3D printing algae-based materials: Pathway towards 4D bioprinting

Algae is a renewable source of various materials that are suitable for 3D printing. Taking a step towards sustainability, the continuously growing industry of 3D printing calls for novel green materials/inks with stable mechanical properties. This paper aims to investigate the 3D printability of algae-based materials and their potential for 4D bioprinting. The sources, printability, and properties of algae-based synthetic polymers, natural hydrogels, and algae cells were reviewed. 4D printability was also explored in terms of hydrogel responsiveness to various types of stimuli and in terms of cell/tissue maturation, and relevant recent progress was reviewed. Results show that PHAs (Polyhydroxyalkanoates) from algae can replace fossil-derived PHAs because they have similar mechanical properties whilst being more environmentally friendly. Algae can also produce a wide range of hydrogel-forming polymers, of which many are already being used as 3D printing inks while others are yet to be developed to suit the printing specifications. Several hydrogels also demonstrate stimuli-responsiveness which make them suitable for 4D printing. Further research is required to overcome the mechanical instability and slow stimuli-responsiveness of natural hydrogels.