Photonic bound states in the continuum (BICs) are non-radiative electromagnetic modes with ultrahigh quality factors that provide extreme light confinement and exceptional refractive-index sensitivity, making them highly attractive for advanced biosensing. Here we report recent progress in the development of integrated nanophotonic biosensors based on BIC-enabled all-dielectric metasurfaces. These large-area, optically transparent platforms support high-Q resonances can be functionalized with biomolecular recognition elements, including aptamers, proteins, and molecularly imprinted polymers, enabling highly selective detection of target analytes at ultralow concentrations down to the femtomolar regime. The combination of ultrahigh sensitivity, microfluidic compatibility, and scalable fabrication underscores the strong potential of BIC metasurfaces for applications in healthcare diagnostics, personalized medicine, and highthroughput bioanalytics. We demonstrate this capability through two representative applications: ultrasensitive detection of transforming growth factor-ss (TGF-ss) using molecularly imprinted polymers and quantitative analysis of SPARCalbumin interactions in a microfluidic platform. The sensor is based on an all-dielectric photonic crystal slab that exploits BIC-induced high-Q resonances to enhance light-matter interactions, enabling highly specific and sensitive biomolecular detection. The results represent promising routes toward further performance improvements and the next generation of nanophotonic sensing technologies. *corresponding author: silvia.romano@cnr.it

Exciton–polariton Bose Einstein condensation (BEC) in atomic monolayers promises nonlinear and reconfigurable quantum photonic platforms operating at ambient conditions. Yet it has remained elusive beyond cryogenic and weakly nonlinear microcavities. Here we demonstrate room-temperature (RT) non-equilibrium polariton condensation in a monolayer of tungsten disulfide (WS₂), enabled by topological light confinement through a bound state in the continuum (BIC) arising from interfering Dirac modes. Strong coupling is confirmed by a ~60 meV Rabi splitting persisting across the lasing threshold. The BIC-imprinted polarization texture transfers to the polariton superfluid, carrying a topological charge of |2|. The BIC dispersion supports omnidirectional negative-mass polaritons that self-trap via a reservoir-induced potential. Above threshold, discrete condensate levels emerge in the Dirac gap and undergo pump-driven blueshifts up to ~28 meV. The evolving loss landscape and a space-variant self-trapping potential enable dynamic spectral control. This RT open-cavity platform supports condensate arrays and integration with van der Waals heterostructures and Moiré superlattices, tracing a pathway toward emerging functionalities.

Secreted protein acidic and rich in cysteine (SPARC) is critical in cell-matrix interactions and tissue remodeling. It influences tumor progression through its affinity for human serum albumin (HSA) - the most abundant plasma protein, which also plays a crucial role in drug delivery. Strong molecular binding leads to a dissociation constant KD in the nanomolar range. Thus, determining KD requires detecting sub-nanomolar concentrations with ultrasensitive methods. This may be crucial for elucidating the nature of SPARC-HSA binding, as their interaction remains a subject of debate. Capturing these interactions accurately requires a platform capable of resolving rapid binding kinetics at extremely low analyte concentrations. In this work, we report on a microfluidics-integrated photonic nanostructure that supports bound states in the continuum (BICs) and is optimized for studying the fast kinetics of high-affinity protein-protein interactions. The unprecedented capability of detecting sub-nanomolar concentrations allows quantifying KD between SPARC and HSA beyond the state of the art. We leverage an all-dielectric photonic crystal slab (PhCS) sustaining two BIC branches arising from gapped Dirac cone dispersion. HSA is covalently immobilized on the PhCS bonded to a PDMS microfluidic chamber. SPARC dissociation is carried out using PBS buffer (pH 7.4), ensuring complete protein release through precise control of the flow rate and continuous spectral monitoring of the BICs. The measured KD=8.2±0.8 nM confirms the strong affinity of SPARC for HSA. This study highlights the potential of BIC-based sensing as a versatile tool for investigating protein interactions. These results also have implications for the optimization of drug delivery systems and cancer treatment strategies.

