Fabrication Of 3D Ordered Porous Patterns In Microchannel

3D ordered porous materials can usually be used as catalysts, separation columns and photocrystals.3D ordered porous patterns have attracted much attention due to application in the microfluidic area. In this thesis, different kinds of 3D ordered porous patterns were fabricated from PS spheres packed template in the PDMS mold. A novel and robust 3D multilayered silica beads-packed microstructure was successfully prepared by transferring the silica beads-packed patterns in the PDMS mold onto surface of silicon wafers.PS spheres were organized into the PDMS mold under the centrifugal force. The 3D ordered macroporous SiCN material was obtained by curing the precursor at low temperature and thermally decomposing the PS spheres at high temperature. The obtained structure was characterized by SEM and optical microscopy. The results shows high-quality 3D ordered macroporous SiCN material could be achieved in a short time using a centrifugal method. During the process we also studied the morphologies of PS spheres after annealing for different periods. The size of necks formed by heating could be controlled in the range of 300 nm to 820 nm. The window sizes of the resulting 3D macroporous SiCN ceramic among the interconnected macropores increased from 258 nm to 740 nm, and the BET surface area was reduced from initial 443 m2 g-1to 337 m2.Even through high-quality 3D ordered porous SiCN material with the tailed window sizes was obtained, it is difficult to achieve the material over a large area on a substrate. PS spheres were organized into the PDMS mold using a directed evaporation-induced self-assembly method. Subsequently, through a microtransfer molding technique, the 3D ordered macroporous perfluoropolyether (FP) patterns with various dimensions were fabricated over a large area on a silicon wafer in relatively short time. Different kinds of porous patterns can be also fabricated using PDMS mold with varying patterns. More importantly, the 3D macroporous FP patterns over a large area were easily built inside a SU-8-50 microchannnel using a photolithography method.Finally, a 3D silica bead-packed microstruture was fabricated by transferring the packed silica spheres inside the PDMS onto the substrate using different soft lithographic technique. It was found that the single-layered silica bead-packed patterns with a high quality could not be achieved using the MIMIC method reported previously. A novel and robust 3D silica bead-packed microstrutures in a single,double and triple layers were fabricated using a microtransfer molding technique combined with a layer-by-layer technique. The stability of silica bead-packed patterns was improved by heating at high temperature. A stable monolithic structure with mechanical integrity was obtained on a silica wafer when heating the silica bead-packed patterns at 950℃. The double-layered silica bead-packed patterns had a bimodal pore distribution in micron and sub-micron range. Moreover, the microstructure was easily embedded inside the SU-8-50 microchannel with the aid of photolithography. Compared with densely packed silica spheres in the channel, the pressure drop was decreased by a factor of 63 when the void fraction of the packed bed in the channel increased from 0.26 to 0.63. The two-layered 3D silica beads-packed microstructure was used as a micro-mixer to enhance the mixing performance of solvents. Utilization of the system results in a fourfold increase in the mixing efficiency in the microchannel.