Towards preserving post-printing cell viability and improving the resolution: Past, present, and future of 3D bioprinting theory

Abstract

Three-dimensional bioprinting as an additive manufacturing technology for constructing biomimetic tissues by the deposition of individual layers is an ever growing and evolving field. Bioprinting has found many applications across tissue engineering and regenerative medicine disciplines, including medical research, regenerating human tissues for transplantation, and conducting stem cell research. In order to maintain the forward momentum of bioprinting, it is necessary to consider major factors limiting bioprinting's capabilities: post-printing cell viability and printing resolution. Computational modeling has the capacity to investigate the impact dynamics of encapsulated cells as they are deposited, with a particular focus on determining the deformation of the encapsulated cell and the rate of deformation, which are dependent on, among other factors, viscoelastic features, droplet size, and velocity. Similarly, computational models can be utilized to optimize filament integrity in extrusion-based bioprinting. By harnessing the power of modeling, experimental parameters can be predicted and fine-tuned to improve cell viability and/or shape fidelity. Herein, we review extrusion-based, droplet-based, and laser-based bioprinting techniques. The respective computational models are then presented, including compound droplet impact models for droplet-based bioprinting, which incorporated a Newtonian-model and viscoelastic features, and computational models applied to extrusion-based bioprinting. We then conclude with the future direction of bioprinting theory.