Mechanical Behaviors of Polymer-Based Composite Reinforcements within High-Field Pulsed Magnets.

The development of pulsed magnets capable of generating magnetic fields exceeding 100 Tesla has been recognized as a crucial pursuit for advancing the scientific research on high magnetic fields. However, the operation of magnets at ultra-high magnetic fields often leads to accidental failures at their ends, necessitating a comprehensive exploration of the underlying mechanisms. To this end, this study investigates, for the first time, the mechanical behaviors of Zylon fiber-reinforced polymers (ZFRPs) within pulsed magnets from a composite perspective. The study begins with mechanical testing of ZFRPs, followed by the development of its constitutive model, which incorporates the plasticity and progressive damage. Subsequently, in-depth analyses are performed on a 95-T double-coil prototype that experienced a failure. The outcomes reveal a notable reduction of approximately 45% in both the radial and axial stiffness of ZFRPs, and the primary reason for the failure is traced to the damage incurred by the end ZFRPs of the inner magnet. The projected failure field closely aligns with the experiment. Additionally, two other magnet systems, achieving 90.6 T and 94.88 T, are analyzed. Finally, the discussion delves into the impact of transverse mechanical strength of the reinforcement and axial Lorentz forces on the structural performance of magnets.

Hybrid CNN-Transformer Network with Circular Feature Interaction for Acute Ischemic Stroke Lesion Segmentation on Non-contrast CT Scans.

Lesion segmentation is a fundamental step for the diagnosis of acute ischemic stroke (AIS). Non-contrast CT (NCCT) is still a mainstream imaging modality for AIS lesion measurement. However, AIS lesion segmentation on NCCT is challenging due to low contrast, noise and artifacts. To achieve accurate AIS lesion segmentation on NCCT, this study proposes a hybrid convolutional neural network (CNN) and Transformer network with circular feature interaction and bilateral difference learning. It consists of parallel CNN and Transformer encoders, a circular feature interaction module, and a shared CNN decoder with a bilateral difference learning module. A new Transformer block is particularly designed to solve the weak inductive bias problem of the traditional Transformer. To effectively combine features from CNN and Transformer encoders, we first design a multi-level feature aggregation module to combine multi-scale features in each encoder and then propose a novel feature interaction module containing circular CNN-to-Transformer and Transformer-to-CNN interaction blocks. Besides, a bilateral difference learning module is proposed at the bottom level of the decoder to learn the different information between the ischemic and contralateral sides of the brain. The proposed method is evaluated on three AIS datasets: the public AISD, a private dataset and an external dataset. Experimental results show that the proposed method achieves Dices of 61.39% and 46.74% on the AISD and the private dataset, respectively, outperforming 17 state-of-the-art segmentation methods. Besides, volumetric analysis on segmented lesions and external validation results imply that the proposed method is potential to provide support information for AIS diagnosis.

Magnetically driven capsules with multimodal response and multifunctionality for biomedical applications.

Untethered capsules hold clinical potential for the diagnosis and treatment of gastrointestinal diseases. Although considerable progress has been achieved recently in this field, the constraints imposed by the narrow spatial structure of the capsule and complex gastrointestinal tract environment cause many open-ended problems, such as poor active motion and limited medical functions. In this work, we describe the development of small-scale magnetically driven capsules with a distinct magnetic soft valve made of dual-layer ferromagnetic soft composite films. A core technological advancement achieved is the flexible opening and closing of the magnetic soft valve by using the competitive interactions between magnetic gradient force and magnetic torque, laying the foundation for the functional integration of both drug release and sampling. Meanwhile, we propose a magnetic actuation strategy based on multi-frequency response control and demonstrate that it can achieve effective decoupled regulation of the capsule's global motion and local responses. Finally, through a comprehensive approach encompassing ideal models, animal ex vivo models, and in vivo assessment, we demonstrate the versatility of the developed magnetic capsules and their multiple potential applications in the biomedical field, such as targeted drug delivery and sampling, selective dual-drug release, and light/thermal-assisted therapy.

Asymmetric magnetic levitation for density-based measurement and analysis.

