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Soft robots are characterized by their mechanical compliance, making them well-suited for various bio-inspired applications. However, the challenge of preserving their flexibility during deployment has necessitated using soft sensors which can enhance their mobility, energy efficiency, and spatial adaptability. Through emulating the structure, strategies, and working principles of human senses, soft robots can detect stimuli without direct contact with soft touchless sensors and tactile stimuli. This has resulted in noteworthy progress within the field of soft robotics. Nevertheless, soft, touchless sensors offer the advantage of non-invasive sensing and gripping without the drawbacks linked to physical contact. Consequently, the popularity of soft touchless sensors has grown in recent years, as they facilitate intuitive and safe interactions with humans, other robots, and the surrounding environment. This review explores the emerging confluence of touchless sensing and soft robotics, outlining a roadmap for deployable soft robots to achieve human-level dexterity. [ABSTRACT FROM AUTHOR]

Photothermal actuators are widely applied in robots, smart devices, and bionic systems. However, asymmetric thermal expansion, the most common mechanism for preparing photothermal actuators, has not been utilized in programmable liquid metal photothermal actuators. In this work, Liquid metal/Polyimide/Polytetrafluoroethylene (LM/PI/PTFE) programmable photothermal actuators based on asymmetric thermal expansion are prepared inspired by the climbing plant tendrils. The "protoplasm that can contract and bend" PTFE tape endows the photothermal actuator with programmable initial morphology. The photothermal properties and flexibility of the liquid metal microspheres, together with the significant property difference between PI and PTFE, endow the photothermal actuator with excellent response angles (130.74 ± 6.45°), response speeds (46.62 ± 2.33° s−1), stability (2000 cycles for 10 h), and load‐carrying capacity, which are not inferior to most of the reported PI photothermal actuators. The LM/PI/PTFE photothermal actuator has been successfully modelled and simulated by finite element analysis (FEA). Based on the programmable initial morphology and the simulation by FEA, this work has designed and prepared a variety of bionic systems and functional robots. The work of LM/PI/PTFE photothermal actuators provides a strategy for designing photothermal actuators and enables the future development of photothermal actuators in bionic systems and robots. [ABSTRACT FROM AUTHOR]

Soft robotic bodies are susceptible to mechanical fatigue, punctures, electrical breakdown, and aging, which can result in the degradation of performance or unexpected failure. To overcome these challenges, a soft self‐healing robot is created using a thermoplastic methyl thioglycolate–modified styrene–butadiene–styrene (MG‐SBS) elastomer tube fabricated by melt‐extrusion, to allow the robot to self‐heal autonomously at room temperature. After repeated damage and being separated into several parts, the robot is able to heal its stiffness and elongation to break to enable almost complete recovery of robot performance after being allowed to heal at room temperature for 24 h. The self‐healing capability of the robot is examined across the material scale to robot scale by detailed investigations of the healing process, healing efficiency, mechanical characterization of the robot, and assessment of dynamic performance before and after healing. The self‐healing robot is driven by a new micro two‐way shape‐memory alloy (TWSMA) spring actuator which achieved a crawling speed of 21.6 cm/min, equivalent to 1.57 body length per minute. An analytical model of the robot is created to understand the robot dynamics and to act as an efficient tool for self‐healing robot design and optimization. This work therefore provides a new methodology to create efficient, robust, and damage‐tolerant soft robots. [ABSTRACT FROM AUTHOR]

The increase of human presence in the subsea and seabed environments necessitates the development of more capable and highly dexterous, innovative underwater manipulators. Biomimetic soft-robot arms represent a promising candidate for such manipulation systems. However, the well-known modeling techniques and control theories of traditional rigid robots do not apply to soft robots. The challenges of kinematic and dynamic modeling of soft robots with infinite degrees of freedom require the development of dedicated modeling methods. A novel procedure for representing soft-robotic arms and their motion in a rigid-body simulation environment is proposed in this paper. The proposed procedure relies on the piecewise constant curvature approach to simplify the very complex model of hyper-redundant soft-robotic arms, making it suitable for real-time applications. The proposed method is implemented and verified to be used in model-mediated teleoperation of the soft arms of a biomimetic robotic squid designed for underwater manipulation as a case study. [ABSTRACT FROM AUTHOR]

Entraining human gait with a periodic mechanical perturbation has been proposed as a potentially effective strategy for gait rehabilitation, but the related studies have mostly depended on the use of a fixed-speed treadmill (FST) due to various practical constraints. However, imposing a constant treadmill speed on participants becomes a critical problem because this speed constraint prohibits the participants from adjusting the gait speed, resulting in significant alterations in natural biomechanics as the entrainment alters the stride frequency. In this study, we hypothesized that the use of a variable-speed treadmill (VST), which enables the participants to continuously adjust their speed, can improve the success rate of gait entrainment and preserve natural gait biomechanics. To test this hypothesis, we recruited 15 young and healthy adults and let them walk on a conventional FST and a self-paced VST while wearing a soft robotic hip exosuit, which applied hip flexion perturbations at various frequencies, ranging from the preferred walking frequency to a 30% increased value. Kinematics and kinetics of the participants’ walking under the two treadmill conditions were measured on two separate days. Experimental results demonstrated a higher success rate of entrainment during VST walking compared to FST walking, particularly at faster perturbation frequencies. Furthermore, walking on VST facilitated the maintenance of natural biomechanics, such as stride length and normalized propulsive impulse, better than walking on FST. The observed improvement, primarily attributed to allowing an increase in walking speed following the increase in the perturbation frequency, suggests that using a self-paced VST is a viable method for exploiting the potentially beneficial therapeutic effects of entrainment in gait rehabilitation. [ABSTRACT FROM AUTHOR]

