Physical unclonable functions generated through chemical methods for anti-counterfeiting

Biomimetic Fingerprint-like Unclonable Optical Anticounterfeiting System with Selectively In Situ-Synthesized Perovskite Quantum Dots Embedded in Spontaneous-Phase-Separated Polymers

Anticounterfeiting technologies meet challenges in the Internet of Things era due to the rapidly growing volume of objects, their frequent connection with humans, and the accelerated advance of counterfeiting/cracking techniques. Here, we, inspired by biological fingerprints, present a simple anticounterfeiting system based on perovskite quantum dot (PQD) fingerprint physical unclonable function (FPUF) by cooperatively utilizing the spontaneous-phase separation of polymers and selective in situ synthesis PQDs as an entropy source. The FPUFs offer red, green, and blue full-color fingerprint identifiers and random three-dimensional (3D) morphology, which extends binary to multivalued encoding by tuning the perovskite and polymer components, enabling a high encoding capacity (about 108570000, far surpassing that of biometric fingerprints). The strategy is compatible with mainstream production techniques that are widely used in traditional low-cost printed anticounterfeiting labels including spray printing, stamping, writing, and laser printing, avoiding complicated fabrication. Macrographical patterns and micro/nanofingerprint patterns with multiscale-tailorable inter-ridge sizes can be fused into a single FPUF label, satisfying different levels of anticounterfeiting requirements. Furthermore, a smart fused scheme of enhanced deep learning and fingerprint characteristic comparison is leveraged, by which high-efficiency, high-accuracy authentication of our FPUFs is achieved even for the increasingly huge FPUF databases and imperfectly captured images from users.

Template-Guided Nondeterministic Assembly of Organosilica Nanodots for Multifunctional Physical Unclonable Functions

Optical physical unclonable functions (PUFs) are gaining attention as a robust security solution for identification in the expanding Internet of Things (IoT). To enhance the security and functionality of PUFs, integrating multiple optical responses─such as fluorescence and structural color─into a single system is essential. These diverse optical properties enable multilevel authentication, where different layers of security can be verified under varying light conditions, greatly reducing the risk of counterfeiting. However, compactly integrating these photonic components poses significant challenges due to the difficulty of aligning and combining their optical behaviors within a limited space. In this study, we address these challenges by employing a template-guided assembly of organosilica nanodots (OSiNDs), which allows for the simultaneous control of solid-state fluorescence, rainbow holography, and PUF patterns. By precisely tuning the dewetting process, the OSiNDs assemble into nanoisland structures that provide enhanced fluorescence brightness and thermal stability while maintaining distinct holographic properties. Our system produces a 4096-bit key with 3228 bits of entropy, a storage density of 1 Gbit/in2, and a low false positive rate of 10-6. Additionally, it includes multilevel anticounterfeiting features that reveal distinct color patterns under different illumination angles, further boosting security. Comprehensive environmental stability and durability tests, including humidity, thermal, and mechanical abrasion resistance, confirm the robustness of the system, ensuring its functionality under real-world conditions. This multifunctional PUF design establishes a standard for secure, compact optical systems, combining high-performance authentication with practical applications in anticounterfeiting.

Strategic engineering of cationic systems for spatial & temporal anti-counterfeiting applications in zero-dimensional Mn(II) halides

While spatial and time-resolved anti-counterfeiting technologies have gained increasing attention owing to their excellent tunable photoluminescence, achieving high-security-level anti-counterfeiting remains a challenge. Herein, we developed a spatial-time-dual-resolved anti-counterfeiting system using zero-dimensional (0D) organic-inorganic Mn(II) metal halides: (EMMZ)2MnBr4 (named M-1, EMMZ=1-Ethyl-3-Methylimidazolium Bromide) and (EDMMZ)2MnBr4 (named M-2, EDMMZ=1-Ethyl-2,3-Dimethylimidazolium Bromide). M-1 shows a bright green emission with a quantum yield of 78 %. It undergoes a phase transformation from the crystalline to molten state with phosphorescence quenching at 350 K. Reversible phase and luminescent conversion was observed after cooling down for 15 s. Notably, M-2 exhibits green light emission similar to M-1 but undergoes phase conversion and phosphorescence quenching at 390 K, with reversible conversion observed after cooling down for 5 s. The photoluminescence switching mode of on(green)-off-on(green) can be achieved by temperature control, demonstrating excellent performance with short response times and ultra-high cyclic reversibility. By leveraging the different quenching temperatures and reversible PL conversion times of M-1 and M-2, we propose a spatial-time-dual-resolved photoluminescence (PL) switching system that combines M-1 and M-2. This system enables multi-fold tuning of the PL switch for encryption and decryption through cationic engineering strategies by modulating temperature and cooling time. This work presents a novel and feasible design strategy for advanced-level anti-counterfeiting technology based on a spatial-time-dual-resolved system.

Chiroptical Synaptic Perovskite Memristor as Reconfigurable Physical Unclonable Functions

Physical unclonable functions (PUFs), often referred to as digital fingerprints, are emerging as critical elements in enhancing hardware security and encryption. While significant progress has been made in developing optical and memory-based PUFs, integrating reconfigurability with sensitivity to circularly polarized light (CPL) remains largely unexplored. Here, we present a chiroptical synaptic memristor (CSM) as a reconfigurable PUF, leveraging a two-dimensional organic-inorganic halide chiral perovskite. The device combines CPL sensitivity with photoresponsive electrical behavior, enabling its application in optoneuromorphic systems, as demonstrated by its ability to perform image categorization tasks within neuromorphic computing. Furthermore, by leveraging a 10 × 10 crossbar array of the CSMs, we develop a PUF capable of generating reconfigurable cryptographic keys based on the combination of neuromorphic potentiation and polarized light conditions. This work demonstrates an integrated approach to optoneuromorphic functionality, data storage, and encryption, providing an alternative approach for reconfigurable memristor-based PUFs.

Time-Encoded Information Encryption with pH Clock Guided Broad-Spectrum Emission by Dynamic Assemblies

With growing threats from counterfeiting-based security breaches, multi-level and specific stimuli-responsive anti-counterfeiting devices and message encryption methods have attracted immense research interest. Fluorescence-based encryption from aggregation-induced emission (AIE)-based materials solves the problems to a considerable extent. However, the development of smarter patterns with hierarchical security levels alongside dynamic display is still challenging. To screen out this complication, we bring forward a pH-switchable fluorescent assembly of an AIEgen and an aliphatic acid. We later temporally direct the molecular assembly with the aid of a chemical trigger-regulated pH clock, generating a transitory multicolor emission, including transient white light generation. The pH-dependent emissions were further implemented in constructing smart multi-input fluorescent chemical AND gates. Subsequently, we integrate the time-gated emissive system to develop an advanced multi-dimensionally secure data encryption strategy. This novel approach enhances anti-counterfeiting measures by introducing an additional layer of security based on temporal characteristics.

