Unclonable security features for additive manufacturing

Leveraging the technology's unique ability to selectively place multiple materials throughout a part volume, the authors demonstrate a new approach for the fabrication of a new physical security feature for additively manufactured parts. Specifically, the authors create photopolymer suspensions featuring quantum dots - a nanoparticle that absorbs ultraviolet light and emits light in the visible spectrum - that are then embedded into objects created by PolyJet material jetting. While the quantum dots appear ordered at the macroscale, their stochastic arrangement at the microscale (via the inkjetted droplet) provide the randomness necessary to serve as the key element of a Physical Unclonable Function, essentially transforming the 3D printed object itself as an anti-counterfeiting system. In this work the authors explore the effects of quantum dot loading on optical signatures of the nanoparticles in the photopolymer matrix. Quantum dot loadings as low as 5 × 10−3 wt.% can be detected inside the object with a fluorescent microscope, while this same concentration is invisible to the naked eye. By adjusting the magnification of the fluorescent microscope, we demonstrate the feasibility of a new paradigm for three-dimensional security patterns.