Search Results (240)

The utilization of existing telecommunication infrastructure for environmental monitoring via opportunistic sensing is rapidly advancing the field of distributed fiber optic sensing (DFOS). However, while custom-engineered sensing cables are highly characterized for hydrostatic pressure, the complex mechanical response of standard armored telecommunication networks remains largely unquantified. This study experimentally investigates the non-linear distributed pressure sensitivity of three commercial telecommunication cables (Anti-Rodent, Duct, and Microcable) across a hydrostatic pressure range of 0 to 800 PSI. Measurements were conducted using Tunable Wavelength Coherent Optical Time Domain Reflectometry (TW-COTDR) with a 20 cm spatial resolution, utilizing a stepped depressurization protocol with 15-min stabilization holds to isolate true steady-state longitudinal strain. The results reveal that protective cable armoring induces severe mechanical non-linearity. The rigid Glass Reinforced Plastic (GRP) rods of the Anti-Rodent cable acted as a structural vault at low pressures before yielding to become highly sensitive above 400 PSI. Conversely, the corrugated steel tape of the Duct cable exhibited high initial sensitivity followed by mechanical stiffening, while the unarmored Microcable maintained a linear response. These findings establish that a single linear calibration coefficient is invalid for heavily armored infrastructure, highlighting the critical need for structural characterization prior to opportunistic field deployments. Full article

This work presents an intrinsic optical fiber sensor based on plasmonic phenomena in modified plastic optical fibers (POFs). The sensing area is achieved by replacing the polymethyl methacrylate (PMMA) core with a molecularly imprinted polymer (MIP) containing gold nanorods (GNRs). Thus, in the sensing area, the MIP acts as both a selective recognition element and an optically sensitive guiding medium where plasmonic phenomena occur. This optical–chemical configuration has been developed as a proof-of-concept for the detection of furfural in aqueous solution. The proposed sensor achieves a limit of detection (LOD) of 27 pM, demonstrates high selectivity for the analyte of interest, and is applicable even in real-world scenarios, as demonstrated by experimental results (a commercially available infant milk). The proposed sensor presents a significant enhancement of the sensor response, of about six orders of magnitude, compared to a conventional configuration where the same (or a similar) mixture of MIP/GNRs is spun over the exposed PMMA of a D-shaped POF area for comparison. Notably, even if this study has been carried out via a proof-of-concept in furfural detection, this substantial improvement is achieved while preserving a simple, portable, and cost-effective optical setup, highlighting the potential of this sensing strategy for the development of highly selective sensors by changing the MIP template. Full article

Accurately characterizing the accumulated plastic deformation of the cement sheath is essential for evaluating wellbore integrity. Fiber Bragg Grating (FBG) technology, noted for its strong immunity to external interference, is employed for in situ monitoring under harsh downhole conditions. This study investigates the accumulated plastic deformation behavior of set cement through uniaxial cyclic loading–unloading tests and proposes a real-time, high-precision, and non-destructive monitoring scheme by integrating FBG sensors into the Casing–Cement–Formation system (CCFS). The results reveal that under uniaxial conditions, cumulative plastic strain increases with stress amplitude, with the plastic strain in a single cycle capable of reaching up to 0.2%. Under identical conditions, FBG measurements exhibit a drift phenomenon, resulting in an error margin of approximately 1.5–2%. Furthermore, within the CCFS, plastic strain exhibits linear accumulation during the initial 2–5 cycles, followed by a deceleration in the accumulation rate. This deceleration is attributed to the redistribution of internal stress induced by plastic strain accumulation. Notably, the addition of silica fume and latex significantly mitigates this deformation. Collectively, these findings validate the effectiveness of FBG technology for downhole integrity assessment and offer a pathway for early failure detection and targeted maintenance. Full article