Soft pneumatic actuators are one of the most promising actuation for soft robots, and great achievements have been obtained. But it remains challenging to endow sensing capabilities to pneumatic actuators, especially for the sensing ability originating directly from the actuator architecture. Herein, a self-sensing pneumatic torsional actuator (SPTA) is designed based on the electromagnetic induction effect and magnetically responsive materials. The SPTA can generate feedback voltage and current with the deformation, in which the sensing function comes from its inherent structure To investigate the mechanical and electrical characteristics, an experimental platform and a finite element model are established, respectively. We find that the torsion angle and output torque increase in nonlinear with the actuating pressure. The maximum torsion angle is 66.35°, which is 84.34% of that for the actuator fabricated by pure rubber. The maximum output torque (24.9 N mm) improves by 23.19% compared with the actuator made by pure rubber. As regards the electrical characteristics, the maximum feedback voltage and current are 2.90 µV and 29.50 nA when the SPTA is actuated by a pressure of −40 kPa. We also demonstrate that the relationship between the torsion angle and the magnetic flux change is approximately linear. Finally, the number of turns of wires, magnetic powders contents, and magnetic direction on the feedback voltage and current are studied. Results show that the feedback voltage and current can be enhanced by increasing the number of turns and magnetic powders contents. We envision that the SPTA would be promising for soft robots to realize their accuracy control and intelligentization. [ABSTRACT FROM AUTHOR]

The field of soft robotics is rapidly progressing toward applications including; wearable electronics, prosthetics, and biomedical devices. This is leading to demand for flexible, embedded high‐performance strain sensors to deliver real‐time feedback on the static configurations and dynamic motions of these robotic devices, to ultimately enable the levels of autonomous control and structural monitoring required for intelligent manipulation. Herein, aerosol jet printing (AJP) technology is utilized to generate arbitrary piezoresistive strain sensor layouts on fibrous paper suitable for direct integration into elastomeric soft robots. A custom graphene nanoplatelet ink with a viscosity of around 2.70 cP has been formulated for optimized atomization and patterning of conductive traces via AJP. Single and multilayer printing onto different paper substrates are explored; with the nominal resistance of the printed tracks varying from 272 to 4900 kΩ depending on paper type and number of layers. Maximum gauge factors of 24.2 ± 1.8 and 56.5 ± 4.5 are determined for sensor surfaces under tensile and compression modes, respectively. To demonstrate the possibility for direct integration of this approach for soft robotics, strain sensors are directly printed onto the strain‐limiting layer of a pneumatic soft robotic gripper, to provide continuous feedback of the gripper over curvatures up to 80 m−1. [ABSTRACT FROM AUTHOR]

Remote stimuli‐responsive movable soft robots without the need for complex 3D deformation processes and specific working environments is an unsolved problem and urgent need. In this work, under the inspiration of mother nature, a novel strategy of simple combination of the bionic bristles structure and the photothermal‐driven reversible shape change liquid crystal polymer (LCP) actuator is proposed to work out this difficulty. The combination structure is designed as unique three parts with two bionic bristle units at the two ends and one LCP unit in the center with a soft connection between them. After matching the driving force and the resistance, the prepared soft robot can realize the earthworm‐like unidirectionally crawl on the paper surface upon near‐infrared light irradiation through the contracting and stretching of LCP with a maximum average speed of 4.4 mm min−1. What's more, the crawling speed of the soft robot can be regulated by varying the irradiation distance of near‐infrared light or the length of the actuators. This strategy realizes the type of remote wireless control soft robot and has potential application ability in other soft robots with various demands. [ABSTRACT FROM AUTHOR]

Amphibious robots, which are expected to move agilely in both land and water environments with huge differences in medium density, have always been a hot spot in the field of robotics. However, limited by the simple structure and drive system, the existing mini‐robots have a relatively single‐movement mode, which limits their ability to move in complex environments. This article fuses two different biomimetic morphological features to create an amphibious mini‐robot: mimicking the body shape and gait of a terrestrial inchworm, and mimicking the superhydrophobic leg shape and gait of an aquatic water strider. The light‐driven approach also brings the advantage of remote wireless manipulation. The mass of the robot is only 8 mg, and it has fast land movement speed (≈0.05 times body length s−1), water surface movement speed (≈0.5 times body length s−1), and some obstacle‐crossing ability (over obstacles of ≈64% of the robot's height). Moreover, the robot can quickly switch from land to water locomotion, which is expected to facilitate emerging applications in various industrial and biomedical settings. [ABSTRACT FROM AUTHOR]

Soft continuum robots, with their flexible and deformable structures, excel in tasks requiring delicate manipulation and navigation through complex environments. Accurate shape sensing is vital to enhance their performance, safety, and adaptability. Unlike rigid sensors, soft sensors conform to the robot’s flexible surfaces, ensuring consistent measurement of shape and motion. This paper introduces a new approach using soft e-textile resistive sensors, which integrate seamlessly with the robot’s structure. These sensors adjust their resistance in response to movements, capturing multidimensional force data. A deep Convolutional Neural Network (CNN) decodes the sensor signals, enabling precise shape estimation and control. Our findings indicate that soft e-textile sensors may surpass traditional rigid sensors in shape sensing and control, significantly improving the functionality of soft continuum robots in challenging applications.

