Amorphous FeSiB/Al 2 O 3 soft magnetic composites were successfully fabricated in this work by applying an external magnetic field perpendicular or parallel to the magnetic toroidal surface, aiming to investigate the influences of magnetic field orientation on their structures and magnetic properties. The results indicate that amorphous FeSiB particles can form chain-like clusters aligned parallel to the direction of the applied magnetic field, which effectively reduces the magnetic reluctance along this direction. The magnetic toroidal with parallel orientation exhibits the highest effective magnetic permeability of 23.8 and a magnetic loss of 43.693 kW/m 3 at 590 kHz and 10mT, which is superior to both the non-oriented and perpendicularly oriented ones due to its optimized microstructure that reduces magnetic reluctance along the working circuit.
Soft magnetic composite materials have a low total loss and high magnetic conductivity and are highly desirable for high-frequency motors, semiconductors, and 5G communication technologies. However, these composites often contain a high-volume fraction of soft magnetic metallic powders and are difficult to process into complex shapes. Herein, iron-based amorphous powders were surface-modified with silane coupling agents (DTMS and KH570) and applied in 3D direct ink writing (DIW). The modified powders exhibit improved compatibility and dispersion in epoxy resin. The optimized 92.3 wt% FeSiB@3.35 wt% KH570/EP slurry shows favorable rheological properties and a dense interfacial microstructure. The printed composite achieves the best magnetic performance (Ms: 137.02 ± 1.2 emu/g, Hc: 6.63 ± 0.2 Oe) and stable permeability up to 1 GHz. The surface modification enhanced slurry fluidity, preventing nozzle blockage and increasing powder loading. Various shaped magnetic cores were successfully fabricated with excellent magnetic properties and printing quality. Our work paves a new way for realizing the high processibility of soft magnetic composites, which lays a foundation for a technique for the wide applications of these materials in various electronic devices.
Zilei Guo,Mengjie Xue,Haitao Zhang,Xiguo Du,Ze Chen,Dong Zhao,Xing Guo,Shengbo Sang
Wearable flexible magnetoelastic sensor for non-invasive real-time uric acid detection in sweat. • Dual-sided functional film eliminates crosstalk between conductive and biorecognition layers. • Magnetic field amplification enables LOD = 1.2 μM and linear range 10–200 μM. • Custom microfluidic patch enables non-skin-contact sensing with efficient sweat management. • Portable detector (5 × 5 cm) shows high accuracy and valid in vivo real-time monitoring. Wearable non-invasive sensors enable continuous detection of uric acid in sweat, thereby facilitating the diagnosis of diseases related to renal and hepatic disorders. Nevertheless, the low uric acid content in human sweat and limitations of current sweat sampling strategies pose major challenges to the development of high-efficiency wearable uric acid sensors. Herein, we report a wearable flexible magnetoelastic (ME) sensor structurally integrated with a functional thin film based on PDMS/Chitosan/FeSiB/CNTs for monitoring uric acid in sweat. The integrated microfluidic patch designed in this work not only achieves sweat collection and directional drainage but also serves as a stable carrier to secure the thin film and magnet. Benefiting from the ME response of FeSiB magnetic particles incorporated inside the thin film, the sensing signal can be significantly amplified by an external magnetic field, which substantially enhances the detection sensitivity toward trace uric acid in sweat. Specifically, one side of the film is designed as a conductive layer, and the other side acts as a biomolecule-modified layer, ensuring that the two functional layers operate independently without mutual interference. Benefiting from this optimized structure, the proposed sensor was employed for testing in simulated sweat and in vivo human trials. Experimental results demonstrate the favorable performance of the sensor for real-time uric acid monitoring in sweat, with a detection limit of 1.2 μM and a wide linear detection range of 20–80 μM, and in the standard uric acid sample, the sensor showed a wider linear range of 10–200 μM, covering the physiological concentration range of uric acid in human sweat. Spiking tests in simulated sweat yielded recoveries from 94.1% to 114.3%, validating its high accuracy. The self-developed portable resistance measurement unit (5 × 5 cm) exhibited a mean relative error of only 0.34% compared with standard instruments, enabling reliable on-site measurement. In vivo tests on healthy volunteers further revealed distinct diurnal variations in sweat uric acid levels, confirming the sensor's great potential for non-invasive and real-time health management. The biosensor presents a promising avenue for uric acid monitoring using adaptable and user-friendly technologies. Download: Download high-res image (359KB) Download: Download full-size image
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