Magnetic Actuation Research Articles

Magnetically Controllable Paper-Based Soft Robots for Colorimetric Detection of Heavy Metal Ions.

Magnetically controllable soft robots are of great interest because they have unique properties compared with conventional rigid counterparts and can be used in diverse applications such as intelligent electronics, bionics, personalized medicine, and cargo grasping. However, the fabrication of such multifunctional soft robots has been challenging because of the integration of dissimilar materials into the robot body. Herein, we designed and fabricated a soft robotic multifunctional system using conventional papers and elastomeric polymers for the colorimetric detection of heavy metal ions (Hg2+ and Fe3+) in water samples. The magnetic actuation of the platforms was shown to correlate with the type of underlying paper and magnetic particle content in the mixtures. Moreover, it was observed that actuation can also be manipulated by controlling the magnetic field strength. A proof-of-concept robotic paper-based Hg2+, Zn2+, and Fe3+ ion detection was demonstrated by combining colorimetric paper sensors and magneto-papers. Our study highlights the significant potential of paper as a material for the fabrication of effective and multifunctional untethered soft robots.

A magnetically driven symmetrical leech-inspired soft robot for various applications

In this study, we present a symmetrical leech-inspired soft robot that employs a magnetic actuation system for precise movement control. The robot weighs only 1.17 g and has a symmetrical micro-concave structure that maintains a stable kinematic posture during high-frequency motion. The gravity generated by the magnets is used to simulate the attraction of the two suckers of the leech. The experimental results show that the micro-concave structure is designed to achieve a robot velocity of up to 22.66 mm/s under 45 Gauss conditions, which is a better kinematic performance compared to the single symmetric structure (with a velocity of 13.2 mm/s). According to our experiments testing the robot in different motion modes, it has shown the ability to stably climb over obstacles, transport objects, and detect solutions, demonstrating its potential for diverse applications in healthcare, emergency rescue, and environmental monitoring.

Confined Z-Pinch Magnetic Nozzle : A New Approach to Space Propulsion System that Utilizes Trapped Charged Particles

This paper provides a theoretical overview of a Z-pinch magnetic nozzle plasma propulsion system designed for Low Earth Orbit (LEO). The system utilizes trapped charged particles from the spacecraft's environment and magnetic confinement to generate thrust, reducing the need for onboard propellants. By employing a magnetic mirror configuration, the plasma is confined and accelerated to create propulsion. The proposed propulsion system is tailored to function in the dynamic space radiation environment of LEO, particularly in polar orbits, accounting for variations in solar activity that affect trapped protons and electrons. The mechanism involves converting magnetic plasma energy into directed kinetic energy, facilitating efficient plasma detachment and momentum transfer to the spacecraft. This study examines the feasibility, design overview, and constraints of implementing this propulsion technology. Key challenges include the variability of the space environment, technological complexities, radiation effects, plasma detachment efficiency, energy requirements, and material durability. Overcoming these challenges through innovative engineering and rigorous testing is essential for successful implementation. The Z-pinch magnetic nozzle plasma propulsion system promises to advance space propulsion technology, offering a more efficient and cost-effective method for satellite operations in LEO. With further research and development, it has the potential to support future satellite missions and space exploration initiatives.

Ferromagnetic Fiber Systems for Multiplexing Neural Recording and Modulation with Spatial Selectivity

AbstractDespite the great success achieved by recently developed neural interfaces, multi‐site monitoring and regulating neural activities with high spatial and temporal selectivity remain a challenge. Here, an implantable, remotely controllable, fiber‐based ferromagnetic system permitting 3D navigation, omnidirectional steering, multiplexing neural recording, and modulation is presented. A family of fibers is fabricated that allows for the heterogeneous integration of ferromagnetic, optical, microfluidic, electrical, and electrochemical components into the proposed multifunctional neural interface. Coupling with magnetic actuation, it is demonstrated that this system can enable optical and chemical modulation of local neural activities across multiple distant regions in rodent brains, while simultaneously allowing the real‐time monitoring of neural electrophysiological and chemical activities. Furthermore, to systematically identify altered patterns of behaviors, brain activities and dopamine release during optogenetic modulation of specific nuclei in Parkinsonian animals this platform is employed. This proposed system with high spatial selectivity, multiplexing sensing and multimodal manipulating capabilities offers a versatile platform to advance both fundamental neuroscience studies and translational applications in neurologic disease treatments.

