Self-Healing Approach toward Catalytic Soft Robots

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

Soft robots are theoretically well-suited to rescue and exploration applications where their flexibility allows for the traversal of highly cluttered environments. However, most existing mobile soft robots are not fast or powerful enough to effectively traverse three dimensional environments. In this paper, we introduce a new mobile robot with a continuously deformable slender body structure, the SalamanderBot, which combines the flexibility and maneuverability of soft robots, with the speed and power of traditional mobile robots. It consists of a cable-driven bellows-like origami module based on the Yoshimura crease pattern mounted between sets of powered wheels. The origami structure allows the body to deform as necessary to adapt to complex environments and terrains, while the wheels allow the robot to reach speeds of up to 303.1 mm/s (2.05 body-length/s). Salamanderbot can climb up to 60-degree slopes and perform sharp turns with a minimum turning radius of 79.9 mm (0.54 body-length).

Advancements and challenges in dielectric elastomer actuator-based biomimetic mobile robots

Thermal Energy Storage (TES) system has emerged as a promising solution of energy demand and supply management, which stores excess thermal energy and releases it when energy demand is high, making it an efficient and cost-effective energy storage solution when combined with renewable energy sources, such as solar and wind power. This study aimed to evaluate the thermal performance of TES units using Computational Fluid Dynamics (CFD) simulations in the ANSYS CFX software package. After comparing the heat storage capacity of conventional Phase Change Material (PCM) and iron oxide/paraffin wax composite ($2 \%$) using industrial residual water, temperature distribution plots and heat flux data were generated in simulations for both cases. Addition of iron oxide nanoparticles significantly improved the heat absorption performance of TES units. Both materials initially exhibited a higher heat absorption rate, which gradually decreased over time. CFD data analysis revealed that iron oxide/paraffin wax material enhanced heat absorption performance by up to $1.3 \%$, which demonstrated the potential of iron oxide nanoparticles in improving the efficiency of TES system and highlighted the advantages of TES system combined with renewable energy sources. By improving heat absorption properties, the incorporation of iron oxide nanoparticles had the potential to increase the lifespan of TES units and significantly reduced maintenance and replacement expenses. This breakthrough, along with the cost savings and energy efficiency offered by TES technology, may encourage its widespread application, thus reducing reliance on fossil fuels and promoting sustainable energy practices.

Magnetic iron oxide nanoparticles were investigated for their potential to enhance biogas production through the anaerobic digestion of fruit and vegetable waste. The nanoparticles were synthesized via co-precipitation and characterized using Atomic Force Microscopy (AFM), UV-visible spectroscopy, and Magnetic Force Microscopy (MFM). MFM analysis revealed a magnetic force of -20 nN at a distance of 42 nm from the nanoparticles, with a magnetic gradient extending up to 100 nm in nanoparticle clusters. Anaerobic digestion experiments, conducted in Erlenmeyer flasks, employed a factorial design to optimize conditions such as moisture content, temperature, and inoculum percentage. Results demonstrated that the addition of iron oxide nanoparticles, at 34°C with 7% inoculum and 42% moisture content, led to a 55.53% reduction in substrate residual compared to control tests without nanoparticles. The presence of lactic acid confirmed the occurrence of acidogenesis, while higher concentrations of acetic acid in nanoparticle-enhanced tests suggested an influence on the acetogenesis phase. Additionally, the nanoparticles showed potential as adsorbents. These findings highlight the potential of magnetic iron oxide nanoparticles as an effective and sustainable method for improving biogas production from organic waste, with implications for urban areas and fueling centers seeking alternative, renewable energy solutions.

Pervaporation with chitosan membranes containing iron oxide nanoparticles

Untethered magnetic soft robots can broaden the working scenarios of robots and have numerous potential applications in space exploration, industry, and medicine. However, existing magnetic soft robots face challenges such as limited reparability, difficulty expanding functions, and difficulty adjusting motion mode. Herein, an efficient and comprehensive laser thermal-curing printing method is proposed for magnetic soft robots. In this method, the directionality and photothermal effect of the infrared laser and thermal-curing property of thermosetting resin are utilized to achieve efficient fabrication, precise repair, and seamless reconstruction of thermosetting resin-based magnetic soft robots. Besides, the method enables reprogrammability of magnetic soft robots by exploiting photothermal-induced demagnetization. Further, the laser thermal-curing printing method is applied to repair a gyro robot for controlled movement; to reconstruct an underwater robot for salvaging cargo, a robot for repairing electrical circuit, and a wheel robot with three-dimensional structure; and to reprogram the motion of a six-leaf magnetic soft robot. These applications demonstrate that the laser thermal-curing printing method achieves the integration of fabrication, reparability, reconfigurability, and reprogrammability for soft robot, which is expected to drive a paradigm shift in soft robotics manufacturing and provide a groundbreaking strategy for fabricating magnetic soft robots with complex structures.

Thermo-aqueous coupling behaviors for shape memory hydrogels: A statistical–mechanical model and simulations faced with experiments

The swim bladder is crucial to underwater robots to enhance their overall performance and to expand their range of motion. However, previous attempts to incorporate this function have failed or have adopted mechanical swim bladders with high-disturbances. This study presents an entirely soft swim bladder capable of controlling buoyancy selectively and noiselessly, making it applicable to sensitive underwater environments. The soft swim bladder, which consists of an elastic cover layer, flexible heating elements, and three expandable pouches filled with low boiling point fluid, can express four modes of motion by varying buoyancy: sinking, suspending, rising, and fast-rising. The varying buoyancy is achieved through liquid-vapor phase transition of the fluid in the selected pouches when Joule heated above its boiling temperature. Moreover, the swim bladder is integrated with a shape memory alloy-based fishtail to form a soft fish robot. The synergy between the bladder and the tail allows the robot to explore a total of ten disparate modes of maneuvers, and their dynamic performance has been evaluated. The results of this study present the potential for the soft swim bladder to be utilized in any underwater robotic applications to enhance their swimming performance.

