• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
• /
• pp.372.1-372.1
• /
• 2016

Recently, there are a lot of diseases all around the world. Out of them, Atherosclerosis (AS) is the most common cause of stroke, cardiovascular mortality, and myocardial infarction. The macrophage-derived foam cell, which is formed by oxidized low-density lipoprotein (oxLDL), is the crucial marker for AS. In this study, we report a label-free capacitance imaging technique with multi-electrode array (MEA). The lipid-rich aorta arch lesions, which are derived from an apolipoprotein-E receptor-deficient (apoE-/-) mouse, exhibit higher capacitance than the lipid-free aorta arch, allowing the capacitance imaging of lipid region in atherosclerosis. To improve the contacts between MEA and tissue, polypyrrole(PPy)-coated multi walled carbon nanotubes (MWNTs) multi electrode array (PPy-MWNTs-MEA) was fabricated. Compared to TiN-MEA, PPy-MWNTs-MEA yielded lower contact impedance and better capacitance images. In addition, we have also developed a flexible MEA using single walled carbon nanotubes on a PET substrate. The lipid region could be discriminated in the capacitance images of the lipid-rich aorta arch lesions measured using flexible MEA, demonstrating a feasibility of in vivo applications.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
• /
• pp.481-484
• /
• 2004

다중 채널 전극 위에 세포를 성장시켜 전극면을 통해 검출되는 신경 신호의 손실을 줄이고 주파수의 변형을 줄이기 위해서 전극과 전해질의 사이의 impedance를 줄이는 것이 바람직하다. 전하 이동을 증대시키기 위해서는 낮은 impedance가 요구되며 이를 위한 전극의 개선 방안으로 전극면이 증착될 기판의 표면을 거칠게 하여 결과적으로 전극면의 표면적을 넓히는 방법을 모색하였다. 기판으로 사용되는 glass(Pyrex#7740)의 구성 물질 중에서 4%를 차지하는 $N^+$ 이온을 황산 용액으로 표면 처리하여 제거함으로써 매끈한 표면을 거칠게 하여 표면적을 넓힐 수 있다. 기판으로 사용되는 glass (pyrex#7740) $1cm{\times}1cm{\times}0.05cm$를 50%, 95% 농도의 황산 용액 내에서 각각 30분, 60분 동안 상온에서 표면처리를 진행하였다. AFM을 이용하여 표면을 관찰한 결과 황산 용액 95%에서 30분간 표면 처리를 진행한 시편에서 최대 $4000{\AA}$정도의 조도를 얻었다. 이후 동일 시편에 대해 전극으로 사용될 Ti/Au를 각각 $500{\AA}/2500{\AA}$ 증착 후 사진식각 공정으로 MEA(Multi-channel electrode array)를 제작하여 impedance를 측정한 결과, 표면 처리 후 impedance가 70% 개선되었음을 측정하였다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 D
• /
• pp.857-859
• /
• 2000

A planar MEA(Multi-channel Electrode Array) has been developed for monitoring the electrical activity of electrogenic cells in a cell culture by an extracellular recording. The material, fabrication process, characterization of the array, cleaning effect and impedance according to opening size by impedance measurement are described.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2002년도 추계학술대회 논문집 전기물성,응용부문
• /
• pp.257-259
• /
• 2002

In investigating the characteristics of a neural network, the use of planar microelectrode array shows several advantages over normal intracellular recording[1]. A transparent indium tin oxide(ITO) multi-electrode array(MEA) was fabricated and its top surface was insulated with photodefinable polyimide(HD-8001) except the exposed area for interfacing between the ITO electrodes and the neuronal cells. The exposed ITO electrodes were platinized in order to reduce the impedance between the electrodes and electrolyte. The one-minute platinization with $0.99nA/{\mu}m^2$ current density reduced the average impedance of the electrodes from $2.5M\Omega\;to\;90k\Omega$ at 1kHz in normal ringer solution. Cardiac cells were cultured on this MEA as a pilot study before neuron culture. The signals detected by the platinized electrodes had larger amplitudes and improved signal to noise ratio(SNR) compared to non-platinized electrodes. It is clear that microelectrodes need to have lower impedance to make reliable extracellular recordings, and thus platinization is essential part of MEA fabrication. Burst spike of cultured olfactory bulb was also detected with the MEA having platinized electrodes.

