Search Results (1,649)

Triboelectric nanogenerators (TENGs) have garnered significant attention due to their high energy conversion efficiency and extensive application potential in energy harvesting and self-powered devices. Recent advancements in electrospun nanofibers, attributed to their outstanding mechanical properties and tailored surface characteristics, have meant that they can be used as a critical material for enhancing TENGs performance. This review provides a comprehensive overview of the developments in electrospun nanofiber-based TENGs. It begins with an exploration of the fundamental principles behind electrospinning and triboelectricity, followed by a detailed examination of the application and performance of various polymer materials, including poly (vinylidene fluoride) (PVDF), polyamide (PA), thermoplastic polyurethane (TPU), polyacrylonitrile (PAN), and other significant polymers. Furthermore, this review analyzes the influence of diverse structural designs—such as fiber architectures, bionic configurations, and multilayer structures—on the performance of TENGs. Applications across self-powered devices, environmental energy harvesting, and wearable technologies are discussed. The review concludes by highlighting current challenges and outlining future research directions, offering valuable insights for researchers and engineers in the field. Full article

Optical power switches are essential components in fiber optic communication systems, requiring minimal losses, a broad operating wavelength range, and high tolerance to fabrication errors for optimal performance. Adiabatic optical power switches inherently meet these criteria and are well suited for manufacturing processes which support large-scale production at low costs. This paper presents the design and simulation of an adiabatic switch with a flat response in the whole 1525–1625 nm wavelength range (C band and L band) for both TE and TM polarizations. The switch is based on the thermo-optic effect induced by local variations in temperature. The impacts of the design parameters, such as the device length and dissipated heat, are analyzed. The simulation results indicate that the switch achieved high efficiency and low insertion losses, highlighting the potential of adiabatic switches for reliable and scalable integration into advanced optical circuits. Full article

An ultra-thin spiral diffractive lens (SDL) was fabricated by using focused ion beam milling on a fiber end-facet coated with a 100 nm thick Au film. Focusing vortex beams (FVBs) were successfully excited by the SDLs due to the coherent superposition of diffracted waves and their azimuth dependence of the phase accumulated from the spiral aperture to the beam axis. The polarization and phase characteristics of the FVBs were experimentally investigated. Results show that the input beams with various polarization states were converted to FVBs, whose polarization states were the same as those of the input beams. Furthermore, the focal length of the SDL and the in-tensity and phase distribution at the focus spot of the FVBs were numerically simulated by the FDTD method in the ultra-wide near-infrared waveband from 1300 nm to 1800 nm. The focal length was tuned from 21.8 μm to 14.7 μm, the intensity profiles exhibited a doughnut-like shape, and the vortex phase was converted throughout the broadband range. The devices are expected to be candidates for widespread applications including optical communications, optical imaging, and optical tweezers. Full article

Palladium (Pd) nanocubes, a type of metallic nanostructure, have demonstrated remarkable optoelectronic properties, garnering significant attention. However, their nonlinear optical characteristics and related device applications remain underexplored. In this study, we report the fabrication of a novel saturable absorber (SA) by depositing Pd nanocubes onto a D-shaped fiber (DF). The Pd nanocubes, with an average size of 12 nm, were synthesized and integrated with a DF, resulting in a highly robust SA with broadband saturable absorption characteristics. When incorporated into Er³⁺-doped laser cavities, the Pd-DF SA enabled the generation of ultrafast pulses with a central wavelength of 1560 nm, a corresponding repetition rate of 26.7 MHz, and a temporal width of 1.85 ps. Our findings highlight the strong potential of the Pd-DF device as a versatile SA for constructing high-energy ultrafast fiber lasers. Full article