BACKGROUND: Magnetic levitation (MagLev) based on negative magnetophoresis represents a promising technology for density-based analysis and manipulation of nonmagnetic objects. This approach has garnered considerable interest across multiple fields, such as chemistry, materials science, and biochemistry, primarily due to its inherent simplicity, precision, and cost-effectiveness. However, it is essential to recognize that frequently used MagLev configurations, including standard MagLev and axial MagLev, are not without their limitations. These configurations often struggle to strike a balance between levitation performance, ease of operation, and visibility. Therefore, it is necessary to develop a new MagLev configuration to address the aforementioned issue. RESULTS: This work describes the development of an innovative MagLev, termed "asymmetric MagLev", achieved by combining a ring magnet and a cylinder magnet as up-down asymmetric magnetic field sources. The asymmetric design overcomes the physical obstacles along the centerline of the standard MagLev, offering unique open-structure advantages, including easy handling of samples, the ability to observe samples from the top or bottom, and no restrictions on the container height. Meanwhile, comparative analysis reveals a considerable enhancement in the working distance of the asymmetric MagLev without significantly sacrificing the measurement range compared to the axial MagLev. Notably, the asymmetric MagLev achieves a remarkable sensitivity of up to about 1.8 × 104 mm (g cm-3)-1, surpassing the axial MagLev by approximately 30 times. Furthermore, experimental results validate the successful application of the asymmetric MagLev in density measurement and quality detection of small-sized objects. SIGNIFICANCE: This pioneering configuration represents the first utilization of up-down asymmetric magnets in the field of MagLev. Through the integration of an axially magnetized ring magnet and a cylinder magnet, the asymmetric MagLev design overcomes the limitations associated with conventional MagLev configurations. This innovative design exhibits outstanding operational capabilities and levitation performance, making it suitable for a wide range of applications in density-based measurement and analysis.

Radial Magnetic Levitation and Its Application to Density Measurement, Separation, and Detection of Microplastics.

This work describes the development of radial magnetic levitation (MagLev) using two radially magnetized ring magnets to solve the problem of limited operational spaces in standard MagLev and the major shortcoming of a short working distance in axial MagLev. Interestingly and importantly, we demonstrate that for the same magnet size, this new configuration of MagLev doubles the working distance over the axial MagLev without significantly sacrificing the density measurement range, whether for linear or nonlinear analysis. Meanwhile, we develop a magnetic assembly method to fabricate the magnets for the radial MagLev, where multiple magnetic tiles with single-direction magnetization are used as assembly elements. On this basis, we experimentally demonstrate that the radial MagLev has good applicability in density-based measurement, separation, and detection and show its advantages in improving separation performance compared with the axial MagLev. The open structure of two-ring magnets and good levitation characteristics make the radial MagLev have great application potential, and the performance improvement brought by adjusting the magnetization direction of magnets provides a new perspective for the magnet design in the field of MagLev.

Magnetic soft robotic bladder for assisted urination.

The poor contractility of the detrusor muscle in underactive bladders (UABs) fails to increase the pressure inside the UAB, leading to strenuous and incomplete urination. However, existing therapeutic strategies by modulating/repairing detrusor muscles, e.g., neurostimulation and regenerative medicine, still have low efficacy and/or adverse effects. Here, we present an implantable magnetic soft robotic bladder (MRB) that can directly apply mechanical compression to the UAB to assist urination. Composed of a biocompatible elastomer composite with optimized magnetic domains, the MRB enables on-demand contraction of the UAB when actuated by magnetic fields. A representative MRB for a UAB in a porcine model is demonstrated, and MRB-assisted urination is validated by in situ computed tomography imaging after 14-day implantation. The urodynamic tests show a series of successful urination with a high pressure increase and fast urine flow. Our work paves the way for developing MRB to assist urination for humans with UABs.

Water-based ferrofluid with tunable stability and its significance in nuclear wastewater treatment.

The treatment of nuclear wastewater is one of the most urgent and arduous tasks currently, but traditional adsorption materials are significantly limited in practice due to their high demands on auxiliary operations (e.g., shaking or centrifugation) caused by poor stability or recyclability. To tackle this challenge, a water-based ferrofluid composed of magnetic nanoparticles grown in polyethylenimine branches is reported and applied to nuclear wastewater treatment. It is demonstrated that the ferrofluid can keep stable spontaneously in a wide pH range (3-11) out of their ultra-small size, strong electropositivity as well as high charge buffering capacity to achieve shaker-free adsorption, and can be magnetically separated after the neutralization of their positive charge to achieve convenient recycle. Meanwhile, it is found that the ferrofluid shows wide pH/adsorbate applicability and strong ion selectivity in radionuclides absorption. Furthermore, it is anticipated to achieve maximum adsorption capacities for U(VI), Sr(II) and Co(II) as high as 331.5, 427.8 and 759.6 mg/g, respectively. With these characteristics, this ferrofluid outperforms other reported adsorbents. In conclusion, this work provides a practical and effective radioactive wastewater treatment strategy, and enlightens the development of materials for other applications facing the dilemma of incompatible stability and recyclability.

Tunable, Sheathless Focusing of Diamagnetic Particles in Ferrofluid Microflows with a Single Set of Overhead Permanent Magnets.

