Table 5.

Desired properties for smart bioinks for 4D bioprinting.

Properties	Requirements
Printability	Processable and compatible with different types of bioprinting technologies Production of dynamic constructs with accurate patterns according to the smart design
Biocompatibility and bioactivity	Supporting cell growth and functionality during in vitro and in vivo development Absence of side effects in the host Facilitating desirable host responses after in vivo deployment
Stimuli-responsiveness	Robust stimuli-responsiveness Enabling fabrication of dynamic constructs with preprogrammed changes in shape, property, and function under stimuli Multiple stimuli-responsive, reversible shape changes, remote and cyclic actuation Enabling multi-step 3D deformation Adaptation to the complex human physiological environments
Biodegradability	Achieving a preprogrammed multi-step shape-shifting process by controlling the degradation rates Matching the growth of neo-tissues after deployment in vivo by designing appropriate degradation kinetics
Mechanical properties	Supporting structural integrity and shape transformation during evolvement of the 4D bioprinted constructs Matching the mechanical properties of target tissues
Cells	Cell sources with high availability High cell viability Comparable cell density to native tissues Excellent cellular functionalities (e.g., proliferation and differentiation) Generation of cell traction force to induce the shape transformation of microstructures