Soft actuators have been an important research focus in robotics due to their advantages in nondestructive contact and excellent motion adaptability, which enable flexible manipulation, extreme environments exploration, and in vivo surgical treatment. Various soft robots actuated electrically, magnetically, optically, and fluidically are built toward different application scenarios. Among them, electrical actuation method is an advanced choice to actuate and control soft actuators that are expected to be compatible and integrated with existing industrial robotic systems and wearable intelligent devices. Current robotic systems have higher requirements on the actuators’ function, which can be explored through material and structural designs. Based on a variety of deformable materials, the structural design enables the soft actuators to span from low dimension to high dimension with further improvement in function. Therefore, in this review, 2D and 3D electrical‐based soft actuators from the perspective of dimension design are introduced, which involve functional materials, structure design, and fabrication technology. Some novel 3D fabrication methods, such as the 3D compressive buckling process, are summarized to build 3D soft robots. This review aims at offering important guidelines for the development of soft actuators and the construction of integrated robotic systems in the future.

Magnetically driven miniature soft robots exhibit fast and dexterous responses to an applied external magnetic field. With remote manipulation, controlled navigation of robots can be realized within hard‐to‐access spaces for potential use in the human body. Existing magnetic miniature soft robots using digital light processing are fabricated from planar sheets, and thus have limited shape transformations and locomotive behaviors. Herein, a multilayer 3D printing method is reported for patterning magnetic nanoparticles in ultraviolet (UV)‐curable polymer matrix. Various multilayer 3D structures within 10 mm in overall size are fabricated with controlled volumes at different parts, which outperform 2D folded shapes in terms of robustness and kinematic flexibility. By programming heterogeneous magnetization within discrete multilayer robot segments, magnetic torque‐induced shape changes including gripping, rolling, swimming, and walking are induced by a global actuation field. Stacked design features with minimum dimension of 200 μm and encoded magnetization with resolution of 350 μm can be realized in the printing process. Meanwhile, enhanced deformation flexibility and formation of orientation‐anchoring mechanisms are created by integrating multiple materials with distinct mechanical and magnetic properties, respectively, which enables the creation of versatile 3D multi‐material actuators.

Soft magnetic manipulators offer the prospect of improved surgical outcomes through their potential for miniaturization and inherently safe tissue interaction. However, independent actuation of multiple manipulators within the same confined workspace is limited by undesired simultaneous actuation and manipulator–manipulator interactions. Herein, for the first time, approaches for the independent magnetic actuation of two magnetic continuum manipulators within the same confined workspace are proposed. A novel modular magnetic soft robot segment design is proposed with modified geometry to provide preferential bending planes and high angles of deflection. This design is integrated into two dual‐segment magnetic manipulators which, when arranged in parallel, can deliver independent bending in two planes of motion. Two distinct independent control strategies are proposed, based on orthogonal manipulator magnetization profiles and local field gradient control, respectively. Each dual‐manipulator configuration is characterized over a sequence of applied magnetic fields and gradients, induced via a dual robotically controlled external permanent magnet system. Manipulator independence, bending range of motion, and twisting behaviors are evaluated as a function of control strategy and manipulator separation distance. To demonstrate the system's potential in clinical scenarios, a dual‐manipulator configuration is adapted to carry an endoscopic camera and optic fiber, respectively. The resultant bimanual system is deployed in the confined anatomy of a skull‐base phantom to simulate minimally invasive ablation of a pituitary adenoma. Independent motion of the camera and tool within the confined workspace demonstrate the potential for an independent magnetic tool manipulation for surgical applications.

Insects can navigate in cluttered spaces and perform challenging functions such as pollination and collective object transport. By exploiting scaling laws and bioinspired designs, insect‐scale micro‐aerial‐vehicles (MAVs) have demonstrated impressive flight capabilities such as in‐flight collision resilience and acrobatic maneuvers. However, existing subgram MAVs are difficult to design, construct, and repair. Coupled with challenges in robot sensing and control, existing subgram MAVs have not achieved insect‐like swarm flight, which limits potential studies of swarm behaviors and future applications such as collective sensing. Herein, a new design and fabrication method is developed to substantially improve the fabrication scalability of subgram MAVs. Based on a small set of design parameters, an automated algorithm generates the laser cut files of microrobotic components. To reduce fabrication and assembly time, stereolithographic 3D printing is used for making static components such as the airframe and connectors. The modular design enables straightforward assembly and repair, which reduces the overall fabrication time by over 2 times. Owing to the ease of fabrication and good reliability, two subgram MAVs demonstrate controlled hovering flight and coordinated lifting of an object. This result lays the foundation for future robotic studies of collective insect flight.

Small‐scale robots need to be agile to perform various tasks in complex environments and the design faces great challenges with limited size and power consumption. However, the advent of advanced functional materials, compliant structures/mechanisms, and flexible fabrication techniques has brought new evolution directions to robotics. These technologies enrich the robots' actuation strategies, improving their performance of small robots while simplifying the complexity of the system and thus making it possible to be applied in diverse scenarios, such as disaster rescue, medical, and environmental exploration. In nature, small organisms have shown numerous efficient survival strategies. They can easily achieve locomotion tasks with low energy consumption. For example, dragonflies complete long flights with the help of wind, and stenus (one kind of rove beetle) uses the surface tension of liquids to dodge prey quickly. Insects are usually considered to be agile, efficient, and intelligent, which is the same requirement as for small robots. Yet the corresponding bioinspired design strategies bring new opportunities and challenges to the development of small‐scale robots. Herein, the development trends of small‐scale robots are analyzed and discussed, and several potential bioinspired synergy strategies are induced, which may be useful for the future design of insect‐level soft robots.

