Figure 4.

Multi-level SU-8 microstructures to fabricate microfluidic chips with channels of different heights. (A) SEM image showing microstructures of a different height. The insert shows an enlarged area of the main channel and perpendicular microchannels of a different height. (B) Optical profilometric 3D scan of middle portion of multi-level microfluidic chip. (i) Overview of a 3D scan. (ii) Height measurements of the main and microchannels. (C) Representative immunofluorescence image of MAP2-positive hiPSC-derived neurons upon 7 days of culture in a multi-level microfluidic chip. Top dashed box shows an enlarged area of neurite protrusions in microchannels. Bottom dashed box shows an enlarged area of hiPSC-derived neurons cultured in the main channel. (D) Photograph of fabricated chip showing fluidic isolation as evident by the blue and red food dyes. White scale bars: 100 µm. Yellow scale bar: 1000 µm.