Mixture Of Magnetic Particles Research Articles

Integrated 3D printing of reconfigurable soft machines with magnetically actuated crease-assisted pixelated structures

Reconfigurable magnetic soft machines have a wide range of applications in soft robotics, aerospace, medical devices and flexible electronics. However, the high-precision reconfiguration of magnetically actuated soft machines is hindered by the absence of rational structural design and integrated manufacturing techniques. Here, we report an innovative design and manufacturing approach to realize magnetically actuated high-precision reconfigurability. We present a crease-assisted pixelated design using a mixture of magnetic particles and phase-change medium as the pixel points, with an elastomer as the crease to connect the pixel points, simulating origami. The design of elastomer creases improves pixel stiffness without loss of reconfigurable accuracy, thereby significantly improves the magnetic particle concentration in the pixel. An effective multi-material 3D printing technique is used to achieve the integrated printing of the designed structure. The resulting magnetically actuated soft machines exhibit remarkable capabilities, achieving small curvature bending and precise reconfiguration with weaker actuating magnetic fields (100mT). The superior performance of this design has been confirmed through demonstrations of crawling and rolling machines, magnetically controlled switches, and logic circuits. The work enhances the reconfiguration accuracy of magnetically actuated soft machines, increasing their potential for soft robotics and flexible electronics applications.

Magnetic Liquid Metals: A Review

AbstractMagnetic liquid metal (MLM) is a mixture of magnetic particles with gallium‐based liquid metals which utilizes an unconventional combination of fluidity, high thermal/electrical conductivity, biocompatibility, and magnetism. Recently, from materials to applications, studies on MLMs have drastically increased. Single or multiple MLMs can be precisely positioned or can act as a carrier for handling other objects. MLMs are also used in biomedical applications such as cancer treatment by hyperthermia and precision delivery of cancer drugs on tumors, or antibacterial coating which kills bacteria. In electronics applications, MLMs are used for magnetic field‐driven patterning of metallic lines, reconfigurable interconnects, electronic tattoos, and reconfigurable electromagnetic wave shielding. Phase change (solid/liquid) of MLMs adds another unique capability, morphing. A combination of innovations in the micro/nano robots and MLMs has huge potential to bring an unprecedented disruptive technology for a wide variety of applications including self‐morphing shape‐recovery robots, highly localized cancer treatment, and reconfigurable stealth/camouflage, among others. This article comprehensively reviews recent developments in MLMs from the materials to methods of preparation, locomotion of MLMs, their applications, and future outlooks.

Spreadable Magnetic Soft Robots with On-Demand Hardening.

Magnetically actuated mobile robots demonstrate attractive advantages in various medical applications due to their wireless and programmable executions with tiny sizes. Confronted with complex application scenarios, however, it requires more flexible and adaptive deployment and utilization methods to fully exploit the functionalities brought by magnetic robots. Herein, we report a design and utilization strategy of magnetic soft robots using a mixture of magnetic particles and non-Newtonian fluidic soft materials to produce programmable, hardened, adhesive, reconfigurable soft robots. For deployment, their ultrasoft structure and adhesion enable them to be spread on various surfaces, achieving magnetic actuation empowerment. The reported technology can potentially improve the functionality of robotic end-effectors and functional surfaces. Experimental results demonstrate that the proposed robots could help to grasp and actuate objects 300 times heavier than their weight. Furthermore, it is the first time we have enhanced the stiffness of mechanical structures for these soft materials by on-demand programmable hardening, enabling the robots to maximize force outputs. These findings offer a promising path to understanding, designing, and leveraging magnetic robots for more powerful applications.

Magnetic Nanomaterials for Arterial Embolization and Hyperthermia of Parenchymal Organs Tumors: A Review.

Magnetic hyperthermia (MH), proposed by R. K. Gilchrist in the middle of the last century as local hyperthermia, has nowadays become a recognized method for minimally invasive treatment of oncological diseases in combination with chemotherapy (ChT) and radiotherapy (RT). One type of MH is arterial embolization hyperthermia (AEH), intended for the presurgical treatment of primary inoperable and metastasized solid tumors of parenchymal organs. This method is based on hyperthermia after transcatheter arterial embolization of the tumor’s vascular system with a mixture of magnetic particles and embolic agents. An important advantage of AEH lies in the double effect of embolotherapy, which blocks blood flow in the tumor, and MH, which eradicates cancer cells. Consequently, only the tumor undergoes thermal destruction. This review introduces the progress in the development of polymeric magnetic materials for application in AEH.

A new loss circulation control strategy combining a cross-linkable polymer and magnetic fluid

This work aims to evaluate a new loss of circulation control mechanism combining a smart fluid based on a mixture of a cross-linkable polymer (PVA) solution and magnetic microparticles. This new technology joins the benefits from magnetorheological fluids and cross-linked polymer gels. Magnetorheological fluids (MRF) containing iron particles in different sizes and concentrations were tested as carriers for the cross-linkable polymer. An empirical model with two parameters was also built to formulate MRF compositions able to have a yield stress that minimizes the fluid loss into reservoir. The results showed that MRF rheological properties could be fine-tuned by manipulating the diameter of the iron particles and particle fractions. Different cross-linkers were tested, chromium (III) acetate was the most adequate for PVA crosslinking reaction carried out in the presence of iron particles and under magnetic field. The results demonstrated that a mixture of magnetic particles and cross-linkable polymers has potential application for loss of circulation control.

