Е-Публикации
Технически университет - София

Abstract: This work presents the development and characterization of a flexible capacitive electrode for non-contact ECG acquisition, fabricated using a simple and cost-effective method from readily available materials. The electrode consists of a multilayer structure with a copper conductor laminated by a polyimide (Kapton®) dielectric layer on a polyurethane support. The impedance and capacitance of the electrode were evaluated under varying textile moisture levels with artificial sweat, as well as after exposure to common disinfectants including ethyl alcohol and iodine tincture. Electrochemical impedance spectroscopy (EIS) and broadband impedance measurements (10−1–105 Hz) confirmed stable capacitive behavior, moderate sensitivity to moisture, and chemical stability of the Kapton–copper interface under conditions simulating repeated use. A custom front-end readout circuit was implemented to demonstrate through-textile ECG signal acquisition. Simulator tests reproduced characteristic waveform patterns, and preliminary volunteer recordings confirmed the feasibility of through-textile acquisition. These results highlight the promise of the electrode as a low-cost platform for future wearable biosignal monitoring technical research.

References

1. World Health Organization Aging and Health Available online: https://www.who.int/news-room/fact-sheets/detail/ageing-and-health (accessed on 16 June 2025)
2. Buyting R. Melville S. Chatur H. White C. Légaré J.-F. Lutchmedial S. Brunt K.R. Virtual care with digital technologies for rural and remote Canadians living with cardiovascular disease CJC Open 2021 4 133 147 10.1016/j.cjco.2021.09.027
3. Olmedo-Aguirre J.O. Reyes-Campos J. Alor-Hernández G. Machorro-Cano I. Rodríguez-Mazahua L. Sánchez-Cervantes J.L. Remote Healthcare for Elderly People Using Wearables: A Review Biosensors 2022 12 73 10.3390/bios12020073 35200334
4. Yuan Y. Liu B. Li H. Li M. Song Y. Wang R. Wang T. Zhang H. Flexible Wearable Sensors in Medical Monitoring Biosensors 2022 12 1069 10.3390/bios12121069 36551036
5. World Health Organization Cardiovascular Diseases (CVDs) Available online: https://www.who.int/news-room/fact-sheets/detail/cardiovascular-diseases-(cvds) (accessed on 11 June 2025)
6. World Health Organization Cardiovascular Diseases Available online: https://www.who.int/health-topics/cardiovascular-diseases/#tab=tab_1 (accessed on 11 June 2025)
7. Cosoli G. Spinsante S. Scalise L. Wrist-worn and chest-strap wearable devices: Systematic review on accuracy and metrological characteristics Measurement 2020 159 107789 10.1016/j.measurement.2020.107789
8. Majumder S. Chen L. Marinov O. Chen C. Mondal T. Deen M. Noncontact Wearable Wireless ECG Systems for Long-Term Monitoring IEEE Rev. Biomed. Eng. 2018 11 306 321 10.1109/RBME.2018.2840336
9. Fong E.-M. Chung W.-Y. A Hygroscopic Sensor Electrode for Fast Stabilized Non-Contact ECG Signal Acquisition Sensors 2015 15 19237 19250 10.3390/s150819237
10. Chi Y.M. Jung T.-P. Cauwenberghs G. Dry-Contact and Noncontact Biopotential Electrodes: Methodological Review IEEE Rev. Biomed. Eng. 2010 3 106 119 10.1109/RBME.2010.2084078
11. Avenel-Audran M. Goossens A. Zimerson E. Bruze M. Contact dermatitis from electrocardiograph-monitoring electrodes: Role of p-tert-butylphenol-formaldehyde resin Contact Dermat. 2003 48 108 111 10.1034/j.1600-0536.2003.480210.x
