3D PRINTING OF MULTI-FUNCTIONAL HYDROGELS

3D printing technology has been widely applied to rapid design and fabrication in recent years. Hydrogels fabricated by 3D printing are spotlighted owing to the emerging demands for complicated soft structures and biocompatible devices. The large variety of hydrogels provides the potential to produce multifunctional structures with hydrogels of different formulations and properties. Herein, we reported two works of 3D printing of multifunctional hydrogels by direct ink writing, a 3D printing technology based on the rheological properties of the hydrogel precursor ink. The first work developed a highly stretchable in situ grown metal-organic framework (MOF), overcomes the longstanding challenge of processing MOF materials into the flexible matrix by 3D printing without compromising on the MOF functionality performance. The prepared MOF hydrogel by facile in situ growth of MOF in 3D printed pAAM/alginate double networks hydrogel matrix exhibits high loading of MOF distributed in the whole hydrogel matrix, can be stretched to over 450 % of its original length and shows the best dye adsorption performance among the existing 3D printed MOF-polymer composites. We anticipate that this method would introduce new opportunities fabrication of complex flexible MOF-polymer composite devices for diverse applications such as wearable, implantable biosensors, flexible electronics. The second work introduces 3D printed segmented dual-gel tubes composed of an active thermally responsive swelling gel (poly N-isopropylacrylamide; pNIPAM) and a passive thermally non-responsive gel (polyacrylamide; pAAM). The dual-gel structures are able to achieve reversible shape deformation including uniaxial elongation, radial expansion, bending, and gripping by thermal actuation. The shape changes are programmable, predictable guided by CAD design and finite element simulations. The dual-gel 4D printing opens new avenues such as stimulus-responsive soft robotics and biomimetic 3D cell scaffold for biomedical engineering, with a high level of customization and tunability in three dimensions