Mode coupling in multimode step-index polymer optical fibers (SI POFs) plays a critical role in determining signal integrity and bandwidth performance in optical communication systems. It originates from intrinsic random perturbations that influence power distribution among propagating modes, making accurate prediction of steady-state distributions (SSDs) essential for reliable system design. In this work, we model mode coupling as a stochastic process using the Langevin equation, incorporating simulated Langevin forces to numerically evaluate modal power evolution and steady-state behavior. The proposed approach demonstrates strong agreement with previously reported experimental results, validating its capability to capture energy redistribution mechanisms induced by fiber imperfections. From a telecommunications perspective, the model provides valuable insights into modal dispersion, bandwidth limitations, and signal degradation in SI POF-based links. These results establish a robust and efficient framework for analyzing and optimizing multimode SI POFs, supporting their application in high-speed data transmission and short-reach optical communication networks. Full article

Haemoglobin (Hb) concentration is a key biomarker for several diseases. Traditional laboratory methods often have limitations due to their time-consuming nature, the need for skilled personnel, or the use of high-cost instrumentation. This work presents a sensing strategy for developing new point-of-care tests (POCTs) for Hb detection via a proof of concept. The proposed sensing approach is implemented using plasmonic plastic optical fiber (POF) sensor chips that integrate an electropolymerized molecularly imprinted polymer (eMIP) film on the plasmonic surface for Hb-selective detection. The developed sensor system demonstrates an ultra-low detection limit of 80 fM in buffer, about five orders of magnitude lower than that of other comparable Hb sensors. Selectivity tests against common interfering proteins, such as bovine serum albumin (BSA) and immunoglobulin G (IgG), confirmed high specificity towards the target analyte. Moreover, the sensor’s performance was tested using a whole-blood sample, yielding results consistent with those of standard haematology analysis. The proposed sensor system, based on simple equipment, provides a quick (about 10 min) and cost-effective (about 10 euros per chip) label-free diagnostic tool for POCTs in real-world scenarios, such as finger-prick sampling, offering a less invasive alternative to traditional laboratory methods, towards devices useful for Internet of Medical Things (IoMT). Full article

To address the demand for low-cost, low-loss, and environmentally friendly optical power dividers in short-range visible light communication (VLC) systems, a low-loss 1 × 2 Y-branch optical splitter based on the integration of a planar optical waveguide (POW) and plastic optical fiber (POF) is proposed and experimentally demonstrated. The device employs a large-core step-index POF with a core diameter of 1 mm, enabling efficient coupling of multimode optical signals. The design and structural optimization of the 1 × 2 POF splitter are simulated by the beam propagation method (BPM). We fabricated the device through a low-cost manual assembly process, followed by packaging and experimental characterization. Measurements at 650 nm on ten samples show a minimum insertion loss of 3.4 dB and a lowest excess loss of 0.8 dB. The splitting ratio ranges from 49.6%:50.4% to 37%:63%, with a minimum uniformity of 0.06, indicating stable power distribution performance. These results confirm that a simple, low-cost fabrication approach can achieve practical optical performance, offering a feasible route toward scalable polymer-based photonic integration. Full article

Cotton, a globally significant crop grown in over 100 countries, sustains a $40 billion market and provides employment for over 350 million people worldwide. However, plastic contamination remains a persistent challenge within the industry, degrading cotton fiber quality and disrupting ginning. Manual inspection and optical machine-vision systems struggle when plastic fragments are concealed by fibers or lack sufficient color contrast. To address these challenges, we developed an ultrasonic phased-array imaging system operating at 40 kHz under field-programmable gate array (FPGA) control. Transmitter elements emit pulsed ultrasound along radial paths, separate reflection receivers record echo amplitudes to form acoustic images, and a set of transmission receivers captures signal attenuation, which is overlaid onto the reflection-based image to highlight potential contaminants. In preliminary laboratory-based tests on both seed cotton and lint samples, the system successfully detected visually obscured plastic fragments as small as $2\mathrm{cm}\times 2\mathrm{cm}$ with an angular resolution limit of $\pm 3°$. Distinct reflection peaks and corresponding attenuation overlays were produced across the field of view, validating the system’s detection capabilities. These results demonstrate the feasibility of using ultrasonic imaging to reveal concealed plastics in cotton processing. Integrating this approach with existing optical methods could enhance contaminant-removal workflows and improve overall fiber quality and processing efficiency. Full article