Hybrid trajectory planning of two permanent magnets for medical robotic applications

Independent robotic manipulation of two large permanent magnets, in the form of the dual External Permanent Magnet (dEPM) system has demonstrated the possibility for enhanced magnetic control by allowing for actuation up to eight magnetic degrees of freedom (DOFs) at clinically relevant scales. This precise off-board control has facilitated the use of magnetic agents as medical devices, including catheter-like soft continuum robots (SCRs). The use of multiple robotically actuated permanent magnets poses the risk of collision between the robotic arms, the environment, and the patient. Furthermore, unconstrained transitions between actuation inputs can lead to undesired spikes in magnetic fields potentially resulting in unsafe manipulator deformation. This paper presents a hybrid approach to trajectory planning for the dEPM platform. This is performed by splitting the planning problem in two: first finding a collision-free physical path for the two robotically actuated permanent magnets before combining this with a path in magnetic space, which permits for a smooth change in magnetic fields and gradients. This algorithm was characterized by actuating each of the eight magnetic DOFs sequentially, eliminating any potential collisions and reducing the maximum undesired actuation value by 203.7 mT for fields and by 418.7 mT/m for gradients. The effect of this planned magnetic field actuation on a SCR was then examined through two case studies. First, a tip-driven SCR was moved to set points within a confined area. Actuation using the proposed planner reduced movement outside the restricted area by an average of 41.3%. Lastly, the use of the proposed magnetic planner was shown to be essential in navigating a multi-segment magnetic SCR to the site of an aneurysm within a silicone brain phantom.

Magneto-mechanically derived diffusion processes in ultra-soft biological hydrogels

Magneto-active hydrogels (MAHs) consist of a polymeric network doped with magnetic particles that enable the material to mechanically respond to magnetic stimuli. This multifunctionality allows for modulation of mechanical properties in a remote and dynamic manner. These characteristics combined with the biocompatibility of hydrogels, make MAHs excellent for drug delivery and biological scaffolds. In this work, ultra-soft biological MAHs with strong magnetostriction are fabricated from human blood plasma (∼20 Pa). The material is experimentally tested using a novel in-house device that allows for a precise control of magnetic actuation conditions, enabling the hydrogel modulation in terms of mechanical deformation and stiffness. We study the impact of magnetic actuation on the solvent expulsion and diffusion dynamics within the polymeric network. To further elucidate the mechanisms driving solvent diffusion processes, a computational framework for modeling the diffusion process of two different species within a magneto-responsive material is proposed. These experimental and computational outcomes open exciting new opportunities for the use of ultra-soft MAHs in bioengineering applications.

Magnetically Actuated Nanomaterials in Biomedical Applications

Magnetic nanomaterials, distinguished by their unique magnetic phenomena, particularly their magnetically actuated capabilities, have found widespread application in the field of nanomedicine. Compared with alternative driving mechanisms, magnetic actuation as a remote, highly permeable, and precisely controllable driving strategy endows nanomaterials with temporal and spatia mobility, making it possible to initiate and cease multiple forms of movement in vivo at will. When coupled with cutting‐edge diagnostic and treating techniques including but not limited to magnetic resonance imaging, magnetothermal therapy, and magnetoelectric stimulation, magnetically actuated nanomaterials offer the potential for visual analysis, provision of reliable molecular information, and effective disease or tissue damage intervention. This review comprehensively outlines the synthesis methodologies, functional strategies, and biomedical applications of magnetically actuated nanomaterials within nanomedicine. Additionally, the future developments and applications of biocompatible magnetically actuated nanomaterials, especially in response to time‐varying magnetic fields, are anticipated.

