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Li G, Liu Y, Chen Y, Li M, Song J, Li K, Zhang Y, Hu L, Qi X, Wan X, Liu J, He Q, Zhou H. Polyvinyl alcohol/polyacrylamide double-network hydrogel-based semi-dry electrodes for robust electroencephalography recording at hairy scalp for noninvasive brain-computer interfaces. J Neural Eng 2023; 20. [PMID: 36863014 DOI: 10.1088/1741-2552/acc098] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2022] [Accepted: 03/02/2023] [Indexed: 03/04/2023]
Abstract
Objective.Reliable and user-friendly electrodes can continuously and real-time capture the electroencephalography (EEG) signals, which is essential for real-life brain-computer interfaces (BCIs). This study develops a flexible, durable, and low-contact-impedance polyvinyl alcohol/polyacrylamide double-network hydrogel (PVA/PAM DNH)-based semi-dry electrode for robust EEG recording at hairy scalp.Approach.The PVA/PAM DNHs are developed using a cyclic freeze-thaw strategy and used as a saline reservoir for semi-dry electrodes. The PVA/PAM DNHs steadily deliver trace amounts of saline onto the scalp, enabling low and stable electrode-scalp impedance. The hydrogel also conforms well to the wet scalp, stabilizing the electrode-scalp interface. The feasibility of the real-life BCIs is validated by conducting four classic BCI paradigms on 16 participants.Main results.The results show that the PVA/PAM DNHs with 7.5 wt% PVA achieve a satisfactory trade-off between the saline load-unloading capacity and the compressive strength. The proposed semi-dry electrode exhibits a low contact impedance (18 ± 8.9 kΩ at 10 Hz), a small offset potential (0.46 mV), and negligible potential drift (1.5 ± 0.4μV min-1). The temporal cross-correlation between the semi-dry and wet electrodes is 0.91, and the spectral coherence is higher than 0.90 at frequencies below 45 Hz. Furthermore, no significant differences are present in BCI classification accuracy between these two typical electrodes.Significance.Based on the durability, rapid setup, wear-comfort, and robust signals of the developed hydrogel, PVA/PAM DNH-based semi-dry electrodes are a promising alternative to wet electrodes in real-life BCIs.
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Affiliation(s)
- Guangli Li
- Hunan Key Laboratory of Biomedical Nanomaterials and Devices, College of Life Science and Chemistry, Hunan University of Technology, Zhuzhou 412007, People's Republic of China.,Department of Neurology, Zhuzhou People's Hospital, Zhuzhou 412008, People's Republic of China
| | - Ying Liu
- Hunan Key Laboratory of Biomedical Nanomaterials and Devices, College of Life Science and Chemistry, Hunan University of Technology, Zhuzhou 412007, People's Republic of China
| | - Yuwei Chen
- Hunan Key Laboratory of Biomedical Nanomaterials and Devices, College of Life Science and Chemistry, Hunan University of Technology, Zhuzhou 412007, People's Republic of China
| | - Mingzhe Li
- Wuhan Greentek Pty. Ltd, Wuhan 430074, People's Republic of China
| | - Jian Song
- Department of Neurosurgery, General Hospital of Central Command Theater of PLA, Wuhan 430012, People's Republic of China
| | - Kanghua Li
- Department of Neurology, Zhuzhou People's Hospital, Zhuzhou 412008, People's Republic of China
| | - Youmei Zhang
- Department of Child Psychology, The Third Hospital of Zhuzhou, Zhuzhou 412003, People's Republic of China
| | - Le Hu
- Wuhan Greentek Pty. Ltd, Wuhan 430074, People's Republic of China
| | - Xiaoman Qi
- Hunan Key Laboratory of Biomedical Nanomaterials and Devices, College of Life Science and Chemistry, Hunan University of Technology, Zhuzhou 412007, People's Republic of China
| | - Xuan Wan
- Hunan Key Laboratory of Biomedical Nanomaterials and Devices, College of Life Science and Chemistry, Hunan University of Technology, Zhuzhou 412007, People's Republic of China
| | - Jun Liu
- Hunan Key Laboratory of Biomedical Nanomaterials and Devices, College of Life Science and Chemistry, Hunan University of Technology, Zhuzhou 412007, People's Republic of China
| | - Quanguo He
- Hunan Key Laboratory of Biomedical Nanomaterials and Devices, College of Life Science and Chemistry, Hunan University of Technology, Zhuzhou 412007, People's Republic of China
| | - Haihan Zhou
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Molecular Science, Shanxi University, Taiyuan 030006, People's Republic of China
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Capillary penetration for the development of a method for the assessment of shelf-life of foods. JOURNAL OF FOOD MEASUREMENT AND CHARACTERIZATION 2022. [DOI: 10.1007/s11694-022-01685-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
AbstractTemperature sensitive foods require monitoring of their time–temperature history in order to assure their safety and high quality. The same holds for other perishable products such as medical and pharmaceutical. The best means to have information on the time–temperature history of a product is by having measurement of these variables along the whole product shelf-life. As an answer to this need several time–temperature indicators have been developed and commercialized for monitoring the quality of food products. In this work a full history time–temperature indicator (TTI) has been designed and developed based on capillary penetration of safe and low surface tension liquids in micro porous polyethylene porous media. For the development of the indicator the appropriate porous media and penetration liquids were selected and capillary penetration of the selected liquids took place at two different temperatures. Based on the results of the capillary penetration experiments the TTI was developed and a prototype was evaluated in a food product in order to assess its capability to be used in food packaging. The results showed that the TTI is simple in use and could provide a quantitative and easy-to-read response. Moreover, the response of the TTI could be calibrated by changing several design parameters, in order to match the quality deterioration kinetics of the specific food product to be monitored.