Soft robots are characterized by their mechanical compliance, making them well-suited for various bio-inspired applications. However, the challenge of preserving their flexibility during deployment has necessitated using soft sensors which can enhance their mobility, energy efficiency, and spatial adaptability. Through emulating the structure, strategies, and working principles of human senses, soft robots can detect stimuli without direct contact with soft touchless sensors and tactile stimuli. This has resulted in noteworthy progress within the field of soft robotics. Nevertheless, soft, touchless sensors offer the advantage of non-invasive sensing and gripping without the drawbacks linked to physical contact. Consequently, the popularity of soft touchless sensors has grown in recent years, as they facilitate intuitive and safe interactions with humans, other robots, and the surrounding environment. This review explores the emerging confluence of touchless sensing and soft robotics, outlining a roadmap for deployable soft robots to achieve human-level dexterity.

Remote stimuli‐responsive movable soft robots without the need for complex 3D deformation processes and specific working environments is an unsolved problem and urgent need. In this work, under the inspiration of mother nature, a novel strategy of simple combination of the bionic bristles structure and the photothermal‐driven reversible shape change liquid crystal polymer (LCP) actuator is proposed to work out this difficulty. The combination structure is designed as unique three parts with two bionic bristle units at the two ends and one LCP unit in the center with a soft connection between them. After matching the driving force and the resistance, the prepared soft robot can realize the earthworm‐like unidirectionally crawl on the paper surface upon near‐infrared light irradiation through the contracting and stretching of LCP with a maximum average speed of 4.4 mm min−1. What's more, the crawling speed of the soft robot can be regulated by varying the irradiation distance of near‐infrared light or the length of the actuators. This strategy realizes the type of remote wireless control soft robot and has potential application ability in other soft robots with various demands.

Amphibious robots, which are expected to move agilely in both land and water environments with huge differences in medium density, have always been a hot spot in the field of robotics. However, limited by the simple structure and drive system, the existing mini‐robots have a relatively single‐movement mode, which limits their ability to move in complex environments. This article fuses two different biomimetic morphological features to create an amphibious mini‐robot: mimicking the body shape and gait of a terrestrial inchworm, and mimicking the superhydrophobic leg shape and gait of an aquatic water strider. The light‐driven approach also brings the advantage of remote wireless manipulation. The mass of the robot is only 8 mg, and it has fast land movement speed (≈0.05 times body length s−1), water surface movement speed (≈0.5 times body length s−1), and some obstacle‐crossing ability (over obstacles of ≈64% of the robot's height). Moreover, the robot can quickly switch from land to water locomotion, which is expected to facilitate emerging applications in various industrial and biomedical settings.

Recent advances in soft robots have been achieved by using compliant materials and exploiting the advantages of the soft structural designs of living organisms. Living organisms (which have theoretically infinite degrees of freedom) are not only mechanically soft but are also capable of smooth harmonic motions, thanks to global coordination and the individual sensing and control of local tissues. Despite improvements in structural designs, few soft robot control frameworks for global object‐oriented behaviors are reported. Such a framework will require the use of multiple segments, with local sensing and independent control using coordinated policies. Here, a class of reinforcement learning based control frameworks for soft robots (with high degrees of freedom) is presented, and their ability to conduct global tasks is demonstrated. Coordinated control policies are formulated to control multiple segments with independently controllable embedded actuators, based on localized proprioceptive self‐sensing capabilities. The control frameworks are employed to develop soft physical robots. Demonstrations and experiments include the forward and backward locomotion of multichannel soft robotic flatworms. This approach is applicable to multifunctional, high degrees of freedom soft robots, as demonstrated by experiments with light‐sensitive locomotion. [ABSTRACT FROM AUTHOR]

Soft continuum robots, inspired by the adaptability and agility of natural soft-bodied organisms like octopuses and elephant trunks, present a frontier in robotics research. However, exploiting their full potential necessitates precise modeling and control for specific motion and manipulation tasks. This study introduces an innovative approach using Deep Convolutional Neural Networks (CNN) for the inverse quasi-static modeling of these robots within the Absolute Nodal Coordinate Formulation (ANCF) framework. The ANCF effectively represents the complex non-linear behavior of soft continuum robots, while the CNN-based models are optimized for computational efficiency and precision. This combination is crucial for addressing the complex inverse statics problems associated with ANCF-modeled robots. Extensive numerical experiments were conducted to assess the performance of these Deep CNN-based models, demonstrating their suitability for real-time simulation and control in statics modeling. Additionally, this study includes a detailed cross-validation experiment to identify the most effective model architecture, taking into account factors such as the number of layers, activation functions, and unit configurations. The results highlight the significant benefits of integrating Deep CNN with ANCF models, paving the way for advanced statics modeling in soft continuum robotics. [ABSTRACT FROM AUTHOR]

Power‐free shape retention enables soft pneumatic robots to reduce energy cost and avoid unexpected collapse due to burst or puncture. Existing strategies for pneumatic actuation cannot attain motion locking for trajectories combining extension and bending, one of the most common modes of operation. Here, a design paradigm is introduced for soft pneumatic actuators to enable zero‐power locking for shape retention in both extension and bending. The underpinning mechanism is the integration of a pneumatic transmitter and a multistable guider, which are programmed to interact for balanced load transfer, flexural and extension steering, and progressive snapping leading to state locking. Through theory, simulations, and experiments on proof‐of‐concept actuators, the existence of four distinct regimes of deformation is unveiled, where the constituents first interact during inflation to attain locking in extension and bending, and then cooperate under vacuum to enable fully reversible functionality. Finally, the design paradigm is demonstrated to realize a soft robotic arm capable to lock at desired curvature states at zero‐power, and a gripper that safely operates with puncture resistance to grasp and hold objects of various shapes and consistency. The study promises further development for zero‐power soft robots endowed with multiple deformation modes, sequential deployment, and tunable multistability. [ABSTRACT FROM AUTHOR]

