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The dynamics of a soft particle suspended in a viscous fluid can be changed by the presence of an elastic boundary. Understanding the mechanisms and dynamics of soft–soft surface interactions can provide valuable insights into many important research fields, including biomedical engineering, soft robotics development, and materials science. This work investigates the anomalous transport properties of a soft nanoparticle near a visco-elastic interface, where the particle consists of a polymer assembly in the form of a micelle and the interface is represented by a lipid bilayer membrane. Mesoscopic simulations using a dissipative particle dynamics model are performed to examine the impact of micelle's proximity to the membrane on its Brownian motion. Two different sizes are considered, which correspond to ≈ 10 − 20 n m in physical units. The wavelengths typically seen by the largest micelle fall within the range of wavenumbers where the Helfrich model captures fairly well the bilayer mechanical properties. Several independent simulations allowed us to compute the micelle trajectories during an observation time smaller than the diffusive time scale (whose order of magnitude is similar to the membrane relaxation time of the largest wavelengths), this time scale being hardly accessible by experiments. From the probability density function of the micelle normal position with respect to the membrane, it is observed that the position remains close to the starting position during ≈ 0.05 τ d (where τd corresponds to the diffusion time), which allowed us to compare the negative excess of mean-square displacement (MSD) to existing theories. In that time range, the MSD exhibits different behaviors along parallel and perpendicular directions. When the micelle is sufficiently close to the bilayer (its initial distance from the bilayer equals approximately twice its gyration radius), the micelle motion becomes quickly subdiffusive in the normal direction. Moreover, the temporal evolution of the micelle MSD excess in the perpendicular direction follows that of a nanoparticle near an elastic membrane. However, in the parallel direction, the MSD excess is rather similar to that of a nanoparticle near a liquid interface. [ABSTRACT FROM AUTHOR]

This paper demonstrates experimental and theoretical research of the magnetostrictive stresses of the magnetorheological elastomer (MRE) films comprised of PDMS and Fe/Fe3O4 nanoparticles. The MRE films possessing three types of microstructures were formed via imposing an external magnetic field or under no magnetic field during the film preparation, whose nanoparticle weight fractions were in the range of 1–40 wt%. The measurement of the film magnetostrictive stresses was carried out by employing the FLX 2320‐S thin film stress measurement system with a special structure used for applying a homogeneous magnetic field to the samples in the process of testing. The experimental data show that the film magnetostrictive stresses are greatly dependent on the nanoparticle concentration and the film microstructure. The theoretical analysis and numerical simulation were performed to obtain a good understanding of the mechanism and the important influencing factors of the film magnetostrictive stresses. For the isotropic specimens, the calculated values of the film magnetostrictive stresses are in good agreement with the measured values. The research results reported in this work could facilitate the applications of MREs to the micro/nano technology field such as MEMS, small‐scale soft robotics, and so on. Highlights: Magnetostrictive stresses of MRE films can be experimentally obtained.Magnetostrictive stress results from magneto‐mechanical coupling.Particle content has an effect on film magnetostrictive stress.Orientation of particle clusters influences film magnetostrictive stress.Size and number of particle clusters affect film magnetostrictive stress. [ABSTRACT FROM AUTHOR]

Liquid metal (LM) elastomer composites offer promising potential in soft robotics, wearable electronics, and human‐machine interfaces. Direct ink write (DIW) 3D printing offers a versatile manufacturing technique capable of precise control over LM microstructures, yet challenges such as interfilament void formation in multilayer structures impact material performance. Here, a DIW strategy is introduced to control both LM microstructure and material architecture. Investigating three key process parameters–nozzle height, extrusion rate, and nondimensionalized nozzle velocity–it is found that nozzle height and velocity predominantly influence filament geometry. The nozzle height primarily dictates the aspect ratio of the filament and the formation of voids. A threshold print height based on filament geometry is identified; below the height, significant surface roughness occurs, and above the ink fractures, which facilitates the creation of porous structures with tunable stiffness and programmable LM microstructure. These porous architectures exhibit reduced density and enhanced thermal conductivity compared to cast samples. When used as a dielectric in a soft capacitive sensor, they display high sensitivity (gauge factor = 9.0), as permittivity increases with compressive strain. These results demonstrate the capability to simultaneously manipulate LM microstructure and geometric architecture in LM elastomer composites through precise control of print parameters, while maintaining geometric fidelity in the printed design. [ABSTRACT FROM AUTHOR]

