Magnetic Manipulation Research Articles

Swimmable Micro‐Battery for Targeted Power Delivery

AbstractThe boom of microelectronic devices and their diverse applications has heightened the demand for innovative and effective energy supply strategies. The longevity of contemporary microelectronic devices predominantly depends on direct human intervention power supply methods, encompassing battery replacement or recharging. However, these methods may falter in specific scenarios, such as when facing liquid conditions in vivo. Here, a concept of swimmable micro‐batteries (MBs) for targeted power delivery is presented. This is achieved through the design of a flexible polydimethylsiloxane/Fe3O4 soft‐magnetic substrate for actuation, polydimethylsiloxane/neodymium‐iron‐boron (NdFeB) hard‐magnetic tabs for precise targeting, and quasi‐solid‐state Zn//MnO2 battery for power generation. These swimmable MBs exhibit an impressive areal capacity of 102.3 µAh cm‐2, remarkable waterproofing, adjustable output voltage or capacity, rapid response, and accurate remote magnetic field manipulation, enabling targeted power supply available. This novel swimmable MB design broadens the function of MBs and may open a new avenue for their future development.

Recent progress in MnBi2nTe3n+1 intrinsic magnetic topological insulators: crystal growth, magnetism and chemical disorder.

The search for magnetic topological materials has been at the forefront of condensed matter research for their potential to host exotic states such as axion insulators, magnetic Weyl semimetals, Chern insulators, etc. To date, the MnBi2nTe3n+1 family is the only group of materials showcasing van der Waals-layered structures, intrinsic magnetism and non-trivial band topology without trivial bands at the Fermi level. The interplay between magnetism and band topology in this family has led to the proposal of various topological phenomena, including the quantum anomalous Hall effect, quantum spin Hall effect and quantum magnetoelectric effect. Among these, the quantum anomalous Hall effect has been experimentally observed at record-high temperatures, highlighting the unprecedented potential of this family of materials in fundamental science and technological innovation. In this paper, we provide a comprehensive review of the research progress in this intrinsic magnetic topological insulator family, with a focus on single-crystal growth, characterization of chemical disorder, manipulation of magnetism through chemical substitution and external pressure, and important questions that remain to be conclusively answered.

Helical magnetic micromotors decorated with nickel ferrocyanide for the active and rapid adsorption of radiocesium in water

Separating radioactive cesium from nuclear waste and contaminated environments is critical to mitigate radiological hazards. In response to this need, remote-controllable and Cs-selective micromotor adsorbents have been considered as a promising technology for rapid in-situ cleanup while minimizing secondary waste and radiation exposure to workers. In this study, we demonstrate the active and rapid removal of a radioactive contaminant from water by leveraging the magnetic manipulation capabilities of a helical and magnetic Ni micromotor coated with Cs-selective nickel ferrocyanide (NiFC). The use of polyvinyl alcohol fibers as a template enables the straightforward preparation of the helical wire structure, allowing for precise control over the diameter and pitch of the helix through simple twisting with Ni wires. By harnessing Ni2+ ions eluted from the Ni micromotor in an acid solution, we successfully fabricate NiFC-coated Ni (NiFC/Ni) micromotors that exhibit a selective removal efficiency greater than 98% for 137Cs, even in the presence of high concentrations of competing Na+ ions. Under the influence of an external magnetic field, the NiFC/Ni micromotor demonstrates rapid motion, achieving a pulling motion (100 body lengths per second) through a magnetic gradient and a tumbling motion (46 body lengths per second) induced by a rotating magnetic field. The tumbling motion of the NiFC/Ni micromotor substantially improves the Cs adsorption rate, resulting in a rate that surpasses that achieved under nonmoving conditions by a factor of 21. This improved adsorption rate highlights the considerable potential of magnetically manipulated micromotor self-propulsion for efficient water-pollution treatment.

