This project will bring unparalleled capabilities of beam pen lithography (BPL) to the fields of 3D bioprinting, biofabrication, and tissue engineering by enabling the rapid construction of large-volume 3D hydrogel structures with the tunable architecture and mechanical properties at the micron scale. Not only will BPL 3D printing allow the construction of considerably more biologically relevant tissue models than currently available, but it will also overcome one of the major problems facing the existing tissue engineering strategies - inadequate tissue perfusion and consequently poor long-term viability - by introducing micropores into the frame of the 3D bioscaffold. The immense utility of BPL has already been proven in 2D nanofabrication using the Company's commercial BPL tools. The proposed research will extend the throughput, diffraction-unlimited <250 nm resolution and maskless design flexibility of BPL to 3D bioprinting. Using this novel biofabrication strategy, a next-generation liver-on-a-chip system will be constructed. An ultra-sensitive, label-free, regenerable electrochemical aptasensor will also be developed through this effort. By integrating the biosensor with the BPL 3D fabricated liver organoid via a highly modular microfluidic platform, real-time monitoring of tissue function and responses to environmental factors will be attained.