Introduction: Wearable exoskeletons are emerging technologies for providing movement assistance and rehabilitation for people with motor disorders. In this study, we focus on the specific gait pathology dropfoot, which is common after a stroke. Dropfoot makes it difficult to achieve foot clearance during swing and heel contact at early stance and often necessitates compensatory movements. Methods: We developed a soft ankle exoskeleton consisting of actuation and transmission systems to assist two degrees of freedom simultaneously: dorsiflexion and eversion, then performed several proof-of-concept experiments on non-disabled persons. The actuation system consists of two motors worn on a waist belt. The transmission system provides assistive force to the medial and lateral sides of the forefoot via Bowden cables. The coupling design enables variable assistance of dorsiflexion and inversion at the same time, and a force-free controller is proposed to compensate for device resistance. We first evaluated the performance of the exoskeleton in three seated movement tests: assisting dorsiflexion and eversion, controlling plantarflexion, and compensating for device resistance, then during walking tests. In all proof-of-concept experiments, dropfoot tendency was simulated by fastening a weight to the shoe over the lateral forefoot. Results: In the first two seated tests, errors between the target and the achieved ankle joint angles in two planes were low; errors of <1.5° were achieved in assisting dorsiflexion and/or controlling plantarflexion and of <1.4° in assisting ankle eversion. The force-free controller in test three significantly compensated for the device resistance during ankle joint plantarflexion. In the gait tests, the exoskeleton was able to normalize ankle joint and foot segment kinematics, specifically foot inclination angle and ankle inversion angle at initial contact and ankle angle and clearance height during swing. Discussion: Our findings support the feasibility of the new ankle exoskeleton design in assisting two degrees of freedomat the ankle simultaneously and show its potential to assist people with dropfoot and excessive inversion. [ABSTRACT FROM AUTHOR]

Physical interaction with patients, for example conducted as part of a diagnostic examination or surgical procedure, provides clinicians with a wealth of information about their condition. Simulating this interaction is of great interest to researchers in both haptics and medical education, and the development of softness changing tactile interfaces is important in recreating the feel of different soft tissues. This paper presents designs for a variety of novel electromechanical and electromagnetic mechanisms for controlling particle jamming-based, hardness changing tactile displays, intended to allow medical trainees to experience these physical interactions in a range of simulation settings such as clinical skills teaching laboratories. Each design is then subjected to a battery of mechanical tests to evaluate its effectiveness compared to the state of the art, as well as their suitability for simulating the physical hardness of different types of soft tissues, previously characterised in established literature. These results demonstrate that all of the technologies presented are able to exhibit a measurable hardness change, with Shore hardness values between 3A and 57A achieved by the most effective constriction-based device. The electromechanical devices based on constriction and compression, and the state-of-the-art pneumatic device, were able to achieve hardness changes within a range that is useful for replicating the softness of organic tissue. The electromechanical and electromagnetic devices were also found to effect their full range of hardness change in less than a second, compared to several seconds for the state-of-the-art. These results show that the performance of softness changing tactile displays can be improved with the electromechanical actuation techniques proposed in this paper, and that such displays are able to replicate the physical characteristics of soft tissues and may therefore be of benefit in medical training and simulation scenarios. [ABSTRACT FROM AUTHOR]

[Display omitted] Replicating the tactile sensing mechanisms, conformity, and feel of real skin is essential for next-generation human–machine interfaces. However, producing tissue-like multilayered geometries and integrating them as e-skin systems requires simplifying and standardizing their manufacture. Here, we present a scalable and cost-effective cure-on-demand strategy for 3D printing nanocomposite silicone rubbers and integrating them into complex soft structures with 1200 % enhanced pressure-strain sensitivity. By utilizing a controlled in-situ mixing of catalyst-cured silicones and shear-driven alignment of carbon nanofibers (CNF), we construct percolated networks with conductivities up to 130 S m−1 layer-by-layer. We investigate the influence of ink composition, printing parameters, geometrical design, and material density on the mechanical properties, stretchability, sensitivity, and antimicrobial activity of 3D printed piezoresistive sensors and build skin-like interfaces that detect minimal deformations like human physiological signs. This customizable, biocompatible, and robust e-skin holds promise for cost-effective integration in rehabilitation medicine, smart robotics applications, and extended reality (XR) interactive experiences. [ABSTRACT FROM AUTHOR]