12. Chen Y.-H. De Beeck M.O. Vanderheyden L. Carrette E. Mihajlović V. Vanstreels K. Grundlehner B. Gadeyne S. Boon P. Van Hoof C. Soft, comfortable polymer dry electrodes for high quality ECG and EEG recording Sensors 2014 14 23758 23780 10.3390/s141223758
13. Chlaihawi A.A. Narakathu B.B. Emamian S. Bazuin B.J. Atashbar M.Z. Development of Printed and Flexible Dry ECG Electrodes Sens. Bio-Sens. Res. 2018 20 9 15 10.1016/j.sbsr.2018.05.001
14. Puurtinen M.M. Komulainen S.M. Kauppinen P.K. Malmivuo J.A.V. Hyttinen J.A.K. Measurement of noise and impedance of dry and wet textile electrodes, and textile electrodes with hydrogel Proceedings of the 2006 International Conference of the IEEE Engineering in Medicine and Biology Society New York, NY, USA 2006 6012 6015 10.1109/IEMBS.2006.260155
15. Meziane N. Yang S. Shokoueinejad M. Webster J.G. Attari M. Eren H. Simultaneous comparison of 1 gel with 4 dry electrode types for electrocardiography Physiol. Meas. 2015 36 513 529 10.1088/0967-3334/36/3/513 25684219
16. Meziane N. Webster J.G. Attari M. Nimunkar A.J. Dry electrodes for electrocardiography Physiol. Meas. 2013 34 R47 R69 10.1088/0967-3334/34/9/R47 24137716
17. Griss P. Enoksson H. Tolvanen-Laakso P. Merilainen S. Ollmar G. Spiked biopotential electrodes Proceedings of the 13th International Conference on Micro Electro Mechanical Systems Miyazaki, Japan 23–27 January 2000 323 328 10.1109/MEMSYS.2000.838537
18. Salvo P. Raedt R. Carrette E. Schaubroeck D. Vanfleteren J. Cardon L. A 3D printed dry electrode for ECG/EEG recording Sens. Actuators A Phys. 2012 174 96 102 10.1016/j.sna.2011.12.017
19. Baek J.Y. An J.H. Choi J.M. Park K.S. Lee S.H. Flexible polymeric dry electrodes for the long-term monitoring of ECG Sens. Actuators A Phys. 2008 143 423 429 10.1016/j.sna.2007.11.019
20. Elango P. Dhanabalan S. Robel M. Sriram S. Bhaskaran M. Dry electrode geometry optimization for wearable ECG devices Appl. Phys. Rev. 2023 10 041408 10.1063/5.0152554
21. Young B. New standards for ECG equipment J. Electrocardiol. 2019 57 S1 S4 10.1016/j.jelectrocard.2019.07.013
22. Torfs T. Chen Y.-H. Kim H. Yazicioglu R.F. Noncontact ECG Recording System with Real Time Capacitance Measurement for Motion Artifact Reduction IEEE Trans. Biomed. Circuits Syst. 2014 8 617 625 10.1109/TBCAS.2014.2359053
23. Portelli A.J. Nasuto S.J. Design and Development of Non-Contact Bio-Potential Electrodes for Pervasive Health Monitoring Applications Biosensors 2017 7 2 10.3390/bios7010002
24. Chen C.C. Lin S.Y. Chang W.Y. Novel Stable Capacitive Electrocardiogram Measurement System Sensors 2021 21 3668 10.3390/s21113668
25. Spinelli E. Guerrero F. García P. Haberman M. A simple and reproducible capacitive electrode Med. Eng. Phys. 2016 38 286 289 10.1016/j.medengphy.2015.12.006
26. Badarov D. Mihov G. Iliev I. Development of analog front-end for capacitive ECG signal acquisition Proceedings of the IEEE International Scientific Conference Electronics (ET) Sozopol, Bulgaria 15–17 September 2021 1 4 10.1109/ET52713.2021.9579902
27. Haberman M.A. Spinelli E.M. García P.A. Guerrero F.N. Capacitive Driven-Right-Leg Circuit Design Int. J. Biomed. Eng. Technol. 2015 17 115 126 10.1504/IJBET.2015.068051
