Search Results (163)

Fe-based amorphous microwires were studied to examine the effect of partial surface nanocrystallization on their magnetic and electrical properties. Controlled annealing was used to induce nanocrystallization within the surface layer of the metallic core. The giant magnetoimpedance (GMI) was found to increase up to 150% compared to the as-cast microwires, which correlates with variations in the electromagnetic skin depth. Magnetic force microscopy (MFM) revealed a pronounced transformation of the magnetic domain structure: inclined and zigzag domains evolved into a ring domain configuration with radially oriented magnetization. This transformation of the domain structure occurred within the same magnetic field range where the maximum impedance response was observed. These results show a strong coupling between surface nanostructuring, domain configuration, and magnetoimpedance behavior, providing insights for optimizing Fe-based microwires for use in high-sensitivity magnetic and mechanical sensors. Full article

This paper explores the potential of amorphous and nanocrystalline glass-coated microwires as highly versatile, miniaturized sensing elements, leveraging their intrinsic nonlinear magnetization dynamics. In magnetic systems, this approach is particularly advantageous because the degree of nonlinearity can be externally tuned using stimuli such as applied magnetic fields, mechanical stress, or temperature variations. From this context, we summarize key properties of microwires—including bistability, a specific easy magnetization direction, internal stress distributions, and magnetostriction—that can be tailored through composition and annealing. In this review, we compare for the first time two key contactless readout methodologies: (i) time-domain detection of the switching field and (ii) frequency-domain harmonic analysis of the induced voltage. These principles have been successfully applied to a broad range of practical sensors, including devices for monitoring mechanical stress in structural materials, measuring temperature in biomedical settings, and detecting magnetic particles. Together, these advances highlight the potential of microwires for embedded, wireless sensing in both engineering and medical applications. Full article

The implementation of photoelectric conversion in photoelectric integrated systems requires the design of photodetectors (PDs) with quick response times and low power consumption. In this work, the self-powered photodetector was prepared by antimony selenide (Sb₂Se₃) microwires (MW)/Se microtube (MT) heterojunction by coating Ag nanowires (NW). The incorporation of Ag-NW involves dual enhancement mechanisms. First, the surface plasmon resonance (SPR) effect amplifies the light absorption across UV–vis–NIR spectra, and the conductive networks facilitate the rapid carrier transport. Second, the type-II band alignment between Sb₂Se₃ and Se synergistically separates photogenerated carriers, while the Ag-NW further suppress the recombination through built-in electric field modulation. The optimized device achieves remarkable responsivity of 122 mA W⁻¹ at 368 nm under zero bias, with a response/recovery time of 8/10 ms, outperforming most reported Sb₂Se₃-based detectors. The heterostructure provides an effective strategy for developing self-powered photodetectors with broadband spectral adaptability. The switching ratio, responsivity, and detectivity of the Sb₂Se₃-MW/Se-MT/Ag-NW device increased by 260%, 810%, and 849% at 368 nm over the Sb₂Se₃-MW/Se-MT device, respectively. These results show that the addition of Ag-NW effectively improves the photoelectric performance of the Sb₂Se₃-MW/Se-MT heterojunction, providing new possibilities for the application of self-powered optoelectronic devices. Full article

The application of intravascular optical coherence tomography (IV-OCT) in neurovascular interventions is constrained by the mechanical inadequacy of conventional catheters in navigating the complex intracranial vasculature. To address this, we modified a coronary IV-OCT catheter, enhancing its mechanical performance for neurovascular applications. The modified catheter featured a 300 mm over-the-microwire segment and a dual-structured shaft (distal 50 mm nonbraided, proximal 250 mm braided) to improve trackability and pushability. We compared the modified and conventional catheters using a benchtop model with a simulated vessel path and an in vivo swine model. Trackability and pushability were quantitatively measured using resistance (N) and advancement distance (mm) in the simulated path. In the animal model, indirect performance metrics included the catheter tension angle (CTA) and pass of catheter (POC) through the fourth curvature of the external carotid artery (ECA). The modified catheter demonstrated superior pushability (172.9 ± 1.96 mm vs. 127.9 ± 2.86 mm, p < 0.05) and increased resistance (1.47 ± 0.036 N vs. 0.69 ± 0.032 N, p < 0.05). In vivo analysis further showed a significantly greater CTA (115.8 ± 8.5° vs. 77.6 ± 10.3°, p < 0.05) and higher POC success rate (83.3% vs. 11.1%, p < 0.05). These results indicate that the modified coronary IV-OCT catheter offers enhanced mechanical performance, suggesting its potential for safe and effective use in neurovascular procedures. Full article