Magnetic analysis of commercial hematite, magnetite, and their mixtures

Magnetic techniques are suitable to detect iron oxides even in trace concentrations. However, since several iron oxides may be simultaneously present in natural and synthetic samples, mixtures of magnetic particles and magnetic interactions between grains can complicate magnetic signatures. Among the iron oxide minerals, hematite (α-Fe2O3) and magnetite (Fe3O4) are the most common. In this work, different commercial hematite powders, normally used as Fe precursor in laboratory synthesis of Fe-containing oxides, were characterized using X-ray diffractometry (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM). The effects of different concentrations of the hematite and magnetite on the magnetic properties of a set of mixtures (from 1 to 10 wt% magnetite) were then investigated by measuring the hysteresis loops, first order reversal curves (FORCs), thermal demagnetization, and isothermal remanent magnetization (IRM) curves. The three commercial hematite powders presented different magnetic behaviors mostly due to the effects of particle size. The magnetic results of mixtures reveal that it is very difficult to identify hematite magnetic signals by means of hysteresis loops, FORCs, or thermal demagnetization when even a small amount of magnetite (>5 wt%) is present due to magnetite’s high specific magnetization. However, IRM was found to be a sensitive method to determine the presence of hematite when magnetite is simultaneously present as high as 10 wt%.

Tensile strength properties of hybrid magnetic composite materials

The Nd-Fe-B-barium ferrite hybrid composite materials with epoxy matrix presented in this paper cover maximum energy product from 1 to 13 MGOe. Mixture of magnetic particles is responsible for high magnetic quality, while the thermosetting resin plays a role in mechanical properties. Samples with various ratio of Nd-Fe-B to barium ferrite in constant weight of epoxy resin are examined by tensile strength measurements. Magnetic measurements carried out by using vibrating sample magnetometer (VSM) show typical hysteresis loop. A structural analysis of composite surface is conducted by scanning electron microscope (SEM). Uniform particle distribution of plate shape Nd-Fe-B particles and spherical barium ferrite agglomerates is essential for both, mechanical and magnetic properties of composite materials. Fine particles are incorporated in-between larger particles in epoxy bulk which lead to improving the properties.

A novel fast and low cost replication technology for high-aspect-ratio magnetic microstructures

This paper describes a new fabrication technology for high aspect ratio magnetic microstructures. These microstructures are made of composite magnetic materials. In this new technology, a master mold was made using photolithography and the mixture of magnetic particles and polymer was used in micro-molding process. The microstructures were then thermally cured at a temperature lower than 80 °C. To demonstrate the feasibility of using the technology in making magnetic microstructures, both hard magnetic and soft magnetic particles were tried in our experiments. The magnetic particle sizes ranged from 2.3 to 44 μm, which sets the limitations in feature sizes achievable for the magnetic microstructures. Different weight ratios were tried, the maximum weight ratio between the magnetic particle and the polymer was over 2:1. For both wall and trench microstructures, the maximum aspect ratio was found to be over 10, which demonstrates its great potential for micro-fabrication applications.

408 砥気混合流体を利用した管内面研磨における粒子挙動の数値解析(T03-2 マイクロナノ理工学:nmからmmまでのテクスチャリングの創成と機能(2),大会テーマセッション,21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

Numerical simulations of particle method based on the Stoke dynamics were performed in order to examine the behavior of suspended particles in the magnetic compound fluid (MCF) polishing of inner capillary surface. In our simulations, the MCF is treated as the mixture of magnetic particles with micron-size and a continuum magnetic fluid. We show that the abrasive particles are located as trips on the inner wall of circular tube between the magnetic poles and in the region furthest away from the central axis when the size of abrasive particles is much larger than that of magnetic particles, while abrasive particles and magnetic particles form chain-like clusters and combined each other under applied magnetic field when the size of abrasive particles is almost the same as that of magnetic particles.

MAGIC polishing

A new type of magnetic fluid whose base liquid can be solidified at room temperature was developed and named “MAG-netic Intelligent Compound (MAGIC)”. This magnetic intelligent compound which is a mixture of magnetic particles, abrasives and certain polymers is a magnetic fluid at high temperatures, but it can be solidified by cooling. During cooling process, the distribution of abrasives in the liquid can be controlled by a magnetic field. Removal rate with MAGIC is almost the same as that of loose abrasive polishing. Surface roughness with MAGIC is smaller than other polishing methods by one-fold 8. Friction of MAGIC against specimen is between those of fixed abrasives and loose abrasives. So it was considered that abrasives scratched the specimen in MAGIC polishing with loose-bonding.

Dynamics of concentrated ferrofluid with labelled particles

In the study of ferrofluid dynamics the separation of self and pair correlation is the essential problem at both intermediate and high concentrations of the magnetic phase. The neutron spin-echo (NSE) total scattering function St(q,t)=βSp(q,t)+(1−β)Ss(q,t) contains both contributions, where the parameter β=σp/(σp+σs) depends on the corresponding cross sections σs,p. To distinguish these different kinds of dynamics we eliminated one of them by using a mixture of magnetic particles with different scattering amplitudes and concentrations. The NSE experiments (LLB, CE-Saclay) at momentum transfer q1≈0.4nm ∼1/Dp (Dp is the particle diameter) and q2≈0.7nm>1/Dp have been carried out for these opposite situations. The functions Sp(q,t),Ss(q,t), from these data behave quite differenly. The autocorrelations reveal a stretched relaxation at low q: Ss(q,t)=exp[−q2Γ(t)/2], where Γ(t)=2Dtα is the squared particle displacement, the exponent α=0.5±0.1 at q1, and α=0.8±0.1 at q2. The magnitude α<1 indicates the strong influence of dipole forces on the motion of a particle. It resembles the segmental relaxation in a polymer chain. On the other hand, the pair correlations show the oscillations (period∼40ns, amplitude∼1nm) mixed with diffusion.