Since 2010, the 3D printing technology has increasingly gained popularity, leading to a growing interest in the watermarking technology for 3D printed objects. Scientists from Nara Institute of Science and Technology (NAIST), composed of Ph.D. Student Arnaud Delmotte, Professor Yasuhiro Mukaigawa, Associate Professor Takuya Funatomi, Assistant Professor Hiroyuki Kubo, and Assistant Professor Kenichiro Tanaka have developed a new method that can embed information in a 3D printed object and retrieve it using a consumer document scanner. The technology can embed information such as serial ID without modifying the shape of the object. What’s more, the user can easily extract the information from a single image of a commercially available document scanner. As scientists noted, their new method can be used on fused deposition modeling (FDM) 3D printers and works by modifying the printed layer thickness on small patches of the surface of an object. In their proposed method, pairs of vertically adjacent layers are selected, and their thickness balance is modified according to the information to be embedded. This thickness balance modification has little effect on the external shape of the object. To prevent the degradation of the external surface of the object, pairs of vertically adjacent layers are selected and the ratio of their respective thicknesses is modified while keeping constant the sum of the two-layer thicknesses. Since a standard layer thickness is about 0.2mm, information can be embedded in a relatively small area ranging from several millimeters to a few centimeters. When it comes to retrieving embedded information, measuring the thickness of material becomes essential.
This new method can do this task effortlessly by using only a common document scanner and does not require any special equipment. The FDM printing process naturally produces some layering artifacts that are visible in the images obtained by a document scanner. These artifacts allow us to measure the thickness of the layers and extract the information.
Scientists noted, “With this method, it is possible to embed various types of information such as a URL that can be linked to Web services, a unique ID that can be used for product tracing, and the printer ID and printing date for batch quality management.” The results of this research were published in the international academic journal IEEE Transactions on Multimedia (TMM) on December 25, 2019.