Achieving room-temperature exciton–polariton condensation represents a frontier challenge in condensed matter physics and optoelectronics. However, its mainstream approach—distributed Bragg reflector (DBR) microcavities—faces widespread application challenges due to complex fabrication and high costs. Here, we report direct observation of the interaction between exciton and microcavity photons in Sn-doped CdS microsheet without extreme fabrication conditions. In situ PL and Raman mapping demonstrate the formation of superlattice structure. Using angle-resolved photoluminescence (ARPL) spectroscopy, we obtain Rabi splitting of polaritons up to 140 meV, and the exciton-like and photon-like components in low-polariton states at different cavity–exciton detuning were revealed at room temperature. Our work demonstrates the origin of optical microcavities and the light–matter coupling in CdS/CdS:SnS₂ superlattice microwires. Full article

Nitrate, as one of the important nutrients in seawater, influences the constant ratio of nitrogen to phosphorus, which is closely related to phytoplankton survival. In this work, a Cu-nanosphere-modified gold microwire electrode was used as the working electrode for determining nitrate in an artificial seawater sample with salinity of 35‰ by a differential pulse voltammetry technique. Under the optimized conditions, the detection linear range is from 1 μM to 2000 μM, the limit of detection is 0.33 μM, and the response time for a single sample is 5 min. Then, to reduce the influence of factors such as temperature, humidity, and microbial environment during sample transporting on the nitrate concentration in real seawater, a portable electrochemical system was introduced for on-site detection. Rapid field determination results show that nitrate levels correlate with tides, proving the portable system’s reliability. Full article

In the pursuit of active elements for bending and curvature sensors, magneto-optical investigations were performed on bent microwires. For the first time, local surface magnetization reversal curves were obtained from various sides of bent Co-rich and Fe-rich microwires. The observed differences in surface magnetization reversal behavior are directly attributed to the transverse distribution of internal mechanical stresses, which range from maximum tensile stress on the outer side of the bent sample to maximum compressive stress on the inner side. Depending on the sample composition and the nature of local stress, distinct magnetic structures—axial, elliptical, and spiral—were identified in different locations on the surface of the microwire. These findings provide valuable insights into the operational mechanisms of bending-sensitive magnetic sensors. Full article

Soft magnetic materials are highly suitable for use as sensors in the monitoring of materials, applications, and processes, with proven effectiveness across various industries. Their ability to be configured as microwires allows excellent integration within composite structures, making them particularly effective for structural health monitoring. Research in this area has enabled the analysis of both hysteresis loops and scattering parameters in transmission and reflection within the microwave frequency range, under conditions such as composite matrix polymerization or when subjecting specimens to different stress states. Consequently, a clear dependence of scattering parameters and impedance on applied stress in composites with magnetic microwire inclusions, which can be monitored, has been demonstrated. However, despite the repeatability of the phenomenon, modeling this behavior is challenging due to the dispersion of results caused by multiple factors and varying conditions that influence outcomes in a conventional environment. This study analyzes the influence of the relative sample position on these measurements and presents results obtained by modifying the position and orientation of microwires through rotation and flipping movements of the test specimen. Full article

Microplastics in aqueous media can be detected through transient oxygen reduction from impacts with an electrified carbon-coated microwire. Each impact is recorded as a spike count in the time domain or as prominent peaks in the frequency domain. The spike count increased from approx. 60 s⁻¹ (pure solution) to 90 s⁻¹ (with microplastics) and 230 s⁻¹ (microplastics in deoxygenated solutions), whereas the frequency domain revealed the presence of spikes in the 7, 21, and 24 Hz regions. The spike count showed a co-variance with the concentration of microparticles, with a linear detection range from 0.02% (w/v) to 0.04% (w/v). The electrochemical sensor, characterized by its simple and cost-effective design, may provide a rapid and user-friendly method for the detection of microplastics. Full article