Enabling Multicolor Information Encryption: Oleylammonium-Halide-Assisted Reversible Phase Conversion between Cs4PbX6 and CsPbX3 Nanocrystals

Recently, halide perovskites have been recognized for their thermochromic characteristics, showing significant potential in information encryption applications. However, the limited luminescence color gamut hinders the encryption of complex multicolor information. Herein, for the first time, multicolor thermochromic perovskites with luminescence covering the entire visible spectrum have been designed. Oleylammonium halide salts facilitate a reversible phase transformation between nonluminescent Cs4PbX6 nanocrystals (NCs) and luminescent CsPbX3 NCs upon heating or cooling. This process occurs without the need for external addition or removal of ligands or metal salts, enabling efficient and intelligent information encryption. A proof-of-concept demonstration successfully encrypts and decrypts multicolor digital information. This work not only advances the understanding of phase transformations in perovskites but also highlights their significant potential for information encryption applications.

Femtosecond Laser-Induced Recrystallized Nanotexturing for Identity Document Security With Physical Unclonable Functions

Counterfeit identity (ID) documents pose a serious threat to personal credit and national security. As a promising candidate, optical physical unclonable functions (PUFs) offer a robust defense mechanism against counterfeits. Despite the innovations in chemically synthesized PUFs, challenges persist, including harmful chemical treatments, low yields, and incompatibility of reaction conditions with the ID document materials. More notably, surface relief nanostructures for PUFs, such as wrinkles, are still at risk of being replicated through scanning lithography or nanoimprint. Here, a femtosecond laser-induced recrystallized silicon nanotexture is reported as latent PUF nanofingerprint for document anti-counterfeiting. With femtosecond laser irradiation, nanotextures spontaneously emerge within 100 ms of exposure. By introducing a low-absorption metal layer, surface plasmon polariton waves are excited on the silicon-metal multilayer nanofilms with long-range boosting, ensuring the uniqueness and non-replicability of the final nanotextures. Furthermore, the femtosecond laser induces a phase transition in the latent nanotexture from amorphous to polycrystalline state, rather than creating replicable relief wrinkles. The random nanotextures are easily identifiable through optical microscopy and Raman imaging, yet they remain undetectable by surface characterization methods such as scanning electron and atomic force microscopies. This property significantly hinders counterfeiting efforts, as it prevents the precise replication of these nanostructures.

Robust and Versatile Biodegradable Unclonable Anti-Counterfeiting Labels with Multi-Mode Optical Encoding Using Protein-Mediated Luminescent Calcite Signatures

Physical unclonable functions (PUFs) are emerging as a cutting-edge technology for enhancing information security by providing robust security authentication and non-reproducible cryptographic keys. Incorporating renewable and biocompatible materials into PUFs ensures safety for handling, compatibility with biological systems, and reduced environmental impact. However, existing PUF platforms struggle to balance high encoding capacity, diversified encryption signatures, and versatile functionalities with sustainability and biocompatibility. Here, all-biomaterial-based unclonable anti-counterfeiting labels featuring multi-mode encoding, multi-level cryptographic keys, and multiple authentication operations are developed by imprinting biomimetic-grown calcites on versatile silk protein films. In this label, the inherent non-clonability comes from the randomized characteristics of calcites, mediated by silk protein during crystal growth. The successful embedding of photoluminescent molecules into calcite lattices, assisted by silk protein, allows the resulting platform to utilize fluorescence patterns alongside birefringence for high-capacity encoding. This design facilitates easy and rapid authentication through Hamming distance and convolutional neural networks using standard cameras and portable microscopes. Moreover, angle-dependent polarization patterns enable multi-level key generation, while multi-spectral fluorescence signals offer multi-channel keys. The developed anti-counterfeiting labels combine biodegradability, green manufacture, easy authentication, high-level complexity, low cost, robustness, patternability, and versatility, offering a practical and high-security solution to combat counterfeiting across various applications.

Multilevel and Flexible Physical Unclonable Functions for High-End Leather Products or Packaging

Counterfeit and substandard high-end leather products have inflicted substantial economic damage worldwide and have tarnished the reputation of the leather industry as a whole. Due to the limited security level, current anti-counterfeiting measures are often vulnerable to attacks. Physically unclonable function (PUF) is regarded as the pinnacle of protection against counterfeiting. Leather, with a distinctive micro-nano porous structure and random creasing patterns, serves as an ideal substrate for optical PUF. Here, a flexible and durable leather-based optical PUF device is introduced that incorporates leather and fluorescent perovskite quantum dots. The fluorescence intensity distributed along the texture of leather offers parametric support for challenge-response pairs. Combined with a self-defined fluorescence pattern, the hierarchical authentication of optical PUF is realized. In conclusion, this innovation offers a desired opportunity for achieving high-security anti-counterfeiting and information traceability.

Self-assembly by anti-repellent structures for programming particles with momentum

Self-assembled configurations are versatile for applications in which liquid-mediated phenomena are employed to ensure that static or mild physical interactions between assembling blocks take advantage of local energy minima. For granular materials, however, a particle's momentum in air leads to random collisions and the formation of disordered phases, eventually producing jammed configurations when densely packed. Therefore, unlike fluidic self-assembly, the self-assembly of dry particles typically lacks programmability based on density and ordering symmetry and has thus been limited in applications. Here, we present the self-assembly of particles with momentum, yielding regular arrays with programmable density and symmetry. The key is to embed anti-repellent structures, i.e. traps, that can capture kinetic particles individually and then robustly hold them against collisions with other momentum granules during a dynamic assembly procedure. By using anti-repellent traps, physical interactions between neighbouring particles can be inhibited, resolving many phenomena related to the uncertainty of space-sharing events in granular packing. With our self-assembly strategy, highly dense yet unjammed configurations are demonstrated, which conserve the inherent randomness in the location information of each granule in the trap and are useful for robust multilevel authentication systems as unique applications.

Circularly Polarized Luminescence in Cellulose-Based Assemblies: Synthesis, Regulation, and Application

Currently, circularly polarized luminescence (CPL) has drawn wide interest in 3D display, information storage, and optical sensing. However, traditional synthetic paths are often accompanied by low chiral optical intensity and complex processes. Cellulose nanocrystals (CNCs), with the properties of liquid crystals, can spontaneously arrange into the left-handed layered nanofilm, which enables them candidates in the construction of CPL materials. Following this approach, this work reviews the synthesis of cellulose-based chiral luminescent materials. The co-assembly technique, in situ intercalation strategy, and defect destruction design are efficient in encapsulating the luminophores into the CNC organization. Next, various strategies on the CPL regulation, including the matching of the photonic bandgap, optical pathway design, and tailored helical structure, are summarized. These offer new sights in the CPL control, mainly focusing on the amplification and inversion of optical signals. Multimodal and convertible chiroptical signals enable the photonic films with practical values in anti-counterfeit, sensing, and handedness induction. Overall, this timely overview summarizes the synthesis, regulation, and application of cellulose-based CPL materials, and aims to inspire the development of the chiral optical materials.

Scalable Reshaping of Diamond Particles via Programmable Nanosculpting

Diamond particles have many interesting properties and possible applications. However, producing diamond particles with well-defined shapes on a large scale is challenging because diamonds are chemically inert and extremely hard. Here, we show that air oxidation, a routine method for purifying diamonds, can be used to precisely shape diamond particles at scale. By exploiting the distinct reactivities of different crystal facets and defects inside the diamond, layer-by-layer outward-to-inward and inward-to-outward oxidation produced diverse diamond shapes including spheres, twisted surfaces, pyramidal islands, inverted pyramids, nanoflowers, and porous polygons. The nanosculpted diamonds had more and finer features that enabled them to outperform the original raw diamonds in various applications. Using experimental observations and Monte Carlo simulations, we built a shape library that guides the design and fabrication of diamond particles with well-defined features that could be critical for anticounterfeiting, optical, and other practical applications. Our study presents a simple, economical, and scalable way to produce shape-customized diamonds for various potential technologies.

