4D bioprinting: a review on smart bio-adaptable technology to print stimuli-responsive materials

3D bioprinting is a sphere of additive manufacturing technology that can print bioactive materials in a 3D architecture making them feasible to use as scaffolds in bone tissue engineering applications. However, these scaffolds suffer from maintaining the time–response-based printing which is desired to print living tissues or cell encapsulated stimulus materials. To realize this, adding time in another dimension to the conventional 3D bioprinting received decent attention in the scientific community and requires understanding the underlying challenges to develop such platforms. Hence, the current review demystifies challenges that envelopes the biological environment, material design and structure–property correlation in printing the biological tissues specifically towards bone tissue engineering applications. This review initially addresses basic understanding and challenges of mechanobiological, material, and mechanosensing interactions towards bone tissue engineering and their need for 4D bioprinting. Further the review will emphasize on the 4D bioprinting in detail and appraise this new state-of-art technology that can revolutionize biomedical industry.