Deformation compensation during buoyancy-enabled inkjet printing of three-dimensional soft tubular structures

Of various tissues being fabricated using bioprinting, three-dimensional (3D) soft tubular structures have often been the focus since they address the need for printable vasculature throughout a thick tissue and offer potential as perfusable platforms for biological studies. Drop-on-demand inkjetting has been favored as an effective technique to print such 3D soft tubular structures from various hydrogel bioinks. During the buoyancy-enabled inkjet fabrication of hydrogel-based soft tubular structures, they remain submerged in a solution, which crosslinks the printed structures and provides a supporting buoyant force. However, because of the low stiffness of the structures, the structural deformation of printed tubes poses a significant challenge to the process effectiveness and efficiency. To overcome this structural deformation during buoyancy-enabled inkjet printing, predictive compensation approaches are developed to incorporate deformation allowance into the designed shape. Circumferential deformation is addressed by a four-zone approach, which includes base, circular, vertical, and spanning zones for the determination of a designed cross section or compensated printing path. Axial deformation is addressed by the modification of the proposed circumferential compensation based on the distance of a given cross section to the junction of a branching tube. These approaches are found to enable the successful fabrication of straight and branching alginate tubular structures with nearly ideal geometry, providing a good foundation for the wide implementation of the buoyancy-enabled inkjetting technique. While inkjetting is studied herein as a model bioprinting process, the resulting knowledge also applies to other buoyancy-enabled bioprinting techniques.