Room temperature field-free switching of perpendicular magnetization through spin-orbit torque originating from low-symmetry type II Weyl semimetal

Spin-orbit torque (SOT) is a promising strategy to deterministically switch the perpendicular magnetization, but usually requires an in-plane magnetic field for breaking the mirror symmetry, which is not suitable for most advanced industrial applications. Van der Waals (vdW) materials with low crystalline symmetry and topological band structures, e.g., Weyl semimetals (WSMs), potentially serve as an outstanding system that may simultaneously realize field-free switching and high energy efficiency. Yet, the demonstration of these superiorities at room temperature has not been realized. Here, we achieve a field-free switching of perpendicular magnetization by using a layered type II WSM, TaIrTe 4 , in a TaIrTe 4 /Ti/CoFeB system at room temperature with the critical switching current density ~2.4 × 10 6 A cm −2 . The field-free switching is ascribed to the out-of-plane SOT allowed by the low crystal symmetry. Our work suggests that using low-symmetry materials to generate SOT is a promising route for the manipulation of perpendicular magnetization at room temperature.

Reconfigurable self-assembly of photocatalytic magnetic microrobots for water purification

The development of artificial small-scale robotic swarms with nature-mimicking collective behaviors represents the frontier of research in robotics. While microrobot swarming under magnetic manipulation has been extensively explored, light-induced self-organization of micro- and nanorobots is still challenging. This study demonstrates the interaction-controlled, reconfigurable, reversible, and active self-assembly of TiO2/α-Fe2O3 microrobots, consisting of peanut-shaped α-Fe2O3 (hematite) microparticles synthesized by a hydrothermal method and covered with a thin layer of TiO2 by atomic layer deposition (ALD). Due to their photocatalytic and ferromagnetic properties, microrobots autonomously move in water under light irradiation, while a magnetic field precisely controls their direction. In the presence of H2O2 fuel, concentration gradients around the illuminated microrobots result in mutual attraction by phoretic interactions, inducing their spontaneous organization into self-propelled clusters. In the dark, clusters reversibly reconfigure into microchains where microrobots are aligned due to magnetic dipole-dipole interactions. Microrobots’ active motion and photocatalytic properties were investigated for water remediation from pesticides, obtaining the rapid degradation of the extensively used, persistent, and hazardous herbicide 2,4-Dichlorophenoxyacetic acid (2,4D). This study potentially impacts the realization of future intelligent adaptive metamachines and the application of light-powered self-propelled micro- and nanomotors toward the degradation of persistent organic pollutants (POPs) or micro- and nanoplastics.

Densely Packed CO2 Aids Charge, Spin, and Lattice Ordering Partially Fluctuated in a Porous Metal-Organic Framework Magnet.

Partial charge fluctuations in the charge-ordered state of a material, often triggered by structural disorders and/or defects, can significantly alter its physical characteristics, such as magnetic long-range ordering. However, it is difficult to post-chemically fix such accidental partial fluctuations to reconstruct a uniform charge-ordered state. Herein, we report CO2 -aided charge ordering demonstrated in a CO2 -post-captured layered magnet, [{Ru2 (o-ClPhCO2 )4 }2 {TCNQ(OMe)2 }] ⋅ CO2 (1⊃CO2 ; o-ClPhCO2 - =ortho-chlorobenzoate; TNCQ(OMe)2 =2,5-dimethoxy-7,7,8,8-tetracyanoquinodimethane). Pristine porous layered magnet 1 had a partially charge-fluctuated ordered state, which provided ferrimagnetic ordering at TC =65 K. Upon loading CO2 , 1 adsorbed one mole of CO2 , forming 1⊃CO2 , and raising TC to 100 K. This was because of the vanishing charge fluctuations without significantly changing the framework structure. This research illustrates the post-accessible host-guest chemistry delicately combined with charge, spin, and lattice ordering in a spongy magnet. Furthermore, it highlights how this innovative approach opens up new possibilities for technology and nanoscale magnetism manipulation.

