• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2003.10a
• /
• pp.356-361
• /
• 2003

Electrochemical micromachining which is not normally considered as a precision process is presented in this paper. The application of voltage Pulses between a tool electrode and a workpiece in an electrochemical environment allows the three-dimensional machining of conducting materials with micrometer precision. In this paper tool-electrodes($5\mu\textrm{m}$ in diameter, 1mm in length) are developed by electrochemical micromaching and micro holes are manufactured using this tool-electrodes we developed already. Micro holes are achieved the accuracy below $50\mu\textrm{m}$ in diameter using ultrashort voltage pulses(0.1-5$\mu\textrm{s}$).

• 한국가시화정보학회:학술대회논문집
• /
• 2007.11a
• /
• pp.77-83
• /
• 2007

This paper presents numerical and experimental works for simultaneous pumping and mixing small liquid using asymmetric microelectrode arrays, based on AC electroosmotic flows. To this end, four arrangements of electrode pairs were considered with diagonal/herringbone shapes. Numerical simulations were made of three-dimensional geometries by using the linear theory. The results indicated that the helical flow motions induced by the electrode arrays play a significant role in the mixing enhancement. The pumping performance was influenced by the slip velocity at the center region of the channel compared to that near the side walls. To validate the numerical predictions, the microfluidic devices were made through MEMS. The flow rate was obtained by using micro PIV, increasing the applied frequency. The electrolyte was potassium chloride solution. The flow patterns above electrodes were visualized to see lateral flow for mixing. The experimental results showed good agreements with the numerical predictions.

• Proceedings of the Korean Society of Applied Pharmacology
• /
• 1992.05a
• /
• pp.29-29
• /
• 1992

척수에서의 통각전달은 말초에서 전달되는 통각정보가 척수내의 척수세포에 전달되면서 시작된다. 척수에 전달된 유해자극 정보는 척수내의 이차감각세포를 통하여 시상으로 전달되고 이로 인해 통증을 느끼게 된다. 이러한 척수내의 세포는 연수등의 여러 부위에 존재하는 신경 세포에 의하여 억제를 받으며 이와 같은 하향성 억제는 뇌에 존재하는 내재진 통계를 설명하는 중요한 인자가 되고 있다. 본 실험은 하부연수에 위치하는 신경핵인 Lateral reticular nucleus가 이러한 하향성 억제를 가졌는가를 알아 보고자 하였다. 이를 위하여 고양이를 마취시키고 척수궁을 절제하여 척수를 노출시키고 미세전극을 꽂아 척수세포의 활성을 기록하였다. 여덟마리의 고양이에서 31개의 척수세포를 기록하였다. 이 세포들 중 WDR세포가 14 (45%), HT가 9 (29%), LT 및 Deep세포가 각각 4 (13%)가 되었다. 이 척수세포에 북외측하부 연수인 lateral reticualr nucleus 주위를 건기자극하면 21개 (68%)의 세포가활성의 억제를 받았고 9개의 (29%) 세포는 아무런 변화가 없었고 1개의 (3%) 세포는 흥분되었다. 전기의 자극은 강도 100$\mu$A이며 자극길이는 100$\mu$S 그리고 100Hz의 주파수를 가진 펄스파였다. 이와같은 북외측하부연수의 전기자국은 신경세포의 자발활성뿐 아니라 수용장 자극에 의한 반응도 억제하였다.

• Proceedings of the KOSOMBE Conference
• /
• v.1997 no.11
• /
• pp.31-34
• /
• 1997

A semiconductor microelectrode array has been successfully used in obtaining single unit recordings from medial giant nerve of clay fish, rat saphenous nerve and abdominal ganglia of aplysia. The recording device fabricated using silicon microfabrication techniques is a depth-probe type and, previously, has been mostly used to record from central nerve system of vertebrates. From invertebrates, and also from peripheral nerves of vertebrates, however, the quality of the recorded signal depends heavily on the recording conditions, such as the proximity of the electrode site to the nerve cells and the size of the neuron. We have modeled the signal to noise ratio as unctions of these parameters and compared the experimental data with the calculated values thus obtained.

• Proceedings of the KOSOMBE Conference
• /
• v.1998 no.11
• /
• pp.209-210
• /
• 1998

Noise characteristics of preamplifier, the most essential part of on-chip signal processing circuitry for the active semiconductor neural probe, is the important factor determining the overall signal-to-noise-ratio (SNR). We present a systematic design method for the optimization of SNR, based on the spectral characteristics of the electrode, circuit noise and extracelluar action potential. Analytical expression is derived to calculate total output noise power. Output SNR of 2-stage CMOS preamplifier is tailored to meet the given specification while the layout area is minimized.