Physical One-Way Functions for Decentralized Consensus Via Proof of Physical Work

Decentralized consensus on the state of the Bitcoin blockchain is ensured by proof of work. It relies on digital one-way functions and is associated with an enormous environmental impact. This paper conceptualizes a physical one-way function that aims to transform a digital, electricity-consuming consensus mechanism into a physical process. Boundary conditions for the security requirements are established and discussed as well as experimentally investigated for a specific setup based on printing and optical analysis of pigment-carrier composites. In the context of the applied methods, this setup promises to be mathematically unclonable, steady, reproducible, collision resistant and non-invertible and illustrates the feasibility of a physical one-way function. Based on this, a framework for proof of physical work is conceptualized, which has the potential of a drastically lower CO2 footprint. This work initiates a progressive, interdisciplinary field of research and demands further investigations with regards to alternative setups, security definitions and strategies for challenging them.

High Defect Tolerance Breaking the Design Limitation of Full-Spectrum Multimodal Luminescence Materials

With the development of optical anti-counterfeiting and the increasing demand for high-level information encryption, multimodal luminescence (MML) materials attract much attention. However, the discovery of these multifunctional materials is very accidental, and the versatile host suitable for developing such materials remains unclear. Here, a grossite-type fast ionic conductor CaGa4O7, characterized by layered and tunnel structure with excellent defect tolerance, is found to meet the needs of various luminescent processes. Almost all luminescent modes, including down/up-conversion luminescence (DCL/UCL), long persistent luminescence (LPL), mechanoluminescence (ML), and X-ray excited optical luminescence (XEOL), are realized in this single host. Full-spectrum (from violet to near-infrared) photoluminescence and ML as well as multicolor XEOL are achieved by simply changing the doped luminescent center. A series of anti-counterfeiting devices, including the quasi-dynamic display of famous paintings, digital information encryption, and multi-color handwritten signatures, are designed to show the encryption of information in temporal and spatial dimensions. This study clarifies the importance of defect tolerance of the host for the development of MML materials, and provides a unique insight into the cross-field applications of special functional materials, which is a new strategy to accelerate the development of novel MML materials.

Circularly Polarized Luminescence Bioimaging Using Chiral BODIPYs: A Model Scaffold for Advancing Unprecedented CPL Microscopy Using Small Full-Organic Probes

Unprecedented circularly polarized luminescence bioimaging (CPL-bioimaging) of live cells using small full-organic probes is first reported. These highly biocompatible and adaptable probes are pivotal to advance emerging CPL Laser-Scanning Confocal Microscopy (CPL-LSCM) as an undeniable tool to distinguish, monitor, and understand the role of chirality in the biological processes. The development of these probes was challenging due to the poor dichroic character associated with the involved CPL emissions. However, the known capability of the BODIPY dyes to be tuned to act as efficient fluorescence bioprobes, together with the capability of the BINOL-O-BODIPY scaffold to enable CPL, allowed the successful design of the first examples of this kind of CPL probes. Interestingly, the developed CPL probes were also multiphoton (MP) active, paving the way for the envisioned MP-CPL-bioimaging. The described full-organic CPL-probe scaffold, based on an optically and biologically tunable BODIPY core, which is chirally perturbed by an enantiopure BINOL moiety, represents, therefore, a simple and readily accessible structural design for advancing efficient CPL probes for bioimaging by CPL-LSCM.

Remote On-Paper Electrochemiluminescence-Based High-Safety and Multilevel Information Encryption

The escalating needs in information protection underscore the urgency of developing advanced encryption strategies. Herein we report a novel chemical approach that enables information encryption by on-paper electrochemiluminescence (ECL). Dendritic porous silica nanospheres modified with polyetherimide and bovine serum albumin were prepared as the chemical ink to write the secret message on a paper. Attaching the paper to an electrode, immersing it in a solution containing tris(2,2'-bipyridyl)ruthenium (Ru(bpy)3 2+) and then applying a suitable voltage, a remote "catalytic route" electrochemical reaction produces ECL that functions as the key to decrypt and visualize the message by imaging. In addition, proteins can be also used as the biological ink to write the secret message, which is then decrypted by a combined use of immunochemistry and ECL imaging as two keys. We believe the ECL-based strategy holds great promise in high-safety and multilevel information encryption, as it is protected not only by encoding, like conventional invisible inks, but also by the unique ECL decoding approach.

Artificial fingerprints engraved through block-copolymers as nanoscale physical unclonable functions for authentication and identification

Besides causing financial losses and damage to the brand's reputation, counterfeiting can threaten the health system and global security. In this context, physical unclonable functions (PUFs) have been proposed to overcome limitations of current anti-counterfeiting technologies. Here, we report on artificial fingerprints that can be directly engraved on a wide range of substrates through self-assembled block-copolymer templating as nanoscale PUFs for secure authentication and identification. Results show that morphological features can be exploited to encode fingerprint-like nanopatterns in binary code matrices representing a unique bit stream of information characterized by high uniqueness and entropy. A strategy based on computer vision concepts for authentication/identification in real-world scenarios is reported. Long-term reliable operation and robust authentication/identification against thermal treatment at cryogenic and high temperatures of the PUF have been demonstrated. These results pave the way for the realization of PUFs embracing the inherent stochasticity of self-assembled materials at the nanoscale.

High-dimensional anticounterfeiting nanodiamonds authenticated with deep metric learning

Physical unclonable function labels have emerged as a promising candidate for achieving unbreakable anticounterfeiting. Despite their significant progress, two challenges for developing practical physical unclonable function systems remain, namely 1) fairly few high-dimensional encoded labels with excellent material properties, and 2) existing authentication methods with poor noise tolerance or inapplicability to unseen labels. Herein, we employ the linear polarization modulation of randomly distributed fluorescent nanodiamonds to demonstrate, for the first time, three-dimensional encoding for diamond-based labels. Briefly, our three-dimensional encoding scheme provides digitized images with an encoding capacity of 109771 and high distinguishability under a short readout time of 7.5 s. The high photostability and inertness of fluorescent nanodiamonds endow our labels with high reproducibility and long-term stability. To address the second challenge, we employ a deep metric learning algorithm to develop an authentication methodology that computes the similarity of deep features of digitized images, exhibiting a better noise tolerance than the classical point-by-point comparison method. Meanwhile, it overcomes the key limitation of existing artificial intelligence-driven classification-based methods, i.e., inapplicability to unseen labels. Considering the high performance of both fluorescent nanodiamonds labels and deep metric learning authentication, our work provides the basis for developing practical physical unclonable function anticounterfeiting systems.

