Liquid metal spiral coil enabled soft electromagnetic actuator

Soft robot is a kind of machine form with flexible deformation capability. Making flexible actuators has recently become a hot research topic in the field. In this study, we demonstrated the facile fabrication of a soft electromagnetic actuator using liquid metal coil of Ga-In alloys, and designed several illustrative mechanical devices, such as jellyfish like robot, soft fishtail and flexible manipulator. Measurements of the liquid metal coil's electrical properties confirmed that the liquid metal coil was mechanically stable under 48% uniaxial strains. Furthermore, the resistance of the liquid metal coil is stable under 60° bending deformation. Tests on the liquid metal coil's driving properties confirmed that the liquid metal coil(55 mm×55 mm×1 mm) could reach the maximum displacement amplitude of 21.5 mm with the current of 0.48 A. It was shown that the electromagnetic interaction between the magnet and the liquid metal coil enables the coil as a highly efficient actuator. The mechanisms lying behind were interpreted and future applications of such system were discussed.

A Modified Iterative Learning Control Approach for the Active Suppression of Rotor Vibration Induced by Coupled Unbalance and Misalignment

This paper proposes a modified iterative learning control(MILC)periodical feedback-feedforward algorithm to reduce the vibration of a rotor caused by coupled unbalance and parallel misalignment.The control of the vibration of the rotor is provided by an active magnetic actuator(AMA).The iterative gain of the MILC algorithm here presented has a self-adjustment based on the magnitude of the vibration.Notch filters are adopted to extract the synchronous(1×Ω)and twice rotational frequency(2×Ω)components of the rotor vibration.Both the notch frequency of the filter and the size of feedforward storage used during the experiment have a real-time adaptation to the rotational speed.The method proposed in this work can provide effective suppression of the vibration of the rotor in case of sudden changes or fluctuations of the rotor speed.Simulations and experiments using the MILC algorithm proposed here are carried out and give evidence to the feasibility and robustness of the technique proposed.

Delivering Microrobots in the Musculoskeletal System

Disorders of the musculoskeletal system are the major contributors to the global burden of disease and current treatments show limited efficacy.Patients often suffer chronic pain and might eventually have to undergo end-stage surgery.Therefore,future treatments should focus on early detection and intervention of regional lesions.Microrobots have been gradually used in organisms due to their advantages of intelligent,precise and minimally invasive targeted delivery.Through the combination of control and imaging systems,microrobots with good biosafety can be delivered to the desired area for treatment.In the musculoskeletal system,microrobots are mainly utilized to transport stem cells/drugs or to remove hazardous substances from the body.Compared to traditional biomaterial and tissue engineering strategies,active motion improves the efficiency and penetration of local targeting of cells/drugs.This review discusses the frontier applications of microrobotic systems in different tissues of the musculoskeletal system.We summarize the challenges and barriers that hinder clinical translation by evaluating the characteristics of different microrobots and finally point out the future direction of microrobots in the musculoskeletal system.

Tailorable,Lightweight and Superelastic Liquid Metal Monoliths for Multifunctional Electromagnetic Interference Shielding

Liquid metal(LM)has become an emerging material paradigm in the electromagnetic interference shielding field owing to its excellent electrical conductivity.However,the processing of lightweight bulk LM composites with finite package without leakage is still a great challenge,due to high surface tension and pump-out issues of LM.Here,a novel confined thermal expansion strategy based on expandable microsphere(EM)is proposed to develop a new class of LM-based monoliths with 3D continuous conductive network.The EM/LM monolith(EM/LMm)presents outstanding performance of lightweight like metallic aerogel(0.104 g cm^(-1)),high strength(3.43 MPa),super elasticity(90%strain),as well as excellent tailor ability and recyclability,rely on its unique gas-filled closed-cellular structure and refined LM network.Moreover,the assembled highly conducting EM/LMm exhibits a recorded shielding effectiveness(98.7 dB)over a broad frequency range of 8.2-40 GHz among reported LM-based composites at an ultra-low content of LM,and demonstrates excellent electromagnetic sealing capacity in practical electronics.The ternary EM/LM/Ni monoliths fabricated by the same approach could be promising universal design principles for multifunctional LM composites,and applicable in magnetic responsive actuator.