Wearable data gloves often suffer from electromagnetic interference, insufficient substrate stability, and limited capability for multi-degree-of-freedom motion measurement. To address these limitations, a flexible glove incorporating a hybrid POF-FBG sensing scheme was designed and fabricated. Plastic optical fibers (POFs) were side-polished and patterned with long-period gratings to improve sensitivity to wrist flexion-extension and abduction-adduction. Then fiber Bragg gratings (FBGs) were embedded in a polydimethylsiloxane substrate and encapsulated using thermoplastic polyurethane fixtures to reduce the influence of skin stretching and improve measurement accuracy of finger-joint angle. Moreover, a thermoplastic polyurethane skeleton with an adaptive sliding-rail structure was 3D printed to maintain the stability of the sensor placement at the joints. Experimental results demonstrated the mean absolute errors of 4.06°, 1.38° and 1.70° for wrist flexion-extension, abduction-adduction and finger-joint bending, respectively, along with excellent gesture classification using a support vector machine algorithm, which indicates great potential in virtual reality interaction and hand rehabilitation applications. Full article

Percentage depth–dose (PDD) distributions are fundamental to characterizing radiation beams in radiotherapy. This review provides an overview of both methods and sensor technologies for measuring PDD in photon, electron, proton, and carbon-ion beams. We summarize conventional dosimetry techniques, including water-phantom scanning with ionization chambers (cylindrical and parallel-plate) and radiochromic film, and discuss their strengths (established accuracy, calibration traceability) and limitations (volume averaging, delayed readout). We then examine emerging sensor technologies designed to improve spatial resolution, speed, and radiation hardness: multi-layer ionization chambers and Faraday cups for one-shot PDD acquisition; scintillator-based detectors (liquid, plastic, and fiber-optic) enabling real-time and high-resolution depth–dose measurements; advanced semiconductor detectors including silicon carbide diodes; as well as novel approaches such as ionoacoustic range sensing for proton beams. For each modality and detector type, we emphasize clinical relevance, measurement accuracy, spatial resolution, radiation durability, and suitability for high dose-per-pulse environments (e.g., FLASH radiotherapy). Current challenges, such as detector response in regions of steep dose gradient, saturation or recombination at ultra-high dose rates, and energy-dependent sensitivity in mixed radiation fields, are analyzed in detail. We also highlight the limitations of each technique and discuss ongoing improvements and prospects for clinical implementation. In summary, no single detector technology fully satisfies all requirements for fast, high-accuracy, high-resolution, radiation-hard PDD measurement, but the integration of emerging sensor innovations into clinical dosimetry promises to enhance the precision and efficiency of radiotherapy quality assurance. Full article

This research aimed to quantify and investigate the morphology of microplastics in skincare and treatment creams related to their chemical composition and the potential risks to human health associated with exposure to microplastics by dermal contact. A total of 21 skincare and treatment cream samples, indicating the target audience (men, women, and children) for each product, and potential diseases were analyzed in terms of the hidden risk of microplastics. To determine the exact number of microplastics to which adults and children are exposed over the course of a year, in-depth research was conducted on the cosmetic care and treatment products used by over 354 respondents from Romania. This study used a free, self-reported questionnaire method, which took into account consumer habits and preferences, as well as any potential medical conditions that could affect exposure. Optical microscopy and micro-FTIR revealed a total of 109 microplastics, with different sizes, colors, and shapes (i.e., fragments and fibers) and various chemical compositions, including mixtures of polymeric and natural structures, as well as 100% synthetic materials, e.g., polyethylene and polyester. The potential health risk of exposure to microplastics in certain cosmetic formulations for adults was assessed by calculating various risk indices, such as the polymer risk index (H), pollution load index (PLI), dermal plastic absorption (DPA), chronic daily dermal exposure (CDDE), risk to human health from dermal absorption (RHHDA), and estimated annual dermal absorption (EADA). These indices were calculated based on the medical conditions and application areas indicated on the labels of the analyzed creams (i.e., skincare and treatment), for both adult and children’s categories, using the fingertip unit (FTU) method for estimating the cream amount. The plastic toxicity of the analyzed samples was assessed using the H and PLI indices. The risk of microplastics to human health from dermal exposure was assessed using the DPA, CDDE, RHHDA, and EADA indices, which showed concerning results regarding the presence of these particles in cosmetic formulations. Full article

