The research on stem cell cultures has attracted much attention due to the recent development of regenerative medicine. Therefore, higher functionalities for devices used for culturing cells are strongly demanded. In this study, we fabricated cell culture sheets using transparent polyimide (PI), parylene (PA), and polyetheretherketone (PEEK) to make polymer materials that had microstructures. We then cultured stromal marrow cells (OP9) on them and investigated the cell alignment within the microstructures. Hot embossing was used to fabricate the microstructures with a width and depth of 5 μm on the polymer substrates. Cultivation of the cells was confirmed on the transparent PI and PA sheets, however, it was not observed on the PEEK sheet. Slight alignment of the cells was also observed along with the microstructures.
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.
Potentials of the transparent polyimide (PI) substrate were investigated for a possible biological cell culture sheet. Stromal marrow cells (OP9) were used to test the cell culture characteristics, and the OP9 cell culture was compared on three kinds of polymer films of transparent PI, parylene (PA), and polyetheretherketone (PEEK). Microtrenches with the width of 5 m and the depth of 5 m were fabricated using hot embossing technique on these films. The cultured cell of OP9 was observed on the transparent PI sheet and PA sheet, but not on PEEK sheet. The culture of OP9 cells were easily observed on the transparent PI sheet using an optical microscope.
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