Soft robotics offers unique advantages in manipulating fragile or deformable objects, human-robot interaction, and exploring inaccessible terrain. However, designing soft robots that produce large, targeted deformations is challenging. In this paper, we propose a new methodology for designing soft robots that combines optimization-based design with a simple and cost-efficient manufacturing process. Our approach is centered around the concept of robotic skins---thin fabrics with 3D-printed reinforcement patterns that augment and control plain silicone actuators. By decoupling shape control and actuation, our approach enables a simpler and cost-efficient manufacturing process. Unlike previous methods that rely on empirical design heuristics for generating desired deformations, our approach automatically discovers complex reinforcement patterns without any need for domain knowledge or human intervention. This is achieved by casting reinforcement design as a nonlinear constrained optimization problem and using a novel, three-field topology optimization approach tailored to fabrics with 3D-printed reinforcements. We demonstrate the potential of our approach by designing soft robotic actuators capable of various motions such as bending, contraction, twist, and combinations thereof. We also demonstrate applications of our robotic skins to robotic grasping with a soft three-finger gripper and locomotion tasks for a soft quadrupedal robot. [ABSTRACT FROM AUTHOR]

This work provides a complete framework for the simulation, co-optimization, and sim-to-real transfer of the design and control of soft legged robots. Soft robots have "mechanical intelligence": the ability to passively exhibit behaviors that would otherwise be difficult to program. Exploiting this capacity requires consideration of the coupling between design and control. Co-optimization provides a way to reason over this coupling. Yet, it is difficult to achieve simulations that are both sufficiently accurate to allow for sim-to-real transfer and fast enough for contemporary co-optimization algorithms. We describe a modularized model order reduction algorithm that improves simulation efficiency, while preserving the accuracy required to learn effective soft robot design and control. We propose a reinforcement learning-based co-optimization framework that identifies several soft crawling robots that outperform an expert baseline with zero-shot sim-to-real transfer. We study generalization of the framework to new terrains, and the efficacy of domain randomization as a means to improve sim-to-real transfer. [ABSTRACT FROM AUTHOR]

Layer jamming technologies, which can alter the stiffness of layered sheets enveloped in an elastic bag via internal vacuum pressure, have typically been used for wearable robots. However, wrinkles on the layer jamming element covering the body impair the feeling of wear and are undesirable. Aligning curved surfaces using sheets without wrinkling requires the sheets to be sufficiently elastic, which reduces the stiffness when used for layer jamming. Mesh sheets (i.e., woven fabrics) cannot elongate along the fibers; however, they can elongate and contract in the diagonal direction by changing their shape. This study proposes using mesh sheets for layer jamming and analytically and experimentally demonstrates their ability to fit curved surfaces without wrinkling. The layer jamming element using mesh sheets changes the bending stiffness in proportion to the internal vacuum pressure and the number of sheets, as in conventional layer jamming. The simple structure and flexibility of the mesh layer jamming are not only suitable for fixing a body or fragile objects but also extend the range of applications using layer jamming technologies. This study also provides a foundation for investigating the wrinkle formation associated with curved surface deformation unique to flexible robots. [ABSTRACT FROM AUTHOR]

This study presents an intelligent soft robotic system capable of perceiving, describing, and sorting objects based on their physical properties. This work introduces a bimodal self‐powered flexible sensor (BSFS) based on the triboelectric nanogenerator and giant magnetoelastic effect. The BSFS features a simplified structure comprising a magnetoelastic conductive film and a packaged liquid metal coil. The BSFS can precisely detect and distinguish touchless and tactile models, with a response time of 10 ms. By seamlessly integrating the BSFSs into the soft fingers, this study realizes an anthropomorphic soft robotic hand with remarkable multimodal perception capabilities. The touchless signals provide valuable insights into object shape and material composition, while the tactile signals offer precise information regarding surface roughness. Utilizing a convolutional neural network (CNN), this study integrates all sensing information, resulting in an intelligent soft robotic system that accurately describes objects based on their physical properties, including materials, surface roughness, and shapes, with an accuracy rate of up to 97%. This study may lay a robotic foundation for the hardware of the general artificial intelligence with capacities to interpret and interact with the physical world, which also serves as an interface between artificial intelligence and soft robots. [ABSTRACT FROM AUTHOR]

Magnetic soft robots featuring untethered actuation and high mechanical compliance have promising applications ranging from bionics to biomedicine. However, their fixed magnetization profiles pose a challenge for adaptive shape transformation in unpredictable environments and dynamic tasks. Herein, a reprogrammable magnetic soft composite is reported by encapsulating magnetic neodymium–iron–boron microparticles with low melting alloy (LMA) and embedding them into the elastomer. Utilizing the phase transition of the LMA, the magnetic microparticles can be reoriented under an external magnetic field and they can be immobilized through LMA solidification, allowing the robot to obtain a new magnetization profile corresponding to its temporary shape. By changing the LMA composition, the robot with multiple programming temperatures can be fabricated and its local magnetization profiles can be selectively programmed in different temperature ranges. A bioinspired crawler with multimode locomotion, a reconfigurable robotic gripper capable of adaptable grasping, and reconfigurable electronic circuits are also demonstrated. This work may pave the way for the next‐generation magnetic soft robots and reconfigurable devices. [ABSTRACT FROM AUTHOR]