Solar-powered miniature robot for on-site oil spill treatment under magnetic steering

Walking on the water surface is an effective method for miniature robots to transport payloads with dramatically decreased interfacial drag. Current aquatic robots reported are generally actuated by a beam of focused light that can trigger asymmetrical deformation, enabling the directional movement through horizontal momentum transfer of photoinduced actuation force to the water. However, the operations are heavily dependent on manual manipulation of the focused light, making the long-term actuation and application of the aquatic robots in vast scenarios challenging. Herein, we developed a kind of water striderinspired robot that can autonomously manage the motion on the water surface under solar irradiation, with their direction steerable by a magnetic field. The motion of this bioinspired robot on the water surface was achieved by the use of a solar cell panel as a driving module to enable propulsive motion based on the conversion of light-electric-mechanical energies. The superhydrophobic design of its leg surfaces enables the aquatic robots with weight-bearing and drag-reducing abilities. With the assistance of magnetic navigation, the bioinspired robot can continuously and controllably locomote to the oily spill floating on the water body and collect them with high efficiency. For further demonstration, the treatment of oil spills in a campus pool with high efficiency has also been achieved. This on-site oil-spill treating strategy, taking advantage of a home-made bioinspired robot actuated by natural sunlight under magnetic steering, shows great potential applications in water-body remediation.

New Generation of Outdoor Vacuum Circuit Breakers with Rated Voltage up to 40.5 kV

The article describes design peculiarities of the novel compact vacuum circuit breaker with rated voltage 40.5 kV. The design incorporates several novel technical solutions： polycarbonate support insulation, mono-stable magnetic actuator, labyrinth pulling insulator, core-type flexible contact and new compact vacuum interrupter （VI）. Phases are encapsulated into silicone rubber providing required creepage distance and excellent tracking resistance. These novelties along with extensive modeling of the mechanical and electrical fields followed by design optimization resulted in weight reduction of more than 50% compared with alternatives available in the market. And this is in spite of built in sensors measuring： phase currents, zero-sequence current, phase voltages.

Detection of pathogenic bacteria by magneto-immunoassays:a review

Magnetic particle-based immunoassays are widely used in microbiology-related assays for both microbial capture,separation,analysis,and detection.Besides facilitating sample operation,the implementation of micro-to-nanometer scale magnetic beads as a solid support potentially shortens the incubation time(for magnetic immuno capture)from several hours to less than an hour.Analytical technologies based on magnetic beads offer a rapid,effective and inexpensive way to separate and concentrate the target analytes prior to detection.Magneto-immuno separation uses magnetic particles coated with specific antibodies to capture target microorganisms,bear the corresponding antigens,and subsequently separate them from the sample matrix in a magnetic field.The method has been proven effective in separating various types of pathogenic bacteria from environmental water samples and in eliminating background interferences.Magnetic particles are often used to capture target cells(pathogenic bacteria)from samples.In most commercially available assays,the actual identification and quantitation of the captured cells is then performed by classical microbiological assays.This review highlights the most sensitive analytic methods(i.e.,long-range surface plasmon resonance and electrochemical impedance spectroscopy)to detect magnetically tagged bacteria in conjunction with magnetic actuation.

A Programmable Inchworm-Inspired Soft Robot Powered by a Rotating Magnetic Field

With the growing demand for miniaturized workspaces,the demand for microrobots has been increasing in robotics research.Compared to traditional rigid robots,soft robots have better robustness and safety.With a flexible structure,soft robots can undergo large deformations and achieve a variety of motion states.Researchers are working to design and fabricate flexible robots based on biomimetic principles,using magnetic fields for cable-free actuation.In this study,we propose an inchworm-shaped soft robot driven by a magnetic field.First,a robot is designed and fabricated and force analysis is performed.Then,factors affecting the soft robot’s motion speed are examined,including the spacing between the magnets and the strength and frequency of the magnetic field.On this basis,the motion characteristics of the robot in different shapes are explored,and its motion modes such as climbing are experimentally investigated.The results show that the motion of the robot can be controlled in a two-dimensional plane,and its movement speed can be controlled by adjusting the strength of the magnetic field and other factors.Our proposed soft robot is expected to find extensive applications in various fields.

