3D printed hydrogels: a promising material for biomedical applications

3D printing is a revolutionary technique which enables 3D virtual models to be transformed into physical 3D objects. Since it was first introduced, nearly 40 years ago, 3D printing has steadily progressed offering significant advancements in the engineering of advanced materials and can be applied to a wide range of industries ranging from aerospace to biomedical. Hydrogels' propitious properties make them ideal candidates for 3D printing applications including inkjet printing, extrusion printing (fused deposition modeling and semisolid extrusion), and laser printing (stereolithography, digital light processing, and two-photon polymerization). The ability of hydrogels to withstand mechanical stress once implanted in the body, absorb biological fluids, and give rise to proper cell growth and proliferation makes them suitable candidates to be utilized in tissue engineering, regenerative medicine, soft robotics, printable electronics, and in vitro tissue modeling. Hydrogels can be fabricated using a natural source or in a synthetic way. Natural hydrogels are desirable, exhibiting good biocompatibility and biodegradability, although optimal properties can be obtained from synthetic hydrogels by tuning their swelling ability, stability, biodegradability, or mechanical strength. In this book chapter, different 3D printing techniques and potential natural and synthetic raw materials are described. Furthermore, recent advances in emerging biomedical applications of hydrogels are discussed. An outlook of the future trends in the hydrogel's field is also present.