Minimally designed thermo-magnetic dual responsive soft robots for complex applications.

Soft electromagnetic devices have great potential in soft robotics and biomedical applications. However, existing soft-magneto-electrical devices would have limited hybrid functions and suffer from damaging stress concentrations, delamination or material leakage. Here, we report a hybrid magnetic-mechanical-electrical (MME) core-sheath fiber to overcome these challenges. Assisted by the coaxial printing method, the MME fiber can be printed into complex 2D/3D MME structures with integrated magnetoactive and conductive properties, further enabling hybrid functions including programmable magnetization, somatosensory, and magnetic actuation along with simultaneous wireless energy transfer. To demonstrate the great potential of MME devices, precise and minimally invasive electro-ablation was performed with a flexible MME catheter with magnetic control, hybrid actuation-sensing was performed by a durable somatosensory MME gripper, and hybrid wireless energy transmission and magnetic actuation were demonstrated by an untethered soft MME robot. Our work thus provides a material design strategy for soft electromagnetic devices with unexplored hybrid functions.

4D printed and multi-stimulus responsive shape memory polymer nanocomposites developed on hydrogen bonding–metal-phenolic sacrificial network: Application for hazardous chemical operations soft robots

Multifunctional nanocomposites which exhibit well-defined physical properties and encode spatiotemporally-controlled responses are emerging as components for advanced responsive systems. For biomedical applications magnetic nanocomposite materials have attracted significant attention due to their ability to respond to spatially and temporally varying magnetic fields. The current state-of-the-art in development and fabrication of magnetic hydrogels toward biomedical applications is described. There is accelerating progress in the field due to advances in manufacturing capabilities. Three categories can be identified: i) Magnetic hydrogelation, DC magnetic fields are used during solidification/gelation for aligning particles; ii) additive manufacturing of magnetic materials, 3D printing technologies are used to develop spatially-encoded magnetic properties, and more recently; iii) magnetic additive manufacturing, magnetic responses are applied during the printing process to develop increasingly complex structural arrangement that may recapitulate anisotropic tissue structure and function. The magnetic responsiveness of conventionally and additively manufactured magnetic hydrogels are described along with recent advances in soft magnetic robotics, and the categorization is related to final architecture and emergent properties. Future challenges and opportunities, including the anticipated role of combinatorial approaches in developing 4D-responsive functional materials for tackling long-standing problems in biomedicine including production of 3D-specified responsive cell scaffolds are discussed.

Soft robotics has significantly impacted many fields in the last decades. However, their current fabrication methodologies are limited by the assemble complexity, limited materials, or long duration. A monolithic thermal casting method for fabrication of elastomer and soft robotics based on thermoset polymer is introduced. In this work, we used simple heating cores to manufacture elastomers and soft actuators. By controlling the heating current and duration, we can adjust the thermal field and consequently change the configuration of the generated elastomer. Due to its short duration (several minutes), this method can benefit the mass production of soft robots for high efficiency. Also, this work offers a new way to design soft robotics without complex molds.

A systematic trend analysis of 3D printing techniques used in specific soft robotic elements

Soft robots, with their inherent flexibility, high environmental adaptability, show great potential in medical and exploration applications that are unmatched by traditional rigid robots. Nonetheless, realizing effective actuation and continuous energy supply, especially for micro-scale soft robots, remains a core challenge. In this paper, the research progress in actuation and energy harvesting technologies for soft robots is systematically reviewed. The actuation aspect covers fluid actuation, photo- and magnetic actuation, deformable material actuation, and mechanical mechanism actuation, etc., and subsequently their principles, advantages and disadvantages, and applications are discussed separately. The energy aspect focuses on autonomous energy harvesting to overcome size and cable limitations and emphasizes electromagnetic field (inductance and solar energy), mechanical energy (piezoelectricity, friction generating electricity), and thermal energy harvesting technologies. The review aims to sort out the existing technologies and look forward to future development directions, such as multifunctional material development, system integration and miniaturization, in order to promote the wide application of soft robots in cutting-edge fields.

From Responsive Molecules to Interactive Materials.

