정전 용량성 결합 전극을 이용한 웨어러블 심전도 측정 시스템 설계에 관한 연구

이재호(Jae-Ho Lee),이영재(Young-Jae Lee),이강휘(Kang-Hwi Lee),강승진(Seng-Jin Kang),김경남(Kyeung-Nam Kim),박희정(Hee-Jung Park),이정환(Jeong-Whan Lee) 대한전기학회 2014 전기학회논문지 Vol.63 No.10

In this study, a new type of electrode device is implemented to measure the capacitance energy and interpret it as the ECG (Electrocardiogram) data. The main idea of this new electrode system is to estimate the capacitance on the skin by assembling a capacitive-coupled circuits and translate into the ECG signal. To measure the coupling energy and estimate the aquired data in terms of heart activity, the capacitive-coupled electrode is garmented with fabrics in the form of a chest band or a vest jacket. To compare the ECG data from the capacitive-coupled electrode with the conventional electrode(Ag-AgCl) system, the corelation coefficient between two signals is computed as 0.9517. Thus, we can conclude the fact that capacitive-coupled electrode system can measure a person"s heart activity without any contact to his or her skin and can the interpreted as the ECG data

Hybrid capacitive deionization with Ag coated carbon composite electrode

Yoon, H.,Lee, J.,Kim, S.,Yoon, J. Elsevier 2017 Desalination Vol.422 No.-

Capacitive deionization (CDI) using capacitive electrodes is highlighted as an alternative desalination technology because of its advantages of low cost and high energy-efficiency. However, the deionization capacity of CDI is somewhat limited because its capacity relies on the double layer capacitance of a carbon electrode. Thus, improving the deionization capacity of a CDI system is one of the most urgent issues in CDI technology. Herein, Ag coated carbon composite electrode employed hybrid CDI system (Ag coated HCDI) was investigated to enhance the deionization performances. The Ag coated carbon composite electrode was made by coating a small amount of Ag onto a carbon capacitive electrode, exhibiting the characteristics of a battery and a capacitor together. As major results, the CDI deionization capacity (88% more), rate (39% more), and charge efficiency (76%@?92%) was dramatically enhanced due to the Ag coating. The significant improvement in deionization performance is explained by the enhanced specific capacity combining the capacitance in the carbon electrode with the Ag mediated charge transfer reaction. In addition, the Ag coated HCDI (73.3kJmole<SUP>-1</SUP>) is superior to membrane assisted CDI (136.7kJmole<SUP>-1</SUP>) in terms of energy consumption for deionization due to its low voltage feasible operation.

Comparison of Pre-amplifier Topologies for Use in Brain-Computer Interface with Capacitively-Coupled EEG Electrodes

백현재,Kwang Suk Park,Hong Ji Lee,임용규 대한의용생체공학회 2013 Biomedical Engineering Letters (BMEL) Vol.3 No.3

Purpose Interest in brain computer interfaces (BCI) has recently increased due to the need for quality of life technologies for disabled people. While brain signal processing and its applications have been widely studied for many decades, BCI seldom requires attention to practical and efficient brain signal sensing methods. Noninvasive electroencephalogram (EEG) measurements using wet adhesive Ag/AgCl electrodes are universally employed for BCI, but have limitations in practical acceptability with regard to portability, comfort and aesthetic design. In order to translate the results of laboratory experiments into practical use, EEGs should be recorded easily without requiring scalp preparation and regardless of the presence of hair. Methods In this paper, general requirements for capacitive measurement of EEG are presented and four different frontends for capacitive EEG electrodes are evaluated: (a) basic voltage follower scheme with high value resistor bias network (Rb), (b) voltage follower scheme with active guarding (second op-amp), (c) reverse current of signal diodes to providing bias current, (d) electrode scheme without any external bias network. We explore the use of capacitively-coupled electrodes for BCI technologies through the use of current popular BCI paradigms such as steady state visual evoked potential, P300and sensory motor rhythm. Results Our experimental results indicate that capacitive electrode technology allows the acquisition of spontaneous EEG signals through hair with average correlation coefficient of 0.7949, 0.7946, 0.6333, 0.6549 for each capacitive electrode at O2 and 0.8433, 0.7822, 0.6253, 0.5427 for each capacitive electrode at C4. Although signal quality is lower and the movement artifacts are larger than those of conventional electrodes, SSVEP was successfully recorded through hair without spectral difference between SSVEP peaks and stimulus peaks except low stimulus frequency (5.45 Hz). P300 responses was measured with significant coefficient of determination (>0.005) except electrode (d). Sensory motor rhythm was suppressed during right hand imagery movement with log ratio value less than zero for all electrodes. Conclusions Further studies are required to apply capacitive measurement technology to uses in diagnostic EEG, but the method can currently be used for simple BCI applications.

