2. 3D and 4D synthetic comparison

The 4D technologies mentioned in this article have their origins in the invention of additive manufacturing in 1984. While additive manufacturing is a simple process to implement in principle (just in principle), the girl born in 2013 envisages a number of interdependent refinements: 4D printing involves so-called active materials in the object created by additive manufacturing, which must be transformed by means of at least one energy stimulus. This energy input enables changes in shape and/or functionality. 3D printing is now industrialized, but research continues to progress in terms of processes and, above all, materials. Below, we examine whether the sophistications found in the international literature are of little or no use for robust application developments in 4D printing.