The possibility of inducing a structural martensitic transformation by applying a magnetic field in meta-magnetic shape memory alloys gives rise to interesting properties such as magnetic actuation, giant magnetoresistance, or giant inverse magneto-caloric effect, which make these alloys very attractive for practical applications in sensing and magnetic refrigeration. Composites made from polymer matrix with meta-magnetic shape memory powder have been recently proposed to overcome the intrinsic brittleness of the bulk alloys. This, in fact, opens the possibility of the use of particles for additive manufacturing purposes. The production, characterization, and optimization of the properties of powder particles are therefore milestones to get valuable functional composites. In the present work, the martensitic transformation and the magnetic properties of Ni45Co5Mn37In13 powder microparticles obtained by ball milling have been studied. Even for very large milling times, a considerable dispersion in the particle size is observed in all the samples. Nevertheless, it is found that the characteristic of the transformation and the magnetic response is exactly the same in those particles with the same particle size, irrespective of the milling time. A direct correlation between size and deformation can be then established, from which the effect of mechanically induced microstructural defects on the magnetism is analyzed. The effect of mechanically induced defects on the magnetocaloric effect and the viability of the use of the studied microparticles for composite elaboration are also analyzed. Polymer composites have been elaborated by embedding the micro/nanoparticles in a mixture of polylactic acid(PLA) and poly-caprolactone(PCL). In order to get 3D printable wires with optimum mechanical properties and good magnetic response, the particles size, polymers fractions, and particles concentration have been varied. The magnetic response and printability of the obtained filaments have also been studied.  Multifunctional magnetic composites based in meta-magnetic shape memory alloys for 3D printing applications

Flexible discretely-magnetized configurable soft robots via laser-tuned selective transfer printing of anisotropic ferromagnetic cells

This article presents a unique soft robot comprised of highly compliant locomotive modules interconnected with jamming-capable flexible envelopes. The modules incorporate origami-inspired actuators and suction cups for robust omnidirectional locomotion, acting as collective elements that drive the system's movement and control. The flexible envelopes enable dynamic interactions with the environment through stiffness modulation via granular jamming. A unified pneumatic actuation system consolidates all robot functions, simplifying the mechanical architecture. The system's capabilities are demonstrated through shape formation, object grasping and transportation, obstacle navigation, and diverse terrain locomotion experiments, highlighting its adaptability and cooperative nature. Furthermore, a simulation-based design optimization approach using a genetic algorithm enhances the system's grasping performance by exploring the different module and envelope configurations. The interconnected soft robot system represents a unique fusion of highly compliant modules and bodies, advancing modular soft robotics for effective environmental interactions.

Asymmetric bending enables rapid and efficient crawling motions in a soft robotic system. However, achieving asymmetric motion in soft robots with temperature‐responsive liquid crystal elastomers (LCEs) necessitates complex Joule heating configurations or precise temperature regulation. Herein, a simple electroless plating method is presented for patterning asymmetric temperature gradients on paper substrates, thereby facilitating the development of Joule heating, caterpillar‐inspired soft robots. Cellulose‐based paper substrates provide distinct advantages due to their porous structure, which enables facile electrode deposition via solution‐based processes and offers high mechanical deformability. Leveraging these material properties, Cu electrodes are asymmetrically deposited onto paper substrates by varying electrode widths. This variation induces differences in electrical resistance, generating significant temperature gradients across the substrate. Furthermore, it is demonstrated that temperature gradients could be modulated by adjusting the extent of Cu enhancement in the electrode patterns. it is fabricated energy‐efficient soft robots capable of directional crawling at a low actuation voltage of 0.5 V by integrating the paper substrate with LCEs in a bilayer architecture. The simplicity of the electrode patterning process, combined with the eco‐friendly nature of paper‐based actuators, presents a promising approach for the scalable and sustainable fabrication of soft robots with complex locomotion capabilities.

Magnetoactive materials, which change shape in response to magnetic fields, hold significant potential for applications in soft robotics, biomedical devices, and morphable structures. However, existing systems often suffer from complex fabrication processes, limited geometric customizability, and inefficient magnetization reprogramming strategies, especially for 3D structures. Here, lightweight magnetic graphene oxide (MGO) bilayer films incorporating hard‐magnetic microparticles are introduced to enable fast, precise, and stable shape‐morphing under magnetic actuation, including in aqueous environments. The paper‐like nature of MGO films allows low‐cost and straightforward fabrication of customized structures through post‐processing steps such as cutting, folding, and assembly. In addition, the hygroscopic properties of GO introduce a humidity‐tunable actuation, offering an extra degree of control. To address the reprogramming challenge, a reversible, high‐throughput, and energy‐efficient strategy is introduced based on the rearrangements of reusable MGO magnetic stickers, enabling multimodal magnetic shape reconfiguration and functional versatility. Their applications are showcased in in situ mechanical state transitions, sequential logic computing, and soft robot locomotion. Finally, a MGO sensoriactuator is demonstrated capable of magnetic actuation and real‐time deformation monitoring, paving the way for closed‐loop soft robotic systems. This work presents a sustainable, reconfigurable, and multifunctional strategy for advancing next‐generation intelligent magnetoactive soft machines.