• Proceedings of the KOSOMBE Conference
• /
• v.1998 no.11
• /
• pp.145-146
• /
• 1998

A planar-type silicon microelectrode array has been fabricated and used successfully in obtaining simultaneous multichannel recordings from peripheral nerve of invertebrates. This paper demonstrates that planar-type semiconductor electrode arrays are useful for studying traveling wave properties of action potential.

• Proceedings of the KOSOMBE Conference
• /
• v.1998 no.11
• /
• pp.147-148
• /
• 1998

In this paper, we developed the process for depth-probe type silicon microelectrode arrays. The process consists of four mask steps only. The steps are for defining sites, windows, and for shaping probe using plasma etch from above, and for shaping using wet etch from below, respectively. The probe thickness is controlled by dry etching, not by impurity diffusion. We used gold electrodes with a triple dielectric system consisting of oxide/nitride/oxide. The shank of the probe taper from 200um to tens of urn tip and has 30 um thickness.

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.12
• /
• pp.191-197
• /
• 2003

As mechanical components are miniaturized, the demand on micro die and mold is increasing. Micro mechanical components usually have high hardness and good conductivity. So micro electrical discharge machining (MEDM) is an effective way to machine those components. In micro cavity fabrication using MEDM, it is observed that the bottom surface of cavity is distorted. Electric charges tend to be concentrated at the sharp edge. At the center of the bottom surface, debris can not be drawn off easily. These two phenomena make the bottom surface of the electrode and workpiece distort. As machining depth increases, the distorted shape of electrode approaches hemisphere. This process is affected by capacitance and the size of electrode. By using a smaller electrode than the desired cavity size and appropriate tool movement, bottom shape distortion can be prevented.

• Proceedings of the Korean Society of Applied Pharmacology
• /
• 1993.04a
• /
• pp.160-160
• /
• 1993

목적: Guinea pig heart의 ATP sensitive $K^{＋}$ channel xenopus oocyte에 발현시켜 연구하고져 본 실험을 행하였다. 실험방법: 기니픽 심장으로부터 ,RNA를 분리하여 50ng/$\mu$l의 농도로 50nl를 xenopusdp 주입하였다. Xenpus oocyte에서 conventional electrode를 이용 막전휘를 측정하였고, pH selective 미세전극으로 세포내 pH를 측정하였다. 막전위에 미치는 potassium channel opener, blocker, KCN의 작용을 관찰하였다. 결과: 기니픽 심장 mRNA를 주입하거나 주입하지 않은 xenopus oocyte에서 $K^{＋}$channel opener인 cromakalin, RP49356등은 과분극을 일으키지 못하였다. 그러나 세포내 ATP 감소제인 KCN은 농도 의존적으로 과분극을 일으켰으나 ,glibenclamide에 의해 차단되는 않았다. mRNA를 주입한 oocyte에서 Na-H 자극제인 NH$_4$Cl은 pH 변동을 일으켜 NA-H exchange를 expression 시켰다. 결론: Xenopus oocyte는 cromakalin등에 의해 open되는 $K^{＋}$channel 은 없었고, 기니픽 심근의 ATP sensitive $K^{＋}$channel로 expression 되지 않았으나 Na-H exchange 는 expression 됨을 알 수 있었다. KCN으로 open 되는 $K^{＋}$channel이 있었으나 glibenclamide에는 차단되지 않는 channel이였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2015.05a
• /
• pp.113-113
• /
• 2015

본 연구에서는 thermal evaporation법을 이용하여 제작한 CdTe 후막의 미세구조, 전기적 특성 및 X-선 조사에 따른 특성을 비교분석하였다. 기판온도를 $370{\sim}450^{\circ}C$로 변화시키며 증착하였으며, CdCl2 첨가에 따른 미세구조 변화를 관찰하였다. CdTe 막의 상 하부에 전극을 형성하여 I-V 특성을 평가하고, 실제 X-ray를 샘플에 조사하여 sensitivity를 측정하였다. 박막형성 초기에는 기판온도가 증가함에 따라 grain size가 증가하였지만, grain uniformity는 감소하였다. X-ray 특성향상을 위해서는 grain size와 uniformity 모두 중요한 인자이기 때문에 uniformity 향상을 위해 Cl을 첨가하였다. 미량의 Cl 첨가에서는 큰 변화를 보이지 않았지만 더 많은 양의 Cl 첨가 시, grain size 와 uniformity 모두 증가되는 것을 확인하였으며, 그에 따라 I-V, X-ray 조사 특성 모두 개선되는 것을 확인할 수 있었다.