Densely Packed CO2 Aids Charge, Spin, and Lattice Ordering Partially Fluctuated in a Porous Metal–Organic Framework Magnet

AbstractPartial charge fluctuations in the charge‐ordered state of a material, often triggered by structural disorders and/or defects, can significantly alter its physical characteristics, such as magnetic long‐range ordering. However, it is difficult to post‐chemically fix such accidental partial fluctuations to reconstruct a uniform charge‐ordered state. Herein, we report CO2‐aided charge ordering demonstrated in a CO2‐post‐captured layered magnet, [{Ru2(o‐ClPhCO2)4}2{TCNQ(OMe)2}] ⋅ CO2 (1⊃CO2; o‐ClPhCO2−=ortho‐chlorobenzoate; TNCQ(OMe)2=2,5‐dimethoxy‐7,7,8,8‐tetracyanoquinodimethane). Pristine porous layered magnet 1 had a partially charge‐fluctuated ordered state, which provided ferrimagnetic ordering at TC=65 K. Upon loading CO2, 1 adsorbed one mole of CO2, forming 1⊃CO2, and raising TC to 100 K. This was because of the vanishing charge fluctuations without significantly changing the framework structure. This research illustrates the post‐accessible host–guest chemistry delicately combined with charge, spin, and lattice ordering in a spongy magnet. Furthermore, it highlights how this innovative approach opens up new possibilities for technology and nanoscale magnetism manipulation.

Direct magnetic manipulation of a Permalloy nanostructure by a focused cobalt-ion beam

Direct magnetic manipulation of a Permalloy nanostructure by a focused cobalt-ion beam

Magnetic and Ferroelectric Manipulation of Valley Physics in Janus Piezoelectric Materials.

The realization of multiferroic materials offers the possibility of multifunctional electronic device design. However, the coupling between the multiferroicity and piezoelectricity in Janus materials is rarely reported. In this study, we propose a mechanism for manipulating valley physics by magnetization reversing and ferroelectric switching in multiferroic and piezoelectric material. The ferromagnetic VSiGeP4 monolayer exhibits a large valley polarization up to 100 meV, which can be effectively operated by reversing magnetization. Interestingly, the antiferromagnetic VSiGeP4 bilayers with AB and BA stacking configurations allow the coexistence of valley polarization and ferroelectricity, supporting the proposed strategy for manipulating valley physics via ferroelectric switching and interlayer sliding. In addition, the VSiGeP4 monolayer contains remarkable tunable piezoelectricity regulated by electron correlation U. This study proposes a feasible idea for regulating valley polarization and a general design idea for multifunctional devices with multiferroic and piezoelectric properties, facilitating the miniaturization and integration of nanodevices.

Acoustic-propelled micro/nanomotors and nanoparticles for biomedical research, diagnosis, and therapeutic applications.

Acoustic manipulation techniques have gained significant attention across various fields, particularly in medical diagnosis and biochemical research, due to their biocompatibility and non-contact operation. In this article, we review the broad range of biomedical applications of micro/nano-motors that use acoustic manipulation methods, with a specific focus on cell manipulation, targeted drug release for cancer treatment and genetic disease diagnosis. These applications are facilitated by acoustic-propelled micro/nano-motors and nanoparticles which are manipulated by acoustic tweezers. Acoustic systems enable high precision positioning and can be effectively combined with magnetic manipulation techniques. Furthermore, acoustic propulsion facilitates faster transportation speeds, making it suitable for tasks in blood flow, allowing for precise positioning and in-body manipulation of cells, microprobes, and drugs. By summarizing and understanding these acoustic manipulation methods, this review aims to provide a summary and discussion of the acoustic manipulation methods for biomedical research, diagnostic, and therapeutic applications.