Laser Doppler vibrometry (LDV) is an essential tool in assessing by evaluating ossicle vibrations. It is used in fundamental research to understand hearing physiology better and develop new surgical techniques and implants. It is also helpful for the intraoperative hearing assessment and evaluation of postoperative treatment results. Traditional volumetric LDVs require access in a straight line to the test object, which is challenging due to the structure of the middle ear and the way the auditory ossicles are accessible. Here, we demonstrate the usage of a fiber-based laser Doppler vibrometer (FLDV) for middle ear diagnostics. Compared to classical vibrometers, the main advantages of this device are the ability to analyze several arbitrarily selected points simultaneously and the flexibility achieved by employing fiber optics to perform analysis in hard-to-reach locations, which are particularly important during endoscopic ear surgery. The device also allows for a simple change in measuring probes depending on the application. In this work, we demonstrate the properties of the designed probe and show that using it together with the FLDV enables recording vibrations of the auditory ossicles of the human ear. The obtained signals enable hearing analysis. Full article

Carbon fiber (CF)-reinforced polyimide (PI) resin matrix composites have great application potential in areas such as rail transport, medical devices, and aerospace due to their excellent thermal stability, dielectric properties, solvent resistance, and mechanical properties. However, the epoxy sizing agent used for traditional carbon fiber cannot withstand the processing temperature of polyimide resin, of up to 350 °C, resulting in the formation of pores or defects at the interface between the fiber and the resin matrix, leading to the degradation of the overall composite properties. To overcome this problem, in this study, a low-molecular-weight thermosetting polyimide sizing agent was prepared and the processability of the sized carbon fiber was optimized by a thermoplastic polyimide. Compared with the unsized carbon fiber polyimide composites, the interfacial properties of the composites after the polyimide sizing treatment were significantly improved, with the interfacial shear strength (IFSS) increasing from 82.08 MPa to 136.27 MPa, the interlaminar shear strength (ILSS) increasing from 103.7 to 124.9 MPa, and the bending strength increasing from 2262.2 MPa to 2562.1 MPa. The sizing agent acts as a bridge between the carbon fiber and polyimide resin, with anchorage and bonding at the interface between the fiber and resin, which are beneficial for enhancing the interface performance of composites. Full article

This study investigates the feasibility of using fiber Bragg grating (FBG) sensors for multipoint thermal monitoring of several power semiconductor devices (PSDs), such as insulated gate bipolar transistors (IGBTs), and rectifiers assembled on a common heatsink in a three-phase inverter. A novel approach is proposed to integrate FBG sensors beneath the baseplates of the IGBT modules, avoiding the need for invasive modifications to the device structure. By strategically positioning multiple FBG sensors, accurate temperature profiles of critical components can be obtained. The experimental results demonstrate the effectiveness of the proposed method, with the temperature measurements from FBG sensors closely matching those obtained using thermal infrared (IR) cameras within ±1.1 °C. This research highlights the potential of FBG sensors for reliable and precise thermal management in power electronic systems, contributing to improved performance and reliability. Full article

This work presents the fabrication of a coaxial fiber triboelectric sensor (CFTES) designed for efficient energy harvesting and gesture detection in wearable electronics. The CFTES was fabricated using a facile one-step wet-spinning approach, with PVDF-HFP/CNTs/Carbon black as the conductive electrode and PVDF-HFP/MoS₂ as the triboelectric layer. The incorporation of 1T phase MoS₂ into the PVDF-HFP matrix significantly improves the sensor’s output owing to its electron capture capabilities. The sensor’s performance was carefully optimized by varying the weight percentage of MoS₂, the thickness of the fiber core, and the CNT ratio. The optimized CFTES, with a core thickness of 156 µm and 0.6 wt% MoS₂, achieved a stable output voltage of ~8.2 V at a frequency of 4 Hz and 10 N applied force, exhibiting remarkable robustness over 3600 s. Furthermore, the CFTES effectively detects human finger gestures, with machine learning algorithms further enhancing its accuracy. This innovative sensor offers a sustainable solution for energy transformation and has promising applications in smart portable power sources and wearable electronic devices. Full article

