Gravity-assisted 3D bioprinting: Using gravity as a design input to build high aspect-ratio structures

Extrusion-based bioprinting (EBB) offers unique advantages for 3D printing of hydrogels including superior structural integrity, high cell density, and continuous deposition. Despite these advantages, the lack of mechanical stability of printed constructs limits the fabrication of high aspect ratio constructs using EBB. Due to this limitation, patterning macroscopic scaffolds to mimic anatomical structures of a high aspect ratio remains a challenge. For example, it is difficult for EBB to print hollow tubes of an appreciable length-to-width ratio without using complicated sacrificial materials in a multi-print process. By using gravity as a 5th-dimensional input (X, Y, Z, time, gravity), we were able to generate high aspect ratio structures without further complication of 3D printer mechanics. Using gravity-assisted bioprinting methods we routinely achieved aspect ratios greater than two times those of similar constructs printed without gravity assistance.