Photon Energy‐Dependent Optical Spin‐Orbit Torque in Heavy Metal–Ferromagnet Bilayers

AbstractThe manipulation of magnetization through optically generated ultrafast spin currents is a fascinating area that needs a thorough understanding for its potential future applications. In this work, a comprehensive investigation of helicity‐driven optical spin‐orbit torque in heavy metal/ferromagnetic metal heterostructures is presented, specifically cobalt capped with gold or platinum, subject to laser pumping at different wavelengths. The results demonstrate up to tenfold enhancement in optical spin‐orbit torque quantum efficiency for gold compared to platinum of the same thickness when pumped with a visible laser. Additionally, the study provides the first experimental analysis of the photon energy dependence of optical spin‐orbit torque and derives the optical spin orientation spectra for both gold/cobalt and platinum/cobalt heterostructures. A key insight gained from the study is the impact of photon energy‐dependent spin transport in the system, which suggests the use of a high photon energy pump for efficient spin transport. These findings highlight the potential of spin current generation and manipulation in gold/ferromagnet heterostructures for a wide range of applications such as all‐optical magnetization switching, spin‐wave generation and control, and spintronic terahertz emission.

A magnetic control enrichment technique combined with terahertz metamaterial biosensor for detecting SARS-CoV-2 spike protein

The highly contagious SARS-CoV-2 virus, responsible for the COVID-19 pandemic continues to pose significant challenges to public health. Developing new methods for early detection and diagnosis is crucial in combatting the disease, mitigating its impact and be prepared for future challenges in pandemic diseases. In this study, we propose a terahertz (THz) biosensing technology that capitalizes on the properties of THz metamaterial in conjunction with magnetic nanoparticles. This approach can accurately identify the SARS-CoV-2 spike protein by pinpointing its location on the THz resonance sources grooved surface. The magnetic nanoparticles are employed to selectively bind with target molecules, and migrate towards the THz metamaterial unit cell when exposed to an applied magnetic field. The presence of target molecules in to the metamaterial variation in the frequency, amplitude, and phase of the resonance response, thus enabling swift, accurate and sensitive detection. To assess the effectiveness of the proposed technique, we have conducted a comparative analysis between real samples on platforms controlled by magnetic manipulation and those without the control. It was confirmed that the proposed THz sensing method demonstrated a linear detection range spanning from 0.005 ng mL−1 to 1000 ng mL−1 with a detection limit of 0.002 ng mL−1. Furthermore, it exhibited a frequency shift of 24 GHz and a stability index of 95%. The THz biosensing technique may pave a new avenue in identifying and preempting the spread of potential pandemic diseases.

Implementing Versatile Programmable Logic Functions Using Two Magnetization Switching Types in a Single Device

AbstractThe efficient manipulation of magnetization using spin‐orbit torques (SOTs) generated by heavy metals and topological insulators has attracted significant attention. However, the symmetry of these conventional materials makes it challenging to achieve deterministic switching of perpendicular magnetization by currents, which prevents the practical application of SOT‐based spintronic devices such as magnetic memories and logics. Here, a composition gradient in a TaxTi1‐x alloy is introduced and the field‐free magnetization switching in TaxTi1‐x/CoFeB heterostructures with controllable SOT efficiencies is realized. Additionally, by engineering the gradient with a tilting angle relative to the current injection arm of the device, highly asymmetric switching loops are achieved, which are attributed to tilted spin polarization. Based on these two switching types, namely field‐free switching and field‐assisted asymmetric switching, five programmable Boolean logic functions are successfully demonstrated using a single device. This work paves the way for high‐density computing‐in‐memory applications with industry compatible artificially‐designed asymmetric SOT materials.

Enhanced spin–orbit torques in strained NiFe/Pt bi-layers on flexible substrate

Magnetization manipulation caused by spin–orbit torque is one of the central themes investigated in spintronics domain. The spin–orbit torque efficiencies can be manoeuvred by application of mechanical strain. In this direction, this study furthers the effort in understanding the evolution of spin–orbit torque efficiencies in mechanically strained ferromagnet (FM)/heavy metal(HM) (Ni81Fe19/Pt) bi-layer films on flexible kapton substrate, by the use of spin torque ferromagnetic resonance (ST-FMR) measurement technique. We report a tensile strain induced enhancement in damping-like and field-like spin–orbit torque efficiencies. The effective damping-like spin torque conductivity increased by 42% on the application of 0.312% tensile strain, which is encouraging from the magnetization switching application point of view. In order to investigate the driving factors behind the enhanced damping-like spin torque conductivity, ab-initio calculations were also carried out. Our findings provide insights into the workings of strain in FM/HM bi-layer stack and is a step forward in the implementation of flexible spintronics devices.