Smartphones equipped with highly integrated sensors are increasingly being recognized as powerful tools for rapid on-site testing. Here, we propose a low-cost, portable, and highly multiplexed smartphone-based spectrometer capable of collecting three types of spectra—transmission, reflection, and fluorescence—by simply replacing the optical fiber attached to the housing. Spectral analysis is performed directly on the smartphone using a custom-developed app. Furthermore, we introduce a high signal-to-noise ratio (SNR) caffeine detection scheme that leverages aspirin and salicylic acid as fluorescent probes, allowing for the rapid and straightforward detection of caffeine in various samples. The fluorescence quenching of the probes was found to be linearly related to the caffeine concentration (0–200 μM), and the recoveries of the commercially available caffeine-containing samples were in the range of 98.0333–105.6000%, with a limit of detection (LOD) of 2.58 μM. The reliability and stability of the on-site assay using the smartphone spectrometer were verified. More importantly, this spectrometer demonstrates great potential as a versatile device for use outside of laboratory settings by enabling different operating modes tailored to various scenarios. Full article

This paper presents a pH sensor with a Mach–Zehnder Interferometer (MZI) that operates in solutions of 4.0, 7.0, and 10.0. The sensor device consists of two tapered sections with dimensions of 1 mm/1 mm/1 mm for down-taper, waist-length, and up-taper, respectively, with a separation of 10 mm. The diameter of the waist is 40 $\mathsf{\mu }$m. This work includes the experimental evaluation of an MZI fiber optic pH sensor at 1559 nm, where 1559 nm represents a specific wavelength chosen for its optimal sensitivity in evaluating the sensor pH detection performance. It is not the central wavelength of the optical fiber, but one of the minimal values selected to enhance the interaction between the evanescent field and the sample, ensuring the reliable detection of pH variations. These sensor dimensions and the functionalized solution of multi-walled carbon nanotubes (MWCNTs) increase the detection of pH in dyes used in the textile industry. Alizarin is a strong anionic red dye that is part of the anthraquinone dye group. The experimental results demonstrated effective detection of pH levels in water contamination involving dye. This development could resolve the problem with Alizarin. The simple fabrication, low cost, and stability of the optical response make this sensor relevant for pH measurements in water contamination. Full article

The importance of gas sensors is apparent as the detection of gases and pollutants is crucial for environmental monitoring and human safety. Gas sensing devices also hold the potential for medical applications as health monitoring and disease diagnostic tools. Gas sensors fabricated from graphene-based fibers present a promising advancement in the field of sensing technology due to their enhanced sensitivity and selectivity. The diverse chemical and mechanical properties of graphene-based fibers—such as high surface area, flexibility, and structural stability—establish them as ideal gas-sensing materials. Most significantly, graphene fibers can be readily tuned to detect a wide range of gases, making them highly versatile in gas-sensing technologies. This review focuses on graphene-based composite fibers for gas sensors, with an emphasis on the preparation processes used to achieve these fibers and the gas sensing mechanisms involved in their sensors. Graphene fiber gas sensors are presented based on the chemical composition of their target gases, with detailed discussions on their sensitivity and performance. This review reveals that graphene-based fibers can be prepared through various methods and can be effectively integrated into gas-sensing devices for a diverse range of applications. By presenting an overview of developments in this field over the past decade, this review highlights the potential of graphene-based fiber sensors and their prospective integration into future technologies. Full article