Abstract Dielectric elastomer actuators (DEAs) are one of the emerging areas of investigation in smart elastomer research and have attracted considerable interests due to their wide‐ranging applications, for instance in automation and soft robotic components. Commonly utilized dielectric elastomers (DEs) such as nitrile butadiene rubber (NBR) and its hydrogenated and carboxylated derivatives along with the dielectric fillers (titanium oxide, barium titanate, etc.) were considered to be one of the most established composite systems demonstrating high actuation performance. When subjected to external electrical field, the DEAs derived from the composites were, therefore, capable of reproducing high energy density and large deformation with fast response time. The recent research emphasizes that tunable material properties eventually triggered the improved actuation performance. The exploration of compliant electrodes fabricated by the conventional and state‐of‐the‐art lithographic methods was also crucial to improve actuation performance for the soft robotic applications. This review summarizes the commonly used DEs and dielectric fillers, their performances and challenges, and outlines the research progress (experimental and theoretical) in the field of actuators. Finally, a brief introduction to DEA‐based soft robotics application is also presented.

Soft robots have gained significant attention in recent years owing to their high safety in human–machine interactions and exceptional adaptability to unpredictable environments. Despite great advances, achieving continuous rotation with tunable stepping angle in soft robots remains a challenge. Herein, inspired by the stepping rotation strategy of the flagellum, an artificial soft rotary motor capable of bidirectional continuous rotation and tunable stepping angles is presented. The motor features a wide range of stepping angles (−72.5° to 73.4°), enabling it to rotate to any angle position with high resolution. The soft motor also exhibits high rotation speed (18.23 r min−1), zero‐energy position‐holding, and excellent durability. Furthermore, the potential applications of the soft rotary motors, including tuning the grasping direction of a soft gripper and adjusting the winding direction of a soft tentacle is demonstrated. This work offers a universal soft fluidic component for soft robots, endowing them with enhanced agility and movement capabilities. [ABSTRACT FROM AUTHOR]

Crosslinked liquid crystal polymers (CLCPs) are a promising type of smart polymer material with excellent two‐way shape memory behavior under the stimulation of various external conditions. Among the various external stimuli, light with the advantages of instantaneity, high accuracy, remote controllability, pollution‐free, etc., has been widely used in the control of CLCPs. Traditional photoresponsive CLCP systems based on photoisomerization are limited by the penetration depth of ultraviolet light, the number of useful photochemical reactions, and long‐term stability. Recently, a strategy for designing photoresponsive CLCPs based on the photothermal effect has attracted scientific attention. Photothermal materials in the CLCP matrix can convert light into heat through plasma resonance or energy transition under the light irradiation of a certain wavelength, and locally heat the CLCP matrix to beyond the liquid crystal‐to‐isotropic phase transition temperature, thus achieving reversible macroscopic deformation. Combining photothermal materials and CLCPs can decrease the dependence on specific photosensitive groups such as azobenzene mesogens and endow photoresponsive CLCPs with design flexibility. Herein, the photothermal‐responsive CLCPs under the stimulations of different light wavelengths and their application fields are reviewed. In addition, the current challenges in the field of photothermal‐responsive CLCPs are summarized, and a brief outlook on future development is proposed. [ABSTRACT FROM AUTHOR]

The exciting development of hydrogels makes it a promising candidate to be applied in various fields. However, it remains a great challenge to store the precursors of hydrogels and to process them after gelation, like synthetic polymer materials. Herein, spidroin‐inspired novel nanogels with extraordinary processability, which can be spun into fibers via direct drawing and fabricated into thermal actuators easily after gelation are prepared. These soluble and spinnable nanogels are composed of a liquid metal core and a poly (acrylic acid) (PAA) shell and are entangled with each other. The as fabricated nanogels and diluted dope solution can be stored >1 month. The as‐spun nanogel fibers with hierarchical structures achiev extraordinary mechanical properties (tensile stress of 575 MPa, toughness of 381 MJ m−3) and supercontraction at 60% RH. Besides, a photothermal actuator is prepared by coating the nanogels on a polyethylene substrate with a commercial shading ink, and the as‐prepared actuator shows a rapid response to near‐infrared light as well as a fast recovery. Molecular dynamics simulation reveals a possible working mechanism of the actuator. This study provides a new strategy to prepare processable nanogels with broad application prospects for smart textiles and soft robots. [ABSTRACT FROM AUTHOR]

Soft robots typically exhibit limited agility due to inherent properties of soft materials. The structural design of soft robots is one of the key elements to improve their mobility. Inspired by the Archimedean spiral geometry in nature, here, a fast‐moving spiral‐shaped soft robot made of a piezoelectric composite with an amorphous piezoelectric vinylidene fluoride film and a layer of copper tape is presented. The soft robot demonstrates a forward locomotion speed of 76 body length per second under the first‐order resonance frequency and a backward locomotion speed of 11.26 body length per second at the third‐order resonance frequency. Moreover, the multitasking capabilities of the soft robot in slope climbing, step jumping, load carrying, and steering are demonstrated. The soft robot can escape from a relatively confined space without external control and human intervention. An untethered robot with a battery and a flexible circuit (a payload of 1.665 g and a total weight of 1.815 g) can move at an absolute speed of 20 mm s−1 (1 body length per second). This study opens a new generic design paradigm for next‐generation fast‐moving soft robots that are applicable for multifunctionality at small scales. [ABSTRACT FROM AUTHOR]