Magnetic/Acoustic Dual-Controlled Microrobot Overcoming Oto-Biological Barrier for On-Demand Multidrug Delivery against Hearing Loss.

Multidrug combination therapy in the inner ear faces diverse challenges due to the distinct physicochemical properties of drugs and the difficulties of overcoming the oto-biologic barrier. Although nanomedicine platforms offer potential solutions to multidrug delivery, the access of drugs to the inner ear remains limited. Micro/nanomachines, capable of delivering cargo actively, are promising tools for overcoming bio-barriers. Herein, a novel microrobot-based strategy to penetrate the round window membrane (RWM) is presented and multidrug in on-demand manner is delivered. The tube-type microrobot (TTMR) is constructed using the template-assisted layer-by-layer (LbL) assembly of chitosan/ferroferric oxide/silicon dioxide (CS/Fe3O4/SiO2) and loaded with anti-ototoxic drugs (curcumin, CUR and tanshinone IIA, TSA) and perfluorohexane (PFH). Fe3O4 provides magnetic actuation, while PFH ensures acoustic propulsion. Upon ultrasound stimulation, the vaporization of PFH enables a microshotgun-like behavior, propelling the drugs through barriers and driving them into the inner ear. Notably, the proportion of drugs entering the inner ear can be precisely controlled by varying the feeding ratios. Furthermore, in vivo studies demonstrate that the drug-loaded microrobot exhibits superior protective effects and excellent biosafety toward cisplatin (CDDP)-induced hearing loss. Overall, the microrobot-based strategy provides a promising direction for on-demand multidrug delivery for ear diseases.

Model-Based Design and Testbed for CubeSat Attitude Determination and Control System with Magnetic Actuation

Model-Based Design and Testbed for CubeSat Attitude Determination and Control System with Magnetic Actuation

Curved Surfaces Induce Metachronal Motion of Microscopic Magnetic Cilia.

Cilia are hair-like organelles present on cell surfaces. They often exhibit a collective wave-like motion that can enhance fluid or particle transportation function, known as metachronal motion. Inspired by nature, researchers have developed artificial cilia capable of inducing metachronal motion, especially magnetic actuation. However, current methods remain intricate, requiring either control of the magnetic or geometrical properties of individual cilia or the generation of a complex magnetic field. In this paper, we present a novel elegant method that eliminates these complexities and induces metachronal motion of arrays of identical microscopic magnetic artificial cilia by applying a simple rotating uniform magnetic field. The key idea of our method is to place arrays of cilia on surfaces with a specially designed curvature. This results in consecutive cilia experiencing different magnetic field directions at each point in time, inducing a phase lag in their motion, thereby causing collective wave-like motion. Moreover, by tuning the surface curvature profile, we can achieve diverse metachronal patterns analogous to symplectic and antiplectic metachronal motion observed in nature, and we can even devise novel combinations thereof. Furthermore, we characterize the local flow patterns generated by the motion of the cilia, revealing the formation of vortical patterns. Our novel approach simplifies the realization of miniaturized metachronal motion in microfluidic systems and opens the possibility of controlling flow pattern generation and transportation, opening avenues for applications such as lab-on-a-chip technologies, organ-on-a-chip platforms, and microscopic object propulsion.