Carbon fiber-reinforced polyetheretherketone (CF/PEEK) thermoplastic composites are increasingly applied in aerospace structures due to their outstanding mechanical and thermal properties. However, their strengthening mechanism and damage evolution under repeated low-velocity impacts remains inadequately explored. This study systematically investigates the mechanical response and failure mechanisms of CF/PEEK laminates subjected to sequential single and second impacts at energy levels of 10 J, 20 J, and 30 J. Through comprehensive analysis of impact parameters (peak load, energy absorption, residual displacement), optical microscopy and ultrasonic C-scan, this study reveals that the load-bearing increase under repeated low-velocity impacts results from the combined effects of multiple mechanisms, including matrix plastic deformation, local compaction, matrix damage, and interlaminar failure. Under initial impacts, laminates exhibit high load-bearing capacity and energy dissipation, which are dominated by plastic deformation and matrix failure at 10 J and 20 J, whereas the 30 J impact causes pronounced fiber failure. An anomalous increase in peak load is observed during secondary impacts, which is attributed to matrix compaction-induced strengthening resulting from the initial impact. Optical microscopy and C-scan quantification demonstrate that, while the initial impact induces compaction-related strengthening, it also causes internal damage, which leads to aggravated damage evolution during the subsequent impact. The findings provide fundamental insights into damage accumulation in thermoplastic composites and directly inform impact-resistant design strategies. Full article

Poly(vinyl butyral) (PVB) displays exceptional adhesion to glass surfaces and high transparency, serving as the dominant interlayer material in laminated glass composites. This study systematically investigates PVB particulate composites, focusing on the interactions between a plasticized PVB matrix and silicate or silica dispersions as reinforcements. PVB composites reinforced with glass flakes, glass fibers, and fumed silica at loadings of 2, 5, and 8 vol% were produced and characterized. Optical microscopy and thermogravimetric analysis were employed to evaluate filler incorporation and dispersion under melt mixing conditions representative of industrial extrusion. Transparency measurements assessed the optical clarity of the composites, while ATR-FTIR was used to identify chemical interactions between PVB and the fillers. Regarding mechanical performance, fumed silica increased tensile strength up to 29 MPa and reduced displacement at fracture by 120%, while high-aspect-ratio flakes and silane-treated fibers only significantly increased composite stiffness. Impact resistance was additionally evaluated, revealing a significant enhancement upon the addition of fibrous reinforcements, especially when silane-treated fibers were used. Fumed silica increased the thermal stability of PVB by 7 °C and reduced water uptake to approximately 4.5%, in contrast to glass flakes, which increased water absorption reaching up to 8–11%. Lastly, the processability of composites was monitored, showing a progressive decrease with increasing filler content for all reinforcements. Overall, this work provides a comprehensive assessment of PVB–silicate/silica interfacial interactions and highlights the design of PVB composites suitable for advanced applications or the upcycling of secondary recycled PVB grades. Full article

