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 highremanence 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.

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. Herein, a new magneto-mechanical metamaterial is presented 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 compression 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 also allows for the global shift of the acoustic behaviors. The combination of magnetic and mechanical actuations, as well as shape memory effects, impart wide tunable properties to a new paradigm of metamaterials.

Shape-morphing magnetic soft materials, composed of magnetic particles in a soft polymer matrix, can transform shape reversibly, remotely, and rapidly, finding diverse applications in actuators, soft robotics, and biomedical devices. To achieve on-demand and sophisticated shape morphing, the manufacture of structures with complex geometry and magnetization distribution is highly desired. Here, a magnetic dynamic polymer (MDP) composite composed of hard-magnetic microparticles in a dynamic polymer network with thermally responsive reversible linkages, which permits functionalities including targeted welding for magnetic-assisted assembly, magnetization reprogramming, and permanent structural reconfiguration, is reported. These functions not only provide highly desirable structural and material programmability and reprogrammability but also enable the manufacturing of functional soft architected materials such as 3D kirigami with complex magnetization distribution. The welding of magnetic-assisted modular assembly can be further combined with magnetization reprogramming and permanent reshaping capabilities for programmable and reconfigurable architectures and morphing structures. The reported MDP are anticipated to provide a new paradigm for the design and manufacture of future multifunctional assemblies and reconfigurable morphing architectures and devices.

The recent decades have witnessed the booming of additive manufacturing (AM), or 3D printing, not only in conventional areas, such as aviation, [1] automobile [2] and construction, [3] but also in various emerging fields, such as electronics, [4] biomedical engineering [5] and soft robotics. [6] The reason is the growing capability of AM to fabricate complex structures, which are challenging to be realized by traditional machining methods. In this advancement, the material library of 3D printing is no longer limited to static materials for structural construction and has expanded to active materials or stimuli-responsive materials, such as shape memory polymers, [7] hydrogels, [8] magnetic soft materials [9] and liquid crystal elastomers (LCEs), [10] driven by the growing need for soft robots, [10h,11] biomedical devices, [5,8a] smart wearable devices, [12] etc. The active nature of stimuli-responsive materials adds the dimension of time to 3D printing and leads to the emerging 4D printing. [8a,13] Among active materials for 4D printing, LCEs are appealing candidates due to their large, reversible and rapid actuation through a nematic-isotropic phase transition upon external stimuli, such as heat, [14] light, [10a,b,15] humidity [16] and electric fields. [17] LCEs are a class of soft active materials that inherit both the entropic elasticity of elastomers and the molecular anisotropy of liquid crystals (or mesogens). The actuation relies on the mesogen alignment, [18] which can be achieved by mechanical stretching, [19] surface shearing [10g] or external fields. [20] 3D/4D printing methods have been developed to fabricate LCE-based structures and align the mesogens. Direct ink writing (DIW) has been explored for printing LCEs. [11,15,21] In DIW, mesogens are aligned along the printing path when the LCE ink is extruded out of the syringe through the nozzle. Different inks have been developed for both high-temperature printing [10c,21a,c] and room-temperature printing. [21d,22] In addition, functionally graded LCEs were achieved by varying printing parameters, [10d,21c,g,23] such as printing temperature, printing speed and nozzle size. Although 3D structures, such as pinecone and saddle-shaped structures, [21c] can be achieved by 2D structures via different actuation strains between layers, the layer-by-layer manner of material deposition in DIW makes LCEs to be printed on the build platform or the previous layers.Liquid crystal elastomers (LCE) are appealing candidates among active materials for 4D printing, due to their reversible, programmable and rapid actuation capabilities. Recent progress has been made on direct ink writing (DIW) or Digital Light Processing (DLP) to print LCEs with certain actuation. However, it remains a challenge to achieve complicated structures, such as spatial lattices with large actuation, due to the limitation of printing LCEs on the build platform or the previous layer. Herein, a novel method to 4D print freestanding LCEs on-the-fly by using laser-assisted DIW w...

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