New materials are advancing the field of soft robotics. Composite films of magnetic iron microparticles dispersed in a shape memory polymer matrix are demonstrated for reconfigurable, remotely actuated soft robots. The composite films simultaneously respond to magnetic fields and light. Temporary shapes obtained through combined magnetic actuation and photothermal heating can be locked by switching off the light and magnetic field. Subsequent illumination in the absence of the magnetic field drives recovery of the permanent shape. In cantilevers and flowers, multiple cycles of locking and unlocking are demonstrated. Scrolls show that the permanent shape of the film can be programmed, and they can be frozen in intermediate configurations. Bistable snappers can be magnetically and optically actuated, as well as biased, by controlling the permanent shape. Grabbers can pick up and release objects repeatedly. Simulations of combined photothermal heating and magnetic actuation are useful for guiding the design of new devices.

A magnetic elastomer is a type of magneto-active smart material where a magnetic field induces a mechanical response. Several methods have been used to optimize performance by controlling the microstructure, such as magnetic annealing. Optimization can also be achieved by introducing anisotropy with Fused Deposition Modeling (FDM), a 3D-printing process that extrudes viscous material in 1D lines to create 2D layers which build to a 3D part. Indeed, FDM features have been shown to manipulate the magnetic anisotropy of rigid printed parts.1 However, printing flexible composite materials presents additional challenges with FDM. Here, FDM structures were printed with thermoplastic polyurethane (TPU) polymer and either 20wt% iron (Fe), 40wt% Fe, 40wt% carbonyl iron (CI), or 40wt% magnetite (Fe3O4/Mag). In order to determine the relative effect of different parameters on the magnetic properties, a series of structures were printed combining each material type (Fe-TPU, CI-TPU, Mag-TPU) with different aspect ratios (1:1 / 2:1), infill percentages (60% / 80% / 100%), and infill orientations (parallel/perpendicular to aspect ratio). A Vibrating Sample Magnetometer was used to obtain magnetic hysteresis loops for comparing magnetic susceptibility between samples. Results demonstrated that infill orientation had the largest effect on susceptibility, aspect ratio had the next greatest effect, and infill percentage had a more nuanced effect (Fig.1). This shows that FDM allows the magnetic anisotropy to manifest through mesoscale anisotropy of a part’s internal structure. These trends were found to form a continuum of tunable magnetic responses (Fig.2). Additionally, the chosen particulate transfers its unique magnetic signature to the composite material. Overall, the highly customizable and nuanced characteristics of 3D-printed magnetic elastomer structures will allow for its use in emerging magneto-mechanical applications such as magnetic actuation and soft robotics.

ABSTRACTSoft robots demonstrate remarkable potential in diverse environments because of their flexibility and compliance. Although various soft robots capable of independently responding to multiple external stimuli have been developed, challenges persist in the integration of multiple responses and the avoidance of interference among them. This study develops an amphibious soft robot with triple‐response capabilities to temperature, humidity, and magnetic fields. Through the implementation of a strong alkali modification strategy on polyimide films, polyimide acid was successfully formed on the surface, enabling the processing of composite films. This composite film was endowed with dual‐responsive characteristics to temperature and humidity. Additionally, by integrating magnetic particles, the composite film constructs a triple‐response feature in conjunction with magnetic driving modules. The soft robot developed from the triple‐responsive composite film can rapidly transition capabilities between submerged/terrestrial and submerged/surface environments, demonstrating exceptional environmental adaptability. This amphibious soft robot can achieve speeds exceeding 4 cm/s (∼12 body lengths/s) in various environments. The maximum speed attainable on the water surface is 9.6 cm/s (∼32 body lengths/s). This performance reached the normal moving speed of insects such as ants and whirligig beetles. Furthermore, by utilizing the cooperative interplay of multiple stimuli‐responsive mechanisms, the soft robot achieves selective swarm manipulation, controllable cargo transportation, and targeted release in complex terrains. It can carry objects weighing up to 2.5 times its own weight. This multimodal actuation strategy reveals significant potential for smart robots' development.