3D/4D Printing Hydrogel Composites: A Pathway to Functional Devices

The past few years have seen the introduction of a number of 3D and 4D printing techniques used to process tough hydrogel materials. The use of 'color' 3D printing technology where multiple inks are used in the one print allows for the production of composite materials and structures that can further enhance the mechanical performance of the printed hydrogel. This article reviews a number of 3D and 4D printing techniques for fabricating functional hydrogel based devices.