Search Results (146)

The development of micro glucose sensors plays a vital role in the management and monitoring of diabetes, facilitating real-time tracking of blood glucose levels. In this paper, we developed a three-layer core-sheath microwire (NW@CuO@Co₃O₄) with nickel wire as the core and copper oxide and cobalt oxide nanowires as the sheath. The unique core-sheath structure of microwire enables it to have both good conductivity and excellent electrochemical catalytic activity when used as an electrode for glucose detecting. The non-enzymatic glucose sensor base on a NW@CuO@Co₃O₄ core-sheath wire exhibits a high sensitivity of 4053.1 μA mM⁻¹ cm⁻², a low detection limit 0.89 μM, and a short response time of less than 2 s. Full article

We provide new experimental studies of the temperature dependence of the giant magnetoimpedance (GMI) effect and hysteresis loops of Fe-rich and Co-rich amorphous microwires with rather different room temperature magnetic properties and GMI effect features. We observed a remarkable modification of hysteresis loops and magnetic field dependence of the GMI ratio upon heating in both of the studied samples. We observed a noticeable improvement in the GMI ratio and a change in hysteresis loops from rectangular to inclined upon heating in Fe-rich microwire. However, the opposite trend was observed in Co-rich microwire, in which, upon heating, the shape of the hysteresis loop changed from linear to rectangular. Generally, the evolution of the shape of the hysteresis loops during heating correlates with the modification of the dependencies of the GMI ratio ΔZ/Z on the magnetic field. For Co-rich microwire, the double-peak magnetic field dependence changed to single-peak, while for Fe-rich microwire, the opposite tendency was observed. The origin of the observed temperature dependences of the hysteresis loop and the GMI effect is discussed, considering internal stresses’ relaxation during heating, the temperature dependencies of the magnetostriction coefficient, and internal stresses, as well as the Hopkinson effect. Full article

A novel approach to protein quantification utilizing a microfluidic platform activated by a magnetic assembly of functionalized magnetic beads around soft magnetic capture centers is presented. Functionalized magnetic beads, known for their high surface area and facile manipulation under external magnetic fields, are injected inside microfluidic channels and immobilized magnetically on the surface of glass-coated soft magnetic microwires placed along the symmetry axis of these channels. A fluorescent (Cy5) immunomagnetic sandwich ELISA is then performed by sequentially flowing the sample and all necessary reagents in the microfluidic channels. Direct protein quantification is performed by magnetically releasing the beads from the microwire and evaluating their fluorescence intensity with the help of a miniature (microfluidic-based) flow cytometer. Measurements of ICAM-1 protein concentration in human blood plasma samples confirm the feasibility of the approach through extensive performance benchmarking. The automation and multiplexing capabilities of the proposed platform further demonstrate its potential for protein quantification in point-of-care settings using microfluidics and miniature flow cytometry instruments. Full article

Minimally invasive endovascular stent electrodes are an emerging technology in neural engineering, designed to minimize the damage to neural tissue. However, conventional stent electrodes often rely on resistive welding and are relatively bulky, restricting their use primarily to large animals or thick blood vessels. In this study, the feasibility is explored of fabricating a laser welding stent electrode as small as 300 μm. A high-precision laser welding technique was developed to join micro-wire electrodes without compromising structural integrity or performance. To ensure consistent results, a novel micro-wire welding with platinum pad method was introduced during the welding process. The fabricated electrodes were integrated with stent structures and subjected to detailed electrochemical performance testing to evaluate their potential as neural interface components. The laser-welded endovascular stent electrodes exhibited excellent electrochemical properties, including low impedance and stable charge transfer capabilities. At the same time, in this study, a simulation is conducted of the electrode distribution and arrangement on the stent structure, optimizing the utilization of the available surface area for enhanced functionality. These results demonstrate the potential of the fabricated electrodes for high-performance neural interfacing in endovascular applications. The approach provided a promising solution for advancing endovascular neural engineering technologies, particularly in applications requiring compact electrode designs. Full article

