Joon-Geun Ha

Conductive microtip electrode array with variable aspect ratio using combination process of reactive ion etching

A micromachining process for a conductive microtip electrode array has been developed using a combination process of reactive ion etching. A localized conical ultra-micro electrode (UME) with submicron width is realized on the tip end for electrochemical measurements. A height of several tens of microns of the silicon microtip is achieved, and the area beyond the UME is covered with dielectric material for electrical insulation. A high-aspect-ratio silicon microtip is fabricated using anisotropic and isotropic etching with varying the gap and diameter of the etch masks. Cyclic voltammetry is conducted to characterize the electrochemical properties of the UMEs. The results indicate that the electrical connection on the UME works successfully, and the measured peak currents were found to be in good agreement with the values estimated from analysis based on conical UME theory.

Fabrication and measurements of high aspect ratio conductive microtip array with localized ultra-micro electrode at the tip end

This paper presents a fabrication and electrochemical characterization of an array of high aspect ratio conductive microtips with localized ultra-micro electrodes (UME) at the tip ends. The proposed microtip was designed to be inserted into the cytosolic space of a cell for the intracellular applications such as metabolic activity sensors and photosynthetic fuel cells. In order to be applied to these applications, the microtip structure with the localized UME was fabricated to achieve the high aspect ratio, small apex radius and the height of tens of micron scale. To fabricate the localized UME, the conductive layer on the microtip surface was revealed only at the tip end while the rest of the conductive layer was insulated electrically.

Implementation of stackable photosynthetic microbial fuel cell structure using stainless steel mesh membrane electrode assembly

This paper presents a fabrication and measurement of stackable photosynthetic microbial fuel cell (MFC) with integrating two cathode chambers in unit cell that increases surface power density compared to conventional photosynthetic MFC structures. Stackable MFC is realized by newly proposed membrane electrode assembly (MEA) structure which includes proton exchange membrane (PEM) and stainless steel mesh anode. A performance of proposed MEA and MFC is characterized by electrochemical impedance spectroscopy (EIS) and current-power curve measurements.

2-D forward optical scanner with glass microlens and isolation blocks using thermal reflow

We present a novel fabrication method of a two-dimensional forward optical scanner with integrated microlens. Glass microlens and electrical isolation blocks were integrated with silicon XY-stage using thermal reflow process. Measured scan angles in X and Y directions at resonance were ±4.9° and ±5.0°, respectively, at atmospheric pressure.