Cellulose-based actuators hold great promise for diverse applications, including soft robotics, biomedicine, and electronics. Achieving reversible motion is crucial to design high performance bio-based actuators. In this study, we explore the impact of carboxymethylation and 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) oxidation on the reversible performance of cellulose-based pH-responsive actuators. Both methods introduce negatively charged groups onto the surface of cellulose fibers, enabling increased water uptake at high pH. However, comparative analyses revealed structural differences, guiding the design of reversible actuators. Carboxymethylated CNFs (CMCNFs) displayed enhanced water uptake and pH sensitivity, attributed to their less cohesive structure. Actuation and reversibility tests on bilayer films validated these findings. This research advances the understanding of cellulose functionalization for tailored actuation, contributing to the development of programmable materials for multiple applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • We proposed an SPA based on a Kresling-like pattern with a rigid skeleton by observing the cloning and moving behaviors from salps. • An extensible inserting structure is innovatively designed to replace the creases in traditional Kresling patterns. • The SPA can perform an axial contraction motion without twisting and a controllable bending motion. • The number of layers of Kresling-like patterns is changeable by adding or reducing skeleton components. • The elongation can reach to above 162% and the output force can reach to above 6.36 N. Biomimetic soft pneumatic actuators (SPA) with Kresling origami patterns have unique advantages over conventional rigid robots, owing to their adaptability and safety. Inspired by cloning and moving behaviors observed from salps, we proposed an SPA based on a Kresling-like pattern with a rigid skeleton. The elongation and output force were tested, and the effectiveness of the applications with the SPA was evaluated. The proposed SPA consists of rigid skeletons and a soft skin. The rigid skeletons are constructed using layers of Kresling-like patterns, while a novel extensible inserting structure is devised to replace the folds found in conventional Kresling patterns. This innovative approach ensures that the SPA exhibits axial contraction/expansion motion without any twisting movement. To mimic the bionic characteristics of swimming and ingesting progress of salps, the proposed SPA can perform an axial contraction motion without twisting and a controllable bending motion based on multi-layered Kresling-like patterns; to mimic the cloning and releasing life phenomena of salps, the number of layers of Kresling-like patterns is changeable by adding or reducing skeleton components according to the practical needs. The experimental elongation results on the SPA with multiple layers of Kresling-like patterns show that the elongation can increase to above 162% by adding layers; the experimental output force results show that the three-layer SPA can provide 6.36 N output force at an air flow rate of 10 L/min, and the output force will continue to increase as the number of layers of Kresling-like pattern increases or the air flow rate increases. Further, we demonstrate the applications of the SPA in soft grippers, scissor grippers, claw grippers and pipe crawlers. Our proposed SPA can avoid twisting in the radial contraction motion with high elongation and output force, and provide the practical guidance for bio-inspired soft robotic applications. [ABSTRACT FROM AUTHOR]

Innovative high-performance composite materials are the need of the hour required by modern manufacturing techniques such as 3D printing due to less weight with high mechanical and thermal properties-based materials required. The application domain of 3D-printed high-performance composite materials includes aerospace, automobile, tissue engineering, soft robotics, sensors, and actuator applications. In this regard, the combination of metal-reinforced polymer composites has emerged as one of the most innovative sources for 3D printing applications in such sectors. The present study detailed the state-of-the-art review of the metal reinforcement in the polymer's matrix fit for 3D printing applications. The reinforcement of the metal in the polymers tunes the mechanical, thermal, chemical, morphological, electrical, and sensing properties that are very crucial for high-performance applications. The main outcomes of this study are to determine the best suitability of composite materials in accordance with requirements. In this study, the high-performance metals reinforcement materials such as Ag, Al, Cu, and Au have been discussed with their potential applications (medical, electronics, household, sports, communications, military, business, industry, marine, energy, civil, aerospace, and the automobile) as per required properties. This study is supported by the direction of future studies for extending the innovations and applications. [ABSTRACT FROM AUTHOR]

Stretchable conductive hydrogels have garnered considerable recognition due to their uses in strain sensors, electronic skins, soft robotics, and actuators. However, many hydrogels have poor mechanical properties limiting widespread implementation. While the development of ultrastretchable and mechanically robust hydrogels remains a challenge, the fabrication of these materials with customized designs is also highly desirable. Herein, a direct‐ink write 3D printable double‐network (DN) hydrogel is reported by integrating a physically cross‐linked κ‐carrageenan and a chemically cross‐linked poly(acrylamide‐co‐hydroxyethyl acrylate‐co‐Pluronic F127‐bisurethane methacrylate) with an ionically cross‐linked coordination between κ‐carrageenan and Fe3+ ions in water–glycerol binary solvent. The DN hydrogel demonstrates excellent stretchability (1770% strain), remarkable toughness (6.24 MJ m−3), high ionic conductivity (1.55 S m−1), biocompatibility, and nondrying behavior. A variety of 3D printed constructs including auxetic structures are fabricated and used as a strain sensor. The sensor exhibited real‐time electrical response to strain to detect human motions demonstrating the practicality of this system. These 3D printable DN hydrogels show great potential for on‐demand fabrication of flexible health‐monitoring devices. [ABSTRACT FROM AUTHOR]