Glass-coated microwires exhibiting magnetic bistability have garnered significant attention as promising wireless sensing elements, primarily due to their rapid magnetization switching capabilities. These microwires consist of a metallic core with diameter d, encased in a glass coating, with a total diameter D. In this study, we investigated how the dimensions of both components and their ratio (d/D) influence the magnetization reversal behavior of Fe-based microwires. While previous studies have focused on either d or d/D individually, our research uniquely considered the combined effect of both parameters to provide a comprehensive understanding of their impact on magnetic properties. The metallic core diameter d varied from 10 to 19 µm and the d/D ratio was in the range of 0.48–0.68. To assess the magnetic properties of these microwires, including the shape of the hysteresis loop, coercivity, remanent magnetization, and the critical length of bistability, we employed vibrating sample magnetometry in conjunction with FORC-analysis. Additionally, to determine the critical length of bistability, magnetic measurements were conducted on microwires with various lengths, ranging from 1.5 cm down to 0.05 cm. Our findings reveal that coercivity is primarily dependent on the d/D parameter. These observations are effectively explained through an analysis that considers the competition between magnetostatic and magnetoelastic anisotropy energies. This comprehensive study paves the way for the tailored design of glass-coated microwires for diverse wireless sensing applications. Full article

The shape memory capabilities of Heusler alloy microwires with two different contents of Fe element instead of Ga element following step-by-step ordering heat treatment were explored based on the stoichiometric ratio of Ni₂MnGa. The melt-drawing technique was used to create the polycrystalline microwires, and the two microwires had Fe atomic contents of 4.7 at.% and 5.5 at.%, respectively. The field emission scanning electron microscope was used to analyze the microwire’s surface condition as well as the microscopic tensile fracture morphology. Using an X-ray diffractometer, the microwires’ crystal structure was identified for phase analysis. Differential scanning calorimetry was used to examine the microwires’ behavior during martensitic transformation. Using a dynamic mechanical stretcher, the elongation and recovery rate of microwires’ one- and two-way shape memory behavior were examined. The findings demonstrated that the microwire phase structure, martensitic transformation behavior, and shape memory capabilities all displayed good properties after the heat treatment was ordered. Full article

Shape memory alloys (SMAs) are becoming a more important factor in actuation technology. Due to their unique features, they have the potential to save weight and installation space as well as reduce energy consumption. The system integration of the generally small-diameter NiTi wires is an important cornerstone for the emerging technology. Crimping, a common method for the mechanical and electrical connection of SMA wires, has several drawbacks when it comes to miniaturization and high-force outputs. For high-force applications, for example, multiple SMA wires in parallel are needed to keep actuation frequencies high while scaling up the actuation force. To meet these challenges, the proposed study deals with the development of a resistance-welding process for manufacturing NiTi wire bundles. The wires are welded to a sheet metal substrate, resulting in promising functional properties and high joint strengths. The welding process benefits from low costs, easy-to-control parameters and good automation potential. A method for evaluating the resistance-welding process parameters is presented. With these parameters in place, a manufacturing process for bundled wire actuators is discussed and implemented. The welded joints are examined by peel tests, microscopy and fatigue experiments. The performance of the manufactured bundle actuators is demonstrated by comparison to a single wire with the same accumulated cross-sectional area. Full article

A preprocessing technique named “spiral annealing” was applied for the first time to magnetic microwires. In this process, the sample was arranged in a flat spiral shape during annealing, and subsequent measurements were conducted on the unbent sample with the induced stress distribution along and transverse to the sample. The research utilized both magnetic and magneto-optical methods. The anisotropy field magnitude in both the volume and surface of the microwire was measured, and for the first time, a direct correlation between the anisotropy field and the curvature of a spirally annealed microwire was established. Additionally, a connection between the type of surface domain structure and the degree of spiral curvature was identified. The preservation of the distribution of spiral annealing-induced magnetic properties both along and across the microwire is a key effect influencing the technological application of the microwire. The range of induced curvature within which a specific helical magnetic structure can exist was also determined. This insight links the conditions of spiral annealing to the selection of microwires as active elements in magnetic sensors. Full article