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Li G, Wang S, Li M, Duan YY. Towards real-life EEG applications: novel superporous hydrogel-based semi-dry EEG electrodes enabling automatically "charge-discharge" electrolyte. J Neural Eng 2021; 18. [PMID: 33721854 DOI: 10.1088/1741-2552/abeeab] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Accepted: 03/15/2021] [Indexed: 12/22/2022]
Abstract
A novel polyacrylamide/polyvinyl alcohol superporous hydrogel (PAAm/PVA SPH)-based semi-dry electrode was constructed for capturing EEG signals at the hairy scalp, showing automatically "charge-discharge" electrolyte concept in EEG electrode development. In this regard, PAAm/PVA SPH was polymerized in-situ in the hollow electrode cavity by freezing polymerization, which acted as a dynamic reservoir of electrolyte fluid. The superporous hydrogel can be completely "charged" with electrolyte fluid, such as saline, in just a few seconds and can be "discharged" through a few tiny pillars into the scalp at a desirable rate. In this way, an ideal local skin hydration effect was achieved at electrode-skin contact sites, facilitating the bioelectrical signal pathway and significantly reducing electrode-skin impedance. Moreover, the electrode interface effectively avoids short circuit and inconvenient issues. The results show that the semi-dry electrode displayed low and stable contact impedance, showing non-polarization properties with low off-set potential and negligible potential drift. The average temporal cross-correlation coefficient between the semi-dry and conventional wet electrodes was 0.941. Frequency spectra also showed almost identical responses with anticipated neural electrophysiology responses. Considering prominent advantages such as a rapid setup, robust signal, and user-friendliness, the new concept of semi-dry electrodes shows excellent potential in emerging real-life EEG applications.
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Affiliation(s)
- Guangli Li
- College of Life Sciences and Chemistry, Hunan University of Technology, Hunan Key Laboratory of Biomedical Nanomaterials and Devices, College of Life Sciences and Chemistry, Hunan University of Technology, Zhuzhou 412007, China, Zhuzhou, 412008, CHINA
| | - Sizhe Wang
- Wuhan NEO Energy Materials Enterprises Ltd.,, Wuhan NEO Energy Materials Enterprises Ltd., Wuhan 430074, China, Wuhan, Hubei Province, 430074, CHINA
| | - Mingzhe Li
- Wuhan Greentek Pty. Ltd., Wuhan Greentek Pty. Ltd., Wuhan 430074, China, Wuhan, Hubei Province, 430074, CHINA
| | - Yanwen Y Duan
- Wuhan Greentek Pty. Ltd., Wuhan Greentek Pty. Ltd., Wuhan 430074, China, Wuhan, Hubei Province, 430074, CHINA
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Abstract
Developing reliable and user-friendly electroencephalography (EEG) electrodes remains a challenge for emerging real-world EEG applications. Classic wet electrodes are the gold standard for recording EEG; however, they are difficult to implement and make users uncomfortable, thus severely restricting their widespread application in real-life scenarios. An alternative is dry electrodes, which do not require conductive gels or skin preparation. Despite their quick setup and improved user-friendliness, dry electrodes still have some inherent problems (invasive, relatively poor signal quality, or sensitivity to motion artifacts), which limit their practical utilization. In recent years, semi-dry electrodes, which require only a small amount of electrolyte fluid, have been successfully developed, combining the advantages of both wet and dry electrodes while addressing their respective drawbacks. Semi-dry electrodes can collect reliable EEG signals comparable to wet electrodes. Moreover, their setup is as fast and convenient similar to that of dry electrodes. Hence, semi-dry electrodes have shown tremendous application prospects for real-world EEG acquisition. Herein, we systematically summarize the development, evaluation methods, and practical design considerations of semi-dry electrodes. Some feasible suggestions and new ideas for the development of semi-dry electrodes have been presented. This review provides valuable technical support for the development of semi-dry electrodes toward emerging practical applications.
