In this study, the electrical conductivity of low-volume samples was measured using a prototype microfluidic chip with electrodes. We were able to show the difference of electrical conductivity in the samples of saline solution (0.9w/v% NaCl solution) with sucrose. The correlation between the electrical conductivity and the viscosity evaluated by the capillary method was shown. This correlation was shown that it is possible to evaluate viscosity based on the Walden's rule with our chip.
At present, there is no suitable mask for the etching process to fabricate micron-level textures on stainless steel. In this paper, we take advantage that Si can be processed as fine structures with a high aspect ratio. We fabricated Si structures with through-holes of 2μm width. This Si structure was applied as a hard mask for dry etching based on Ar+ ions of stainless steel,and the aspect ratio obtained is about 2, the effectiveness of Si hard mask is confirmed.
A transparent high density thin-film-transistor microelectrode array (TFT-µEA) was investigated, for the first time, to apply to real-time electrophysiological monitoring on glucose-stimulated insulin secretion dynamics of pancreatic β cells at higher resolution than conventional microelectrode arrays (MEAs). TFT-µEAs employed in this work are designed based on the switch matrix architecture, which incorporates a large sensing area (15.6 mm × 15.6 mm) with a 150 × 150 array of indium-tin-oxide (ITO) microelectrodes placed at a 100 µm pixel pitch. TFT-µEAs coated with poly-L-lysine and laminin enabled to culture rat insulinoma β line iGL for at least 7 days without cell death, which was determined by conventional cell viability tests based on a fluorescent staining method. Real-time action potentials of iGL cells stimulated by 15 mM glucose were successfully observed in similar to those in a conventional MEAs. These results are the first step towards the development of a multimodal TFT-µEAs device for electrophysiological, biochemical and optical analyses of the pancreatic islets. TFT-µEAs would extremely be promising platforms in the bioanalysis field for neurochemistry and electrophysiology.
In this study, we examined the film quality improvement and the etching characteristics of BHF and KOH solutions of SiON films prepared by reactive sputtering, and their application to MEMS processes. From these results, it was found that the sputtered SiON film can be patterned by a normal photo resist film because it dissolves relatively easily in BHF solution, and that it has good tolerance of KOH etching and is effective as a protective film in the diaphragm process. Finally, the MEMS process of the piezo-resistive pressure sensor was proposed, and the sample was actually prepared. As a result, the sputtered SiON film produced in this experiment can be sufficiently adapted in the MEMS process, and it is effective for the simplicity and cost reduction of the MEMS process. It is expected that it is possible to propose a new MEMS process by these advantages of the sputtered SiON film.
Currently, research on olfactory and taste sensors is being actively conducted, and the demand for molecular recognition is increasing. We have successfully developed an electrochemical sensor called Light Addressable Amperometric Sensor (LAAS). In this study, we used our organic-inorganic hybrid type LAAS with CuPc/n-Si/Al structure to verify its behavior in molecular recognition. As a starting point, we investigated the simplest reaction, hydrophobic bonding, as part of molecular recognition. The gold working electrodes on LAAS were modified by Self-Assembled Monolayer. We evaluated the device in terms of concentration dependency and image measurement. The measurements were carried out using a solution with redox substances and quinine as a hydrophobic substance. As a result, we confirmed the concentration dependence that the LAAS current value increases as the concentration of quinine increases. We also confirmed the reproducibility of the sensor because a device with the same characteristics was successfully fabricated by the same process.