The rapid and sensitive detection of bacterial contaminants using low-cost and portable point-of-need (PoN) biosensors has gained significant interest in water quality monitoring. Cell-imprinted polymers (CIPs) are emerging as effective and inexpensive materials for bacterial detection as they provide specific binding sites designed to capture whole bacterial cells, especially when integrated into PoN microfluidic devices. However, improving the sensitivity and detection limits of these sensors remains challenging. In this study, we integrated CIP-functionalized stainless steel microwires (CIP-MWs) into a microfluidic device for the impedimetric detection of E. coli bacteria. The sensor featured two parallel microchannels with three-electrode configurations that allowed simultaneous control and electrochemical impedance spectroscopy (EIS) measurements. A CIP-MW and a non-imprinted polymer (NIP)-MW suspended perpendicular to the microchannels served as the working electrodes in the test and control channels, respectively. Electrochemical spectra were fitted with equivalent electrical circuits, and the charge transfer resistances of both cells were measured before and after incubation with target bacteria. The charge transfer resistance of the CIP-MWs after 30 min of incubation with bacteria was increased. By normalizing the change in charge transfer resistance and analyzing the dose–response curve for bacterial concentrations ranging from 0 to 10⁷ CFU/mL, we determined the limits of detection and quantification as 2 × 10² CFU/mL and 1.4 × 10⁴ CFU/mL, respectively. The sensor demonstrated a dynamic range of 10² to 10⁷ CFU/mL, where bacterial counts were statistically distinguishable. The proposed sensor offers a sensitive, cost-effective, durable, and rapid solution for on-site identification of waterborne pathogens. Full article

pH regulation in human biofluids is a crucial step for disease diagnosis and health monitoring. Traditional pH sensors are limited by their bulky size in wearable systems, and fragile glass tips require frequent calibration, thus limiting their use in continuous monitoring. Flexible sensors, particularly those utilizing microwires and thread-based substrates, present advantages for small sample analysis, including natural breathability and suitability for bandage or textile integration. This study examines iridium oxide and silver–silver chloride coated on thin gold wires, fabricated using sol–gel and dip-coating processes known for their simplicity. The flexible microwires demonstrated promising pH performance from a study of their pH characteristics, sensitivity, hysteresis, and potential drift. Electrodes tested in microwells allowed for small sample volumes and localized pH measurement in a controlled environment. Additional integration into fabrics for sweat sensing in wearables highlighted their potential for continuous, real-time health monitoring applications. Full article

This review is a comprehensive overview of recent advancements in underwater in situ heavy metal voltammetric analyzers (UIHVAs). It explores various types of in situ voltammetric analyzers, including the voltammetric in situ profiling system, submersible integrated multi-channel trace metal sensing probes, vibrating gold microwire electrode voltammetric analyzers, and electrochemical analyzers designed for on-site flow measurements. It also covers electrochemical sensors based on flexible liquid crystal polymers, deep-sea mercury sensors, and other in situ electrochemical analyzers. This review systematically examines the research and development progress of microelectrode arrays, screen-printed, carbon, bismuth, antimony, and lab-on-a-chip electrodes. The final section looks at key trends in the research and development of voltammetric analyzers, highlighting the exploration of novel working electrodes, the integration of smart monitoring and data analysis technologies, and the promotion of interdisciplinary collaboration and innovation. From a global perspective, in situ heavy metal voltammetric analysis technology has demonstrated significant applicability in various fields, such as environmental monitoring, marine science, and biogeochemistry. This technology holds considerable potential for further development. However, extensive research and continuous improvement are required to improve detection performance. We are convinced that with continued technological advances and dedicated research efforts, these challenges can be overcome and will pave the way for the widespread application of UIHVAs. Full article

Electroactive microfiber-based scaffolds aid neural tissue repair. Carbon microfibers (CMFs) coated with the conducting polymer poly(3,4-ethylenedioxythiophene) doped with poly[(4-styrenesulfonic acid)-co-(maleic acid)] (PEDOT:PSS-co-MA) provide efficient support and guidance to regrowing axons across spinal cord lesions in rodents and pigs. We investigated the electrical and structural performance of PEDOT:PSS-co-MA-coated carbon MFs (PCMFs) for long-term, biphasic electrical stimulation (ES). Chronopotentiometry and electrochemical impedance spectroscopy (EIS) allowed the characterization of charge transfer in PCMFs during ES in vitro, and morphological changes were assessed by scanning electron microscopy (SEM). PCMFs that were 4 mm long withstood two-million-biphasic pulses without reaching cytotoxic voltages, with a 6 mm length producing optimal results. Although EIS and SEM unveiled some polymer deterioration in the 6 mm PCMFs, no significant changes in voltage excursions appeared. For the preliminary testing of the electrical performance of PCMFs in vivo, we used 12 mm long, 20-microfiber assemblies interconnected by metallic microwires. PCMFs-assemblies were implanted in two spinal cord-injured pigs and submitted to ES for 10 days. A cobalt–alloy interconnected assembly showed safe voltages for about 1.5 million-pulses and was electrically functional at 1-month post-implantation, suggesting its suitability for sub-chronic ES, as likely required for spinal cord repair. However, improving polymer adhesion to the carbon substrate is still needed to use PCMFs for prolonged ES. Full article