Magnetostrictive and Kinematic Model Considering the Dynamic Hysteresis and Energy Loss for GMA

Due to the influence of magnetic hysteresis and energy loss inherent in giant magnetostrictive materials （GMM）, output displacement accuracy of giant magnetostrictive actuator （GMA） can not meet the precision and ultra precision machining. Using a GMM rod as the core driving element, a GMA which may be used in the field of precision and ultra precision drive engineering is designed through modular design method. Based on the Armstrong theory and elastic Gibbs free energy theory, a nonlinear magnetostriction model which considers magnetic hysteresis and energy loss characteristics is established. Moreover, the mechanical system differential equation model for GMA is established by utilizing D＇Alembert＇s principle. Experimental results show that the model can preferably predict magnetization property, magnetic potential orientation, energy loss for GMM. It is also able to describe magnetostrictive elongation and output displacement of GMA. Research results will provide a theoretical basis for solving the dynamic magnetic hysteresis, energy loss and working precision for GMA fundamentally.

Magnetic Kirigami by Laser Cutting

Magnetic kirigami with tunable configurations under magnetic actuation is of significant interest in various emerging fields.However,there remains a grand challenge to develop magnetic kirigami with a facile fabrication strategy,programmable mag-netization,and functionality.In this work,we present a novel magnetic kirigami that is readily fabricated by the laser cutting technique.The magnetic kirigami consists of an array of magnetic microplates,each with a programmed magnetization.By applying an actuation magnetic field,each microplate can rotate and even flip,allowing for predesigned kirigami configura-tions.By further coating the surface of the microplate array,the magnetic kirigami can be programmed with functionality.We demonstrate a potential application of information encryption by engineering magnetic kirigami into a magneto-responsive QR code.Providing a simple fabrication strategy,our work paves the way for other applications of magnetic kirigami.

Magnetic Actuation Systems and Magnetic Robots for Gastrointestinal Examination and Treatment

Magnetic actuation technology(MAT)provides novel diagnostic tools for the early screening and treatment of digestive cancers,which have high morbidity and mortality rates worldwide.The application of magnetic actuation systems and magnetic robots in gastrointestinal(GI)diagnosis and treatment to provide a comprehensive reference manual for scholars in the field of MAT research are reviewed.It describes the basic principles of magnetic actuation and magnetic field safety,introduces the design,manufacturing,control,and performance parameters of magnetic actuation systems,as well as the applicability and limitations of each system for different parts of the GI tract.It analyzes the characteristics and advantages of different types and functions of magnetic robots,summarizes the challenges faced by MAT in clinical applications,and provides an outlook on the future prospects of the field.

3D-printed tissue repair patch combining mechanical support and magnetism for controlled skeletal muscle regeneration

Physical forces,such as magnetic and mechanical stimulation,are known to play a significant role in the regulation of cell response.In the present study,a biomimetic regeneration patch was fabricated using E-jet 3 D printing,which integrates mechanical and magnetic stimulation in a biocompatible"one-pot reaction"strategy when combined with a static magnetic field(SMF).The magneto-based therapeutic regeneration patch induced myoblasts to form aligned and multinucleated myotubes,regulated the expression of myogenic-related genes,and activated the p38αmitogen-activated protein kinase pathway via the initiation of myogenic differentiation.To validate the efficiency of the proposed strategy,the regeneration patch was implanted into mice and exposed to a suitable SMF,which resulted in significantly enhanced in vivo skeletal muscle regeneration.The findings demonstrated that appropriate external physical stimulation provides a suitable biophysical microenvironment that is conducive to tissue regeneration.The method used in the present study represents a promising technique to induce the regeneration of damaged skeletal muscle tis sue.