Electrochemical analysis of slurry electrodes for flow-electrode capacitive deionization

Choo, Ko Yeon,Yoo, Chung Yul,Han, Moon Hee,Kim, Dong Kook Elsevier 2017 Journal of Electroanalytical Chemistry Vol.806 No.-

<P><B>Abstract</B></P> <P>Due to recent advancements in electrochemical devices such as batteries, fuel cells, and supercapacitors, novel electrochemical processes for industrial plant scale including water treatment and desalination are being actively investigated. Slurry electrodes for flow-electrode capacitive deionization (FCDI) are representative process technology with continuous and easy scale-up characteristics. These characteristics are feasible as slurry electrodes can be flowed in microchannels, instead of stacking conventional electrodes fixed on plates. However, the electrochemical properties of slurry electrodes for electrochemical process engineering have not been clearly identified, compared to those of conventional fixed electrodes. In the present study, we investigated the electrochemical properties of capacitive slurry electrodes with changes in carbon content and electrolyte salt concentration using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and deionization/regeneration cycle tests with newly fabricated button-type cells. The CV patterns were rectangular, symmetrical, and reversible at a scan rate of 2mV/s, indicating electrical double-layer capacitive behavior. The results of the EIS and cycle tests demonstrated that increasing the carbon content and electrolyte salt concentration in slurry electrodes improved the cell efficiency due to the higher capacitance and lower total resistance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Novel electrochemical cells suitable for slurry electrodes were developed. </LI> <LI> The electrochemical properties of slurry electrodes were affected by their composition. </LI> <LI> Increasing the carbon content of slurry electrodes led to a higher capacitance. </LI> <LI> Increasing the electrolyte salt concentration of slurry electrodes improved the cell efficiency. </LI> </UL> </P>

축전식 탈염 공정을 위한 메조포러스 탄소 전극

이동주,박진수,Lee, Dong-Ju,Park, Jin-Soo 한국전기화학회 2014 한국전기화학회지 Vol.17 No.1

다공성의 활성탄소와 상대적으로 입자크기가 더 작은 carbon black을 여러 비율로 혼합하여 다양한 적층배열 구조를 갖는 축전식 탈염용 전극을 제조하였고 활성탄소만 존재하는 전극과 비교 분석하였다. 연구 결과 carbon black의 양이 증가할수록 탄소체의 배열 구조가 조밀해지는 것을 관찰하였고, mesopore가 약 10% 증가하는 것으로 나타났다. 순환전압전류법을 이용하여 축전용량을 살펴보았을 때 carbon black만으로는 이온흡착에 대한 영향이 거의 없지만 활성탄소체와 혼합하여 carbon black의 양이 증가할수록 비축전용량 역시 증가하는 것을 관찰하였다. 최종적으로 셀에 전극을 채용하여 탈염실험을 수행한 결과, carbon black의 양이 가장 많이 함유된 전극의 탈염 성능이 가장 우수하였고, pH의 변화의 폭이 가장 좁았다. 또한, 축전된 전하의 분석을 통해 비페러데이 전류의 비율이 증가하는 것으로 나타나 페러데이 반응에 대한 영향이 감소하는 것을 관찰하였다. 이는 carbon black의 첨가로 전극의 적층배열 구조가 변형함으로써 mesopore의 비율이 증가해 페러데이 반응에 의한 영향이 감소하였고, 탈염 성능 역시 증가하는 것을 알 수 있었다. Carbon electrodes for capacitive deionization were fabricated through mixing two different carbon powders (activated carbon powder, carbon black) with different particle sizes to investigate physical or electrochemical properties and finally desalination performances of the electrodes with various compositions of two carbon powders in weight and were compared with the electrode consisting of activated carbon. As a result, the electrode structure became more packed as increasing the amount of carbon black and resulted in 10% increase in mesopore fraction. The specific capacitance obtained from cyclic voltammograms of various electrodes showed that the electrode containing carbon black only had 107.4 F/g, while the specific capacitance of the electrode having more amount of carbon black increased and was higher than the one having no carbon black. The results of desalination runs in a capacitive deionization cell exhibited that the electrode having the highest amount of carbon black (1 wt%) in this study had the highest desalting efficiency, and no significant pH variation was observed during the runs. It was analyzed using accumulated charge that the fraction of non-Faraday current increased as the amount of carbon black increased in the electrodes. It can be concluded that the addition of carbon black changed the electrode structure resulting in an increase in the fraction of mesopore and finally enhanced the desalting efficiency by decreasing Faraday current.