The ability to switch adhesion strength is a highly desirable property for adhesives applied in a wet environment. The major challenges involve the presence of a water layer between the substrate and adhesive, and the incorporation of efficient switching mechanisms. Despite the recent progresses in devising such systems, there exist several intrinsic limitations in the current strategies, such as high residual adhesion, the use of solid–liquid transition, or thin film configurations. Herein, a channeled poly(N‐isopropylacrylamide) (PNIPAm) hydrogel containing bio‐inspired dopamine‐comonomers is reported, which undergoes temperature‐controlled reversible switching of underwater adhesion on both hydrophilic and hydrophobic surfaces. The introduction of microscopic channels inside the hydrogel, achieved by removing a sacrificial agarose network, greatly facilitates water removal from the interface and thus promotes underwater adhesive strength. On glass, the maximum adhesive stress of the channeled hydrogel can reach six times that of hydrogels without channels. Additionally, high switching efficiency and low residual adhesion can be achieved by the thermal phase transition of the PNIPAm network, also demonstrated by the capture and release of lightweight, irregular, fragile, and biological objects using the hydrogel. The channeling strategy provides implications for designing future underwater adhesive systems for, e.g., soft robotics or biomedical applications. [ABSTRACT FROM AUTHOR]

Soft robotics, an emerging field that focuses on the development of robots utilizing soft, flexible, and deformable materials, is revolutionizing traditional robotics (reliant on rigid materials and motors) and broadening its range of applications and potential uses. In addition, by emulating the structure, function, and characteristics of biological systems, bioinspired materials are facilitating significant progress in a diverse array of soft robotic applications. This review offers an overview of bioinspired materials employed in soft robotics, exploring their potential applications, challenges, and future research directions. For an intuitive understanding, soft robots based on the primary abilities required and the habitats (terrestrial, aquatic, aerial) of the animals and plants they mimic are categorized. Furthermore, real‐world applications of developed soft robots in everyday human life are presented. The novel category classification and comprehensive analysis presented in this review provide insights into the development of soft robotic systems with the potential to transform various industries and enhance quality of life. [ABSTRACT FROM AUTHOR]

Inflatable multistable materials have significantly advanced the design of shape‐preserving soft robotic arms, offering substantial benefits in terms of shape adaptability, energy efficiency, and safety, ensuring operational reliability even in the event of sudden power loss. However, existing strategies for realizing multistable arms often limit themselves to a single mode of multistability, commonly with rotationally symmetric designs favoring extension stability and asymmetric designs inducing bending stability. To address the limitation, this study introduces a pioneering platform termed multimodal multistability that utilizes geometrical frustration. A single cylindrical symmetric cell, designed for extension bistability, could achieve frustrated multistable states in bending by controlling the cell with multiple degrees of freedom incorporated pneumatic actuator. This platform extends the spectrum of attainable stable trajectories while preserving essential attributes of arms, such as load‐bearability, programmability, and reversibility of shape changes. Leveraging a pneumatic system with four degrees of freedom for pressure control, not only enables capturing previously unexplored stable configurations in mechanical metastructures but also allows for the control of their deformation modes. With applications spanning space exploration, medical instruments, and rescue missions, the multimodal multistability promises unparalleled flexibility and efficiency in the design and operation of soft robots. [ABSTRACT FROM AUTHOR]

Humans can grab and identify objects by capturing the features of physical shape, temperature, and material. However, creating artificial sensors with finger‐like tactile capabilities is challenging due to the contradiction between structural compliance and multifunctional sensing. Here, a sensory system for a robot hand that can achieve object recognition is reported. The sensor with a simple horizontal sensing structure can respond to strain, material, and temperature stimuli using piezoresistive, triboelectric, and thermoelectric effects. A machine learning algorithm to train and classify tactile sensing signals, enabling a high accuracy of 98.5% in recognizing five objects is also developed. This work contributes to the development of sensory systems for object recognition in soft robotics. [ABSTRACT FROM AUTHOR]