This study investigates the influence of process parameters on the fabrication and mechanical performance of Scalmalloy® lattice structures produced via laser powder bed fusion (PBF-LB) and their mechanical responses at different cell size. A full-factorial design of experiments was employed to evaluate the effect of scan speed, hatch distance, and downskin power on internal porosity and dimensional accuracy. Regression models revealed significant relationships, with optimised parameters identified at a scan speed of 700 mm/s, hatch distance of 0.13 mm, and downskin power of 80 W. Mechanical characterisation through tensile tests of bulk samples and compression tests of lattice structures highlighted the strengthening effects of the heat treatment. Experimental data on quasi-elastic gradient and yield strength were compared to predictions from the Ashby–Gibson model, revealing a partial agreement but noticeable deviations attributed to cell geometry and manufacturing defects. The scaling laws observed differed from the classical model, particularly in the yield strength exponent, indicating the need for empirical models tailored to metallic lattices. This work provides key insights into the optimisation of PBF-LB parameters for Scalmalloy® and underlines the complex interplay between process parameters, structural design, and mechanical behaviour.

Coralline algae (Corallinophycidae, Rhodophyta) have adapted to a broad range of marine habitats, including low-light mesophotic zones, yet the potential role of their high-Mg calcite skeleton in light harvesting remains poorly investigated. Here, we examine the skeletal architecture of Lithothamnion crispatum rhodoliths through X-ray micro-computed tomography (μ-CT) and scanning electron microscopy (SEM), revealing a distinct Voronoi-like tessellation of the epithallial cells associated with a nearly hyperuniform arrangement of submicrometric pores. This structural organization can promote the penetration of scattered light into the thallus, enhancing photon availability in deeper tissues. To further assess the optical implications of the skeleton morphology, we integrated full-wave finite element method (FEM) and ray-tracing simulations, demonstrating that the combination of calcite birefringence and quasi-ordered cell filaments facilitates the superposition of the optical field with chloroplast-rich regions, particularly within a spectral range relevant to deep-water photosynthesis. Our findings highlight for the first time a potential biophotonic function of coralline algal skeletons, opening new perspectives on the role of biomineralization in light manipulation and energy capture in mesophotic habitats. This may help explain the remarkable evolutionary success of coralline algae in low-light environments compared to fleshy macroalgae.

Characterization of dispersion surfaces (DS) in photonic crystals (PhCs) can predict striking topological features, such as bound states in the continuum (BICs). Precise measurement of dispersion, particularly near the Γ-point, is crucial since even subtle geometric deviations significantly impact the distribution of topological charges and associated polarization singularities. Here, we propose a novel technique to measure DS of PhC slabs with high angular accuracy of up to 3 x 10^(-4) radians, and spectral accuracy of 0.2 nm within an expanded region of the Brillouin zone. Remarkably, our technique is diffraction- and aberration-free as it does not rely on optical imaging but rather on spectral mapping. The analysis of DS presented in this work demonstrates the robustness of our technique, and enables us to distinguish anisotropic BICs along a specific symmetry axis from isotropic states around the Γ-point. Moreover, the experimental DS obtained supply the information necessary to study and identify super-BICs.

The integration of advanced materials and photonic nanostructures can lead to enhanced biodetection capabilities, crucial in clinical scenarios and point-of-care diagnostics, where simplified strategies are essential. Herein, a molecularly imprinted polymer (MIP) photonic nanostructure is demonstrated, which selectively binding to transforming growth factor-beta (TGF-β), in which the sensing transduction is enhanced by bound states in the continuum (BICs). The MIP operating as a synthetic antibody matrix and coupled with BIC resonance, enhances the optical response to TGF-β at imprinted sites, leading to an augmented detection capability, thoroughly evaluated through spectral shift and optical lever analogue readout. The validation underscores the MIP-BIC sensor capability to detect TGF-β in spiked saliva, achieving a limit of detection of 10 fM and a resolution of 0.5 pM at physiological concentrations, with a precision of two orders of magnitude above discrimination threshold in patients. The MIP tailored selectivity is highlighted by an imprinting factor of 52, showcasing the sensor resistance to interference from other analytes. The MIP-BIC sensor architecture streamlines the detection process eliminating the need for complex sandwich immunoassays and demonstrates the potential for high-precision quantification. This positions the system as a robust tool for biomarker detection, especially in real-world diagnostic scenarios.

Large-area and transparent all-dielectric metasurfaces supporting photonic bound states in the continuum (BICs) offer several inherent advantages for highly sensitive biosensing applications. A BIC represents a unique mode within the energy spectrum of free-space waves that remains uncoupled with free-space radiation, resulting in a divergent radiative Q-factor and a topological singularity in reciprocal space. In this study, the synergistic combination of photonic crystal slabs (PhCS) supporting bound states in the continuum (BIC) with aptamers and molecularly imprinted polymers (MIPs) offers a groundbreaking approach to achieving ultrahigh sensitivity in detecting mycotoxins in wine and cytokines in artificial saliva. Mycotoxins, toxins produced by certain fungi, pose significant health risks when present in food and beverages like wine. Our research endeavors represent a significant step forward in the field of biosensing, offering a pathway toward the development of versatile, efficient, and reliable sensing platforms with broad applications across scientific, industrial, and societal domains.

