Residual stresses in 4D printed structures: A review on causes, effects, measurements, mitigations and its applications

3D printing of stimulus responsive materials or smart materials are referred to as 4D printing. The ability of these materials to change their shape or properties over time is considered the fourth dimension. 4D printed parts possess residual stress just as any other manufactured object. Residual stress is that which remains in an object despite the absence of a load. It may develop during the printing process, or post printing. This paper presents an original review on the causes, adverse effects, measurement techniques, and mitigation of residual stresses in 4D printing. A simple sequence for checking the adverse effects of residual stress on 4D printed parts, and applying mitigation techniques is proposed. Building on the review, discussions on original results from design strategy, experimentation, characterization, and finite element analysis were presented. The applications of residual stress mitigation, and the prospects of this work are also discussed.