• 대한전기학회논문지:시스템및제어부문D
• /
• 제51권9호
• /
• pp.423-430
• /
• 2002

The fabrication and experimentation of multi-channel electrodes which enable detecting and recording of multi-site neuronal signals have been investigated. A multi-channel electrode array was fabricated by depositing 2000${\AA}$ thick Au layer on the 1000${\AA}$ thick Ti adhesion layer on a glass wafer. The metal paths were patterned by wet etching and passivated by depositing a PECVD silicon nitride insulation layer to prevent signals from intermixing or cross-talking. After placing a thin slice of rat cerebellar granule cell in the culture ring located in central portion of the multi-channel electrode plate, a neuronal signal from an electrode which is in contact with the cerebellar granule cell has been detected. It was found that the electrode impedance ranges 200㏀∼1㏁ and the impedance is not changed by cleaning with nitric acid. Also, the impedance is inversely proportion to the exposed electrode area and the cross-talk is negligible when the electrode spacing is bigger than 600$\mu\textrm{m}$. The amplitude and frequency of the measured action potential were 38㎷ and 2㎑, which are typical values. From the experimental results, the fabricated multi-channel electrode array proved to be suitable for multi-site neuronal signal detection for the analysis of a complicated cell network.

• 한국입자에어로졸학회지
• /
• 제13권3호
• /
• pp.111-118
• /
• 2017

전기수력학 (Electrohydrodynamic, EHD) 프린팅 기술은 전기장을 이용하여 일반 프린팅 기술보다 더 작은 크기의 액적을 분사하고 패터닝할 수 있는 장점을 갖고 있다. EHD 프린팅은 일반적으로 인쇄 노즐이나 기판을 X-Y 방향으로 움직여 패턴을 제작하는 방식으로 사용되어 왔으나 본 연구에서는 다중전극 어레이 (Multielectrode array, MEA)를 이용하여 원하는 기판위에 2차원의 패터닝이 가능함을 연구하였다. 특히, 약물전달장치 등의 바이오메디칼 디바이스로의 응용이 가능한 생분해성 고분자와 염료를 혼합한 잉크의 EHD 프린팅을 시도하였으며 노즐이나 기판의 움직임 없이 안정적으로 분사할 수 있는 2차원 범위에 대한 연구를 통해 최소 약 $6{\mu}m$ 크기를 갖는 패턴을 노즐 위치로부터 수평방향으로 약 1 mm 범위까지 안정적 패터닝이 가능함을 확인하였다. 또한, MEA 전극 간의 거리에 의한 패턴 조밀도의 한계를 극복하기 위해 MEA와 인쇄가 이루어지는 기판과의 상대적 이동을 통해 더 조밀한 패터닝이 가능함을 보여주었다.

• Journal of Semiconductor Engineering
• /
• 제1권3호
• /
• pp.88-98
• /
• 2020

As biosensors are widely used in the medical field, flexible devices compatible with live animals have aroused great interest. Especially, significant research has been carried out to develop implantable or skin-attachable devices for real-time bio-signal sensing. From the device point of view, various biosensor types such as field-effect transistors (FETs) and multi-electrode arrays (MEAs) have been reported as diverse sensing strategies. In particular, the flexible FETs and MEAs allow semiconductor engineering to expand its application, which had been impossible with stiff devices and materials. This review summarizes the state-of-the-art research on flexible FET and MEA biosensors focusing on their materials, structures, sensing targets, and methods.