This review article provides an in-depth analysis of recent advancements in the fabrication, structural characterization, and magnetic properties of Heusler alloy glass-coated microwires, focusing on Co₂FeSi alloys. These microwires exhibit unique thermal stability, high Curie temperatures, and tunable magnetic properties, making them suitable for a wide range of applications in spintronics, magnetic sensing, and biomedical engineering. The review emphasizes the influence of geometric parameters, annealing conditions, and compositional variations on the microstructure and magnetic behavior of these materials. Detailed discussions on the Taylor–Ulitovsky fabrication technique, X-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM) provide insights into the structural properties of the microwires. The magnetic properties, including room-temperature behavior, temperature dependence, and the effects of annealing, are thoroughly examined. The potential applications of these microwires in advanced spintronic devices, magnetic sensors, and biomedical technologies are explored. The review concludes with future research directions, highlighting the potential for further advancements in the field of Heusler alloy microwires. Full article

This study presents the optimization of a laser ablation process designed to achieve the precise removal of polyamide coatings from ultra-thin platinum wires. Removing polymer coatings is a critical challenge in high-reliability manufacturing processes such as aerospace thermocouple fabrication. The ablation process must not only ensure the complete removal of the polyamide insulation but also maintain the tensile strength of the wire to withstand mechanical handling in subsequent manufacturing stages. Additionally, the exposed platinum surface must exhibit low surface roughness to enable effective soldering and be free of thermal damage or residual debris to pass strict visual inspections. The wires have a total diameter of 65 µm, consisting of a 50 µm platinum core encased in a 15 µm polyamide coating. By utilizing a UV laser with a wavelength of 355 nm, average power of 3 W, a repetition rate range of 20 to 200 kHz, and a high-speed marking system, the process parameters were systematically refined. Initial attempts to perform the ablation in an air medium were unsuccessful due to inadequate thermal control and incomplete removal of the polyamide coating. Hence, a water-assisted ablation technique was explored to address these limitations. Experimental results demonstrated that a scanning speed of 1200 mm/s, coupled with a line spacing of 1 µm and a single ablation pass, resulted in complete coating removal while ensuring the integrity of the platinum substrate. The incorporation of a water layer above the ablation region was considered crucial for effective heat dissipation, preventing substrate overheating and ensuring uniform ablation. The laser’s spot diameter of 20 µm in air and a focal length of 130 mm introduced challenges related to overlap control between successive passes, requiring precise calibration to maintain consistency in coating removal. This research demonstrates the feasibility and reliability of water-assisted laser ablation as a method for a high-precision, non-contact coating material. Full article

We studied the influence of annealing on the magnetic properties and microstructure of ultrathin (metallic nucleus diameter ≈ 5 μm, total diameter ≈ 19 μm) Heusler-type NiMnGa glass-coated microwires prepared using the Taylor–Ulitovsky method. The as-prepared NiMnGa microwires exhibit unexpectedly strong magnetic anisotropy, characterized by a coercivity exceeding 3 kOe at room temperature. Furthermore, their Curie temperature (T_c) lies above room temperature. Additionally, a spontaneous exchange bias of approximately 120 Oe is observed in the as-prepared sample at 100 K. Annealing the microwires leads to a decrease in coercivity, spontaneous exchange bias, and T_c values. Notably, the annealing process shifts the T_c of the samples closer to room temperature, making them more suitable for magnetic solid-state refrigeration applications. Moreover, the hysteresis observed in the temperature dependence of magnetization for the samples annealed for 1 h and 2 h, along with the magnetic softening observed at around 260 K, is attributed to a first-order phase transformation. The observed changes are discussed in the context of internal stress relaxation after annealing, the nanocrystalline structure of both the as-prepared and annealed samples, the recrystallization process, and the magnetic ordering of phases identified in the as-prepared sample and those appearing during recrystallization. The glass coating on microwires offers benefits like better flexibility and resistance to damage and corrosion. However, it is important to recognize that this coating can substantially alter the microwires’ magnetic characteristics. Consequently, precise control over the annealing process is vital to obtain the specific martensitic transformation needed. Full article