Defect Regulation Strategy of Porous Persistent Phosphors for Multiple and Dynamic Information Encryption

Optical encryption technologies based on persistent luminescence material have currently drawn increasing attention due to the distinctive and long-lived optical properties, which enable multi-dimensional and dynamic optical information encryption to improve the security level. However, the controlled synthesis of persistent phosphors remains largely unexplored and it is still a great challenge to regulate the structure for optical properties optimization, which inevitably sets significant limitations on the practical application of persistent luminescent materials. Herein, a controlled synthesis method is proposed based on defect structure regulation and a series of porous persistent phosphors is obtained with different luminous intensities, lifetime, and wavelengths. By simply using diverse templates during the sol-gel process, the oxygen vacancy defects structures are successfully regulated to improve the optical properties. Additionally, the obtained series of porous Al2O3 are utilized for multi-color and dynamic optical information encryption to increase the security level. Overall, the proposed defect regulation strategy in this work is expected to provide a general and facile method for optimizing the optical properties of persistent luminescent materials, paving new ways for broadening their applications in multi-dimensional and dynamic information encryption.

DNA-Based Chemical Unclonable Functions for Cryptographic Anticounterfeit Tagging of Pharmaceuticals

Counterfeit products are a problem known across many industries. Chemical products such as pharmaceuticals belong to the most targeted markets, with harmful consequences for consumer health and safety. However, many of the currently used anticounterfeit measures are associated with the packaging, with the readout method and level of security varying between different solutions. Identifiers that can be directly and safely mixed into the product to securely authenticate a batch would be desirable. For this purpose, we propose the use of chemical unclonable functions based on pools of short random DNA oligos, which allow the integration of a cryptographic authentication system into chemical products. We demonstrate and characterize a simplified workflow for readout, showing that results are robust and clearly differentiate between the correct tag and a counterfeit. As a proof of concept, we demonstrate the labeling of an acetaminophen formulation with a chemical unclonable function. The acetaminophen was successfully authenticated from a subsample of the product at a DNA admixing concentration of below 50 ng/g. Stability tests revealed that the readout is stable at room temperature for several years, exceeding the shelf life of most drug products. Our work thus shows that chemical unclonable functions are a valid alternative to state-of-the-art anticounterfeit methods, enabling a secure authentication scheme that is physically linked to the product and safe for consumption. The method is widely applicable beyond pharmaceuticals, allowing for more secure product tracing across industries.

Coffee-Ring Mediated Thinning and Thickness-Dependent Dewetting Modes in Printed Polymer Droplets Coupled with Assembly of Quantum Dots for Anti-Counterfeiting

Molecular transport processes in printed polymer droplets hold enormous importance for understanding wetting phenomena and designing systems in applications such as encoding, electronics, photonics, and sensing. This paper studies thickness-dependent dewetting modes that are activated by thermal annealing and driven by interfacial interactions within microscopically confined polymeric features. The printing of poly(2-vinylpyridine) is performed in a regime where coffee-ring effects lead to strong thinning of the central region of the deposit. Thermal annealing leads to two different modes of dewetting that depend on the thickness of the central region. Mode I refers to the formation of randomly positioned small features surrounded by large hemispherical ones located along the periphery of the printed features and occurs when the central regions are thin. Observed at large central thicknesses, Mode II mediates significant molecular transport from edges toward the center of the printed droplet with thermal annealing and forms a hemispherical feature from the initial ring-like deposit. The selective adsorption of red, green, and blue emitting quantum dots over the poly(2-vinylpyridine) results in photoluminescent patterns. The selective assembly of photoluminescent quantum dots over patterned surfaces leads to deterministic and stochastic features beneficial to creating security labels for anti-counterfeiting applications.

Scalable Multistep Imprinting of Multiplexed Optical Anti-counterfeiting Patterns with Hierarchical Structures

Multiplexed optical techniques with multichannel patterns provide powerful strategies for high-capacity anti-counterfeiting. However, it is still a big challenge to meet the demands of achieving high encryption levels, excellent readability, and simple preparation simultaneously. Herein, we use a multistep imprinting technique, leveraging surface work-hardening to massively produce multiplexed encrypted patterns with hierarchical structures. These patterns with coupled nano- and microstructures can be instantaneously decoded into different pieces of information at different view angles under white light illumination. By incorporating perpendicular nano- and microgratings, we achieve four-channel encoded patterns, enhancing anti-counterfeiting capacity. This versatile method works on various metal/polymer materials, offering high-density information storage, direct visibility, broad material compatibility, and low-cost mass production. Our high-performance anti-counterfeiting patterns show significant potential in real-world applications.

Dynamic metal-ligand coordination enables a hydrogel with rewritable dual-mode pattern display

The realization of dual-mode information display in the same material is of great significance to the expansion of information capacity and the improvement of information security. However, the existing systems lose the ability to re-encode information once they are constructed. Here, dynamic metal-ligand coordination is introduced into a novel hydrogel-based optical platform that allows rewritable dual-mode information display. The hydrogel system consists of a hard lamellar structure of poly(dodecylglyceryl itaconate) (pDGI) and soft double networks of poly(acrylamide)/poly(acrylic acid) (PAAm/PAAc) containing fluorescent carbon dots (CDs). As the carboxylic acid groups can coordinate with metal ions such as Al3+, the layer spacing of the lamellar structure is reduced while CDs aggregate, leading to the blue shift of the structural color and the red shift of the fluorescent color. Additionally, the metal chelating agent, ethylenediaminetetraacetic acid (EDTA), is able to strip away Al3+ ions and restore the two colors, realizing an erasable dual-mode information display. This study opens up a path for the development of new materials and technologies for rewritable dual-mode information protection.

Dual Aliovalent Dopants Cu, Mn Engineered Eco-Friendly QDs for Ultra-Stable Anti-Counterfeiting

Doping in semiconductor quantum dots (QDs) using optically active dopants tailors their optical, electronic, and magnetic properties beyond what is achieved by controlling size, shape, and composition. Herein, we synergistically modulated the optical properties of eco-friendly ZnInSe2/ZnSe core/shell QDs by incorporating Cu-doping and Mn-alloying into their core and shell to investigate their use in anti-counterfeiting and information encryption. The engineered "Cu:ZnInSe2/Mn:ZnSe" core/shell QDs exhibit an intense bright orange photoluminescence (PL) emission centered at 606 nm, with better color purity than the undoped and individually doped core/shell QDs. The average PL lifetime is significantly extended to 201 ns, making it relevant for complex encryption and anti-counterfeiting. PL studies reveal that in Cu:ZnInSe2/Mn:ZnSe, the photophysical emission arises from the Cu state via radiative transition from the Mn 4T1 state. Integration of Cu:ZnInSe2/Mn:ZnSe core/shell QDs into poly(methyl methacrylate) (PMMA) serves as versatile smart concealed luminescent inks for both writing and printing patterns. The features of these printed patterns using Cu:ZnInSe2/Mn:ZnSe core/shell QDs persisted after 10 weeks of water-soaking and retained 70 % of PL emission intensity at 170 °C, demonstrating excellent thermal stability. This work provides an efficient approach to enhance both the emission and the stability of eco-friendly QDs via dopant engineering for fluorescence anti-counterfeiting applications.

Programmable multimode optical encryption of advanced printable security inks by integrating structural color with Down/Up- conversion photoluminescence

Optical information encryption with high encoding capacities can significantly boost the security level of anti-counterfeiting in the scenario of guaranteeing the authenticity of a wide scope of common and luxury goods. In this work, a novel counterfeiting material with high-degree complexity is fabricated by microencapsulating cholesteric liquid crystals and triplet-triplet annihilation upconversion fluorophores to integrate structural coloration with fluorescence and upconversion photoluminescence. Moreover, the multimode security ink presents tailorable optical behaviors and programmable abilities on flexible substrates by various printing techniques, which offers distinct information encryption under different optical modes. The advanced strategy provides a practical versatile platform for high-secure-level multimode optical inks with largely enhanced encoding capacities, programmability, printability, and cost-effectiveness, which manifests enormous potentials for information encryption and anti-counterfeiting technology.

