Search Results (734)

Plastic pollution raises concerns for health and the environment. Plastics are not biodegradable but gradually erode to microplastic and nanoplastic particles spreading almost everywhere. Nanoplastics exhibit colloidal behavior. Thereby, their analysis can be accomplished by refractometry, preferably by an on-chip tool. We present a study of such colloids using a microfabricated Fabry–Pérot cavity with curved mirrors, which holds a capillary micro-tube used both for fluid handling and light collimation, resulting in an optically stable microresonator. Despite the numerous scatterers within the sample, the sub-millimeter scale cavity provides the advantages of reduced interaction length while maintaining light confinement. This significantly reduces optical loss and hence keeps resonance modes with quality factors (resonant frequency/bandwidth) above 1100. Therefore, small quantities of colloids can be measured by the interference spectral response through the shift in resonant wavelengths. The particles’ Brownian motion potentially causing perturbations in the spectra can be overcome either by post-measurement cross-correlation analysis or by avoiding it entirely by taking the measurements at once by a wideband source and a spectrum analyzer. The effective refractive index of solutions with solid contents down to 0.34% could be determined with good agreement with theoretical predictions. Even lower detection capabilities might be attained by slightly altering the technique to cause particle aggregation achieved solely by light. Full article

This paper presents the design and fabrication of a triboelectric nanogenerator based on a Quadruple Parallel-cavity Helmholtz Resonator (4C–HR TENG) for the efficient harvesting of noise energy in marine engine room environments. The device utilizes sound waves to drive periodic contact and separation between polytetrafluoroethylene (PTFE) particles in the resonant cavity and the vibrating diaphragm as well as the upper electrode plate, thereby converting sound energy into mechanical energy and finally into electrical energy. The device consists of an acoustic waveguide with a length of 350 mm and both width and height of 60 mm, along with a Helmholtz Resonator with a diameter of 60 mm and a height of 40 mm. Experimental results indicate that under resonance conditions with a sound pressure level of 109.8 dB and a frequency of 110 Hz, the device demonstrates excellent output performance, achieving a peak output voltage of 250 V and a current of 4.85 μA. We analyzed and investigated the influence mechanism of key parameters (filling ratio, sound pressure level, the height between the electrode plates, and particle size) on the output performance. Through COMSOL Multiphysics simulation analysis, the sound pressure enhancement effect and the characteristic of concentrated diaphragm center displacement at the first-order resonance frequency were revealed, verifying the advantage of the four-cavity structure in terms of energy distribution uniformity. In practical applications, the minimum responsive sound pressure level corresponding to the operating frequency range of the 4C–HR TENG was determined. The output power reaches a maximum of 0.27 mW at a load resistance of 50 MΩ. At a sound pressure level of 115.1 dB, the device can charge a 1 μF capacitor to 4.73 V in just 32 s and simultaneously illuminate 180 LEDs in real-time, demonstrating its potential for environmental noise energy harvesting and micro-energy supply applications. This study provides new insights and experimental evidence for the efficient recovery of noise energy. Full article

This work investigates the structural, acoustic, and thermo-oxidative degradation behavior of elastomeric composites made from neat EPDM and recycled devulcanized EPDM (EPDMd) blends, both with and without silica (SiO₂). SiO₂ plays a complex role in degradation, possibly acting as a catalyst and also affecting the properties of the materials. Samples were subjected to accelerated degradation at 80 °C for 30 days. The characterization included the mechanical, spectroscopical (FTIR-ATR), thermal (TGA), and morphological (SEM) studies of the samples. Given EPDM’s use in construction as a sound-absorber, its acoustic properties were also analyzed. The determination of the mechanical properties shows that the incorporation of SiO₂ improves the Young’s modulus (YM), maintains the tensile strength (TS) at similar values, and causes a decrease in elongation at break (EB). The content of EPDMd slightly decreases both the TS and the EB and increases the YM. The thermo-oxidative degradation of the studied composites does not affect the TS values, but it increases the YM for the samples with and without SiO₂ for EPDMd contents higher than 40 phr, and decreases the EB for samples with and without SiO₂ for all EPDMd contents. The FTIR-ATR, TGA, and SEM results show that the addition of SiO₂ catalyzes the thermo-oxidative degradation process, while the EPDMd inhibits structural degradation. Migration of the ZnSt₂ included in the formulations to the surface is common in these elastomers. In this case, EPDMd forms microaggregates, which retain the exudation of ZnSt₂ crystals, especially in the non-degraded samples. The degraded samples present irregular structures, with microcavities, cracks, and occlusions, which increase the acoustic absorption mainly at frequencies below 1500 Hz. Full article