1P-713 Development of CDI Electrode and System for the Water Treatment Process

박남수,강경석,이영석 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1

The capacitive deionization (CDI) process is a technology employed to remove ionic materials when a potential is applied on the carbon electrodes. CDI is operated at a low potential region so that an electrochemical reaction does not occur on the electrode surface. Therefore the process is highly advantageous and low energy consumption. Also, the regeneration of the electrode is very simple and environmentally friendly technology. Because of these advantages, CDI technology will be easy to apply to water treatment process. Therefore, we have developed high performance CDI electrodes for water treatment process and have successfully applied the developed CDI system using this electrodes. The durability test was carried out using a pilot device and it was confirmed that the operation was stable. The CDI technology has great advantages in high hardness concentration, low energy consumption and high water recovery rate, which is advantageous to apply in the world water treatment market.

Capacitive Monitoring of Bio and Neuro Signals

김정훈,이승민,이상훈 대한의용생체공학회 2014 Biomedical Engineering Letters (BMEL) Vol.4 No.2

Capacitive electrode is emerging as a useful tool for theinconspicuous monitoring of bio- and neuro-signal. It operateswith the displacement currents instead of the real chargecurrents, and its electrolytic electrode–skin interface isreplaced by a dielectric material, an electrically insulatedlayer or air. Here, we introduce the basic principles ofcapacitive recording of biosignals and categorize the variouscapacitive recording methods as ‘built-in’, ‘helmet’, ‘bandand film’ and ‘pad and chip’ type, and describe the detailedfeatures of each method. Each type is designed according tothe signal type and anatomical position. Especially the‘built-in’ type is focused on electrocardiogram (ECG) in ourreal life. Insulators in the applications are also selected byvarious materials and we described. A recent progress inmicroelectromechanical system (MEMS) technology enabledthe capacitive measurement of bio and neuro signals and webriefly mention the contribution of MEMS technology. Conclusively, we describe the future potential applications ofcapacitive monitoring beyond the laboratory environment.

이중 주파수 전원의 용량성 결합 플라즈마 식각장비에서 전극하전에 의한 입사이온 에너지분포 변화연구

최명선,김곤호,장윤창,이석환 한국반도체디스플레이기술학회 2014 반도체디스플레이기술학회지 Vol.13 No.3

The effect of electrode charging on the ion energy distribution (IED) was investigated in the dual-frequency capacitively coupled plasma source which was powered of 100MHz RF at the top electrode and 400 kHz bias on the bottom electrode. The charging property was analyzed with the distortion of the measured current and voltage waveforms. The capacitance and the resistance of electrode sheath can change the property of ion and electron charging on the electrode so it is sensitive to the plasma density which is controlled by the main power. The ion energy distribution was estimated by equivalent circuit model, being compared with the measured distribution obtained from the ion energy analyzer. Results show that the low frequency bias power changes effectively the low energy population of ion in the energy distribution.

Sulfonated Poly(Ether Ether Ketone)을 코팅한 이온선택성 복합탄소전극의 제조 및 전기화학적 특성 분석

최재환,박찬미 한국공업화학회 2013 공업화학 Vol.24 No.3

Sulfonated poly(ether ether ketone) (SPEEK) with a certain degree of sulfonation were synthesized by reacting PEEK and sulfuric acid at different reaction time. Then ion-selective composite carbon electrodes (ISCCE) were fabricated by coating the prepared SPEEK on the surface of carbon electrodes. The specific capacitance and resistance of the ISCCE were analyzed by electrical impedance spectroscopy. The ion exchange capacities (IEC) of the SPEEKs were measured in the range of 1.60∼2.57 meq/g depending on the sulfonation time. The SPEEK more than 2.5 meq/g of IEC was considered unsuitable for fabricating the ISCCE because it was dissolved in water. The specific capacitance of the prepared ISCCE increased with increasing the IEC of coated SPEEKs and the capacitance was improved up to about 20% compared to that of uncoated carbon electrode. In addition, the electrical resistance of coating layer decreased significantly with increasing the IEC of coated SPEEKs. It is expected that the desalination efficiency of conventional capacitive deionization process can be improved by using the prepared ISCCE coated with SPEEK.

Thompson-Lampard 정리를 적용한 마이크로미터 변위 측정을 위한 비접촉식 전기용량 센서 개발

金漢俊(Han Jun Kim),姜銓洪(Jeon Hong Kang),韓相玉(Sang Ok Han) 대한전기학회 2006 전기학회논문지 B Vol.55 No.9

Non-contacting capacitive sensor based on Thompson-Lampard theorem have been fabricated and characterized for measuring of ㎛ order displacements. To overcome disadvantages of the existed capacitive sensors of parallel plate type with 2-electrodes and 3-electrodes, the developed new sensor was designed to have 4-electrodes with a constant gap of 0.2 ㎜ between the electrodes. Two of the electrodes were used as a high potential electrode and a low one, the other two electrodes were used as guard electrodes. These electrodes were made from copper using RF sputtering system on a sapphire plate with diameter 17 ㎜ and thickness 0.7 ㎜. This sensor can be used for measuring the distance not only between the sensor and metallic target connected to ground potential but also non-metallic target without ground connection.