A novel visual biosensor for mercury detection based on a cleavable phosphorothioate-RNA probe and microfluidic bead trap

Mercury ion (Hg2+) detection plays a crucial role in safeguarding the environment and protecting human health. In this study, we developed a microfluidic biosensing platform that utilizes a phosphorothioate-RNA (PS-RNA) probe and gold-coated magnetic nanoparticles to quantify Hg2+ visually. The PS-RNA probe was linked to gold-coated magnetic nanoparticles via Au–S interaction and biotin–avidin interaction and then combined with polystyrene microspheres to form a self-assembled structure called a magnetic bead-AuNP-probe-polystyrene (MAPP) bead. We designed and fabricated a microfluidic chip that contained only a magnetic separator and a particle trap. The presence of Hg2+ cut the PS-RNA probe, leading to the separation of magnetic beads and polystyrene microspheres. The MAPP was removed by the magnetic separator, while the cut polystyrene microspheres flowed along the channel and accumulated in the particle trap, forming a long visible strip. The length of the polystyrene microsphere strip was proportional to the Hg2+ concentration. The microfluidic biosensing platform exhibited high sensitivity and specificity for Hg2+ detection, with a detection limit of 21.9 nM. By integrating the microfluidic magnetic manipulation system with a sensitive nucleic acid probe, we developed an automated and visual biosensor that is a valuable reference for the on-site visual detection of heavy metal ions.

Closed-Loop Magnetic Manipulation for Robotic Transesophageal Echocardiography

This article presents a closed-loop magnetic manipulation framework for robotic transesophageal echocardiography (TEE) acquisitions. Different from previous work on intracorporeal robotic ultrasound acquisitions that focus on continuum robot control, we first investigate the use of magnetic control methods for more direct, intuitive, and accurate manipulation of the distal tip of the probe. We modify a standard TEE probe by attaching a permanent magnet and an inertial measurement unit (IMU) sensor to the probe tip and replacing the flexible gastroscope with a soft tether containing only wires for transmitting ultrasound and IMU data and show that six-degree-of-freedom (DOF) localization and five-DOF closed-loop control of the probe can be achieved with an external permanent magnet based on the fusion of internal inertial measurement and external magnetic field sensing data. The proposed method does not require complex structures or motions of the actuator and the probe compared with existing magnetic manipulation methods. We have conducted extensive experiments to validate the effectiveness of the framework in terms of localization accuracy, update rate, workspace size, and tracking accuracy. In addition, our results obtained on a realistic cardiac tissue-mimicking phantom show that the proposed framework is applicable in real conditions and can generally meet the requirements for teleoperated TEE acquisitions.

Giant Nonvolatile Electric Field Control of Proximity‐Induced Magnetism in the Spin–Orbit Semimetal SrIrO3

AbstractWith its potential for drastically reduced operation power of information processing devices, electric field control of magnetism has generated huge research interest. Recently, novel perspectives offered by the inherently large spin–orbit coupling of 5d transition metals have emerged. Here, nonvolatile electrical control of the proximity‐induced magnetism in SrIrO3 based back‐gated heterostructures is demonstrated. Up to a 700% variation of the anomalous Hall conductivity (σAHE) and Hall angle (ΘAHE) as function of the applied gate voltage Vg is reported. In contrast, the Curie temperature TC ≈ 100 K and magnetic anisotropy of the system remain essentially unaffected by Vg indicating a robust ferromagnetic state in SrIrO3 which strongly hints to gating‐induced changes of the anomalous Berry curvature. The electric‐field induced ferroelectric‐like state of SrTiO3 enables nonvolatile switching behavior of σAHE and ΘAHE below 60 K. The large tunability of this system, opens new avenues toward efficient electric‐field manipulation of magnetism.