Dynamics of resonant magnetoelectric effect in a magnetoactive elastomer based cantilever: Magnetic field induced orientation transition and giant frequency tuning

Magnetoelectric (ME) effects in composite heterostructures containing mechanically coupled ferromagnetic and piezoelectric layers enable the mutual transformation of magnetic and electric fields and form the basis for the development of magnetic field sensors, actuators and energy harvesters. Promising materials for such composite structures are magnetoactive elastomers (MAE), which are silicone matrices with ferromagnetic particles uniformly distributed within them. The strong dependence of MAE properties on magnetic fields and their low rigidity enable contactless control of ME effects characteristics within such structures. In this work we have experimentally investigated the dynamics of resonant ME effects in a structure consisting of a MAE layer with carbonyl iron particles and a layer of polyvinylidene fluoride piezopolymer in a cantilever geometry. For the structure magnetized in a plane along the axis, the frequency tuning of the bending oscillations reached 360 % at the fields up to 2 kOe, and the maximum ME conversion coefficient was 1.74 V/(Oe·cm). For the structure magnetized perpendicular to the plane, an orientation transition was observed, which manifested itself as a jump-like bending of the structure to the angle up to ∼850 at magnetic field above the critical value. The frequency tuning by the magnetic field reached 185 %, and the maximum ME conversion coefficient was 135 V/(Oe·cm). A model has been developed that qualitatively describes the dynamics of ME effect in composite cantilever structures with a MAE layer for different orientations of the applied magnetic field.

Magnetoactive, Kirigami-Inspired Hammocks to Probe Lung Epithelial Cell Function

IntroductionMechanical forces provide critical biological signals to cells. Within the distal lung, tensile forces act across the basement membrane and epithelial cells atop. Stretching devices have supported studies of mechanical forces in distal lung epithelium to gain mechanistic insights into pulmonary diseases. However, the integration of curvature into devices applying mechanical forces onto lung epithelial cell monolayers has remained challenging. To address this, we developed a hammock-shaped platform that offers desired curvature and mechanical forces to lung epithelial monolayers.MethodsWe developed hammocks using polyethylene terephthalate (PET)-based membranes and magnetic-particle modified silicone elastomer films within a 48-well plate that mimic the alveolar curvature and tensile forces during breathing. These hammocks were engineered and characterized for mechanical and cell-adhesive properties to facilitate cell culture. Using human small airway epithelial cells (SAECs), we measured monolayer formation and mechanosensing using F-Actin staining and immunofluorescence for cytokeratin to visualize intermediate filaments.ResultsWe demonstrate a multi-functional design that facilitates a range of curvatures along with the incorporation of magnetic elements for dynamic actuation to induce mechanical forces. Using this system, we then showed that SAECs remain viable, proliferate, and form an epithelial cell monolayer across the entire hammock. By further applying mechanical stimulation via magnetic actuation, we observed an increase in proliferation and strengthening of the cytoskeleton, suggesting an increase in mechanosensing.ConclusionThis hammock strategy provides an easily accessible and tunable cell culture platform for mimicking distal lung mechanical forces in vitro. We anticipate the promise of this culture platform for mechanistic studies, multi-modal stimulation, and drug or small molecule testing, extendable to other cell types and organ systems.

Topological optimal design of composite magnetic actuators to improve driving force and thermal conductivity

Topological optimal design of composite magnetic actuators to improve driving force and thermal conductivity

Liquid metal complexing Fe3O4 nanoparticles enable rapid polymerization of magnetically conductive hydrogels for various flexible electronics

Hydrogels have recently emerged as promising materials for the next-generation of bioelectronic, due to their similarities to biological tissues, versatility in electrical, mechanical, and bio-functional engineering. This study discoveries that the free radicals produced by co-sonication of Fe3O4 nanoparticles (Fe3O4 NPs) and liquid metal (LM) in aqueous solution can initiate the polymerization of acrylamide to prepare hydrogels. A suspension of LM- Fe3O4 was created and successfully initiated fast polymerization (< 2 min) of acrylamide to form a robust hydrogel with superior conductive properties. The hydrogel has all-encompassing adhesive properties, is highly injectable, and possesses magnetic actuation capabilities. Utilizing the conductive and magnetic properties of hydrogels, a dual control sensor for Morse code transmission was created. Employing the in-situ polymerization properties, a series of flexible electronic devices have been fabricated with hydrogel, including plant leaf electrodes, injectable plant electronic devices and zinc ion batteries. This work presents an unconventional strategy for integrating plants with electronics on the platform of hydrogels, which provides current research ideas in the fields of plant electrophysiology and wearable electronics.