There has been increasing interest in the use of magnetic fluids to manipulate diamagnetic particles in microfluidic devices. Current methods for diamagnetic-particle focusing in magnetic fluids require either a pair of repulsive magnets or a diamagnetic sheath flow. We demonstrate herein a tunable, sheathless focusing of diamagnetic particles in a microchannel ferrofluid flow with a single set of overhead permanent magnets. Particles are focused into a single stream near the bottom wall of a straight rectangular microchannel, where a magnetic-field minimum is formed as a result of the magnetization of the ferrofluid. This focusing can be readily switched off and on by removing and replacing the permanent magnets. More importantly, the particle-focusing position can be tuned by shifting the magnets with respect to the microchannel. We perform a systematic experimental study of the parametric effects of the fluid-particle-channel system on diamagnetic-particle focusing in terms of a defined particle-focusing effectiveness.

High speed displacement measurement based on electro-magnetic induction applied to electromagnetically driven ring expansion.

Investigating the mechanism of electromagnetic forming (EMF) becomes a hot topic in the field of metal forming. The high speed up to 200 m/s in EMF makes it a real challenge to capture the forming process. To this end, a new method for measuring displacement at high speed based on electromagnetic induction has been developed. Specifically this is used to measure the displacement of an expanding metal ring driven by a pulsed magnetic field; this is one of the basic EMF processes. The new method is simple and practical, and it combines high-speed response with adequate precision. The new measurement system consists of a printed circuit board (PCB) and a Rogowski probe. Eleven coaxial annular detecting probes are arranged in the PCB plate to acquire induced voltage at different positions, and a Rogowski probe is used to measure the current in the driving coil. The displacement of the ring is deduced by analyzing the output voltages of the detecting probes and the Rogowski probe. The feasibility of the method is verified by comparing the results with pictures from a high speed camera taken simultaneously.

Superparamagnetic Iron Oxide Nanoparticle-Mediated Forces Enhance the Migration of Schwann Cells Across the Astrocyte-Schwann Cell Boundary In vitro.

Schwann cells (SCs) are one of the most promising cellular candidates for the treatment of spinal cord injury. However, SCs show poor migratory ability within the astrocyte-rich central nervous system (CNS) environment and exhibit only limited integration with host astrocytes. Our strategy for improving the therapeutic potential of SCs was to magnetically drive SCs to migrate across the astrocyte-SC boundary to intermingle with astrocytes. SCs were firstly magnetized with poly-L-lysine-coated superparamagnetic iron oxide nanoparticles (SPIONs). Internalization of SPIONs showed no effect upon the migration of SCs in the absence of a magnetic field (MF). In contrast, magnetized SCs exhibited enhanced migration along the direction of force in the presence of a MF. An inverted coverslip assay showed that a greater number of magnetized SCs migrated longer distances onto astrocytic monolayers under the force of a MF compared to other test groups. More importantly, a confrontation assay demonstrated that magnetized SCs intermingled with astrocytes under an applied MF. Furthermore, inhibition of integrin activation reduced the migration of magnetized SCs within an astrocyte-rich environment under an applied MF. Thus, SPION-mediated forces could act as powerful stimulants to enhance the migration of SCs across the astrocyte-SC boundary, via integrin-mediated mechanotransduction, and could represent a vital way of improving the therapeutic potential of SCs for spinal cord injuries.

Note: Magnetic targeting for enhancement of the activation efficiency of G protein-coupled receptor with a two-pair coil system.

Insufficient contact of drug with target cells is a primary reason for limited efficiency of G protein-coupled receptor activation. To overcome this limitation, a simple approach based on magnetic targeting for enhancing drug delivery towards the cell surfaces using magnetic nanoparticles and a two-pair coil system consisting of Helmholtz and Maxwell coils was reported. As a proof of the concept, comparative experiments on G protein-coupled receptor activation process were carried out and results show that the efficiency of G protein-coupled receptor activation can be increased about 6 times in the experiments with the aid of the proposed magnetic targeting system.

Configurations and control of magnetic fields for manipulating magnetic particles in microfluidic applications: magnet systems and manipulation mechanisms.

The use of a magnetic field for manipulating the motion of magnetic particles in microchannels has attracted increasing attention in microfluidic applications. Generation of a flexible and controllable magnetic field plays a crucial role in making better use of the particle manipulation technology. Recent advances in the development of magnet systems and magnetic field control methods have shown that it has great potential for effective and accurate manipulation of particles in microfluidic systems. Starting with the analysis of magnetic forces acting on the particles, this review gives the configurations and evaluations of three main types of magnet system proposed in microfluidic applications. The interaction mechanisms of magnetic particles with magnetic fields are also discussed.