Scalable Photo-Responsive Physical Unclonable Functions via Particle Kinetics

The increasing menace of counterfeiting and information theft underscores the urgent need for security platforms compatible with both micro- and nanoelectronics. Existing methods for anticounterfeiting labeling and cryptographic systems rely on unclonable patterns derived from the unpredictable variability of physical phenomena. However, these approaches impose limitations on the scalability of security components. Here we present a scalable platform for photoresponsive physically unclonable functions based on oxide particle kinetics in polymer solutions. The stochastic agglomeration process occurring during the formation of polymer films with dispersed oxide particles yields random patterns, with pixel sizes scalable from micro to nanoscales. We produce mechanically flexible and self-destructible optical unclonable function patterns utilizing oxide aggregates on a polymer film. Moreover, we establish a strategy for generating electrical unclonable patterns on a conducting polymer film. This involves covering the polymer film with an aggregate pattern mask, which serves as an ultraviolet-blocking layer for randomly exposing the film to ultraviolet ozone treatment. These unclonable patterns constitute robust and compact security systems, exhibiting effective resilience against machine-learning attacks (∼50% prediction error for training data sets of 1000). The developed scalable platforms for physically unclonable functions provide a hardware solution for robust cryptographic applications.

Understanding the Coordination Chemistry and Structural and Photophysical Properties of EuII- and SmII-Containing Complexes of Hexamethylhexacyclen and Noncyclic Tetradentate Amines

Ligands play a crucial role in supporting or stabilizing the divalent oxidation state of lanthanide metals. To expand the range of ligands used to chelate divalent lanthanide ions, we synthesized and studied the structural and photophysical properties of complexes of EuII and SmII with hexamethylhexacyclen, 1,1,4,7,10,10-hexamethyltriethylenetetramine, tris[2-(dimethylamino)ethyl]amine, and tris[2-(isopropylamino)ethyl]amine as supporting ligands. Coordination of hexamethylhexacyclen, an analogue of 18-crown-6, generates sterically crowded complexes of EuII and SmII that are either seven or eight coordinate and adopt a range of geometries that differ from those of their 18-crown-6 counterparts and from those of lanthanide-containing complexes with the acyclic tetradente tertiary amine ligands included in this report. The emission spectra of EuII(hexamethylhexacyclen) show a moderate sensitivity to counterion identity and are more red-shifted compared to those of complexes of EuII with 18-crown-6 and the hexamethylated aza derivative of 2.2.2-cryptand. In addition, the morphology of hexamethylhexacyclen in [LnI(hexamethylhexacyclen)]I was found to resemble that of thermally stable alkalides of the form [M(hexamethylhexacyclen)]Na- (M = K+ or Cs+), suggesting that hexamethylhexacyclen could be an interesting ligand for strongly reducing lanthanide ions.

Realizing Bright-Dark Dual-Field Multimode Optical Signals in Photochromic Apatite Phosphors for Security Identification

Regulating defect distribution in inorganic phosphors is paramount for realizing multimode dual-field optical signals for high security level identification but remains an ongoing challenge. Here, we propose a strategy of equivalent anion doping and nonequivalent cation doping to successfully regulate the trap distribution and density in Ba5(PO4)3Cl:F-,Eu2+,Ce3+ (BPCF-AG) phosphors. Due to the coexistence of shallow and deep traps for different photon processes, the BPCF-AG exhibits simultaneous photochromism in a bright field and tetramode luminescence (photoluminescence, afterglow, 980 nm photostimulated luminescence, and 650/532 nm photostimulated afterglow) in a dark field. The trap roles responsible for versatile optical behaviors are investigated by thermoluminescence curves, and a reasonable mechanism is proposed. In addition, we design a series of demonstrations for security identification and information encryption based on the dual-field multimode optical signals of BPCF-AG to illustrate its potential application scenarios.

7D High-Dynamic Spin-Multiplexing

Multiplexing technology creates several orthogonal data channels and dimensions for high-density information encoding and is irreplaceable in large-capacity information storage, and communication, etc. The multiplexing dimensions are constructed by light attributes and spatial dimensions. However, limited by the degree of freedom of interaction between light and material structure parameters, the multiplexing dimension exploitation method is still confused. Herein, a 7D Spin-multiplexing technique is proposed. Spin structures with four independent attributes (color center type, spin axis, spatial distribution, and dipole direction) are constructed as coding basic units. Based on the four independent spin physical effects, the corresponding photoluminescence wavelength, magnetic field, microwave, and polarization are created into four orthogonal multiplexing dimensions. Combined with the 3D of space, a 7D multiplexing method is established, which possesses the highest dimension number compared with 6 dimensions in the previous study. The basic spin unit is prepared by a self-developed laser-induced manufacturing process. The free state information of spin is read out by four physical quantities. Based on the multiple dimensions, the information is highly dynamically multiplexed to enhance information storage efficiency. Moreover, the high-dynamic in situ image encryption/marking is demonstrated. It implies a new paradigm for ultra-high-capacity storage and real-time encryption.

Robust two-color physically unclonable patterns from controlled aggregation of a single organic luminophore

This research presents a new approach to create two-color luminescent physically unclonable functions (PUFs) using an organic luminophore with tunable emission colors. These PUFs offer high security and stable performance, significantly enhancing anti-counterfeiting capabilities by exponentially increasing encoding capacity through dual-color integration and complex pattern formation.

Traceable Optical Physical Unclonable Functions Based on Germanium Vacancy in Diamonds

Physical unclonable functions (PUFs) have emerged as an unprecedented solution for modern information security and anticounterfeiting by virtue of their inherent unclonable nature derived from distinctive, randomly generated physical patterns that defy replication. However, the creation of traceable optical PUF tags remains a formidable challenge. Here, we demonstrate a traceable PUF system whose unclonability arises from the random distribution of diamonds and the random intensity of the narrow emission from germanium vacancies (GeV) within the diamonds. Tamper-resistant PUF labels can be manufactured on diverse and intricate structural surfaces by blending diamond particles into polydimethylsiloxane (PDMS) and strategically depositing them onto the surface of objects. The resulting PUF codes exhibit essentially perfect uniformity, uniqueness, reproducibility, and substantial encoding capacity, making them applicable as a private key to fulfill the customization demands of circulating commodities. Through integration of a digitized "challenge-response" protocol, a traceable and highly secure PUF system can be established, which is seamlessly compatible with contemporary digital information technology. Thus, the GeV-PUF system holds significant promise for applications in data security and blockchain anticounterfeiting, providing robust and adaptive solutions to address the dynamic demands of these domains.