The rapid and accurate detection of SARS-CoV-2 biomarkers remains a critical requirement for effective outbreak control and decentralized diagnostics. Although RT-PCR is the current gold standard, its reliance on centralized laboratories and long processing times limits its applicability in point-of-care settings. In this context, optical biosensing platforms based on surface plasmon resonance (SPR) offer attractive features, including label-free, real-time, and quantitative detection. This study explores the use of synthetic receptors for the highly sensitive detection of the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein. Specifically, soft molecularly imprinted polymer nanoparticles (nanoMIPs) were employed as synthetic receptors and integrated into a high-sensitivity, portable plasmonic platform based on a D-shaped plastic optical fiber (POF) SPR sensor. The nanoMIPs were selectively imprinted against the RBD, characterized by Dynamic Light Scattering (DLS), Isothermal Titration Calorimetry (ITC), and Scanning Electron Microscopy (SEM) to confirm nanoMIPs size, binding properties, and surface morphology. Next, the nanoMIPs were immobilized onto a gold-coated sensing surface, enabling enhanced specificity, affinity, and signal amplification compared to conventional biological recognition elements. The resulting RBD-SPR-nanoMIPs sensor demonstrated promising analytical performance, exhibiting high selectivity against potentially interfering proteins and an anticipated sensitivity suitable for RBD detection at femtomolar concentrations. The inherent stability of nanoMIPs suggests the potential for reusable SPR sensing platforms, paving the way for next-generation synthetic receptor-based plasmonic biosensors. Full article

Retinal astrocytes reside mainly in the nerve fiber layer and are central to shaping retinal vessels and maintaining neurovascular balance. Derived from the optic nerve head, they spread across the inner retina to form a meshwork that both supports and instructs the emerging superficial vascular plexus. Immature astrocytes supply vascular endothelial growth factor-A(VEGF-A) to guide endothelial sprouting, while signals from growing vessels promote astrocyte maturation and strengthen the blood–retinal barrier. In disorders such as diabetic retinopathy and neovascular age-related macular degeneration, these cells show marked plasticity. Reactive astrogliosis can sustain VEGF and inflammation, favoring fragile, leaky neovessels, whereas alternative astrocyte states help reinforce barrier function and release anti-angiogenic factors. Located at the core of the neurovascular unit, astrocytes communicate continuously with endothelial cells, pericytes and neurons. This review integrates data from single-cell profiling and advanced imaging to outline astrocyte development, morphology and key signaling pathways (VEGF, PDGF, Wnt/Norrin, Eph/ephrin), and considers how tuning astrocyte polarization might be exploited to preserve retinal vascular integrity. Full article

For hot-rolled ferritic stainless steels with preferential α-fiber texture, the strong α-fiber texture is retained after annealing, greatly affecting the texture and plastic formability during the subsequent cold-rolling process. For optimizing the texture of hot-rolled steels toward the favorable γ-fiber type, it is essential to control the annealing temperature in the annealing process. To investigate the evolution of the microstructure, texture, and properties of hot-rolled ferritic stainless steel with preferential α-fiber orientation, a series of annealing tests was performed at the lab scale at 800, 840, 880, 910, 930, and 950 °C for 3 min. The microstructure, texture, and grain boundary characteristics of the tested samples were analyzed using optical microscopy (OM) and electron back-scattered diffraction (EBSD). The mechanical properties and plastic strain ratio (r-value) were determined through universal tensile testing. The results show that at temperatures above 840 °C, more than 93% of recrystallization occurs, leading to significant microstructural refinement. The α-fiber texture intensity typically diminishes with rising temperature, whereas the γ-fiber texture initially weakens during the early stages of recrystallization (below 840 °C) and subsequently exhibits a slight increase at higher temperatures. The improved formability of the material is mainly attributed to microstructural refinement and texture refinement, as reflected by the I(γ)/I(α) texture intensity ratio. At an annealing temperature of 930 °C, the I(γ)/I(α) ratio peaks at 0.85, static toughness is maximized, the strain-hardening exponent (n) reaches a high value of 0.28, and the maximum average plastic strain ratio ($\overline{r}$) is 0.96. This result represents the optimum balance between mechanical properties and formability, making it suitable for subsequent cold-rolling. Full article