Biomass materials and their application in 4D printing

Four-dimensional (4D) printing technology is a revolutionary development that produces structures that can adapt in response to external stimuli. However, the responsiveness and printability of smart materials with shape memory properties, which are necessary for 4D printing, remain limited. Biomass materials derived from nature have offered an effective solution due to their various excellent and unique properties. Biomass materials have been abundant in resources and low in carbon content, contributing to the then-current global green energy-saving goals, including carbon peaking and carbon neutrality. This review focused on different sources of biomass materials used in 4D printing, including plant-based, animal-based, and microbial-based biomass materials. It systematically outlined the responsive deformation mechanisms of printed objects that contained biomass materials and delved into the roles and unique advantages of biomass materials in those printed objects. Leveraging these advantages, the review discussed the potential applications of biomass materials in biomedicine, food printing, and other fields to support ongoing development and application efforts. Additionally, it emphasized the crucial role played by bio-fabrication technologies utilizing biomass materials in the integration of biomass materials with 4D printing. Finally, this paper discussed the then-current challenges and potential future directions of biomass materials in 4D printing, aiming to promote the effective development of biomass materials in 4D printing applications.