Fully Integrated Microfluidic Device for Magnetic Bead Manipulation to Assist Rapid Reaction and Cleaning.

Methods to manipulate magnetic beads are essential factors to determine the efficiency and dimension of an in vitro diagnostic system. Currently, using movable permanent magnets and planar electromagnets is still the major approach to achieve magnetic bead control, causing significant constraint in the miniaturization of in vitro diagnostic systems. Here, we propose techniques to construct a fully integrated microfluidic device that can conduct automatic magnetic bead manipulation as well as rapid chemical reaction and cleaning in a minimized dimension similar to a USB disk. The device combines the precision control of multiple electromagnetic coils with the compactness of microfluidic channels, leading to one of the smallest automatic magnetic bead manipulation systems that can complete several major magnetic bead-based operation steps such as sample injection, reaction, cleaning, and collection. The influencing factors such as coil driving parameters, surface treatment of the microchannels, and properties of magnetic particles have also been investigated to optimize the device performance. The device can drive mixtures of Fe3O4 microparticles and polymer magnetic beads (PMBs) with a weight ratio of 1:1 at a maximum speed of 0.5 cm·s-1 and reduce the time for DNA binding and dissociation reactions from 20 min to only 48 s. This device has significantly advanced the conventional manipulation methods of magnetic beads and has demonstrated the possibility to construct an automatic and ultraminiaturized in vitro diagnostic system that may facilitate portable or even wearable chemical analysis.

All-solid integratable device of electric field control of magnetism based on hydrogen ion migration in La1−xSrxMnO3

Field-effect transistors based on semiconductor integration technology have come to a bottleneck, while electric field control of magnetism has great potential for applications in next-generation magnetic memory and calculators based on electron spins. Magnetic properties manipulation from a mechanism of ion migration driven by an electric field has the advantages of low energy consumption, nonvolatility, reproducibility, and durability. Here, we introduce a solid-state integratable hydrogen ion storage electrolyte silicon phosphate as the gate to achieve reversible control of magnetoresistance, magnetism, and magnetic interaction in the La1−xSrxMnO3/SrTiO3 ferromagnetic system. The controllable double-exchange interaction and spin scattering mechanism sketch the theoretical physical picture for these results. This work is expected to open up additional opportunities in the translation of electric control of magnetism into practical applications.

Lab‐in‐a‐Bead: Magnetic Janus Bead Probe for the Detection of Biomarkers in Blood

AbstractRemotely handled miniaturized colorimetric sensor platforms with multiple functionalities are able to mimic conventional laboratory operations with reduced assets. The integration of a magnetic phase in a miniaturized hydrogel sensor system allows the manipulation of the sensor, under a magnetic field, in a programmable manner. However, dark color interferences from conventional magnetic phases (Fe3O4, Fe2O3, and Fe micro/nanoparticles) affect the signal readout, hindering the colorimetric response. Therefore, a novel Janus bead configuration is introduced and tested by the localized incorporation of ferromagnetic iron microparticles into a TiO2 nanotubes/alginate hydrogel bead biosystem, under an applied magnetic field. The so‐called hydrogel Janus bead shows both, magnetic translocation and biosensing properties in the same bead. These beads are used for the direct colorimetric analysis of biomarkers in blood. The surface of the Janus bead prevents the biofouling of red blood cells, keeping the sensor surface clean for accurate optical colorimetric analysis. Moreover, the external magnetic manipulation of the bead permits precise control of the time and position of the bead in the sample. Therefore, multiple functionalities are presented by a single magnetic TiO2 nanotubes/alginate Janus bead such as actuation, low biofouling, and sensing, positioning this technology as a truly Lab‐in‐a‐Bead System.