We analyze the formal equivalence between the electromagnetic energy conservation law derived from Maxwell’s equations in an optical microcavity and the conservation of a probability fluid associated with the de Broglie–Bohm theory for an effective massive particle describing a photon in this cavity. This work is part of a critical analysis of recent experiments by Sharoglazova et al. carried out with a view to refuting the de Broglie–Bohm theory. Furthermore, the consequences of our analysis for microphotonics go far beyond these experiments. In particular, extensions that take into account photon spin and stochastic aspects associated with radiative or absorption losses are considered. From the point of view of symmetries and probability current, here the effective photon behaves like a spin-1/2 particle. Full article

Surface-imprinted polymer (SIP)-based biomimetic sensors are promising for direct whole-bacteria detection; however, the commonly used fabrication approach (micro-contact imprinting) often suffers from limited imprint density, heterogeneous template distribution, and poor reproducibility. Here, we introduce a photolithography-defined master stamp featuring E. coli mimics, enabling high-density, well-oriented cavity arrays (3 × 10⁷ imprints/cm²). Crucially, the cavity arrangement is engineered such that the SIP layer functions simultaneously as the bioreceptor and as a diffraction grating, enabling label-free optical quantification by reflectance changes without additional transduction layers. Finite-difference time-domain (FDTD) simulations are used to model and visualize the optical response upon bacterial binding. Proof-of-concept experiments using a differential two-well configuration confirm concentration-dependent detection of E. coli in PBS, demonstrating a sensitive, low-cost, and scalable sensing concept that can be readily extended to other bacterial targets by redesigning the photolithographic master. Full article

The authentication of wood species is of paramount significance to market regulation and product quality control in the construction industry. While classification based on microscopic wood cell structures serves as a critical reference for this task, the high inter-class similarity of cell structures and the inherent biological anisotropy of fine textures pose significant challenges to existing methods. Due to their generic design, standard deep learning models often struggle to capture these fine-grained directional features and suffer from catastrophic feature loss during global pooling, particularly under limited sample conditions. To bridge this gap between general-purpose architectures and the specific demands of wood texture analysis, this paper proposes CM-EffNet, a lightweight fine-grained classification framework based on an improved EfficientNetV2 architecture. Firstly, a data augmentation strategy is employed to expand a collected dataset of 226 wood species from 3673 to 29,384 images, effectively mitigating overfitting caused by small sample sizes. Secondly, a Coordinate Attention (CA) mechanism is integrated to embed positional information into channel attention. This allows the network to precisely capture long-range dependencies between cell walls and vessels cavities, successfully decoding the challenge of textural anisotropy. Thirdly, a MixPooling strategy is introduced to replace traditional global average pooling, enabling the collaborative extraction of background context and salient fine-grained details to prevent the loss of critical micro-features. Systematic experiments demonstrate that CM-EffNet achieves a recognition accuracy of 96.72% and a training accuracy of 98.18%. Comparative results confirm that the proposed model offers superior learning efficiency and classification precision with a compact parameter size. This makes it highly suitable for deployment on mobile terminals connected to portable microscopes, providing a rapid and accurate solution for on-site timber market regulation and industrial quality control. Full article

Iron powder represents a promising carbon-free, sustainable fuel, yet its practical utilisation in combustion has not yet been realised. Achieving stable, efficient iron-only flames is challenging, and the environmental impact of hybrid iron-hydrocarbon combustion, including particle emissions, is not fully understood. This study investigates hybrid methane–iron powder flames to assess iron’s role in modifying gas and particle phase emissions and its potential as a sustainable energy carrier. The combustion of iron was investigated at both the single particle and powder flow scales. Experimental diagnostics combined high-speed and microscopic imaging, ex situ particle sizing, in situ gas analysis, and aerosol measurements using an Aerodynamic Particle Sizer (APS™) and a Scanning Mobility Particle Sizer (SMPS™). For single particle combustion, high-speed imaging revealed rapid particle heating, oxide shell growth, cavity formation, micro-explosions, and nanoparticle release. For powder combustion, at 0.5 g/min and 1.26 g/min, the experiment yielded oxidation fractions of 15.15% and 23.43%, respectively, and increased CO₂ emissions by 0.22–0.35 vol% relative to methane–air flames, while NOx changes were negligible. Aerosol analysis showed a supermicron mode at ~2 µm and submicron ultrafine particles of 89% <100 nm with a modal diameter of ~56 nm. The observed ultrafine particle emissions highlight the need to evaluate health, material-loss, and fuel-recycling implications. Burner optimisation or premixed strategies could reduce CO₂ emissions while enhancing iron oxidation efficiency. Full article

