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Liquid crystal elastomers (LCEs) are a stimuli-responsive material which has been intensively studied for applications including artificial muscles, shape morphing structures, and soft robotics, due to its capability of large, programmable, and fully reversible strains. To fully take advantage of LCEs, rapid, untethered, and programmable actuation methods are highly desirable. Here, we report a liquid crystal elastomer-liquid metal (LCE-LM) composite, which enables ultrafast actuations and high heating programmability by eddy current induction heating. The composite consists of LM sandwiched between two 3D-printed LCE layers via direct ink writing (DIW). When subject to a high-frequency alternating magnetic field, the composite can be actuated in milli-seconds. By moving the magnetic field, the eddy current can be spatially controlled for selective actuation. Additionally, sequential heating is achievable by programming the LM thickness distribution in a specimen. With these capabilities, the LCE-LM composite is further exploited for multimodal deformation of a pop-up structure, on ground omnidirectional robotic motion, in water targeted object manipulation, and crawling.

Wireless millimeter-scale origami robots that can locomote in narrow spaces and morph their shapes have recently been explored with great potential for biomedical applications. Existing millimeter-scale origami devices usually require separate geometrical components for locomotion and functions, which increases the complexity of the robotic systems and their operation upon limited locomotion modes. Additionally, none of them can achieve both on-ground and in-water locomotion. Here we report a magnetically actuated amphibious origami millirobot that integrates capabilities of spinning-enabled multimodal locomotion, controlled delivery of liquid medicine, and cargo transportation with wireless operation. This millirobot takes full advantage of the geometrical features and folding/unfolding capability of Kresling origami, a triangulated hollow cylinder, to fulfill multifunction: its geometrical features are exploited for generating omnidirectional locomotion in various working environments, including on unstructured ground, in liquids, and at air-liquid interfaces through rolling, flipping, and spinning-induced propulsion; the folding/unfolding is utilized as a pumping mechanism for integrated multifunctionality such as controlled delivery of liquid medicine; furthermore, the spinning motion provides a sucking mechanism for targeted solid cargo transportation. This origami millirobot breaks the conventional way of utilizing origami folding only for shape reconfiguration and integrates multiple functions in one simple body. We anticipate the reported magnetic amphibious origami millirobots have the potential to serve as minimally invasive devices for biomedical diagnoses and treatments.

Shape morphing magnetic soft materials, composed of magnetic particles in a soft polymer matrix, can transform shapes reversibly, remotely, and rapidly, finding diverse applications in actuators, soft robotics, and biomedical devices. To achieve on-demand and sophisticated shape morphing, the manufacturing of structures with complex geometry and magnetization distribution is highly desired. Here, we report a magnetic dynamic polymer composite composed of hard-magnetic microparticles in a dynamic polymer network with thermal-responsive reversible linkages, which permit functionalities including targeted welding, magnetization reprogramming, and structural reconfiguration. These functions not only provide highly desirable structural and material programmability and reprogrammability but also enable the manufacturing of structures with complex geometry and magnetization distribution. The targeted welding is exploited for modular assembling of fundamental building modules with specific logics for complex actuation. The magnetization reprogramming enables altering the morphing mode of the manufactured structures. The shape reconfiguration under magnetic actuation is coupled with network plasticity to remotely transform two-dimensional tessellations into complex three-dimensional architectures, providing a new strategy of manufacturing functional soft architected materials such as three-dimensional kirigami. We anticipate that the reported magnetic dynamic polymer provides a new paradigm for the design and manufacturing of future multifunctional assemblies and reconfigurable morphing architectures and devices.

Mechanical metamaterials are architected manmade materials that allow for unique behaviors not observed in nature, making them promising candidates for a wide range of applications. Existing metamaterials lack tunability as their properties can only be changed to a limited extent after the fabrication. In this paper, we present a new magneto-mechanical metamaterial that allows great tunability through a novel concept of deformation mode branching. The architecture of this new metamaterial employs an asymmetric joint design using hard-magnetic soft active materials that permits two distinct actuation modes (bending and folding) under opposite-direction magnetic fields. The subsequent application of mechanical forces leads to the deformation mode branching where the metamaterial architecture transforms into two distinctly different shapes, which exhibit very different deformations and enable great tunability in properties such as mechanical stiffness and acoustic bandgaps. Furthermore, this metamaterial design can be incorporated with magnetic shape memory polymers with global stiffness tunability, which further enables the global shift of the acoustic behaviors. The combination of magnetic and mechanical actuations, as well as shape memory effects, imbue unmatched tunable properties to a new paradigm of metamaterials., Comment: 20 pages, 6 figures

Shape-programmable soft materials that exhibit integrated multifunctional shape manipulations, including reprogrammable, untethered, fast, and reversible shape transformation and locking, are highly desirable for a plethora of applications, including soft robotics, morphing structures, and biomedical devices. Despite recent progress, it remains challenging to achieve multiple shape manipulations in one material system. Here, we report a novel magnetic shape memory polymer composite to achieve this. The composite consists of two types of magnetic particles in an amorphous shape memory polymer matrix. The matrix softens via magnetic inductive heating of low-coercivity particles, and high-remanence particles with reprogrammable magnetization profiles drive the rapid and reversible shape change under actuation magnetic fields. Once cooled, the actuated shape can be locked. Additionally, varying the particle loadings for heating enables sequential actuation. The integrated multifunctional shape manipulations are further exploited for applications including soft magnetic grippers with large grabbing force, sequential logic for computing, and reconfigurable antennas. Keyword: shape memory polymers, soft active materials, magnetic soft material, soft robotics, soft material computing

Magnetic-responsive composites that consist of soft matrix embedded with hard-magnetic particles have recently been demonstrated as robust soft active materials for fast-transforming actuation. However, the deformation of the functional components commonly attains only a single actuation mode under external stimuli, which limits their capability of achieving tunable properties. To greatly enhance the versatility of soft active materials, we exploit a new class of programmable magnetic-responsive composites incorporated with a multifunctional joint design that allows asymmetric multimodal actuation under an external stimulation. We demonstrate that the proposed asymmetric multimodal actuation enables a plethora of novel applications ranging from the basic 1D/2D active structures with asymmetric shape-shifting to biomimetic crawling and swimming robots with efficient dynamic performance as well as 2D metamaterials with tunable properties. This new asymmetric multimodal actuation mechanism will open new avenues for the design of next-generation multifunctional soft robots, biomedical devices, and acoustic metamaterials.