Reprogrammable and reconfigurable mechanical computing metastructures with stable and high-density memory.

Mechanical computing encodes information in deformed states of mechanical systems, such as multistable structures. However, achieving stable mechanical memory in most multistable systems remains challenging and often limited to binary information. Here, we report leveraging coupling kinematic bifurcation in rigid cube-based mechanisms with elasticity to create transformable, multistable mechanical computing metastructures with stable, high-density mechanical memory. Simply stretching the planar metastructure forms a multistable corrugated platform. It allows for independent mechanical or magnetic actuation of individual bistable element, serving as pop-up voxels for display or binary units for various tasks such as information writing, erasing, reading, encryption, and mechanologic computing. Releasing the pre-stretched strain stabilizes the prescribed information, resistant to external mechanical or magnetic perturbations, whereas re-stretching enables editable mechanical memory, akin to selective zones or disk formatting for information erasure and rewriting. Moreover, the platform can be reprogrammed and transformed into a multilayer configuration to achieve high-density memory.

Immune Cell-Based Microrobots for Remote Magnetic Actuation, Antitumor Activity, and Medical Imaging.

Translating medical microrobots into clinics requires tracking, localization, and performing assigned medical tasks at target locations, which can only happen when appropriate design, actuation mechanisms, and medical imaging systems are integrated into a single microrobot. Despite this, these parameters are not fully considered when designing macrophage-based microrobots. This study presents living macrophage-based microrobots that combine macrophages with magnetic Janus particles coated with FePt nanofilm for magnetic steering and medical imaging and bacterial lipopolysaccharides for stimulating macrophages in a tumor-killing state. The macrophage-based microrobots combine wireless magnetic actuation, tracking with medical imaging techniques, and antitumor abilities. These microrobots are imaged under magnetic resonance imaging and optoacoustic imaging in soft-tissue-mimicking phantoms and ex vivo conditions. Magnetic actuation and real-time imaging of microrobots are demonstrated under static and physiologically relevant flow conditions using optoacoustic imaging. Further, macrophage-based microrobots are magnetically steered toward urinary bladder tumor spheroids and imaged with a handheld optoacoustic device, where the microrobots significantly reduce the viability of tumor spheroids. The proposed approach demonstrates the proof-of-concept feasibility of integrating macrophage-based microrobots into clinic imaging modalities for cancer targeting and intervention, and can also be implemented for various other medical applications.

Upscaling waste human hairs into micro/nanorobots for adsorptive removal of micro/nanoplastics

The escalating spread of micro/nanoplastics (MPs/NPs), originating from plastic waste fragmentation in the environment, is a growing global concern with detrimental effects on aquatic ecosystems. Previous methods for MPs/NPs treatment/removal poses significant challenges such as filtration, sedimentation efficiency, potential introduction of additional pollutants and expensive fabrication steps. In the current work, for the first-time keratin (KER)-based biohybrid micro/nanorobots obtained by facile decorations of iron-oxide microspheres with magnetic capabilities designed to dynamically remove (MPs/NPs) through various chemical/physical interactions, precise magnetic actuation, and improved surface functionalities. By integrating iron-oxide microspheres, keratin biohybrids achieve accurate motility and manipulation via external magnetic field regulation. This fuel free keratin magnetic micro/nanorobots (KMNRs) exhibit notable adsorptive removal efficiencies of 95% and 82% for (MPs/NPs) in water, offering diverse potentiality. Additionally, KMNRs demonstrated excellent recyclability, enhancing their sustainability. With eco-friendly, cost-effective, and real-world application attributes, designed KMNRs present an appealing approach to addressing MPs/NPs pollution.

