Materials vs digits: A review of embedded anti-counterfeiting fingerprints in three-dimensional printing

Ongoing breakthroughs in the development of functional printing materials are leading to rapid and widespread industrialization of three-dimensional (3D) printing, accompanied by increasingly urgent requirements for methods to prevent problems such as tampering, counterfeiting and destruction of 3D printed products. Anticounterfeiting of 2D printed products has a long history, but its methods are not suitable for application to 3D printed products, as the latter products have embedding that is substantially different to that of the former products. This review article analyses anti-counterfeiting techniques for 2D printed products, proposes two embedding strategies for 3D printing based on material-responsive properties and 3D digital information, and summarizes the progress and performance of the corresponding anti-counterfeiting methods. It is shown that among the embedded anti-counterfeiting methods that exploit the responsive properties of materials, methods based on optical properties, spectral properties and deformation properties of 3D printing materials are the focus of research on embedding anti-counterfeiting materials into 3D printed objects. In addition, it is demonstrated that state-of-the-art embedding-based anti-counterfeiting methods use 3D digital information interactions and depend on 3D digital watermarks, 3D identification codes and radio-frequency tagging. Finally, a detailed discussion is provided on the generation, integration, extension, detection and prediction of embedded security features that can be printed synchronously with a functional structure. This offers a unique perspective on standardization of embedding-based anti-counterfeiting methods used in 3D printing.