Developing rationally designed dynamic hydrogels and polymers as inks for 3D printing is in the limelight today. They would enable us to precisely fabricate complex structures in high resolutions and modular platforms with smart functions (e.g., self-healing and self-recovery), as well as tunable mechanical, chemical, and biological properties. In this paper, we explore recent developments in dynamic hydrogels and polymers as inks for 3D printing and discuss their properties and applications in tissue engineering, biomedicine, soft robotics, and sensors. The main scope of the paper is to give a deeper understanding of the field in terms of chemistry, physics, and associated properties. Moreover, the challenges and prospects of hydrogel/polymer inks will be discussed. We envisage that 3D printed dynamic hydrogels and polymers will provide unprecedented opportunities in designing and fabricating smarter structures.

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This study examines the influence of deposition layer thickness on the mechanical properties of printed ABS material when manufacturing using Fused Filament Fabrication (FFF). Tensile and compression testing was performed to ASTM standards on samples printed with layer thickness between 0.2mm and 0.8mm. Results found material strength and stiffness was greatest using smaller layer thicknesses, compared with larger layer thicknesses e.g. (0.2) = 31.5 MPa, (0.2) = 38.2 MPa, compared with (0.8) = 23.0 MPa, (0.8) =31.0 MPa. The recorded changes in mechanical properties are explained by mechanisms relating to manufacturing residual porosity, the number of deposited layers promoting interlayer bonding strength, and the extrusion process resulting in material shear hardening. Findings have implications on the ability to reduce the overall part print time using a method of increased material deposition, and may have profound implications on comparative part integrity when utilising large volume deposition printing formats with unmodified ABS polymer. The findings from this study also highlight the need for current mechanical testing standards to accommodate appropriate guidelines for the testing of 3D printed material, given the wide variance of measured tensile and compression properties based on layer thickness and printed geometry.

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