The application of biosensors in neurolinguistics has significantly advanced the detection and mapping of language areas in the brain, particularly for individuals with brain trauma. This study explores the role of biosensors in this domain and proposes a conceptual model to guide their use in research and clinical practice. The researchers explored the integration of biosensors in language and brain function studies, identified trends in research, and developed a conceptual model based on cluster and thematic analyses. Using a mixed-methods approach, we conducted cluster and thematic analyses on data curated from Web of Science, Scopus, and SciSpace, encompassing 392 articles. This dual analysis facilitated the identification of research trends and thematic insights within the field. The cluster analysis highlighted Functional Magnetic Resonance Imaging (fMRI) dominance and the importance of neuroplasticity in language recovery. Biosensors such as the Magnes 2500 watt-hour (WH) neuromagnetometer and microwire-based sensors are reliable for real-time monitoring, despite methodological challenges. The proposed model synthesizes these findings, emphasizing biosensors’ potential in preoperative assessments and therapeutic customization. Biosensors are vital for non-invasive, precise mapping of language areas, with fMRI and repetitive Transcranial Magnetic Stimulation (rTMS) playing pivotal roles. The conceptual model serves as a strategic framework for employing biosensors and improving neurolinguistic interventions. This research may enhance surgical planning, optimize recovery therapies, and encourage technological advancements in biosensor precision and application protocols. Full article

Recent developments of orthopedic implant applications have discovered a variety of new metallic biomaterials known as β-type titanium alloys. The μ-WEDM (micro-wire electro discharge machining) surface treatment technique, capable of improving the surface properties of orthopedic implants, was studied in a machining Ti-29Nb-13Ta-4.6Zr alloy. This study aimed to evaluate material removal rate (MRR), kerf width, average surface roughness, microhardness and antibacterial response at different machining parameters which are capacitance (1 nF, 10 nF and 100 nF) and gap voltage (80 V, 95 V and 110 V). The Taguchi method was used to optimize the mentioned output parameters, while ANOVA (analysis of variance) described the significance and contribution of capacitance and gap voltage. Grey relation analysis (GRA) was conducted to perform multiple output optimization. For antibacterial response, cultivations of B. subtilis, E. coli, P. aeruginosa and S. aureus bacteria on treated surfaces for 72 h were performed. As the results, optimal values of MRR, kerf width, crater area, average surface roughness and microhardness were equal to 0.0637 mm³/min, 93.0 μm, 21.8 μm², 0.348 μm and 442 HV, respectively. Meanwhile, μ-WEDM treatment improved antibacterial properties while the highest antibacterial response was achieved at the lowest average surface roughness resulting in least biofilm formation on treated surfaces. Full article

(1) Background: Medical devices, especially neuromodulation devices, are often explanted for a variety of reasons. The removal process imparts significant forces on these devices, which may result in device fracture and tissue trauma. We hypothesized that a device’s form factor interfacing with tissue is a major driver of the force required to remove a device, and we isolated helical and linear electrode structures as a means to study atraumatic removal. (2) Methods: Ductile linear and helical microwire structure electrodes were fabricated from either Gold (Au) or Platinum–Iridium (Pt-Ir, 90-10). Removal forces were captured from synthetic gel models and following chronic implantation in rodent and porcine models. Devices were fully implanted in the animal models, requiring a small incision (<10 mm) and removal via tissue forceps. (3) Results: Helical devices were shown to result in significantly lower maximal removal forces in both synthetic gel and rodent studies compared to their linear counterparts. Chronically (1 yr.), the maximal removal force of helical devices remained under 7.30 N, for which the Platinum–Iridium device’s tensile failure force was 32.90 ± 2.09 N, resulting in a safety factor of 4.50. (4) Conclusions: An open-core helical structure that can freely elongate was shown to result in reduced removal forces both acutely and chronically. Full article