Soft robots, which exhibit distinguishing features in terms of compliance, adaptability, and safety, have been expansively adopted in various niche applications. For soft robots, innovative actuators have been designed based on smart materials enabling the robots to perform flexible and versatile functions, whereas extra spaces and accessories to accommodate motors and power devices have been eliminated to achieve structural optimisation. Herein, different types of actuation mechanisms for soft robots are summarised to reflect the state-of-the-art research and applications. Major characteristics of the actuation mechanisms are updated. Design methodologies of the actuation mechanisms are discussed in detail. Furthermore, their advantages, disadvantages, and application potential are compared and summarised. In the end, based on our knowledge and understanding, new thoughts and recommendations to further develop the actuation mechanisms are put forward. This review is useful to support the conclusion that, through incorporating actuation mechanisms and advanced intelligent technologies, soft robots tend to create disruptive innovations in applications. [ABSTRACT FROM AUTHOR]

Magnetic soft robots capable of wirelessly controlled programmable deformation and locomotion are desirable for diverse applications. Such multi‐variable actuation ideally requires a polymer matrix with a well‐defined range of softness and stretchability (Young's modulus of 0.1–10 MPa, high stretchability >200%). However, this defined mechanical range excludes most polymer candidates, leaving only a limited number of available polymers (e.g., PDMS, Ecoflex) with covalently cross‐linked networks that may lead to non‐recyclable robots and further potential threats to environment. Herein, based on the synergistic effects of reduced cross‐linking density and intermolecular hydrogen bonding, a dynamic covalent polyimine is newly designed as polymer matrix and magnetic microparticles as fillers, and integrate defined softness and stretchability, full chemical recyclability, rapid room‐temperature healability and multimodal actuation into a single magnetic soft robot. The polyimine is soft and stretchable enough to process soft robots in various geometries by simple laser cutting, without the need to pre‐design the geometry to suit target scenarios. Through a cyclic depolymerization/repolymerization, this full recycling restores 100% of the robots' mechanical properties and rapid deformability/mobility to their original level within seconds and heals quickly within minutes when damaged, facilitating ideal cyclic material economy for soft robots in diverse scenarios. [ABSTRACT FROM AUTHOR]

Soft robots are featured with safe interaction, good adaptability, and strong flexibility due to their own material composition and structural peculiarities. Nowadays, they are widely used in medical services, agricultural harvesting, disaster relief and rescue, underwater exploration and other fields. This paper provides a summary of soft robotic drive modes and drive materials, and classifies soft robotic drive modes into flexible fluid drive and smart material drive according to whether smart materials are included or not, where flexible fluid drive is illustrated from the three aspects of soft body structure, material and power source. With the development of smart materials, this paper proposes the connection between smart materials and soft robots for the first time, summaries the exposition from the aspects of principle, materials and structure, and finally discusses the soft robot drive and looks forward to its future development. [ABSTRACT FROM AUTHOR]

Smart materials respond to environmental signals by changing their microstructure and physical properties. Programming multiple behaviors and functions into a single material could increase its utility and adaptability to ever‐changing environmental conditions. A swellable and stretchable metamaterial hydrogel or "metasponge" engineered to morph into customized sizes and shapes that dynamically tune its physical properties and functions is reported. Multiple case studies that take advantage of the morphing properties of the metasponge, including robotic actuation, light guidance, optical and sonic invisibility ("cloaking"), adaptation of propulsion mode, sampling, and multiple biomedical applications, are illustrated. Developing multifunctional smart materials in which logic is programmed into the materials rather than electronic components could pave a new path to autonomy and dynamic responses in soft robots, sensors, and actuators. [ABSTRACT FROM AUTHOR]

A fundamental challenge of pneumatically powered soft robotic devices is the scalability of fluidic control systems to address each actuated degree of freedom, as the required electromechanical valves are bulky and expensive. Previous solutions have compromised the reprogrammability and/or the bandwidth of the fluidic system. This article describes and models a fluidic subsystem, a fluidic matrix circuit (FMC), that enables the independent control of many (N2$N^{2}$) actuators using a limited number (2N$2 N$) of electromechanical valves. The fundamental unit, a fluidic logic module (FLM), generates a bidirectional pressure signal (vacuum or positive pressure) based on the state of the mass flow through it. Thus and array of pneumatic actuators can be addressed individually using an array of FLMs integrated into a matrix (i.e., an FMC), with electromechanical valves to switch the mass flow through each row and column of the matrix. The resulting refresh rates are an order of magnitude faster than previous approaches. This concept with a prototype FMC able to control 25 actuators using 10 electromechanical valves for applications including a fluidic shape display and a wearable haptic vest is demonstrated. This approach could enable more complex and sophisticated soft robotic devices with scalable control hardware. [ABSTRACT FROM AUTHOR]