Multilevel Anti-counterfeiting Barcode with Enhanced Information Encryption Based on Stimulus-Responsive Digital Polymers

In response to the escalating challenges of counterfeiting due to technological and socioeconomic advancements, a novel trilevel anti-counterfeiting Quick Response (QR) code system has been developed. This system integrates digital polymers with QR code and stimulus-responsive chromophores, i.e., rhodamine B (RB), rhodamine 6G (R6G), and spiropyran (SP), to provide a sophisticated security solution. This advanced barcode remains concealed until specific stimuli reveal it and can be scanned by a smartphone, enabling first and second level anti-counterfeiting. For the third level of security, the encrypted information within the digital polymers can only be deciphered using tandem mass spectrometry. This innovative approach not only enhances security features but also offers reversible visibility and a complex verification process. This trilevel system surpasses traditional single-level anti-counterfeiting methods and holds significant potential for future applications in protecting brand authenticity and managing data storage, contributing new concepts and techniques to the field of high-security anti-counterfeiting materials.

Uncovering the Recent Progress of CNC-Derived Chirality Nanomaterials: Structure and Functions

Cellulose nanocrystal (CNC), as a renewable resource, with excellent mechanical performance, low thermal expansion coefficient, and unique optical performance, is becoming a novel candidate for the development of smart material. Herein, the recent progress of CNC-based chirality nanomaterials is uncovered, mainly covering structure regulations and function design. Undergoing a simple evaporation process, the cellulose nanorods can spontaneously assemble into chiral nematic films, accompanied by a vivid structural color. Various film structure-controlling strategies, including assembly means, physical modulation, additive engineering, surface modification, geometric structure regulation, and external field optimization, are summarized in this work. The intrinsic correlation between structure and performance is emphasized. Next, the applications of CNC-based nanomaterials is systematically reviewed. Layer-by-layer stacking structure and unique optical activity endow the nanomaterials with wide applications in the mineralization, bone regeneration, and synthesis of mesoporous materials. Besides, the vivid structural color broadens the functions in anti-counterfeiting engineering, synthesis of the shape-memory and self-healing materials. Finally, the challenges for the CNC-based nanomaterials are proposed.

Physical Unclonable Functions with Hyperspectral Imaging System for Ultrafast Storage and Authentication Enabled by Random Structural Color Domains

Physical unclonable function (PUF) is attractive in modern encryption technologies. Addressing the disadvantage of slow data storage/authentication in optical PUF is paramount for practical applications but remains an on-going challenge. Here, a highly efficient PUF strategy based on random structural color domains (SCDs) of cellulose nanocrystal (CNC) is proposed for the first time, combing with hyperspectral imaging system (HIS) for ultrafast storage and authentication. By controlling the growth and fusion behavior of the tactoids of CNC, the SCDs display an irregular and random distribution of colors, shapes, sizes, and reflectance spectra, which grant unique and inherent fingerprint-like characteristics that are non-duplicated. Based on images and spectra, these fingerprint features are used to develop two sets of PUF key generation methods, which can be respectively authenticated at the user-end and the manufacturer-front-end that achieving a high coding capacity of at least 22304. Notably, the use of HIS greatly shortens the time of key reading and generation (≈5 s for recording, 0.5-0.7 s for authentication). This new optical PUF labels can not only solve slow data storage and complicated authentication in optical PUF, but also impulse the development of CNC in industrial applications by reducing color uniformity requirement.

Spatially and Temporally Programmable Transparency Evolutions in Hydrogels Enabled by Metal Coordination toward Transient Anticounterfeiting

Hydrogels have emerged as promising candidates for anticounterfeiting materials, owing to their unique stimulus-responsive capabilities. To improve the security of encrypted information, efforts are devoted to constructing transient anticounterfeiting hydrogels with a dynamic information display. However, current studies to design such hydrogel materials inevitably include sophisticated chemistry, complex preparation processes, and particular experimental setups. Herein, a facile strategy is proposed to realize the transient anticounterfeiting by constructing bivalent metal (M2+)-coordination complexes in poly(acrylic acid) gels, where the cloud temperature (Tc) of the gels can be feasibly tuned by M2+ concentration. Therefore, the multi-Tc parts in the gel can be locally programmed by leveraging the spatially selective diffusion of M2+ with different concentrations. With the increase of temperature or the addition of a complexing agent, the transparency of the multi-Tc parts in the gel spontaneously evolves in natural light, enabling the transient information anticounterfeiting process. This work has provided a new strategy and mechanism to fabricate advanced anticounterfeiting hydrogel materials.

Circularly Polarized Luminescence from Pure and Eu-Doped Trigonal TbPO4·nH2O Nanocrystals

In this contribution, we describe the preparation, by means of a precipitation reaction from aqueous solution at 40 °C, and the structural characterization of nanocrystalline powders of trigonal Tb1-xEuxPO4·nH2O (with x = 0, 0.005, 0.01, 0.05, and 0.1; n tentatively assigned as 0.67) which crystallize in the two possible P3121 or P3221 enantiomorphic space groups. While the volume of the crystal lattice is not significantly affected by the Tb3+/Eu3+ substitution, the average crystallite size seems to depend on the Eu3+ dopant concentration and ranges from 13 to 30 nm. The desired handedness of the crystals has been induced by using, during the synthesis, one of the two possible enantiomers of tartaric acid (l or d). The analysis of the luminescence excitation and emission spectra, together with the decay kinetics of the 5D4 Tb3+ excited state, suggests the presence of a very efficient Tb3+ → Eu3+ energy transfer process in the Eu3+-doped orthophosphates. Upon excitation of Tb3+ ions at 368 nm, the enantiomorphic powders grown with l- or d-tartaric acid (i.e., l-TbPO4·0.67H2O/d-TbPO4·0.67H2O, l-Tb0.995Eu0.005PO4·0.67H2O/d-Tb0.995Eu0.005PO4·0.67H2O, and l-Tb0.9Eu0.1PO4·0.67H2O/d-Tb0.9Eu0.1PO4·0.67H2O) exhibited mirror circularly polarized luminescence signals in the visible spectral region (in the green and/or in the red).

Transparency-changing elastomers by controlling of the refractive index of liquid inclusions

Complex materials that change their optical properties in response to changes in environmental conditions can find applications in displays, smart windows, and optical sensors. Here a class of biphasic composites with stimuli-adaptive optical transmittance is introduced. The biphasic composites comprise aqueous droplets (a mixture of water, glycerol, and surfactant) embedded in an elastomeric matrix. The biphasic composites are tuned to be optically transparent through a careful match of the refractive indices between the aqueous droplets and the elastomeric matrix. We demonstrate that stimuli (e.g., salinity and temperature change) can trigger variations in the optical transmittance of the biphasic composite. The introduction of such transparency-changing soft matter with liquid inclusions offers a novel approach to designing advanced optical devices, optical sensors, and metamaterials.

Flexible Physical Unclonable Functions Based on Non-deterministically Distributed Dye-Doped Fibers and Droplets

The development of new anticounterfeiting solutions is a constant challenge and involves several research fields. Much interest is currently devoted to systems that are impossible to clone, based on the physical unclonable function (PUF) paradigm. In this work, a new strategy based on electrospinning and electrospraying of dye-doped polymeric materials is presented for the manufacturing of flexible free-standing films that embed simultaneously different PUF keys. The proposed films can be used to fabricate novel anticounterfeiting labels having three encryption levels: (i) a map of fluorescent polymer droplets, with random positions on a dense yarn of polymer nanofibers, (ii) a characteristic fluorescence spectrum for each label, and (iii) the unique speckle patterns that every label produces when illuminated with coherent laser light shaped in different wavefronts. The intrinsic uniqueness introduced by the manufacturing process encodes enough complexity into the optical anticounterfeiting tag to generate thousands of cryptographic keys. The simple and cheap fabrication process as well as multilevel authentication makes such colored polymeric unclonable tags a practical solution in the secure protection of goods in our daily life.