Metamaterials (MMs)-based terahertz (THz) biosensors hold promise for clinical diagnosis, featuring label-free operation, simple, rapid detection, low cost, and multi-cell-type discrimination. However, liquid around cells causes severe interference to sensitive detection. Most existing MMs-based cell biosensors detect dead cells without culture medium (losing original morphology), hindering stable, sensitive multi-cell discrimination. Here, a terahertz biosensor composed of a microcavity and MMs can be used to detect and discriminate multiple cell types within suspension. Its detection mechanism relies on cellular size (radius)/density in suspension, which induces effective permittivity (ε_eff) differences. By designing MMs’ split rings with luxuriant gaps, the biosensor achieves a theoretical sensitivity of ~328 GHz/RIU, enabling sensitive responses to suspended cells. It shows a robust, increasing frequency shift (610–660 GHz) over 72 h of cell apoptosis. Moreover, it discriminates nerve cells, glioblastoma (GBM) cells, and their 1:1 mixture with obviously distinct frequency responses (~650, ~630, ~620 GHz), which suggests effective and reliable multi-cell-type recognition. Overall, this study and its measurement method should pave the way for metamaterial-based terahertz biosensors for living cell detection and discrimination, and this technology may inspire further innovations in tumor investigation and treatment. Full article

During the process of defect detection in Micro-Electro-Mechanical Systems (MEMSs), there are many problems with the metallographic images, such as complex backgrounds, strong texture interference, and blurred defect edges. As a result, bond wire breaks and internal cavity contaminants are difficult to effectively identify, which seriously affects the reliability of the whole machine. To solve this problem, this paper proposes a MEMS small-object defect detection method, YOLO-DST (Dynamic Channel–Spatial Modeling and Triplet Attention-based YOLO), based on dynamic channel–spatial blocks and multi-attention fusion. Based on the YOLOv8s framework, the proposed method integrates dynamic channel–space blocks into the backbone and detection head to enhance feature representation across multiple defect scales. The neck of the network integrates multiple triple attention mechanisms, effectively suppressing the background interference caused by complex metallographic textures. Combined with the small-object perception enhancement network based on a Transformer, this method improves the capture ability and stability of the model for the detection of bond wire breaks and internal cavity contaminants. In the verification stage, a MEMS small-object defect dataset covering typical metallographic imaging was constructed. Through comparative experiments with the existing mainstream detection models, the results showed that YOLO-DST achieved better performance in indicators such as Precision and mAP@50%. Full article

In the microinjection molding process, continuous monitoring is important for optimization of the process and control. In microfluidic or lab-on-chip devices, defective microfeatures can compromise biological assays and diagnostic results, and therefore, the quality of these features is a critical issue. Microfeatures can be inspected using advanced inspection and microscopic techniques, but these are expensive, time-consuming, and difficult to use for full-scale production. We present here a new technique for quality control of microfeatures, which uses the filling of a controlled microcavity inside or outside the molded part as a quality control tool for filling microfeatures. Micro gaps (checkpoints) are used as an indicator of microfeature filling. Two micro gaps can be used for filling (checkpoints) as a Go/No-Go gauge. Full article

Chemical and thermal shifts in the oral cavity can damage the surface of 3D-printed hybrid resin–ceramic materials, and research on these effects is still limited. This study investigated the effects of pH and temperature variations on the surface roughness (Ra) of two milled materials, a resin nanoceramic (Cerasmart^®; CS) and a polymer-infiltrated ceramic network (Vita Enamic^®; EN), and a 3D-printed (VarseoSmile Crown plus^®; VS) material. A total of 135 rectangular specimens (12 × 14 × 2 mm), 45 per material, were aged for 30 days under acidic (pH 5), alkaline (pH 9), cold (5 °C), and hot (60 °C) conditions, with neutral (pH 7, 37 °C) as a control. Ra was measured before and after aging using an optical micro-coordinate system. Two-way ANOVA and Tukey’s test assessed the effects of material type and aging condition. Paired t-tests evaluated changes over time. Variations in pH did not significantly increase Ra for any materials. Cold and hot temperatures increased Ra for the milled materials (p < 0.001). VS showed greater stability than the milled materials (CS and EN) despite its higher Ra both before and after aging under all conditions. All Ra values remained below the clinical threshold for biofilm accumulation (0.2 µm) under all conditions. Full article

Microwave heating technology has gained extensive application in various fields, including food processing and drying, material synthesis, and waste treatment, due to its advantages of high efficiency, selectivity, and rapid response. However, the inherent non-uniform electromagnetic field distribution within metallic microwave cavities leads to uneven heating. This issue severely constrains the large-scale industrial application of microwave heating, particularly its extension into high-precision, high-value-added industrial sectors like 3D printing, curing, and microwave plasma micro/nano-fabrication. To address this challenge, extensive research efforts have been undertaken in both academia and industry, focusing on improving microwave heating uniformity, resulting in the proposal of various methods. This review summarizes these methods for enhancing microwave heating uniformity and specifically outlines recent research progress on novel techniques based on artificial electromagnetic surfaces. It aims to offer valuable references and guidance for the broader application of microwave heating technology. Full article