Two different magnetoelastic Metglas materials with distinct shapes were compared as sensing elements for the structural health monitoring of concrete beams. One had a ribbon shape, while the other had a microwire shape. The sensing elements were attached to different concrete beams, and a crack was introduced into each beam. The beams were subjected to flexural vibrations, and their deformations were recorded wirelessly by coils, detecting the magnetic signals emitted due to the magnetoelastic nature of the sensors. Fast Fourier Analysis of the received signal revealed the bending mode frequencies of the beams, which serve as a “signature” of their structural health. In these spectra, the ribbon-shaped sensor exhibited a 1.4-times stronger signal than the microwire sensor. However, the extracted mode frequencies were nearly identical, with differences of less than 1% both before and after damage. This indicates that both sensors can be used equivalently to monitor structural damage in concrete beams. The damage-related relative frequency shifts ranged from −0.01 to −0.03, with similar results for both sensors. Thermal annealing was also studied and appeared to significantly enhance the signal by 10–30%, likely due to the relaxation of internal stresses induced during the rapid solidification synthesis of these materials. This enhancement was more pronounced in the ribbon-shaped sensor. This study is the first to utilize a magnetoelastic microwire sensor for damage detection in concrete beams. Full article

Background/Objectives: Intracranial macroelectrode implantation is a pivotal clinical tool in the evaluation of drug-resistant epilepsy, allowing further insights into the localization of the epileptogenic zone and the delineation of eloquent cortical regions through cortical stimulation. Additionally, it provides an avenue to study brain functions by analyzing cerebral responses during neuropsychological paradigms. By combining macroelectrodes with microelectrodes, which allow recording the activity of individual neurons or smaller neural clusters, recordings could provide deeper insights into neuronal microcircuits and the brain’s transitions in epilepsy and contribute to a better understanding of neuropsychological functions. In this study, one or two hybrid macro-micro electrodes were implanted in the anterior-inferior insular region in patients with refractory epilepsy. We report our experience and share some preliminary results; we also provide some recommendations regarding the implantation procedure for hybrid electrodes in the insular cortex. Methods: Stereoelectroencephalography was performed in 13 patients, with one or two hybrid macro-microelectrodes positioned in the insular region in each patient. Research neuropsychological paradigms could not be implemented in two patients for clinical reasons. In total, 23 hybrid macro-microelectrodes with eight microcontacts each were implanted, of which 20 were recorded. Spiking activity was detected and assessed using WaveClus3. Results: No spiking neural activity was detected in the microcontacts of the first seven patients. After iterative refinement during this process, successful recordings were obtained from 13 microcontacts in the anterior-inferior insula in the last four patients (13/64, 20.3%). Hybrid electrode implantation was uneventful with no complications. Obstacles included the absence of spiking activity signals, unsuccessful microwire dispersion, and the interference of environmental electrical noise in recordings. Conclusions: Human microelectrode recording presents a complex array of challenges; however, it holds the potential to facilitate a more comprehensive understanding of individual neuronal attributes and their specific stimulus responses. Full article

Background: Tandem Lesions (TLs) or Tandem Occlusions (TOs) are characterized by simultaneous high-grade stenosis or occlusion of the proximal extracranial internal carotid artery and the intracranial terminal internal carotid artery or its branches. These lesions can result in stroke and pose significant challenges to endovascular treatment. This study introduces and evaluates the “T-Top technique” as an innovative approach to address TLs, assessing its safety and technical efficacy. Methods: Data from acute ischemic stroke (AIS) patients treated with the T-Top technique between September 2022 and September 2023 were retrospectively analyzed. The technique involves using the pusher wire of a stent retriever as a microwire to guide a monorail angioplastic balloon to the extracranial carotid stenosis, performing angioplasty simultaneously with stent retriever anchorage. Clinical outcomes, procedural data, and safety were assessed. Results: Successful reperfusion (mTICI > 2b) was achieved in 91% of cases, with a median groin puncture to final recanalization time of 50 min. Favorable clinical outcomes (mRS < 3) were observed in 69% of patients, with a low mortality rate of 6% after 90 days. Conclusions: The T-Top technique offers a rapid and reliable strategy for TL treatment, improving reperfusion rates and clinical outcomes. Further studies are warranted to validate its efficacy in larger cohorts. This technique holds promise for enhancing endovascular treatment outcomes in patients with Tandem Lesions. Full article