Search for: All records

ABSTRACT Electromagnetic (EM) fields have been used in technologies such as communication, imaging, and energy transfer. In recent years, there has been growing interest in exploiting EM fields for the actuation of functional materials, enabling applications in soft robotics, biomedical devices, active metamaterials, and shape‐morphing systems. These materials are often composites that incorporate EM‐responsive components, granting them a remarkable versatility in responsiveness. Specifically, EM fields can induce actuation through static magnetic force and torque, Lorentz forces, or thermal effects via eddy currents and magnetic hysteresis losses. In addition, EM fields can be harnessed for sensing, wireless communication, and power transfer, extending their role far beyond actuation. The coexistence of such diverse mechanisms makes EM one of the most powerful and integrative external stimuli for multifunctional materials. This review provides the first holistic overview of EM‐active material systems. We systematically organize recent progress in EM‐based actuation, sensing, communication, and wireless power transfer, highlighting the fundamental principles, experimental demonstrations, and emerging design strategies. Approaches that integrate multiple EM‐driven functionalities and the role of optimization and machine learning in advancing design and control are discussed. By consolidating these advances, this review establishes a roadmap for the development of next‐generation EM‐enabled intelligent materials and devices. 

Abstract Navigating the complex and high‐flow environment of human vasculature remains a major challenge for conventional endovascular tools and externally actuated tethered systems. While catheter‐based approaches are the clinical standard, their limited steerability and force transmission hinder access to tortuous or distal vessels, especially in the brain. Untethered robotic systems have emerged as a promising alternative for enhanced flexibility and reachability. However, most designs struggle against the high, pulsatile blood flow in human arteries. Here, the study presents a magnetically actuated milli‐spinner robot that overcomes existing limitations in navigating complex and high‐flow vasculature. Capable of swimming at 23 cm·s⁻¹(73 body lengths per second), the milli‐spinner enables rapid, stable navigation through complex vasculature. This performance is driven by its hollow cylindrical structure with integrated helical fins and slits, which together generate a spinning‐induced flow field that enhances propulsion efficiency and allows the robot to maintain stability and control even in dynamic, pulsatile blood flow environments. In addition to its navigation capabilities, the milli‐spinner enables multifunctional treatment, including localized suction and shear for efficient clot removal, targeted drug delivery, and in situ embolization for aneurysm treatment. These features establish the milli‐spinner as a versatile and powerful platform for next‐generation, untethered endovascular interventions. 

Abstract Active metamaterials are a type of metamaterial with tunable properties enabled by structural reconfigurations. Existing active metamaterials often achieve only a limited number of structural reconfigurations upon the application of an external load across the entire structure. Here, a selective actuation strategy is proposed for inhomogeneous deformations of magneto‐mechanical metamaterials, which allows for the integration of multiple elastic wave‐tuning functionalities into a single metamaterial design. Central to this actuation strategy is that a magnetic field is applied to specific unit cells instead of the entire metamaterial, and the unit cell can transform between two geometrically distinct shapes, which exhibit very different mechanical responses to elastic wave excitations. The numerical simulations and experiments demonstrate that the tunable response of the unit cell, coupled with inhomogeneous deformation achieved through selective actuation, unlocks multifunctional capabilities of magneto‐mechanical metamaterials such as tunable elastic wave transmittance, elastic waveguide, and vibration isolation. The proposed selective actuation strategy offers a simple but effective way to control the tunable properties and thus enhances the programmability of magneto‐mechanical metamaterials, which also expands the application space of magneto‐mechanical metamaterials in elastic wave manipulation. 

Abstract Magneto-mechanical metamaterials possess unique and tunable properties by adjusting their shape configurations in response to an external magnetic field. Their designs and functionalities are diverse and are utilized in a wide variety of applications, such as highly tunable elastic and electromagnetic wave filters and targeted shape morphing. In this perspective, we examine the general background of magneto-mechanical metamaterials and their diverse applications. The possible future directions in the field are also thoroughly discussed. 

Abstract Shape morphing that transforms morphologies in response to stimuli is crucial for future multifunctional systems. While kirigami holds great promise in enhancing shape-morphing, existing designs primarily focus on kinematics and overlook the underlying physics. This study introduces a differentiable inverse design framework that considers the physical interplay between geometry, materials, and stimuli of active kirigami, made by soft material embedded with magnetic particles, to realize target shape-morphing upon magnetic excitation. We achieve this by combining differentiable kinematics and energy models into a constrained optimization, simultaneously designing the cuts and magnetization orientations to ensure kinematic and physical feasibility. Complex kirigami designs are obtained automatically with unparalleled efficiency, which can be remotely controlled to morph into intricate target shapes and even multiple states. The proposed framework can be extended to accommodate various active systems, bridging geometry and physics to push the frontiers in shape-morphing applications, like flexible electronics and minimally invasive surgery. 

Abstract 2D metamaterials have immense potential in acoustics, optics, and electromagnetic applications due to their unique properties and ability to conform to curved substrates. Active metamaterials have attracted significant research attention because of their on‐demand tunable properties and performances through shape reconfigurations. 2D active metamaterials often achieve active properties through internal structural deformations, which lead to changes in overall dimensions. This demands corresponding alterations of the conforming substrate, or the metamaterial fails to provide complete area coverage, which can be a significant limitation for their practical applications. To date, achieving area‐preserving active 2D metamaterials with distinct shape reconfigurations remains a prominent challenge. In this paper, magneto‐mechanical bilayer metamaterials are presented that demonstrate area density tunability with area‐preserving capability. The bilayer metamaterials consist of two arrays of magnetic soft materials with distinct magnetization distributions. Under a magnetic field, each layer behaves differently, which allows the metamaterial to reconfigure its shape into multiple modes and to significantly tune its area density without changing its overall dimensions. The area‐preserving multimodal shape reconfigurations are further exploited as active acoustic wave regulators to tune bandgaps and wave propagations. The bilayer approach thus provides a new concept for the design of area‐preserving active metamaterials for broader applications. 

Abstract Origami has emerged as a powerful mechanism for designing functional foldable and deployable structures. Among various origami patterns, a large class of origami exhibits rotational symmetry, which possesses the advantages of elegant geometric shapes, axisymmetric contraction/expansion, and omnidirectional deployability, etc. Due to these merits, origami with rotational symmetry has found widespread applications in various engineering fields such as foldable emergency shelters, deformable wheels, deployable medical stents, and deployable solar panels. To guide the rational design of origami-based deployable structures and functional devices, numerous works in recent years have been devoted to understanding the geometric designs and mechanical behaviors of rotationally symmetric origami. In this review, we classify origami structures with rotational symmetry into three categories according to the dimensional transitions between their deployed and folded states as three-dimensional to three-dimensional, three-dimensional to two-dimensional, and two-dimensional to two-dimensional. Based on these three categories, we systematically review the geometric designs of their origami patterns and the mechanical behaviors during their folding motions. We summarize the existing theories and numerical methods for analyzing and designing these origami structures. Also, potential directions and future challenges of rotationally symmetric origami mechanics and applications are discussed. This review can provide guidelines for origami with rotational symmetry to achieve more functional applications across a wide range of length scales.