Three-dimensional fabrication of heterogeneous microstructures using soft membrane deformation and optofluidic maskless lithography.

We propose a method for high-throughput generation of 3D microstructures using a membrane-mounted microfluidic channel. Utilizing an optofluidic maskless lithography system, photopolymerized 3D microstructures are fabricated in a layer-by-layer fashion with the thickness of each layer controlled by the deformation of the membrane. The combination of low numerical aperture optical systems for photopolymerization and a soft membrane for height control allows large area projection lithography with high vertical resolution, overcoming the trade-off between vertical resolution and the field-of-view. The material composition of each layer is varied using microfluidic control of photocurable resin and composite microstructures with heterogeneity in both lateral and vertical directions are generated. Using this technique, we demonstrate three-dimensional patterning of different types of cells in a hydrogel for a microfluidic platform to study co-culture and cell-to-cell interactions. The proposed technique is fast and simple, allowing parallel synthesis of complex heterogeneous 3D microstructures and in situ biomaterial patterning for microfluidic bioassays.