Laser micro-drilling was applied to Fe substrates to enhance the interfacial properties of carbon fiber-reinforced polymer/iron laminates. This architecture is referred to as a resin-interlocked Fe-CFRP hybrid composite. Inspired by human hair follicles’ exceptional adhesion and filling efficiency, novel biomimetic frustum-integrated cylindrical cavities were engineered for Fe surface modification. Experimental results demonstrate that laser-processed surfaces with varied hole geometries (conical, conical frustum, cylindrical, and frustum-integrated cylindrical cavities) exhibit significantly improved interfacial performance compared to untreated Fe controls. Specifically, RI-Fe/CFRP specimens containing frustum-integrated cylindrical cavities achieved the highest shear strength, with a 44.8% increase over non-drilled counterparts. Subsequent molecular dynamics simulations confirmed the critical role of the cavity geometry, demonstrating that the frustum-integrated cylindrical cavity elevates the Fe–Diglycidyl ether of bisphenol-A interfacial energy and van der Waals interactions by 45.44% and 50.66%, respectively, versus the flat surface. The interfacial energy enhancement mechanism via distinct hole configurations was systematically studied. Furthermore, comprehensive micro-hole topology analysis elucidated the reinforcement mechanism in resin-interlocked Fe-CFRP hybrid composites. Results demonstrate that frustum-integrated cylindrical cavities significantly enhance DGEBA-3,3′-diaminodiphenyl sulfone fluidity during interface simulation, promoting mechanical interlocking and optimized resin-filling efficiency. Laser micro-drilling effectively improves Fe-DGEBA interfacial performance. These findings provide critical insights for designing high-performance composites in aerospace and automotive applications. Full article

We report a high-performance photomultiplication-type organic photodetector (OPD) based on a poly[2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylenevinylene]:[6,6]-phenyl-C₆₁-butyric acid methyl ester (MDMO-PPV:PC₆₁BM) active layer operating in the ultrastrong coupling regime. Systematic optimization of the PC₆₁BM ratio in reference non-cavity devices confirms that trap-assisted hole injection from the Ag contact enables external quantum efficiencies (EQEs) exceeding 2000% and fast transient responses under 521 nm illumination, close to the absorption peak of MDMO-PPV. Incorporation of the optimized PC₆₁BM ratio into a λ/2 microcavity produces well-resolved lower (LP) and upper (UP) polariton branches with a pronounced Rabi splitting of approximately 0.9 eV, confirming the establishment of ultrastrong light–matter coupling. The resulting cavity OPD exhibits a distinct wavelength-dependent response compared with its non-cavity counterpart, achieving maximum EQEs of 838% at 450 nm (near the UP mode) and 445% at 628 nm (corresponding to the LP mode). These spectral responses are attributed to cavity-induced field modulation, which enhances exciton generation beyond the primary absorption band of MDMO-PPV. Overall, this work demonstrates that combining photomultiplication mechanisms with cavity-field engineering provides an effective strategy for realizing narrowband, high-gain polaritonic photodetectors that surpass the spectral response limitations of conventional organic semiconductors. Full article

Light–matter interactions in optical microcavities attract much attention due to their potential for controlling properties of materials. Among the various types of optical microcavities, porous silicon microcavities (pSiMCs) are of special interest because of their relatively simple fabrication procedure, tunable porosity, and large specific surface area, which make them highly suitable for a wide range of optoelectronic and sensing applications. However, the fabrication of pSiMCs with precisely controlled parameters, which is crucial for effective light–matter coupling, remains challenging due to the multiple variables involved in the process. In addition, the parameter characterizing the capacity of pSiMCs for confining light inside the cavity (the quality factor, QF) rarely exceeds 100. Here, we present advanced methods and protocols for controlled fabrication of pSiMCs at room temperature, combining theoretical and numerical simulations and experimental validation of microcavity structural parameters for enhancing light–matter interactions. This systemic approach has been used to design and fabricate pSiMCs with an about twofold increased QF and correspondingly improved optical performance; the theoretical modeling shows that its further development is expected to increase the QF even more. In addition, we fabricated hybrid fluorescencent structures with the R6G dye embedded into the optimized pSiMCs. This provided a 5.8-fold narrowing of the R6G fluorescence spectrum caused by light–matter coupling, which indicated enhancement of the fluorescence signal at the eigenmode wavelength due to an increased rate of spontaneous emission in the cavity. The proposed methodology offers precise theoretical simulation of microcavities with the parameters required for specific practical applications, which facilitates optimization of microcavity design. The controllable optical properties of pSiMCs make them promising candidates for a wide range of applications where improved spectral resolution, and increased luminescence efficiency are required. This paves the way for further innovations in photonic systems and optoelectronic devices. Full article