Browsing by Subject "Anti-counterfeiting"

Now showing 1 - 3 of 3

Open Access
SERS-active linear barcodes by microfluidic-assisted patterning
(Elsevier, 2020-09-28) Pekdemir, S.; Ipekci, H. H.; Serhatlıoğlu, Murat; Elbuken, C.; Onses, M. S.
Simple, low-cost, robust, and scalable fabrication of microscopic linear barcodes with high levels of complexity and multiple authentication layers is critical for emerging applications in information security and anti-counterfeiting. This manuscript presents a novel approach for fabrication of microscopic linear barcodes that can be visualized under Raman microscopy. Microfluidic channels are used as molds to generate linear patterns of end-grafted polymers on a substrate. These patterns serve as templates for area-selective binding of colloidal gold nanoparticles resulting in plasmonic arrays. The deposition of multiple taggant molecules on the plasmonic arrays via a second microfluidic mold results in a linear barcode with unique Raman fingerprints that are enhanced by the underlying plasmonic nanoparticles. The width of the bars is as small as 10 μm, with a total barcode length on the order of 100 μm. The simultaneous use of geometric and chemical security layers provides a high level of complexity challenging the counterfeiting of the barcodes. The additive, scalable, and inexpensive nature of the presented approach can be easily adapted to different colloidal nanomaterials and applications.
Open Access
Structurally colored physically unclonable functions with ultra-rich and stable encoding capacity
(Wiley-VCH Verlag GmbH & Co. KGaA, 2024-12-10) Esidir, A.; Ren, Mn.; Pekdemir S.; Kalay, M.; Kayacı, N.; Günaltay, N.; Usta, H.; Xuang, X.; Önses, Mustafa Serdar
Identity security and counterfeiting assume a critical importance in the digitized world. An eﬀective approach to addressing these issues is the use of physically unclonable functions (PUFs). The overarching challenge is a simultaneous combination of extremely high encoding capacity, stable operation, practical fabrication, and a widely available readout mechanism. Herein this challenge is addressed by designing an optical PUF via exploiting the thickness-dependent structural color formation in nanoscopic ﬁlms of ZnO. The structural coloration ensures authentication using widely available bright-ﬁeld-based optical readout, whereas the metal oxide provides a high degree of structural stability. True physical randomness in spatial position is achieved by physical vapor deposition of ZnO through stencil masks that are fabricated by pore formation in polycarbonate membranes via photothermal processing of stochastically positioned plasmonic nanoparticles. Structural coloration emerges from thin ﬁlm interference as conﬁrmed via simulation studies. The rich color variation and stochastic deﬁnition of domain size and geometry result in chaotic features with an encoding capacity that approaches (6.4×10⁵)$^{(2752×2208)}$ . Deep learning-based authentication is further demonstrated by transforming these chaotic features into unbreakable codes without ﬁeld limitations. This ultra-rich encoding capacity, coupled with outstanding thermal and chemical stability, forms a new cutting edge for state-of-the-art PUF-based encoding systems.
Open Access
Transferrable SERS barcodes
(Wiley-VCH Verlag GmbH & Co. KGaA, 2022-06-13) Sahin, F.; Pekdemir, S.; Sakir, M.; Gozutok, Z.; Önses, Mustafa Serdar
The demand for encoded surfaces has increased significantly over the past decade driven by the rapid digitalization of the world. Surface-enhanced Raman scattering (SERS) offers unique capabilities in generation of encoded surfaces. The challenge is the limited versatility of SERS-based encoding systems in terms of the applicable surfaces. This study addresses this challenge by using a temporary tattoo approach together with simplified fabrication of SERS-active patterns by ink-jet printing of a particle-free reactive silver ink. Plasmonic silver nanostructures form on the tattoo paper upon ink-jet printing and a brief thermal annealing. The SERS activity is sufficient to detect taggant molecules of rhodamine 6G, methylene blue, and rhodamine B with a nanomolar level sensitivity. Raman-active taggants can be incorporated into the ink, for drop-on-demand patterning of multiple molecules in 1D and 2D barcode geometries. The SERS barcodes can be effectively transferred to a range of different substrates retaining high plasmonic activity and geometric integrity. The presented approach decouples the SERS-active pattern preparation from the final substrate and greatly improves the versatility of the barcodes.