4D printing: a critical review of current developments, and future prospects

Due to the strong demand for low-cost and highly efficient products, various approaches are currently being explored and applied so as to contribute to the development and optimization of 4D printing technology. Significant progress is being made in this area of advanced manufacturing, and this comparative study helps to understand the latest developments in materials, additive techniques, and future prospects for this technology. It should, however, be noted that a large amount of progress still remains to be made. While some of the research has focused on the performance of the materials, the rest has focused on the development of new methods and techniques in additive manufacturing. This review critically evaluates the current 4D printing technologies, including the development and optimization of printing methods as well as to the printed objects. Previous developments in this area and contributions to the modern trend in manufacturing technology are briefly summarized. The review is divided into three sections. Firstly, the existing printing methods along with the frequently used printing materials as well as the processing parameters, and the factors which influence the quality and mechanical performances of the printed objects are discussed. Secondly, the optimization techniques, such as topology, shape, structure, and mechanical property, are described. Thirdly, the latest development and applications of additive manufacturing are depicted, and suggestions concerning the scope of future research are put forward.