Technological considerations for 4D printing: an overview

4D printing utilizes additive manufacturing methods to produce stimulus-responsive components that can change its shape from one to another when subject to appropriate stimuli. The use of 4D printing technology is expected to significantly become more widespread with more applications across bio-medical, aerospace, and defence industries. This paper discusses emerging applications for 4D printing and suitable stimulus-responsive materials for 4D printing. In terms of designing for 4D printing, aspects of the shape memory effect (SME) including one-way SMEs, two-way SMEs and three-way SMEs are presented. Materials and structures in the form of homogenous compositions and heterogeneous compositions are discussed, as well as different types of shape-shifting behaviours such as self-folding, self-assemblies, and self-dis-assemblies. Finally, current software and examples are presented together with the existing limitations that need to be overcome to achieve widespread adoption of 4D printing.