Scientists Discover A New Method to Embed Information In 3D-printed Products

A team of scientists from the Nara Institute of Science and Technology (NAIST), recently published the result of their research in the International Academic Journal IEEE Transactions on (TMM) Multimedia in which they reported finding a new method for embedding information in 3D-printed objects.

The team composed of PhD student Arnaud Delmotte, Assistant Professor Kenichiro Tanaka, Assistant Professor Takuya Funatomi, Assistant Professor Hiroyuki Kubo and Professor Yasuhiro Mukaigawa said their discovery would make it easy to hide information in 3D-printed objects from ordinary users without modifying the shape of the object.

The paper further explained the new technology allows the embedded information such as a serial product ID to be extracted using commercially available document scanners.

This new technology is just one out of other several technologies for 3D printing – with the most common method consisting of a precise deposing of layers of molten plastic on top of each other. This method of deposing layers of melted plastic on top of each other is known as Fused Deposition Modeling (FDM). The FDM process involves deposing layers of constant thickness.

While on the other hand, in the proposed method, pairs of vertically adjacent layers are selected, and their thickness balance modified according to the information to be embedded. These patches can be applied to multiple regions of the object to make it resistant to attacks such as cropping an image, local surface degradation, local deformation, or printing error.

However, the thickness modification does not in any way affect the external shape of the object.

Also, you can measure the precise thickness of the printed layers by scanning the object with a commercially available document scanner, this way, you can easily detect inconsistencies in layer thickness and extract the embedded information.

A Bit of Background and Purpose:

As the researchers explained: “Digital watermarking is a technology that embeds information inside digital content such as audio, video, image and 3D models. Some methods, such as QR code and barcode, visibly integrate data.

Other methods, however, embed information covertly, with additional data hidden and not perceptible to the user.”

With the growing interest in 3D printing technology, attention is now being focused on how to use watermarking technology in 3D printed objects.

Until recently, users had to use the best laptop for graphic design to edit their 3D models, but now it is possible to add any information during printing.

The researchers further explained what they hoped their work would achieve. In their words: “We proposed a new method to embed information during the printing of an object.”

According to the researchers, their focus is to minimize the impact and distortion of the outer shape of the object while embedding additional information which might affect the original function of the object.

How the new method works:

The researchers contrasted how the commonly used FDM method and their proposed process works.

According to them: There are several technologies for 3D printing. Chief among them is the Fused Deposition Modeling, which consists of deposing layers of molten plastic on top of each other.

To achieve the desired object thickness using the FDM method, you will have to strictly control the position and flow of the printing nozzle such that the deposed plastic layers follow a controlled path and specific thickness. This way, you can ensure the plastic flow produces an even layer of thickness.

In the new method, according to the paper published by the researchers, the plastic flow is modified during the print, which allows you to change the layer thickness for embedding some additional information locally.

To prevent distortion in the physical surface of the printed object pairs of vertically adjacent layers are selected, and the ratio of their respective thickness is modified while keeping constant the sum of the two-layer thicknesses.

Now, when you consider that the standard layer thickness is about 0.2mm, information can be embedded in a relatively small area ranging from several millimeters to a few centimeters, the report read.

How does the new method retrieve the embedded information?

Usually, to retrieve embedded information from a 3D printed object, you will have to measure the thickness of the object. However, according to the researchers, their proposed method can do this measurement using only an ordinary document scanner and does not require any special equipment.

Explaining their process further, the paper highlighted that FDM printing process naturally produces some layering artefacts that are visible in the images obtained by a document scanner. These artefacts, the researchers say allow them to measure the thickness of the layers and extract embedded information.

Future application of the technology

With this method, the researchers believed, it is possible to embed various types of information such as a unique ID for product tracing, which can come in handy in fighting counterfeiting. For embedding URL that can be linked to web services and for embedding printer ID and printing date for batch quality management.

Reference:

Arnaud Delmotte, Kenichiro Tanaka, Hiroyuki Kubo, Takuya Funatomi, Yasuhiro Mukaigawa. Blind Watermarking for 3D Printed Objects by Locally Modifying Layer Thickness. IEEE Transactions on Multimedia, 2019; 1 DOI: 10.1109/TMM.2019.2962306