Photonic bound states in the continuum (BICs), embedded in the spectrum of free-space waves 1 , 2 with diverging radiative quality factor, are topologically non-trivial dark modes in open-cavity resonators that have enabled important advances in photonics 3 , 4 . However, it is particularly challenging to achieve maximum near-field enhancement, as this requires matching radiative and non-radiative losses. Here we propose the concept of supercritical coupling, drawing inspiration from electromagnetically induced transparency in near-field coupled resonances close to the Friedrich–Wintgen condition 2 . Supercritical coupling occurs when the near-field coupling between dark and bright modes compensates for the negligible direct far-field coupling with the dark mode. This enables a quasi-BIC field to reach maximum enhancement imposed by non-radiative loss, even when the radiative quality factor is divergent. Our experimental design consists of a photonic-crystal nanoslab covered with upconversion nanoparticles. Near-field coupling is finely tuned at the nanostructure edge, in which a coherent upconversion luminescence enhanced by eight orders of magnitude is observed. The emission shows negligible divergence, narrow width at the microscale and controllable directivity through input focusing and polarization. This approach is relevant to various physical processes, with potential applications for light-source development, energy harvesting and photochemical catalysis.

Plasmonic and Photonics applications of superconducting materials, suggested at first by the necessity to minimize the dissipative losses of conventional metals in the high frequency ranges, are topics of growing interest in Optics. In this perspective, GdSr2RuCu2O8-δ (Gd1212) Rutheno-Cuprate Superconductor presents very promising properties, showing both superconducting and magnetically ordered phases coexisting in the same cell. To investigate its features, the fabrication of macroscopic crystallographically oriented samples is necessary. The use of melt texturing techniques has shown to be among the most effective ways to achieve the best characteristics, although the fabrication of high-quality Gd1212 samples is intrinsically difficult. To reach a better understanding of Gd1212 incongruent melting reaction, a series of bulk samples annealed at temperatures below and above the melting temperature was prepared. Raman Microscopy and Mapping performed on molten and re-solidified samples revealed the presence of different phases, corresponding to those identified in our previous studies. These observations were also confirmed by XRD, TGA-DTA, and SEM+EDS characterisations. Secondary phases formation showed a strong dependence on the temperature of the annealing treatments. Susceptibility and magnetization measurements show both superconducting and magnetic transitions and a contribution of different spurious magnetic phases as suggested by EDS.

The non‐trivial polarization topology of bound states in the continuum (BICs) provides new strategies in nanophotonics. The polarization topology depends on the geometric parameters and energy‐momentum dispersion of the system and can be engineered to add specific functionalities for light molding. Herein, such a possibility is investigated by studying the topology of the polarization states associated with the optical field radiated by BICs when Dirac‐cone‐degeneracy is lifted. The opening of a pseudogap in the Dirac cone dispersion of square‐lattice dielectric photonic crystal slabs is achieved by tuning the slab thickness. First, the emergence of half‐integer topological charges without the requirement of BIC annihilation is theoretically shown, which instead occurs when in‐plane inversion symmetry is broken. Then, using spin‐to‐orbital angular momentum conversion, the theory of half‐integer topological charges mediated by BICs is demonstrated and experimentally proved. The same device is able to give rise to vortices with different orbital angular momentum depending on the way it is illuminated, thus improving the potential of optical multiplexing. In addition, the additive character of the topology‐induced phase‐vortex generation is finally demonstrated for both integer and half‐integer charges using also vortex states as input beams, which is of relevance for information delivery.

A giant enhancement of upconversion luminescence (UCPL) from an all-dielectric metasurface supporting bound states in the continuum (BICs) engineered with lanthanide-doped nanocrystals is herein demonstrated. The strong-coupling mechanism occurring at the edge of the photonic superstructure leads to an UCPL radiance enhancement of ~10 8 .