Learning Soft Millirobot Multimodal Locomotion with Sim-to-Real Transfer.

With wireless multimodal locomotion capabilities, magnetic soft millirobots have emerged as potential minimally invasive medical robotic platforms. Due to their diverse shape programming capability, they can generate various locomotion modes, and their locomotion can be adapted to different environments by controlling the external magnetic field signal. Existing adaptation methods, however, are based on hand-tuned signals. Here, a learning-based adaptive magnetic soft millirobot multimodal locomotion framework empowered by sim-to-real transfer is presented. Developing a data-driven magnetic soft millirobot simulation environment, the periodic magnetic actuation signal is learned for a given soft millirobot in simulation. Then, the learned locomotion strategy is deployed to the real world using Bayesian optimization and Gaussian processes. Finally, automated domain recognition and locomotion adaptation for unknown environments using a Kullback-Leibler divergence-based probabilistic method are illustrated. This method can enable soft millirobot locomotion to quickly and continuously adapt to environmental changes and explore the actuation space for unanticipated solutions with minimum experimental cost.

An asymmetric rotor model under external, parametric, and mixed excitations: Nonlinear bifurcation, active control, and rub-impact effect

This article explores the nonlinear dynamical analysis and control of a [Formula: see text] DOF system that emulates the lateral vibration of an asymmetric rotor model under external, multi-parametric, and mixed excitation. The linear integral resonant controller ([Formula: see text]) has been coupled to the rotor as an active damper through a magnetic actuator. The complete mathematical model, governing the nonlinear interaction among the rotor, controller, and actuator, is derived based on electromagnetic theory and the principle of solid mechanics. This results in a discontinuous [Formula: see text] DOF system coupled with two [Formula: see text] DOF systems, incorporating the rub-impact effect between the rotor and stator. The complicated mathematical model is investigated using analytical techniques, employing the perturbation method, and validated numerically through time response, basins of attraction, bifurcation diagrams, [Formula: see text] chaotic test, and Poincaré return map. The main findings indicate that the asymmetric system model may exhibit nonzero bistable forward whirling motion under external excitation. Additionally, it can whirl either forward or backward under multi-parametric excitation, besides the trivial stable solution. Furthermore, in the case of mixed excitation, the rotor displays nontrivial tristable solutions, with two corresponding to forward whirling orbits and the other one corresponding to backward whirling oscillation. These findings are validated through the establishment of different basins of attraction. Finally, the performance of the [Formula: see text] in mitigating rotor vibrations and averting nonlinear catastrophic bifurcations under various excitation conditions. Furthermore, the rotor’s dynamical behavior and stability are explored in the event of an abrupt failure of one of the connected controllers. The outcomes demonstrate that the proposed [Formula: see text] effectively eliminates dangerous nonlinearities, steering the system to respond akin to a linear system with controllable oscillation amplitudes. However, the sudden controller failure induces a local rub-impact effect, leading to a nonlocal quasiperiodic oscillation and restoring the dominance of the nonlinearities on the system’s response.

Mechanics of magnetic-shape memory polymers

Magnetic-shape memory polymers (M-SMPs) can not only undergo rapid and reversible deformation in response to magnetic actuation but also lock the actuated shape upon cooling, which has great potential in applications such as soft robotics, active metamaterials, and shape-morphing systems. In this work, we develop a constitutive model for M-SMPs with finite deformation. The constitutive model considers the Helmholtz free energy contributed by the thermally responsive shape memory polymers and the magnetically responsive particles, leading to a magneto-thermomechanical framework. It is shown that the developed model can capture the thermomechanical as well as magneto-elastic responses of M-SMPs at different temperatures. Simplified beam models for M-SMPs are presented to show the material's versatile functionalities including fast and reversible deformation, selective/sequential actuation, and shape locking. We envision that the constitutive framework and the simplified beam models presented in this work can serve as useful tools to guide the rational design of M-SMP-based functional structures and devices.