Freedom of design, mass customisation, waste minimisation and the ability to manufacture complex structures, as well as fast prototyping, are the main benefits of additive manufacturing (AM) or 3D printing. A comprehensive review of the main 3D printing methods, materials and their development in trending applications was carried out. In particular, the revolutionary applications of AM in biomedical, aerospace, buildings and protective structures were discussed. The current state of materials development, including metal alloys, polymer composites, ceramics and concrete, was presented. In addition, this paper discussed the main processing challenges with void formation, anisotropic behaviour, the limitation of computer design and layer-by-layer appearance. Overall, this paper gives an overview of 3D printing, including a survey on its benefits and drawbacks as a benchmark for future research and development.

Additive manufacturing (3D printing): A review of materials, methods, applications and challenges

The bioink: A comprehensive review on bioprintable materials.

Bioprinting 3D microfibrous scaffolds for engineering endothelialized myocardium and heart-on-a-chip.

The worldwide demand for the organ replacement or tissue regeneration is increasing steadily. The advancements in tissue engineering and regenerative medicine have made it possible to regenerate such damaged organs or tissues into functional organ or tissue with the help of 3D bioprinting. The main component of the 3D bioprinting is the bioink, which is crucial for the development of functional organs or tissue structures. The bioinks used in 3D printing technology require so many properties which are vital and need to be considered during the selection. Combination of different methods and enhancements in properties are required to develop more successful bioinks for the 3D printing of organs or tissue structures. This review consists of the recent state-of-art of polymer-based bioinks used in 3D printing for applications in tissue engineering and regenerative medicine. The subsection projects the basic requirements for the selection of successful bioinks for 3D printing and developing 3D tissues or organ structures using combinations of bioinks such as cells, biomedical polymers and biosignals. Different bioink materials and their properties related to the biocompatibility, printability, mechanical properties, which are recently reported for 3D printing are discussed in detail. Many bioinks formulations have been reported from cell-biomaterials based bioinks to cell-based bioinks such as cell aggregates and tissue spheroids for tissue engineering and regenerative medicine applications. Interestingly, more tunable bioinks, which are biocompatible for live cells, printable and mechanically stable after printing are emerging with the help of functional polymeric biomaterials, their modifications and blending of cells and hydrogels. These approaches show the immense potential of these bioinks to produce more complex tissue/organ structures using 3D bioprinting in the future.

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Recent trends in bioinks for 3D printing.

3D printing alias additive manufacturing can transform 3D virtual models created by computer-aided design (CAD) into physical 3D objects in a layer-by-layer manner dispensing with conventional molding or machining. Since the incipiency, significant advancements have been achieved in understanding the process of 3D printing and the relationship of component, structure, property and application of the created objects. Because hydrogels are one of the most feasible classes of ink materials for 3D printing and this field has been rapidly advancing, this Review focuses on hydrogel designs and development of advanced hydrogel-based biomaterial inks and bioinks for 3D printing. It covers 3D printing techniques including laser printing (stereolithography, two-photon polymerization), extrusion printing (3D plotting, direct ink writing), inkjet printing, 3D bioprinting, 4D printing and 4D bioprinting. It provides a comprehensive overview and discussion of the tailorability of material, mechanical, physical, chemical and biological properties of hydrogels to enable advanced hydrogel designs for 3D printing. The range of hydrogel-forming polymers covered encompasses biopolymers, synthetic polymers, polymer blends, nanocomposites, functional polymers, and cell-laden systems. The representative biomedical applications selected demonstrate how hydrogel-based 3D printing is being exploited in tissue engineering, regenerative medicine, cancer research, in vitro disease modeling, high-throughput drug screening, surgical preparation, soft robotics and flexible wearable electronics. Incomparable by thermoplastics, thermosets, ceramics and metals, hydrogel-based 3D printing is playing a pivotal role in the design and creation of advanced functional (bio)systems in a customizable way. An outlook on future directions of hydrogel-based 3D printing is presented.

Qingment Pi

Papers

Direct 3D bioprinting of perfusable vascular constructs using a blend bioink