A 3D hard-magnetic rod model based on co-rotational formulations

Hard-magnetic soft materials have attracted broad interests because of their flexible programmability,non-contact activation and rapid response in various applications such as soft robotics,biomedical devices and flexible electronics.Such multifunctional materials consist of a soft matrix embedded with hard-magnetic particles,and can exhibit large deformations under external magnetic stimuli.Here,we develop a three-dimensional(3D)rod model to predict spatial deformations(extension,bending and twist)of slender hard-magnetic elastica.The model follows Kirchhoff hypothesis and thus reduces the 3D magneto-elastic energy function to a one-dimensional(1D)form.Besides,the co-rotational formulation is applied to describe rigid body motion,and explicit time integration is adopted for the nonlinear resolution.Moreover,we explore finite bending,post-buckling and twisting of hard-magnetic elastica under external magnetic fields with different directions and amplitudes.Representative examples with various configurations show superior efficiency and accuracy of the model(the difference less than 1%with only a small number of elements)compared to conventional solid element.Our model could be used to guide rational designs on programmable shape morphing of ferromagnetic slender structures.

Magnetic Actuated Shape-memory Helical Microswimmers with Programmable Recovery Behaviors

Inspired by bacterial flagella in nature,magnetic helical microswimmer is an ideal model to perform complex task in a low Reynolds number environments.Shape Memory Polymers(SMPs)with desirable properties are considered as one of the most preferred options for the development of small-scale robots.However,fabricating and programming strategies are still challenging.Here,we report an approach to fabricate helical microswimmers based on thermoplastic SMP(polylactic acid).Melt-spun polylactic acid fibers containing magnetic particles were enwound to form helical microstructures.Their shape recovery behaviors were programmed by annealing and pre-deformation.Three forms of helical microswimmers(constant-helix-angle conical helix,constant-pitch conical helix,and straight helix)with controlled morphological parameters were tailored.The obtained microswimmers showed 3D locomotion capability under rotating magnetic fields.The maximum swimming velocity of microswimmers was nearly six body lengths per second,and the near-wall swimming of conical helixes along their sharp end exhibited a smaller drift.Moreover,we demonstrated programmed shape-switching processes(spring-like contraction and elongation,coiling and uncoiling)and self-repairing of the microswimmers.As demonstrations of potential applications,tasks of mobile microstent,cargo delivery,and minimally invasive injection were carried out.The multifunctional shape-memory microswimmers have immense potential in a variety of applications.

Design and Characterization of Magnetically Actuated Helical Swimmers at Submillimeter-scale

Bacteria with helical flagella show an ideal mechanism to swim at low Reynolds number. For application of artificial mi- croswimmers, it is desirable to identify effects of structural and geometrical parameters on the swimming performance. In this study, a double-end helical swimmer is proposed based on the usual single-end helical one to improve the forward-backward motion symmetry, The propulsion model of the artificial helical microswimmer is described. Influences of each helix parameter on the swimming velocity and propulsion efficiency are further analyzed. The optimal design for achieving a maximum propulsion velocity of submillimeter scale swimmers is performed based on some constraints. An experimental setup consisting of three-pair of Helmholtz coils is built for the helical microswimmers. Experiments of microswimmers with several groups of parameters were performed, and the results show the validity of the analysis and design.

On-chip immunomagnetic bead swarm based on magnetic actuation and mechanical vibration for biological detection

Immunomagnetic bead(IMB)-based detection has great potential for biomedical applications.Passive and active strategies,including microfluidics and magnetic actuation methods,have been developed to mix IMBs and analytes efficiently.However,cost-effective on-site detection using a simple microfluidic chip is challenging,and miniaturization of the magnetic driving device is imperative for portability.In this study,we propose a novel mixing method for an on-chip IMB swarm via magnetic actuation and mechanical vibration.A microfluidic chip system coupled with double spiral magnetic coils and a vibration motor was fabricated.The aggregation behavior of IMBs under magnetic fields and the diffusion behavior of the IMB swarm under mechanical vibration were analyzed in detail.Based on the synergetic effects of magnetic actuation and mechanical vibration,we achieved the highly efficient capturing of Vibrio parahaemolyticus DNA and goat anti-human immunoglobulin G by mixing the IMB swarm with the microfluidic chip.In this case,the antigen detection rate could reach~94.4%.Given its fascinating features,such IMB-microfluidic detection demonstrates significant potential for biomedical applications.