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Affiliation(s)
- Guang-Li Li
- Hunan Key Laboratory of Biomedical Nanomaterials and Devices, College of Life Sciences and Chemistry, Hunan University of Technology, Zhuzhou 412007, People's Republic of China
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In-service characterization of a polymer wick-based quasi-dry electrode for rapid pasteless electroencephalography. ACTA ACUST UNITED AC 2018; 63:349-359. [DOI: 10.1515/bmt-2016-0193] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Accepted: 03/28/2017] [Indexed: 11/15/2022]
Abstract
Abstract
A novel quasi-dry electrode prototype, based on a polymer wick structure filled with a specially designed hydrating solution is proposed for electroencephalography (EEG) applications. The new electrode does not require the use of a conventional electrolyte paste to achieve a wet, low-impedance scalp contact. When compared to standard commercial Ag/AgCl sensors, the proposed wick electrodes exhibit similar electrochemical noise and potential drift values. Lower impedances are observed when tested in human volunteers due to more effective electrode/skin contact. Furthermore, the electrodes exhibit an excellent autonomy, displaying an average interfacial impedance of 37±11 kΩ cm2 for 7 h of skin contact. After performing bipolar EEG trials in human volunteers, no substantial differences are evident in terms of shape, amplitude and spectral characteristics between signals of wick and commercial wet electrodes. Thus, the wick electrodes can be considered suitable to be used for rapid EEG applications (electrodes can be prepared without the presence of the patient) without the traditional electrolyte paste. The main advantages of these novel electrodes over the Ag/AgCl system are their low and stable impedance (obtained without conventional paste), long autonomy, comfort, lack of dirtying or damaging of the hair and because only a minimal cleaning procedure is required after the exam.
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Geogiou D, Kalogianni EP. Height-time and weight-time approach in capillary penetration: Investigation of similarities and differences. J Colloid Interface Sci 2017; 495:149-156. [PMID: 28199853 DOI: 10.1016/j.jcis.2017.02.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Revised: 02/03/2017] [Accepted: 02/03/2017] [Indexed: 11/30/2022]
Abstract
Capillary penetration is commonly used in a wide range of applications such as oil recovery, textile engineering and food technology. Furthermore, it is a useful tool for surface characterization of powders and porous media. Two are the commonest experimental methods to study capillary penetration: the height-time and the weight-time technique. However, it is not clear whether the two approaches provide the same results. This work aims to investigate similarities and differences between the two approaches and assess whether it is possible to replace one with another. To this end, capillary penetration experiments were performed in different porous media where the pore size distribution and shape varied. Height and weight data were recorded simultaneously. It was found that results of the two experimental approaches are not always equivalent and that this depends on the porous medium properties. In some cases results depended on the degree of saturation of the porous medium with the penetrating liquid. An analysis of weight-time data to provide pore size distribution as a function of pore volume is proposed. Furthermore, two different approaches of the fractal theory were applied and the time exponent, the material fractal dimension and the tortuosity fractal dimension were determined.
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Affiliation(s)
- Despoina Geogiou
- Department of Food Technology, Alexander Technological Educational Institution of Thessaloniki, P.O. Box 141, 57400 Thessaloniki, Greece.
| | - Eleni P Kalogianni
- Department of Food Technology, Alexander Technological Educational Institution of Thessaloniki, P.O. Box 141, 57400 Thessaloniki, Greece.
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Wang F, Li G, Chen J, Duan Y, Zhang D. Novel semi-dry electrodes for brain-computer interface applications. J Neural Eng 2016; 13:046021. [PMID: 27378253 DOI: 10.1088/1741-2560/13/4/046021] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVES Modern applications of brain-computer interfaces (BCIs) based on electroencephalography rely heavily on the so-called wet electrodes (e.g. Ag/AgCl electrodes) which require gel application and skin preparation to operate properly. Recently, alternative 'dry' electrodes have been developed to increase ease of use, but they often suffer from higher electrode-skin impedance and signal instability. In the current paper, we have proposed a novel porous ceramic-based 'semi-dry' electrode. The key feature of the semi-dry electrodes is that their tips can slowly and continuously release a tiny amount of electrolyte liquid to the scalp, which provides an ionic conducting path for detecting neural signals. APPROACH The performance of the proposed electrode was evaluated by simultaneous recording of the wet and semi-dry electrodes pairs in five classical BCI paradigms: eyes open/closed, the motor imagery BCI, the P300 speller, the N200 speller and the steady-state visually evoked potential-based BCI. MAIN RESULTS The grand-averaged temporal cross-correlation was 0.95 ± 0.07 across the subjects and the nine recording positions, and these cross-correlations were stable throughout the whole experimental protocol. In the spectral domain, the semi-dry/wet coherence was greater than 0.80 at all frequencies and greater than 0.90 at frequencies above 10 Hz, with the exception of a dip around 50 Hz (i.e. the powerline noise). More importantly, the BCI classification accuracies were also comparable between the two types of electrodes. SIGNIFICANCE Overall, these results indicate that the proposed semi-dry electrode can effectively capture the electrophysiological responses and is a feasible alternative to the conventional dry electrode in BCI applications.
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Affiliation(s)
- Fei Wang
- Department of Psychology, School of Social Sciences, Tsinghua University, Beijing 100084, People's Republic of China. Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing 100084, People's Republic of China
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Assessing a novel polymer-wick based electrode for EEG neurophysiological research. J Neurosci Methods 2016; 267:126-31. [DOI: 10.1016/j.jneumeth.2016.04.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Revised: 04/11/2016] [Accepted: 04/12/2016] [Indexed: 11/19/2022]
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