16th NANOSCIENCE & NANOTECHNOLOGY CONFERENCE, Ankara, Turkey, 5 - 08 September 2022, pp.214
There is an urgent need for novel encoded surfaces in anti-counterfeiting and authentication applications. Particularly, counterfeit products and infringement of intellectual property constitute a significant threat to national security, world economy and human health. Almost 10% of the commercial goods in the world are either counterfeit or pirated. In addition to their significance for anti-counterfeiting, encoded surfaces are becoming critical in hardware and data security, driven by the rapid digitization of the world.
Encoded surfaces have been conventionally prepared by deterministic pathways. In this approach, discrete geometries are patterned on the surface of objects for encoding.1 One-dimensional and two-dimensional barcodes are widely utilized examples to this approach. Despite their effectiveness in addressable encoding and rapid read out, these patterns can be duplicated due to their deterministic nature of fabrication using reproducible processes. A solution to this challenge is the use of stochastic processes in surface encoding. Physically unclonable functions (PUFs) consist of random structures with a specific response and are impossible to replicate by both the manufacturer and third parties.2-5 PUFs can be fabricated by using stochastic physical and chemical processes. Novel hybridization of deterministic and stochastic pathways is needed to benefit from the advantages of both approaches.
Herein we present strategies for integrating deterministic and stochastic encoding approaches in the same platform. The random domains of nanoscale materials are formed by electrospraying. PUFs can be constructed in a rapid, low-cost and versatile manner based on random placement of polymer materials, thanks to the electrohydrodynamic instability.6 To fabricate PUFs within one-dimensional and two-dimensional barcodes, electrospraying is adapted with conventional microfabrication methods. In one approach, electrospraying is performed through stencil masks fabricated by laser engraving. The use of same masks with screen printing, allows for practical patterning of materials within barcoded regions for effective read-out of the first security layer, whereas the random patterns directly formed on these barcodes constitute the second layer. In a complementary approach, the use lithographically prepared templates will be discussed. Nanoscale materials can be effectively incorporated for generating complex and difficult to replicate responses. The additive characteristic of electrospraying allows for multiplex deposition of these nanomaterials, thereby improving the encoding capacity. The addressable PUFs will facilitate rapid and accurate authentication of the encoded surfaces.