Characteristic investigation of permanent magnet actuator for vacuum contactors operating with an intrinsically safe low voltage

This paper reports a new application of permanent magnet actuator for vacuum contactors.A novel permanent magnet(PM) actuator to drive a vacuum contactor with intrinsically safe and low supply voltage is proposed.PM is mounted on the static iron of the contactor to enhance its holding force and reliability.While only one coil is used to break the vacuum contactor,two series coils are deployed to yield a high magnetomotive force to realize the making operation.The electrical circuit equation,mechanical equation and magnetic field are all coupled in the simulation.A prototype is manufactured and tested to validate and showcase the performance of the contactor which is equipped with the proposed PM actuator.

Fabrication of cellulose based superhydrophobic microspheres for the production of magnetically actuatable smart liquid marbles

Cellulose microspheres were fabricated on the basis of sol-gel transition using NaOH/urea/H_(2)O as the solvent system.These microspheres had an average diameter of about 30μm.Upon modification with Fe_(3)O_(4) and poly(DOPAm-co-PFOEA),superhydrophobic magnetic cellulose microspheres were generated,which were analyzed by FTIR,TG,XRD,XPS and water contact angle tests.Magnetic cellulose microspheres contained approximately 15 wt%of Fe_(3)O_(4).Poly(DOPAm-co-PFOEA)/Fe_(3)O_(4)/cellulose microspheres and had a low surface energy and a high water-repellency.These superhydrophobic microspheres were also converted into liquid marbles via an easily scalable process.

Design of 4D printed shape-changing tracheal stent and remote controlling actuation

has a good application prospect.The biodegradable stent can effectively reduce the damage to patients and improve the therapeutic performance of stents.In this work,a series of shape memory polylactic acid(Fe_(3)O_(4))composite tracheal stents were manufactured by 4D printing.The composite tracheal stents with different structures were designed.Moreover,with the addition of magnetic particles Fe3 O4,the shape memory PLA/Fe_(3)O_(4)composite tracheal stent has a magnetic driving effect.Under the magnetic field,the shape recovery process is completed within 40 s,and the shape recovery rate is more than 99%.Moreover,the 4D printed tracheal stent was also triggered by the irradiation of infrared lamp to realize the remote controlling recovery.The research on the structure design and driving method of 4D printing tracheal stent expands the application scope of shape memory polymer composites in biomedical field,provides a new way for personalized implantable medical devices and minimally invasive surgery.It is of great significance for better precision medical treatment.

Shape memory poly(ether ether ketone)s with tunable chain stiffness,mechanical strength and high transition temperatures

Shape memory polymers,with intrinsic enhanced strength and high thermal stability,are highly demanded in aerospace,engineering manufacturing,and spatial structures.In this paper,we develop a series of thermoplastic shape memory poly(ether ether ketone)s(PEEKs)for the first time,achieving an excellent shape memory ability,high strength,and great thermal stability via a condensation polymerization.Through tuning the proportion of different bisphenol monomers,the flexibility of molecular main chains is adjusted,resulting in the regulation of transition temperature and mechanical performances.Synthesized PEEKs possess the tunable T_(g) from 143.3°C to 178.6°C,the enhanced tensile strength from 48.4 to 65.1 MPa,and Young’s modulus from 0.45 to 1.8 GPa,in addition to the excellent heat-triggered shape memory effect,as indicated by high recovery ratio(94%–98.9%)and fixity ratio(over 99.5%).Furthermore,after incorporating the magnetocaloric Fe_(3)O_(4) particles,the composites exhibit remotely noncontact magnetic-triggered shape memory behaviors(Fe_(3)O_(4) content over 10 wt%).These synthesized T_(g) tunable shape memory PEEKs and the composites have wide utilization potential in fields of engineering and aerospace structures,owing to the excellent mechanical properties,thermal stability,unique programmable deformation ability,and remote actuation.