Self-oscillation, a control approach inspired by biological systems, demonstrates an autonomous, continuous, and regular response to constant external environmental stimuli. Until now, most self-oscillation systems have relied on a static external environment that continuously supplies energy, while materials typically absorb ambient energy only intermittently. In this article, we propose an innovative self-oscillation of liquid crystal elastomer (LCE) fiber-slide system driven by a self-flickering light source, which can efficiently regulate the energy input in sync with the self-oscillating behavior under constant voltage. This system primarily consists of a photo-responsive LCE fiber, a slider that includes a conductive segment and an insulating segment, a light source, and a conductive track. Using the dynamic LCE model, we derive the governing equation for the motion of the LCE fiber-slider system. Numerical simulations show that the LCE fiber-slide system under constant voltage exhibits two distinct motion phases, namely the stationary phase and the self-oscillation phase. The self-oscillation occurs due to the photo-induced contraction of the LCE fiber when the light source is activated. We also investigate the critical conditions required to initiate self-oscillation, and examine key system parameters influencing its frequency and amplitude. Unlike the continuous energy release from the static environmental field in most self-oscillation systems, our LCE fiber-slide self-oscillation system is driven by a self-flickering light source, which dynamically adjusts the energy input under a constant voltage to synchronize with the self-oscillating behavior. Our design features advantages such as spontaneous periodic lighting, a simple structure, energy efficiency, and ease of operation. It shows significant promise for dynamic circuit systems, monitoring devices, and optical applications. Full article

Recent advancements in novel fiber-coupled and portable terahertz (THz) spectroscopic imaging technology have accelerated applications in nondestructive testing (NDT). Although the polarization information of THz waves can play a critical role in material characterization, there are few demonstrations of polarization-resolved THz imaging as an NDT modality due to the deficiency of such polarimetric imaging devices. In this paper, we have inspected industrial carbon fiber composites using a portable and handheld imaging scanner in which the THz polarizations of two orthogonal channels are simultaneously captured by two photoconductive antennas. We observed significant polarimetric differences between the two-channel images of the same sample and the resulting THz Stokes vectors, which are attributed to the anisotropic conductivity of carbon fiber composites. Using both polarimetric channels, we can visualize the superficial and underlying interfaces of the first laminate. These results pave the way for the future applications of THz polarimetry to the assessment of coatings or surface quality on carbon fiber-reinforced substrates. Full article

A logic gate is typically an electronic device with a Boolean or other type of function, e.g., adding or subtracting, including or excluding according to its logical properties. They can be used in electronic, electrical, mechanical, hydraulic, and pneumatic technology. This paper presents a new method for generating logic gates based on optical systems with an emission frequency equal to that used in current telecommunications systems. It uses an erbium-doped fiber laser in its monostable operating region, in contrast to most results published in the literature, where multistable behavior is required to induce dynamic changes, and where a DC voltage signal in the laser pump current provides the control between obtaining the different logic operations. The proposed methodology facilitates the generation of the gates, since it does not require taking the optical system to critical power levels that could damage the components. It is based on using the same elements that the EDFL requires to operate. The result is a system capable of generating up to five stable and robust logic gates to disturbances validated in numerical simulation and experimental setup. This eliminates the sensitivity to the initial conditions affecting the possible logic gates generated by the system and the need to add noise to the system (as is performed in works based on stochastic logic resonance). The experimental observations confirm the numerical results and open up new aspects of using chaotic systems to generate optical logic gates without bistable states. Full article

Recently, two completely different types of lasers—a fiber laser and a gas-discharge laser—were combined into a single device by demonstrating 2.03 µm laser generation in He-Xe plasma that was produced by a microwave discharge directly inside a hollow-core fiber. This new type of laser—a gas-discharge fiber laser—provides excellent opportunities to greatly enrich the wavelength range of the operation of fiber lasers. In this work, we investigate a He-Kr gas mixture as an active medium of this new type of laser. As a result, a He-Kr gas-discharge fiber laser is demonstrated for the first time. The laser was pumped by a microwave discharge in a He:Kr (40:1) mixture that was filled into a revolver fiber with the hollow-core diameter of 130 µm. The total gas pressure was about 100 torr. With broadband mirrors of the laser resonator, generation was observed simultaneously at wavelengths of 2190 and 2523 nm. The output power of the He-Kr gas-discharge fiber laser was about 1 mW. Full article