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 topdown 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.