Dual-Mode Hydrogels with Structural and Fluorescent Colors toward Multistage Secure Information Encryption

Constructing an anti-counterfeiting material with non-interference dual optical modes is an effective way to improve information security. However, it remains challenging to achieve multistage secure information encryption due to the limited stimulus responsiveness and color tunability of the current dual-mode materials. Herein, a dual-mode hydrogel with both independently tunable structural and fluorescent colors toward multistage information encryption, is reported. In this hydrogel system, the rigid lamellar structure of poly(dodecylglyceryl itaconate) (pDGI) formed by shear flow-induced self-assembly provides the restricted domains wherein monomers undergo polymerization to form a hydrogel network, producing structural color. The introduction of fluorescent monomer 6-acrylamidopicolinate (6APA) as a complexation site provides the possibility of fluorescent color formation. The hydrogel's angle-dependent structural color can be controlled by adjusting the crosslinking density and water content. Additionally, the fluorescence color can be modulated by adjusting the ratio of lanthanide ions. Information of dual-mode can be displayed separately in different channels and synergistically overlayed to read the ultimate message. Thus, a multistage information encryption system based on this hydrogel is devised through the programed decryption process. This strategy holds tremendous potential as a platform for encrypting and safeguarding valuable and authentic information in the field of anti-counterfeiting.

Water-sensitive fluorescent microgel inks to produce verifiable information for highly secured anti-counterfeiting

The decryption and verification of encrypted information via a simple and efficient method is always difficult and challenging in the field of information security. Herein, a series of water-sensitive fluorescent microgels are fabricated for highly secured anti-counterfeiting with authenticity identification. The initial negatively charged microgels (MG) are made up of N-isopropylacrylamide (NIPAM), acrylic acid (AAc) and anthracen-9-yl acrylate (9-ANA, blue fluorescent monomer). The prepared MGs can bind cationic fluorescent dyes such as 5-aminofluorescein (FITC, green fluorescent dye) and rhodamine B (Rh B, red fluorescent dye) via electrostatic interaction, emitting multi-fluorescent colors based on the fluorescence resonance energy transfer (FRET) process. Furthermore, the fluorescence colors of MG-derived systems can be rapidly changed by swelling in water, which can block the FRET process and change the aggregation state of dyes. With the assistance of inkjet printing, multi-color security patterns can be designed and encoded, which can be revealed by UV irradiation and further verified by water stimulation. This study has pioneered a novel strategy to verify the authenticity of decrypted information, which greatly improves the security level of information.

Contrasting impact of coordination polyhedra and site symmetry on the electronic energy levels in nine-coordinated Eu(III) and Sm(III) crystals structures determined from single crystal luminescence spectra

Lanthanide luminescence is characterised by "forbidden" 4f-4f transitions and a complicated electronic structure. Our understanding of trivalent lanthanide(III) ion luminescence is centered on Eu3+ because absorbing and emitting transitions in Eu3+ occur from a single electronic energy level. In Sm3+ both absorbing and emitting multiplets have a larger multiplicity. A band arising in transitions from the first emitting state multiplet to the ground state multiplet will have nine lines for a Sm3+ complex. In this study, high-resolution emission and excitation spectra were used to determine the electronic energy levels for the lowest multiplet and first emitting multiplet in four Sm3+ compounds with either tricapped trigonal prismatic TTP or capped square antiprismatic cSAP coordination polyhedra but different site symmetry. This was achieved by the use of Boltzmann distribution population analysis and experimentally determined transition probabilities from emission and excitation spectra. Using this analysis it was possible to show the effect of changing three oxygen atoms with three nitrogen atoms in the donor set for two compounds with the same coordination polyhedra and site symmetry. This work celebrates the 40th anniversary of Kirby and Richardson's first report of [Eu(ODA)3]3- luminescence.

Step-wise changes in the excited state lifetime of [Eu(D2O)9]3+ and [Eu(DOTA)(D2O)]- as a function of the number of inner-sphere O-H oscillators

Lanthanide luminescence is dominated by quenching by high-energy oscillators in the chemical environment. The rate of non-radiative energy transfer to a single H2O molecule coordinated to a Eu3+ ion exceeds the usual rates of emission by an order of magnitude. We know these rates, but the details of these energy transfer processes are yet to be established. In this work, we study the quenching rates of [Eu(D2O)9]3+ and [Eu(DOTA)(D2O)]- in H2O/D2O mixtures by sequentially exchanging the deuterons with protons. Flash freezing the solutions allows us to identify species with various D/H contents in solution and thus to quantify the energy transfer processes to individual OH-oscillators. This is not possible in solution due to fast exchange in the ensembles present at room temperature. We conclude that the energy transfer processes are accurately described, predicted, and simulated using a step-wise addition of the rates of quenching by each O-H oscillator. This documents the sequential increase in the rate of the energy transfer processes in the quenching of lanthanide luminescence, and further provides a methodology to identify isotopic impurities in deuterated lanthanide systems in solution.

Tm3+ mediated multicolor luminescence of NaYbF4:Er,Tm@NaYF4 for advanced anti-counterfeiting

Lanthanide doped multicolor luminescent materials have attracted extensive attention due to their advanced anti-counterfeiting properties. However, designing a simple, hard-to-copy and multicolor anti-counterfeiting strategy based on upconversion nanoparticles (UCNPs) remains a huge challenge. Herein, a strategy to modulate luminescence color by altering the mediating action of Tm3+ was proposed. As a proof of concept, the mediating action of Tm3+ was explored in NaYbF4:30%Er,1%Tm@NaYF4 by changing the doping ratio of Yb3+/Er3+/Tm3+, and red, yellow and blue luminescence was successfully obtained. Then, NaYbF4:x%Er,1%Tm@NaYF4 (x = 2, 10, 30, 50, 99), NaYbF4:x%Er@NaYF4 (x = 2, 10, 30, 50, 100) and NaYbF4:1%Tm@NaYF4:x%Er@NaYF4 (x = 2, 10, 30, 50, 100) were synthesized to further identify that the mediating action of Tm3+ was related to the doping ratio and distance between dopant ions. In addition, the luminescence color of NaYbF4:30%Er,1%Tm@NaYF4 changed from red to yellow with the increase of excitation power density. Based on the above, NaYbF4:Er,Tm@NaYF4 UCNPs show excellent performance in anti-counterfeiting of paintings, thus revealing their great potential in advanced anti-counterfeiting applications.

