Abstract. This article presents on a simple sub-micron wire fabrication by means of local anodic oxidation atomic force microscopy technique. The silicon-based structure consists of two adjacent terminals serve as probing pads and connected with a wire width less than 200 nm. The pad dimension and wire length are 49 µm 2 and 11 µm each, respectively. The fabrication process is conducted at room temperature 24 -27 °C with 50 -60 % relative humidity and operated by commercial atomic force microscopy without any modification done. Furthermore, the local oxidation is performed using gold coated AFM probe tip and assisted by the used of special language supported by the equipment software. In addition, 9.0 V applied voltage with 2 µm / sec writing speed is used to realize the oxidation process. I-V characteristic of bare device shows there is a current flow through the device when a range of voltage is applied. By using this local anodic oxidation technique, the silicon wire-based structure is fabricated and used as gas sensor sensing part. The silicon device demonstrates an increase in resistance as introduced to gas environment. The silicon wire device shows relative sensitivity of 35 % to the oxygen gas.
The detection of coliform bacteria which contain the disease-causing microorganism is a useful indication for water contamination. Currently, the emerging of technology in molecular biology research and industry is in demand for portable and miniaturized system. This paper demonstrates the development and integration of microfluidic and optical absorbance measurement device for portable coliform bacteria detection. The microfluidic device was fabricated with glass and polydimethylsiloxane (PDMS) material using photolithography, replica molding (soft lithography), and oxygen plasma bonding techniques. Then, the optical absorbance measurement device for coliform bacteria detection was developed using 470 nm blue light emitting diode (LED), photo detector, ARDUINO microcontroller, liquid crystal display (LCD), and mechanical elements. The coliform bacteria suspension sample was inserted into the microfluidic device and the presence of coliform bacteria was analyzed using the developed optical absorbance measurement device. The absorbance measurement from the prototype and colony number of the coliform bacteria samples were collected and analyzed. The final analysis had indicated that the developed prototype was able to detect the coliform bacteria in suspension at the lowest detection of 17,200 CFU/ml.
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