aslam, A.R.; Drakakis, E.M.; Heidari, H.; Altaf, M.A.B.; Saadeh, W. A Closed-Loop Ear-Worn Wearable EEG System with Real-Time Passive Electrode Skin Impedance Measurement for Early Autism Detection. Sensors 2024, 24, 7489. https://doi.org/10.3390/s24237489
Sheeraz M, Aslam AR, Drakakis EM, Heidari H, Altaf MAB, Saadeh W. A Closed-Loop Ear-Worn Wearable EEG System with Real-Time Passive Electrode Skin Impedance Measurement for Early Autism Detection. Sensors. 2024; 24(23):7489. https://doi.org/10.3390/s24237489
Chicago/Turabian StyleSheeraz, Muhammad, Abdul Rehman Aslam, Emmanuel Mic Drakakis, Hadi Heidari, Muhammad Awais Bin Altaf, and Wala Saadeh. 2024. "A Closed-Loop Ear-Worn Wearable EEG System with Real-Time Passive Electrode Skin Impedance Measurement for Early Autism Detection" Sensors 24, no. 23: 7489. https://doi.org/10.3390/s24237489
APA StyleSheeraz, M., Aslam, A. R., Drakakis, E. M., Heidari, H., Altaf, M. A. B., & Saadeh, W. (2024). A Closed-Loop Ear-Worn Wearable EEG System with Real-Time Passive Electrode Skin Impedance Measurement for Early Autism Detection. Sensors, 24(23), 7489. https://doi.org/10.3390/s24237489