Silicon Vacancies Diamond/Silk/PVA Hierarchical Physical Unclonable Functions for Multi-Level Encryption

Physical unclonable functions (PUFs) have emerged as a promising encryption technology, utilizing intrinsic physical identifiers that offer enhanced security and tamper resistance. Multi-level PUFs boost system complexity, thereby improving system reliability and fault tolerance. However, crosstalk-free multi-level PUFs remain a persistent challenge. In this study, a hierarchical PUF system that harnesses the spontaneous phase separation of silk fibroin /PVA blend and the random distribution of silicon-vacancy diamonds within the blend is presented. The thermodynamic instability of phase separation and inherent unpredictability of diamond dispersion gives rise to intricate random patterns at two distinct scales, enabling time-efficient hierarchical authentication for cryptographic keys. These patterns are complementary yet independent, inherently resistant to replication and damage thus affording robust security and reliability to the proposed system. Furthermore, customized authentication algorithms are constructed: visual PUFs authentication utilizes neural network combined structural similarity index measure, while spectral PUFs authentication employs Hamming distance and cross-correlation bit operation. This hierarchical PUF system attains a high recognition rate without interscale crosstalk. Additionally, the coding capacity is exponentially enhanced using M-ary encoding to reinforce multi-level encryption. Hierarchical PUFs hold significant potential for immediate application, offering unprecedented data protection and cryptographic key authentication capabilities.

Robust Optical Physical Unclonable Function Based on Total Internal Reflection for Portable Authentication

Physical unclonable functions (PUFs) utilize uncontrollable manufacturing randomness to yield cryptographic primitives. Currently, the fabrication of the most generally employed optical PUFs mainly depends on fluorescent, Raman, or plasmonic materials, which suffer inherent robustness issues. Herein, we construct an optical PUF with high environmental stability via total internal reflection (TIR-PUF) perturbed by randomly distributed polymer microspheres. The response image is transformed into encoded keys via an iterative binning procedure. The concentration of the polymer solution is optimized to debias the bit nonuniformity and maximize encoding capacity. The constructed TIR-PUF shows significantly high encoding capacity (2370) and markedly low total authentication error probability (1.614 × 10-23). The intra-Hamming distance is as low as 0.068, indicating the excellent readout reliability of TIR-PUF. The environmental stability of TIR-PUF has demonstrated promising results under a range of challenging conditions such as ultrasonic washing, high temperature, ultraviolet irradiation, and severe chemical environments. Moreover, the challenge-response pairs of our TIR-PUFs are demonstrated on an authentication system with low-power dissipation, lightweight components, and wireless imaging capture, rendering the possibility of portable authentication for practical applications.

Dual Challenge-Response Systems of a Three-Dimensional "Bionic" Fluorescent Physically Unclonable Function Label

Inspired by the light and dark variations observed in natural cloud clusters under sunlight, we propose a three-dimensional (3D) "bionic" fluorescent physically unclonable function (PUF) label. The minimalist preparation process eliminates the need for expensive traditional instruments, thus offering new insight into the widespread adoption of 3D PUF labels. The Eu(CCA)3(H2O)2 powder, which is the first to propose its secondary building unit, was chosen as the fluorescent material. Its 3D morphology is preserved in the resin to mimic cloud-like structures. Furthermore, the luminescent properties are elucidated through experimental tests and first-principles calculations. To overcome the coding capacity limitation of traditional two-dimensional (2D) fluorescent PUF labels, a dual challenge-response system model is proposed. The shallow and deep models provide anticounterfeiting information from macro and micro perspectives, respectively. This successfully increases the encoding capacity from 210×10 to 2100×10000 for a 10 × 10 pixel binary code. Therefore, 3D "bionic" fluorescent PUF labels strike a balance between the simple usage of PUF labels and enhanced label security.

Fine Optimization of Colloidal Photonic Crystal Structural Color for Physically Unclonable Multiplex Encryption and Anti-Counterfeiting

Robust anti-counterfeiting techniques aim for easy identification while remaining difficult to forge, especially for high-value items such as currency and passports. However, many existing anti-counterfeiting techniques rely on deterministic processes, resulting in loopholes for duplication and counterfeiting. Therefore, achieving high-level encryption and easy authentication through conventional anti-counterfeiting techniques has remained a significant challenge. To address this, this work proposes a solution that combined fluorescence and structural colors, creating a physically unclonable multiplex encryption system (PUMES). In this study, the physicochemical properties of colloidal photonic inks are systematically adjusted to construct a comprehensive printing phase diagram, revealing the printable region. Furthermore, the brightness and color saturation of inkjet-printed colloidal photonic crystal structural colors are optimized by controlling the substrate's hydrophobicity, printed droplet volume, and the addition of noble metals. Finally, fluorescence is incorporated to build PUMES, including macroscopic fluorescence and structural color patterns, as well as microscopic physically unclonable fluorescence patterns. The PUMES with intrinsic randomness and high encoding capacity are authenticated by a deep learning algorithm, which proved to be reliable and efficient under various observation conditions. This approach can provide easy identification and formidable resistance against counterfeiting, making it highly promising for the next-generation anti-counterfeiting of currency and passports.

Photorewriting, Time-Resolved Encryption, and Unclonable Anticounterfeiting with Artificial Intelligence Authentication via a Reversible Photoswitchable System

In the fields of photolithographic patterning, optical anticounterfeiting, and information encryption, reversible photochromic materials with solid-state fluorescence are emerging as a potential class of systems. A design strategy for reversible photochromic materials has been proposed and synthesized through the introduction of photoactive thiophene groups into the molecular backbone of aryl vinyls, compounds with unique aggregation-induced emission properties, and solid-state reversible photocontrollable fluorescence and color-changing properties. This work develops novel photochromic inks, films, and cellulose hydrogels for enhancing the security of information encryption and anticounterfeiting technologies. They achieve rapid and reversible color change under ultraviolet light irradiation. Dependent upon the rate of color change, higher levels of time-resolved security can be achieved. This feature is important for enhancing the confidentiality of encrypted information and the reliability of security labels. Color-changing cellulose hydrogels, inks, and films consisting of three photochromic fluorescent molecules have quick photoactivity, great photoreversibility and photostability, and good processability, making them ideal for time-delayed anticounterfeiting and smart encryption. Furthermore, specialized algorithms are used to construct convolutional neural networks, and image analysis is performed on these systems, thus solving the current problem of the time-consuming information decryption process. This artificial intelligence method offers new opportunities for enhanced data encryption.

Dynamic multicolor emissions of multimodal phosphors by Mn2+ trace doping in self-activated CaGa4O7

The manipulation of excitation modes and resultant emission colors in luminescent materials holds pivotal importance for encrypting information in anti-counterfeiting applications. Despite considerable achievements in multimodal and multicolor luminescent materials, existing options generally suffer from static monocolor emission under fixed external stimulation, rendering them vulnerability to replication. Achieving dynamic multimodal luminescence within a single material presents a promising yet challenging solution. Here, we report the development of a phosphor exhibiting dynamic multicolor photoluminescence (PL) and photo-thermo-mechanically responsive multimodal emissions through the incorporation of trace Mn2+ ions into a self-activated CaGa4O7 host. The resulting phosphor offers adjustable emission-color changing rates, controllable via re-excitation intervals and photoexcitation powers. Additionally, it demonstrates temperature-induced color reversal and anti-thermal-quenched emission, alongside reproducible elastic mechanoluminescence (ML) characterized by high mechanical durability. Theoretical calculations elucidate electron transfer pathways dominated by intrinsic interstitial defects and vacancies for dynamic multicolor emission. Mn2+ dopants serve a dual role in stabilizing nearby defects and introducing additional defect levels, enabling flexible multi-responsive luminescence. This developed phosphor facilitates evolutionary color/pattern displays in both temporal and spatial dimensions using readily available tools, offering significant promise for dynamic anticounterfeiting displays and multimode sensing applications.