Dr. Beyah and a team of researchers from Georgia Tech and Rutgers University have developed a three-layer system to verify that components produced using additive manufacturing have not been compromised.
Tech Briefs: Could you describe your system?
Dr. Raheem Beyah: It has three components. The first is acoustic measurement of the 3D printer in operation. When compared to a reference recording of a correct print, this acoustic monitoring — done with an inexpensive microphone and filtering software — can detect changes in the printer’s sound that may indicate installation of malicious software.
The second is physical tracking of printer components. To create the desired object, the printer’s extruder and other components should follow a consistent mechanical path that can be observed with inexpensive sensors. Variations from the expected path could indicate an attack.
Third is detection of nanorods in finished components. Using Raman spectroscopy and computed tomography (CT), we can detect the location of gold nanorods that have been mixed with the filament material used in the 3D printer. Variations from the expected location of those particles could indicate a quality problem with the component.
Tech Briefs: Why do you need three components?
Dr. Beyah: Since it’s layered, you might pick up a scenario that one layer might miss, but another wouldn’t. Acoustic and spatial are real-time protection mechanisms and are used in parallel. The materials phase is after the fact, so we can detect anything that gets through. Tech Briefs: What kinds of sensors do you use for the physical tracking? Dr. Beyah: We use a linear potentiometer and a gyroscopic sensor to reconstruct the coordinates of the printer’s motion.
Tech Briefs: Were the gold nanorods just used for your test, or would they be embedded in the final manufactured object?
Dr. Beyah: You actually embed them in the final object. We need a contrast agent to use as a 3D digital watermark. We embed the nanoparticles in certain locations, then we can go back later and use computed tomography and Raman spectroscopy to look inside the object to see if the nanorods are actually where we positioned them.
Tech Briefs: What are the next steps in your research?
Dr. Beyah: The first thing to look at is the effects of a noisy environment. The equipment itself also emits RF, so we have to look into that. We’re also investigating the use of a camera to monitor the printer’s components and other techniques to see through the object. We might be able to do the latter without embedding nanoparticles — there might be other contrast agents. Also, we might be able to utilize the EM radiation from the machine to give us information about how the extruder is operating.
Tech Briefs: Could this also be used in quality control?
Dr. Beyah: Yes. The print can go offscript or out of pattern. It could just be some sort of malfunction. With our technique, since the pattern is online, you can detect problems in process, and we can stop the machine at that point — it won’t take hours; you can stop it immediately once you detect an error.