Gd1212 (GdSr 2 RuCu 2 O 8-y ) is a superconductor, isostructural to Y123 (YBa 2 Cu 3 O 7-x ), whose high interest is due to the coexistence of superconducting and magnetic ordered phases in the same unit cell. Up to now the best superconducting properties for Gd1212 have been achieved by TSG (Top-Seeded Melt-Textured growth), a well-known technique used to grow high quality samples from High Temperature Superconductors characterized by a peritectic melting reaction. Due to the relevant production of liquid during the melting of Y123-like materials, the standard TSG procedure involves the addition of secondary phases in the starting powders mixture, generally the peritectic solid phase or one of its precursors, to enhance the structural stability of pellets during the process. This practice also provides additional pinning centers in the final samples, improving their Superconducting features. Unfortunately, Gd1212 peritectic reaction produces an insufficient amount of liquid phase, so preventing from obtaining wide crystallographic domains, and the addition of the peritectic solid phase Gd1210 (GdSr 2 RuO 6 ), although beneficial on the superconducting properties, even worsen this problem. In this work we tried to grow larger Gd1212 domains by inverting the usual approach: i.e., by adding in the precursor powders some peritectic liquid phase (CuO) instead of Gd1210. Anyway, previous analyses suggested us that the chemistry of Gd1212 melting may change for excess CuO mixtures. We have characterized the obtained samples by means of Raman spectroscopy and mapping, data were compared with those of Gd1210-doped and pure Gd1212 samples, results confirm our hypothesis of different melting reaction for CuO rich samples.

High quality factor (Q) optical biosensors find many applications, from environmental monitoring to food safety and clinical diagnostics. In particular, bound states in the continuum (BICs) can be implemented in planar large-area nanostructures for facile microfluidic integration and straightforward interrogation. In this paper the interference leading to the Friedrich–Wintgen type BIC is engineered to make high-Q flat dispersion bands over a large set of interrogation angles. A thorough numerical study is first carried out to adapt the process to an aptasensor scheme. Then, experiments are carried out tracking the high-Q bands evolution forming around the avoided crossing point as a function of the interaction of ochratoxyn A with the bioprobe. An excellent LOD of 2.3 pg/mL is achieved, and a large FOM > 160 RIU−1 is estimated despite the sub-monolayer adsorbate film of thickness ∼ 10 nm. The proposed sensing architecture can be extended to other mycotoxins and small molecules, finding application in many fields for monitoring physical and biochemical processes.

The ability to control light at the nanoscale is at the basis of contemporary photonics and plasmonics. In particular, properly engineered periodic nanostructures not only allow the inhibition of propagation of light at specific spectral ranges or its confinement in nanocavities or waveguides, but make also possible field enhancement effects in vibrational, Raman, infrared and fluorescence spectroscopies, paving the way to the development of novel high-performance optical sensors. All these devices find an impressive analogy in nearly-periodic photonic nanostructures present in several plants, animals and algae, which can represent a source of inspiration in the development and optimization of new artificial nano-optical systems. Here we present the main properties and applications of cutting-edge nanostructures starting from several examples of natural photonic architectures, up to the most recent technologies based on metallic and dielectric metasurfaces.

A novel hyperspectral sensing imaging taking advantage of engineered all-dielectric metasurfaces supporting bound states in the continuum here is discussed. This approach combines surface-enhanced fluorescence and res- onant shift both based on high-Q resonances in proximity of bound states in the continuum. The amplification of the optical field on resonance allows increasing the fluorescence emission of a dye as a function of the spatial- variant dielectric environment in the near-field of the structure. We first demonstrate the fluorescence emission amplification by resonant pump matching in microscopy configuration. Then, we take advantage of Fano reso- nances in the fluorescence emission to map the spatially variant environment of biological cells. To demonstrate the real implementation of the proposed BIC-enhanced imaging as a platform for biosensing, hyperspectral maps of prostate cancer cells are experimentally reconstructed.

Abstract Large-area and transparent all-dielectric metasurfaces sustaining photonic bound states in the continuum (BICs) provide a set of fundamental advantages for ultrasensitive biosensing. BICs bridge the gap of large effective mode volume with large experimental quality factor. Relying on the transduction mechanism of reactive sensing principle, herein, we first numerically study the potential of subwavelength confinement driven by topological decoupling from free space radiation for BIC-based biosensing. Then, we experimentally combine this capability with minimal and low-cost optical setup, applying the devised quasi-BIC resonator for PNA/DNA selective biosensing with real-time monitoring of the binding event. A sensitivity of 20 molecules per micron squared is achieved, i.e. ≃0.01 pg. Further enhancement can easily be envisaged, pointing out the possibility of single-molecule regime. This work aims at a precise and ultrasensitive approach for developing low-cost point-of-care tools suitable for routine disease prescreening analyses in laboratory, also adaptable to industrial production control.