Four-dimensional (4D) bioprinting, in which the concept of time is integrated with three-dimensional (3D) bioprinting as the fourth dimension, with the goal of constructing complex, functional structures. 4D bioprinting can be used to fabricate dynamic 3D-patterned biological architectures that will change their shapes under various stimuli by employing stimuli-responsive materials. The functional transformation and maturation of printed cell-laden constructs over time are also regarded as 4D bioprinting, providing unprecedented potential for bone tissue engineering.

reference:

Wan, Z., Zhang, P., Liu, Y., Lv, L. and Zhou, Y., 2020. Four-dimensional bioprinting: Current developments and applications in bone tissue engineering. Acta biomaterialia, 101, pp.26-42.