3D printers can quickly produce large quantities of products that have all been tweaked or modified in unique ways, a process called "mass customization." For example, 500 people might order a certain kind of doll, but some may want black eyes and some may want purple, while others may desire a certain nose or mouth.
With mass customization, there comes a new challenge: How is it possible to keep track of all those objects, each one the tiniest bit different?
Researchers at Microsoft have developed an answer: a new method of marking objects without leaving a visual trace on the exterior.
The method involves creating objects with various internal gaps, or bubbles, that form patterns. These patterns can then be observed using a Terahertz scanner, a device that has been used in airport security since 2007.
Terahertz, or THz, radiation is a type of electromagnetic light that is not visible to the human eye and also doesn't harm organic matter like nuclear radiation does. It can also pass through most plastics, fabric, wood and organic material, making it ideal for imaging the insides of objects. By analyzing the rate at which the Terahertz radiation beams pass through the object, the scanner can locate the gaps that make up the ID pattern.
Microsoft calls this type of tag an InfraStruct. It's similar in concept to a barcode or a QR code, but the mark is structural, not visual, and therefore doesn't have to be on the outside of an object.
This method is particularly easy to implement with 3D-printed objects, as the printers work by creating an object layer by layer, so adding the pattern is a relatively simple modification.
3D printers capable of printing in multiple materials, such as different types of polymers or even metal, could easily create a different type of InfraStruct. If you were to make one of those layers a different material than the rest, a Terahertz scanner would detect it because the radiation would pass through that layer at a different rate than the rest.