Culturing cellular tissues inside a microchannel using an artificial three-dimensional (3D) microstructure is normally conducted to elucidate and reproduce a biological function. The thick photoresist SU-8, which has a microscale resolution and high aspect ratio, is widely used for the fabrication of microchannels and scaffolds having 3D structures for cell culture. However, it is difficult to accurately fabricate a mesh structure with a pore size that is smaller than the cells that has an overall height greater than 50 μm because of the deterioration of the verticality of exposure light and the diffusion of acid, which accelerates the crosslinking reaction in the SU-8 layer. In this study, we propose a method of integrating a vertical porous membrane into a microchannel. The resolution of the vertical porous membrane becomes more accurate through inclined oxygen ashing, without degrading the robustness. Because a single mask pattern is required for the proposed method, assembly error is not generated using the assembly-free process. The fabricated vertical porous membrane in the microchannel contained micropores that were smaller than the cells and sufficiently robust for a microfluidic system. HepG2 cells were attached three-dimensionally on the fabricated vertical porous membrane to demonstrate 3D cell culture.
Keywords: SU-8; assembly-free; biomicrofluidics; inclined exposure; inclined oxygen ashing; vertical porous membrane.