28. Khalili M. GholamHosseini H. Lowe A. Kuo M.M. Motion artifacts in capacitive ECG monitoring systems: A review of existing models and reduction techniques Med. Biol. Eng. Comput. 2024 62 3599 3622 10.1007/s11517-024-03165-1 39031328
29. Nagai S. Anzai D. Wang J. Motion artefact removals for wearable ECG using stationary wavelet transform Healthc. Technol. Lett. 2017 4 138 141 10.1049/htl.2016.0100 28868151
30. He Z. Min H. Skin-induced motion artifact removal for ambulatory electrocardiography IEEE Sens. J. 2022 22 15033 15043 10.1109/JSEN.2022.3186301
31. Stanešić A. Klaić L. Cindrić D. Cifrek M. Temporal Stability of Signal Quality in Non-Contact Biopotential Electrodes Sensors 2025 25 3077 10.3390/s25103077
32. Lee J.S. Heo J. Lee W.K. Lim Y.G. Kim Y.H. Park K.S. Flexible Capacitive Electrodes for Minimizing Motion Artifacts in Ambulatory Electrocardiograms Sensors 2014 14 14732 14743 10.3390/s140814732
33. Tang Y. Chang R. Zhang L. Yan F. Ma H. Bu X. Electrode Humidification Design for Artifact Reduction in Capacitive ECG Measurements Sensors 2020 20 3449 10.3390/s20123449
34. Leicht L. Eilebrecht B. Weyer S. Leonhardt S. Teichmann D. Closed-Loop Control of Humidification for Artifact Reduction in Capacitive ECG Measurements IEEE Trans. Biomed. Circuits Syst. 2017 11 300 313 10.1109/TBCAS.2016.2613097
35. Cui R. Zheng X. Wang K. Chen H. Chen W. Chen C. Luo J. Exploring Key Factors on Capacitive ECG Signal Quality Under Practical Considerations IEEE Trans. Instrum. Meas. 2024 73 4011614 10.1109/TIM.2024.3470044
36. Toral V. Castillo E. Albretch A. Romero F.J. García A. Rodríguez N. Lugli P. Morales D.P. Rivadeneyra A. Cost-effective printed electrodes based on emerging materials applied to biosignal acquisition IEEE Access 2020 8 127789 127800 10.1109/ACCESS.2020.3008945
37. Naser S.A. Hameed A.A. Hussein M.A. Corrosion behavior of some jewelries in artificial sweat AIP Conf. Proc. 2020 2213 020030 10.1063/5.0000111
38. Coull N.A. West A.M. Hodder S.G. Wheeler P. Havenith G. Body mapping of regional sweat distribution in young and older males Eur. J. Appl. Physiol. 2021 121 109 125 10.1007/s00421-020-04503-5
39. Svoboda M. Sotner R. Polak L. Practical aspects of impedance measurement using operational amplifier and oscilloscope Proceedings of the 2022 32nd International Conference Radioelektronika (RADIOELEKTRONIKA) Kosice, Slovakia 21–22 April 2022 1 4 10.1109/RADIOELEKTRONIKA54537.2022.9764942
40. Keysight Technologies Impedance Measurement Handbook: A Guide to Measurement Technology and Techniques 6th ed. Keysight Technologies Santa Rosa, CA, USA 2020
41. Polachan K. Chatterjee B. Weigand S. Sen S. Human Body–Electrode Interfaces for Wide-Frequency Sensing and Communication: A Review Nanomaterials 2021 11 2152 10.3390/nano11082152
42. Wang T.W. Lin S.F. Negative impedance capacitive electrode for ECG sensing through fabric layer IEEE Trans. Instrum. Meas. 2020 70 4002308 10.1109/TIM.2020.3045187
43. Uguz D.U. Tufan T.B. Uzun A. Leonhardt S. Antink C.H. Physiological motion artifacts in capacitive ECG: Ballistocardiographic impedance distortions IEEE Trans. Instrum. Meas. 2020 69 3297 3307 10.1109/TIM.2020.2971336
44. Lazanas A.C. Prodromidis M.I. Electrochemical impedance spectroscopy─a tutorial ACS Meas. Sci. Au 2023 3 162 193 10.1021/acsmeasuresciau.2c00070 37360038

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