The development of novel physically unclonable functions (PUFs) is of growing interest and fluorescent organic semiconductors (f‐OSCs) offer unique advantages of structural versatility, solution‐processability, ease of processing, and great tuning ability of their physicochemical/optoelectronic/spectroscopic properties. The design and ambient atmosphere facile fabrication of a unique organic light‐emitting physically unclonable function (OLE‐PUF) based on a green‐emissive fluorescent oligo(p‐phenyleneethynylene) molecule is reported. The OLE‐PUFs have been prepared by one‐step, brief (5 min) thermal annealing of spin‐coated nanoscopic films (≈40 nm) at a modest temperature (170 °C), which results in efficient surface dewetting to form randomly positioned/sized hemispherical features with bright fluorescence. The random positioning of molecular domains generated the unclonable surface with excellent uniformity (0.50), uniqueness (0.49), and randomness (p > 0.01); whereas the distinctive photophysical and structural properties of the molecule created the additional security layers (fluorescence profile, excited‐state decay dynamics, Raman mapping/spectrum, and infrared spectrum) for multiplex encoding. The OLE‐PUFs on substrates of varying chemical structures, surface energies and flexibility, and direct deposition on goods via drop‐casting are demonstrated. The OLE‐PUFs immersed in water, exposed to mechanical abrasion, and read‐out repeatedly via fluorescence imaging showed great stability. These findings clearly demonstrate that rationally engineered solution‐processable f‐OSCs have a great potential to become a key player in the development of new‐generation PUFs.

From anti-counterfeiting to biotechnology applications, there is a strong demand for encoded surfaces with multiple security layers that are prepared by stochastic processes and are adaptable to deterministic fabrication approaches. Here, we present dewetting instabilities in nanoscopic (thickness <100 nm) polymer films as a form of physically unclonable function (PUF). The inherent randomness involved in the dewetting process presents a highly suitable platform for fabricating unclonable surfaces. The thermal annealinginduced dewetting of poly(2-vinyl pyridine) (P2VP) on polystyrenegrafted substrates enables fabrication of randomly positioned functional features that are separated at a microscopic length scale, a requirement set by optical authentication systems. At a first level, PUFs can be simply and readily verified via reflection of visible light. Area-specific electrostatic interactions between P2VP and citrate-stabilized gold nanoparticles allow for fabrication of plasmonic PUFs. The strong surface-enhanced Raman scattering by plasmonic nanoparticles together with incorporation of taggants facilitates a molecular vibration-based security layer. The patterning of P2VP films presents opportunities for fabricating hybrid security labels, which can be resolved through both stochastic and deterministic pathways. The adaptability to a broad range of nanoscale materials, simplicity, versatility, compatibility with conventional fabrication approaches, and high levels of stability offer key opportunities in encoding applications.

The ability to encode unclonable information using low-cost materials and processes is of significant interest for anti-counterfeiting and information security applications. In this study, we present a versatile approach based on electrospraying of polymer solutions to generate randomly positioned complex features as a form of physically unclonable function (PUF). The key advantage of this approach is that readily available low-cost bulk polymeric materials can form small and complex features using a simple process. Polymers of varying composition and molecular weight, together with different solvents and electrospraying conditions, are systematically explored to construct the parameter space for PUFs of varying characteristics. Besides the randomness in the spatial positions and sizes of features, the key advantage of the presented approach is the ability to generate complex 3D shapes, which are very difficult, if not impossible to fabricate with the most advanced fabrication techniques. The inclusion of photoluminescent molecules establishes an additional security layer. The additive nature of operation enables multiplexing, i.e., deposition of multiple materials on the same substrate. The fabricated PUFs have an average uniformity of 0.533 and uniqueness of 0.495, which are highly close to an ideal value of 0.5. The authentication is effectively performed using a feature detection algorithm without the need for markers and precisely defined rotation angles, greatly relaxing constraints associated with the imaging. Direct application of PUFs on the label of goods and authentication via a handheld microscope demonstrate the practical utility of the presented approach.