• 대한의용생체공학회:의공학회지
• /
• 제28권1호
• /
• pp.17-23
• /
• 2007

Long-term potentiation (LTP) of synaptic transmission is the most widely studied model for learning and memory. However its mechanisms are not clearly elucidated and are a subject for intense investigation. Previous attempts to decipher cellular mechanisms and network properties involved a current-source density analysis (CSDA) of the LTP from small animal hippocampus measured with a limited number of microelectrodes (typically <3), only revealing limited nature of spatiotemporal dynamics. Recent advancement in multi-electrode array (MEA) technology allows continuous and simultaneous recordings of LTP with more than 60 electrodes. However CSDA via the standard Laplacian transform is still limited due to its relatively high sensitivity toward noise, inability of resolving overlapped current sources and sinks, and its requirement for tissue conductivity values. In this study, we propose a new methodology for improved CSDA. Independent component analysis and its joint use (i.e., Joint-ICA) are applied to extract spatiotemporal components of LTP. The results show that ICA and Joint-ICA are capable of extracting independent spatiotemporal components of LTP generators. The ICs of LTP indicate the reversing roles of current sources and sinks which are associated with LTP.

• The Korean Journal of Physiology and Pharmacology
• /
• 제13권6호
• /
• pp.443-448
• /
• 2009

For successful visual perception by visual prosthesis using electrical stimulation, it is essential to develop an effective stimulation strategy based on understanding of retinal ganglion cell (RGC) responses to electrical stimulation. We studied RGC responses to repetitive electrical stimulation pulses to develop a stimulation strategy using stimulation pulse frequency modulation. Retinal patches of photoreceptor-degenerated retinas from rd1 mice were attached to a planar multi-electrode array (MEA) and RGC spike trains responding to electrical stimulation pulse trains with various pulse frequencies were observed. RGC responses were strongly dependent on inter-pulse interval when it was varied from 500 to 10 ms. Although the evoked spikes were suppressed with increasing pulse rate, the number of evoked spikes were >60% of the maximal responses when the inter-pulse intervals exceeded 100 ms. Based on this, we investigated the modulation of evoked RGC firing rates while increasing the pulse frequency from 1 to 10 pulses per second (or Hz) to deduce the optimal pulse frequency range for modulation of RGC response strength. RGC response strength monotonically and linearly increased within the stimulation frequency of 1~9 Hz. The results suggest that the evoked neural activities of RGCs in degenerated retina can be reliably controlled by pulse frequency modulation, and may be used as a stimulation strategy for visual neural prosthesis.

• The Korean Journal of Physiology and Pharmacology
• /
• 제19권2호
• /
• pp.167-175
• /
• 2015

A retinal prosthesis is being developed for the restoration of vision in patients with retinitis pigmentosa (RP) and age-related macular degeneration (AMD). Determining optimal electrical stimulation parameters for the prosthesis is one of the most important elements for the development of a viable retinal prosthesis. Here, we investigated the effects of different charge-balanced biphasic pulses with regard to their effectiveness in evoking retinal ganglion cell (RGC) responses. Retinal degeneration (rd1) mice were used (n=17). From the ex-vivo retinal preparation, retinal patches were placed ganglion cell layer down onto an $8{\times}8$ multielectrode array (MEA) and RGC responses were recorded while applying electrical stimuli. For asymmetric pulses, 1st phase of the pulse is the same with symmetric pulse but the amplitude of 2nd phase of the pulse is less than $10{\mu}A$ and charge balanced condition is satisfied by lengthening the duration of the pulse. For intensities (or duration) modulation, duration (or amplitude) of the pulse was fixed to $500{\mu}s$($30{\mu}A$), changing the intensities (or duration) from 2 to $60{\mu}A$(60 to $1000{\mu}s$). RGCs were classified as response-positive when PSTH showed multiple (3~4) peaks within 400 ms post stimulus and the number of spikes was at least 30% more than that for the immediate pre-stimulus 400 ms period. RGC responses were well modulated both with anodic and cathodic phase-1st biphasic pulses. Cathodic phase-1st pulses produced significantly better modulation of RGC activity than anodic phase-1st pulses regardless of symmetry of the pulse.