Flexible miniature robots are expected to enter difficult-to-reach areas invivo to carry out targeted operations, attracting widespread attention. However, it is challenging for the existing soft miniature robots to substantially alter their stable shape once the structure is designed. This limitation leads to a fixed motion mode, which subsequently restricts their operating environment. In this study, we designed a biocompatible flexible miniature robot with a variable stable form that is capable of adapting to complex terrain environments through multiple movement modes. Inspired by the reversible stretching reaction of alginate saline gel stimulated by changes in environmental ion concentration, we manufactured a morphologically changeable super-soft hydrogel miniature robot body. According to the stretch and contraction shapes of the flexible hydrogel miniature robot, we designed magnetic fields for swing and rolling motion modes to realize multi-shape movement. The experimental results demonstrate that the deflection angle of the designed flexible miniature robot is reversible and can reach a maximum of 180°. The flexible miniature robot can complete forward swinging in the bar stretch state and tumbling motion in the spherical state. We anticipate that flexible hydrogel miniature robots with multiple morphologies and multimodal motion have great potential for biomedical applications in complex, unstructured, and enclosed living environments.

The rapid advancement of artificial intelligence has spurred widespread interest in artificial muscles as core actuating components for soft robotics. Twisted and coiled artificial muscles (TCAMs), a novel class of soft actuators fabricated by twisting and coiling high-performance fibers, exhibit notable advantages, including low cost, high flexibility, long cycle life, large actuation strain, and high energy density. The TCAMs can generate multiple motion modes, including bending, twisting, contraction/extension, and buckling in response to external stimuli. The TCAMs demonstrate significant potential for application in fields such as soft robotics and wearable assistive devices. This review comprehensively examines the developmental trajectory and current research landscape of TCAMs, synthesizes progress in actuation strategies, actuation mechanisms, and machine learning applications, and concludes with perspectives on future research directions. We further assess persistent challenges in hysteresis suppression and manufacturing reproducibility, proposing cross-disciplinary solutions toward deployable artificial muscle systems.

Soft robots with magnetic responsiveness exhibit diverse motion modes and programmable shape transformations. While the fixed magnetization configuration facilitates coupling control of robot posture and motion, it limits individual posture control to some extent. This poses a challenge in independently controlling the robot's transformation and motion, restricting its versatile applications. This research introduces a multifunctional helical robot responsive to both light and magnetism, segregating posture control from movements. Light fields assist in robot shaping, achieving a 78% maximum diameter shift. Magnetic fields guide helical robots in multimodal motions, encompassing rotation, flipping, rolling, and spinning-induced propulsion. By controlling multimodal locomotion and shape transformation on demand, helical robots gain enhanced flexibility. This innovation allows them to tightly grip and wirelessly transport designated payloads, showcasing potential applications in drug delivery, soft grippers, and chemical reaction platforms. The unique combination of structural design and control methods holds promise for intelligent robots in the future.

A light-powered liquid crystal elastomer semi-rotary motor

Self-rolling of a planar hydrogel sheet represents an advanced approach for fabricating a tubular construct, which is of significant interest in biomedicine. However, the self-rolling tube is usually lacking in remote controllability and requires a relatively tedious fabrication procedure. Herein, we present an easy and controllable approach for fabricating self-rolling tubes that can respond to both magnetic field and light. With the introduction of magnetic nanorods in a hydrogel precursor, a strain gradient is created across the thickness of the formed hydrogel sheet during the photopolymerization process. After the removal of the strain constraint, the nanocomposite sheet rolls up spontaneously. The self-rolling scenario of the sheet can be tuned by varying the sheet geometry and the magnetic nanorod concentration in the hydrogel precursor. The nanocomposite hydrogel tube translates in the presence of a magnetic field and produces heat upon a near-infrared (NIR) light illumination by virtue of the magnetic and photo-thermal properties of the magnetic nanorods. The self-rolling tube either opens up or expands its diameter under NIR light irradiation depending on the number of rolls in the tube. With the use of a thermo-responsive hydrogel material, we demonstrate the magnetically guided motion of the chemical-bearing nanocomposite hydrogel tube and its controlled chemical release through its light-mediated deformation. The approach reported herein is expected to be applicable to other self-rolling polymer-based dry materials, and the nanocomposite hydrogel tube presented in this work may find potential applications in soft robot and controlled release of drug.

The development of the spherical robot to meet the requirements of high-speed and high-precision tasks is of great importance. In this study, a fractional-order adaptive integral hierarchical sliding mode controller (F-AIHSMC) is proposed. F-AIHSMC enables the spherical robot to have better controlled performance when facing unknown disturbances and system chattering, which can seriously affect the high-speed and high-precision motion of the spherical robot. We establish the standard dynamic model of the spherical robot for high-speed linear motion first, and then use the feedforward compensation method to compensate the controllable influencing factors in the motion process. According to the standard dynamic model, the integral term and fractional calculus methods are integrated into the hierarchical sliding mode controller, and the adaptive method is used to evaluate and compensate unknown disturbances in the high-speed motion process. In order to verify the efficiency of the proposed F-AIHSMC, we test its control effect using the BYQ-GS spherical robot. The experimental results demonstrate that, compared with the classical hierarchical sliding mode controller and the adaptive hierarchical sliding mode controller, the F-AIHSMC has obvious advantages in response speed, convergence speed, stability and robustness when being applied to the control of high-speed linear motion of spherical robot. Moreover, the advantages of its control performance are more highlighted with the increase of the speed of the spherical robot.