Unlike conventional rigid machines, soft robots generally have unique operation styles that rely heavily on soft matter engineering and smart material systems. Owing to the superior merits of both metals and fluids, liquid metal smart materials are increasingly being innovatively used as soft actuators and sensors to construct soft robots. To promote further development and prosperity in this field, this review organizes and summarizes the typical progress in liquid metal smart materials, with a special focus on their robotic response behaviors. In particular, the article emphasizes the concept of smart composite systems consisting of liquid metals and synergistic substances (e.g., solutions, particles, and polymers). The response behaviors of liquid metal smart materials under the actions of external factors (electricity, magnetism, ultrasound, light, heat, etc.) are examined and the smart properties occurring during these responses, such as motion, transformation, self‐organization, adaptive healing, and autonomous sensing, are identified. Furthermore, soft actuators, control systems, and robots based on liquid metal smart materials are summarized and elaborated upon. Finally, the potential directions worth pursuing and challenges are outlined. It is expected that this review will stimulate further investigations into liquid metal smart materials with the aim of building a new generation of soft robots. [ABSTRACT FROM AUTHOR]

In recent years, soft robots gain increasing attention as a result of their compliance when operating in unstructured environments, and their flexibility that ensures safety when interacting with humans. However, challenges lie on the difficulty to develop control algorithms due to various limitations induced by their soft structure. In this paper, we introduce a novel technique that aims to perform motion control of a modular bio-inspired soft-robotic arm, with the main focus lying on facilitating the qualitative reproduction of well-specified periodic trajectories. The introduced method combines the notion behind two previously developed methodologies both based on the Movement Primitive (MP) theory, by exploiting their capabilities while coping with their main drawbacks. Concretely, the requested actuation is initially computed using a Probabilistic MP (ProMP)-based method that considers the trajectory as a combination of simple movements previously learned and stored as a MP library. Subsequently, the key components of the resulting actuation are extracted and filtered in the frequency domain. These are eventually used as input to a Central Pattern Generator (CPG)-based model that takes over the generation of rhythmic patterns at the motor level. The proposed methodology is evaluated on a two-module soft arm. Results show that the first algorithmic component (ProMP) provides an immediate estimation of the requested actuation by avoiding time-consuming training, while the latter (CPG) further simplifies the execution by allowing its control through a low-dimensional parameterization. Altogether, these results open new avenues for the rapid acquisition of periodic movements in soft robots, and their compression into CPG parameters for long-term storage and execution.

Magnetic soft robots featuring untethered actuation and high mechanical compliance have promising applications ranging from bionics to biomedicine. However, their fixed magnetization profiles pose a challenge for adaptive shape transformation in unpredictable environments and dynamic tasks. Herein, a reprogrammable magnetic soft composite is reported by encapsulating magnetic neodymium–iron–boron microparticles with low melting alloy (LMA) and embedding them into the elastomer. Utilizing the phase transition of the LMA, the magnetic microparticles can be reoriented under an external magnetic field and they can be immobilized through LMA solidification, allowing the robot to obtain a new magnetization profile corresponding to its temporary shape. By changing the LMA composition, the robot with multiple programming temperatures can be fabricated and its local magnetization profiles can be selectively programmed in different temperature ranges. A bioinspired crawler with multimode locomotion, a reconfigurable robotic gripper capable of adaptable grasping, and reconfigurable electronic circuits are also demonstrated. This work may pave the way for the next‐generation magnetic soft robots and reconfigurable devices.

The monitoring of the grasping behavior of variable stiffness grippers has emerged as a challenge due to the increasing use of soft grippers in logistics sorting applications. In this research, a flexible multifunctional sensor is developed by combining a liquid metal microchannel structure with a granular single electrode which detects the bending angle and stiffness of the flexible gripper in real‐time. The novel works by integrating triboelectric nanogenerator with particle interference variable stiffness and detects the stiffness of the soft finger. It is found that increasing the loading force on the gripper by a factor of 2.39 does not affect the kinematic characteristics. The size of the grasped object is determined with 96% accuracy by detecting the resistance offered to the stretched liquid metal during the bending of the soft finger. A soft grasping system is built with multifunctional flexible sensors and the real‐time signal feedback during the grasp‐move‐release process of objects of different diameters and weights is demonstrated. Besides providing a theoretical and experimental foundation of variable stiffness and nondestructive grasping of the soft gripper, the anthropomorphism of the soft grasping gripper is implemented by employing a novel sensor. [ABSTRACT FROM AUTHOR]

Cheetahs achieve high‐speed movement and unique athletic gaits through the contraction and expansion of their limbs during the gallop. However, few soft robots can mimic their gaits and achieve the same speed of movement. Inspired by the motion gait of cheetahs, here the resonance of double spiral structure for amplified motion performance and environmental adaptability in a soft‐bodied hopping micro‐robot is exploited. The 0.058 g, 10 mm long tethered soft robot is capable of achieving a maximum motion speed of 42.8 body lengths per second (BL/s) and a maximum average turning speed of 482° s−1. In addition, this robot can maintain high speed movement even after flipping. The soft robot's ability to move over complex terrain, climb hills, and carry heavy loads as well as temperature sensors is demonstrated. This research opens a new structural design for soft robots: a double spiral configuration that efficiently translates the deformation of soft actuators into swift motion of the robot with high environmental adaptability. [ABSTRACT FROM AUTHOR]

Liquid‐crystal polymers are a type of representative material combining the order‐disorder transition of liquid crystals and the superior properties of polymers. The phase transition from the liquid‐crystal phase to the isotropic state of mesogens causes large, controllable, and reversible deformation of polymers; thus, liquid‐crystal polymers have emerged as one of the most valuable candidates for shape‐morphing materials. Therefore, this review will focus on the recent development of shape‐morphing liquid‐crystal polymers, including the modes of energy conversions, material design strategies and further applications. In the main, novel material design methods and a wide range of application of shape‐morphing liquid‐crystal polymers are discussed. [ABSTRACT FROM AUTHOR]