Microfluidic devices employing dielectrophoresis (DEP) have been widely studied and applied in the manipulation and analysis of single cells. However, several pre-processing steps, such as the preparation of purified target samples and buffer exchanges, are necessary to utilize DEP forces for suspended cell samples. In this paper, a sequential cell-processing device, which is composed of pre-processing modules that employ deterministic lateral displacement (DLD) and a single-cell trapping device employing an electroactive microwell array (EMA), is proposed to perform the medium exchange followed by arraying single cells sequentially using DEP. Two original microfluidic devices were efficiently integrated by using the interconnecting substrate containing rubber gaskets that tightly connect the inlet and outlet of each device. Prostate cancer cells (PC3) suspended in phosphate-buffered saline buffer mixed with microbeads were separated and then resuspended into the DEP buffer in the integrated system. Thereafter, purified PC3 cells were trapped in a microwell array by using the positive DEP force. The achieved separation and trapping efficiencies exceeded 94% and 93%, respectively, when using the integrated processing system. This study demonstrates an integrated microfluidic device by processing suspended cell samples, without the requirement of complex preparation steps.
Low frequency noise radiated from highway bridges due to fast moving heavy vehicles, is giving rise to a new traffic problem. In order to solve this problem, it is necessary to consider the reduction of noise and control of bridge vibrations. In this research, measurements of low frequency noise radiated from highway bridges and measurements of bridge vibration were carried out. From these results, the radiation efficiency of the slabs of the highway bridges was determined. Four types of bridge were measured, steel composite girder bridges, steel plate girder bridges, steel truss bridges and PC-girder (T) bridges. From experimental formulae for the radiation efficiency, and from vibration acceleration levels, the sound pressure levels and 1/3 octave band spectra of the low frequency noise radiated from the slabs were predicted. As a result, the sound pressure level at an arbitrary point can be predicted by measuring the vibration acceleration level of the bridge. Predictive calculation results agreed relatively well with measured values, particularly at locations close to the bridges.
Improved fabrication processes of a micro electroosmotic flow pump using hot embossing are described. The microchannels in the micropump were fabricated by hot embossing on a polymethylmethacrylate (PMMA) substrate. A silicon micromachined mold was pressed into the PMMA substrate at a temperature of 145 °C to form microchannel patterns on the substrate. The depth and width of the microchannels were 50 μm and 100 μm, respectively. Aluminum electrodes were deposited using thermal vacuum deposition. A UV ozone treatment was performed to improve adhesion between the PMMA substrate and a PMMA capping layer. This UV ozone treatment enhanced adhesion and resulted in the reduction of the adhesion temperature as low as 70 °C, and nearly no deformation of the microchannels was observed. As a result, the electroosmotic flow pump exhibited the flow rate of 0.5 μl/min when a voltage of 50 V was given between the electrodes separated 8 mm each other.
Improved fabrication processes of an all-polyimide micro electroosmotic flow pump using hot embossing are described. Microchannels in the micropump were fabricated by hot embossing on a transparent polyimide substrate. A silicon micromachined mold was pressed into the transparent polyimide substrate at a temperature of 300 oC to form microchannel patterns on the substrate. The depth and width of the microchannels were 25 μm and 50 μm, respectively. A UV ozone treatment was performed to improve adhesion between the transparent polyimide substrate and film capping layer. This UV ozone treatment enhanced adhesion and resulted in the reduction of the adhesion temperature as low as 100 oC, and nearly no deformation of the microchannels was observed. As a result, the electroosmotic flow pump exhibited the flow rate of 0.7 μl/min when a voltage of 50 V was given between the electrodes separated 20 mm each other.
The transfer printing of Au micropatterns onto a polyimide (PI) film was investigated, and the optimum transfer conditions were obtained. In this study, micropatterns with widths of 25 μm and 75 μm were successfully transferred onto a PI film at a molding temperature of 150 °C for 5 s under a molding pressure of 2.5 MPa. This technique is expected to provide simplified processes in fabricating wiring patterns in microelectromechanical systems.
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