Bottom-up and top-down VAT photopolymerization bioprinting for rapid fabrication of multi-material microtissues

Over the years, three-dimensional (3D) bioprinting has attracted attention for being a highly automated manufacturing system that allows for the precise design of living constructs where cells and biomaterials are displaced in predefined positions to recreate cell–matrix and cell–cell interactions similar to native tissues. Such technologies rarely offer multi-material features. In this paper, we present a new approach for bioprinting of multi-material tissue constructs using VAT photopolymerization at high resolution and fidelity. We developed a versatile dual-mode bioprinter that can easily be modulated to print in both top-down and bottom-up approaches. The custom-built platform was then used to fabricate microtissues and hydrogel microfluidic models. Combining bottom-up and top-down biofabrication tools can offer an optimal solution for hard–soft multi-material composites and for bioprinting tissue–tissue interface models. We demonstrated the possibility for hard–soft multi-material bioprinting by generating musculoskeletal tissue with integrated microvasculature. Combining multiple material bioprinting and microfluidic chips shows advantages in two aspects: precise regulation of microenvironment and accurate emulation of multi-tissue interfaces.