Dielectric elastomers (DEs) are widely studied and applied as an artificial muscle owing to their combined features of large actuation strain, fast response, high energy density, and low noise. However, scalable fabrication of dielectric elastomer actuators (DEAs) with low driving voltages (100 s of volts) and high mechanical outputs remains challenging, which significantly limits their wider applications. In this work, processable, high‐performance dielectric elastomer (PHDE) ultra‐thin film based multilayer DEAs (PUT‐MDEAs) through an optimized dry‐stacking process are fabricated. The obtained ten‐layer PUT‐MDEAs show actuation at 200 V and reach a maximum areal strain of ≈80% at 800 V. They deliver a blocked force of 0.1 N and an energy density of 22 J kg−1 at 200 V and achieve a blocked force of 0.7 N and an energy density of 50 J kg−1 at 700 V. In addition, large‐area PUT‐MDEAs are fabricated using the scalable dry‐stacking method, and  adopted to build low‐driving‐voltage soft pumps and robotic fish, showing their potential for practical applications. [ABSTRACT FROM AUTHOR]

Highlights Flexible pressure sensors (FPS) are crucial for emerging applications like wearable electronics, human activity monitoring, and soft robotics. This study reports a scalable and cost‐effective approach to fabricate high‐performance piezoresistive FPS based on polyurethane‐silicone rubber (PU‐SR) nanocomposites. The synergistic integration of nitrogen‐doped bamboo‐shaped carbon nanotubes (N‐BCNT) and carbon black (CB) nanofillers within the PU‐SR matrix was achieved via a novel dip‐coating and impregnation method. This technique enabled uniform nanofiller dispersion, enhancing electrical conductivity and mechanical stability. Comprehensive characterization using x‐ray photoelectron spectroscopy (XPS), zeta potential, high‐resolution transmission electron microscopy (HRTEM), and micro‐computed tomography (Micro‐CT) elucidated the structural features and morphological aspects. The optimized N‐BCNT:CB/PU‐SR nanocomposite exhibited exceptional piezoresistive performance, with a sensitivity of 0.4 kPa−1 in the 0–120 kPa range and 0.07 kPa−1 in the 180–1000 kPa range, along with remarkable durability over cyclic loading. When deployed as an electronic skin (e‐skin), the sensor accurately detected various human motions, including finger, wrist, elbow, and knee movements, as well as twisting and stretching actions. This work shows a promising route towards fabricating cost‐effective, flexible, and high‐performance pressure sensors with significant implications for wearable technologies and soft robotics. Hybrid Nanocomposite sensors achieve high sensitivity over a broad pressure range. N‐CNTs and CB enhance piezoresistivity and durability in PU‐SR nanocomposites. Flexible sensors detect multi‐joint human motions accurately. Alternative dip‐coating technique ensures uniform nanofiller distribution. Cost‐efficient sensors design suitable for wearable e‐skin applications. [ABSTRACT FROM AUTHOR]

Hydrogel‐based actuators are innovative materials that exhibit responsive and dynamic behavior in response to external stimuli, making them promising candidates for a wide range of applications in fields such as soft robotics. We employ 3D printing to create layered rectangles, using a passive ink composed of gelatin methacryloyl (GelMA) and an active ink consisting of GelMA and poly(N‐isopropylacrylamide) (PNIPAM). Our aim is to assess and compare the bending capabilities of these structures based on their layer arrangements in a buffer above the lower critical solution temperature. Therefore, an asymmetric rectangular structure is selected as the shape‐changing component in the tail of a 3D printed fish‐shaped hydrogel actuator. We show that gold nanostars integrated into the actuators serve as photothermal elements, enabling the fish tail to repeatedly bend when near infrared light is turned on and off. Our effort illustrates the potential of combining 3D printing, responsive hydrogels and photothermal elements with near infrared light towards soft robotic applications. This combination yields actuators capable of shape‐shifting without requiring localized light or transitioning between environments with varying temperatures. [ABSTRACT FROM AUTHOR]

Eutectogels, composed of deep eutectic solvents (DESs) and polymeric networks, are promising as pivotal components in flexible energy storage, soft robotics, wearable electronic devices, etc. However, an inherent trade‐off between ionic conductivity and mechanical properties, which stems from the antagonism between the DES and polymeric networks, restricts the advancement of eutectogels. Herein, a sequentially enhanced strategy via freeze‐casting, solvent exchanges, and wet annealing to construct supramolecular poly(vinyl alcohol) (PVA) eutectogels with ultratough mechanical properties and high ionic conductivity is proposed. The trade‐off is reconciled by building aligned through‐pores to facilitate efficient ion transport and by further rationally regulating the aggregation structures of PVA chains to reinforce the supporting networks. Consequently, the resulting supramolecular PVA eutectogels demonstrate state‐of‐the‐art mechanical‐conductive comprehensive performances among existing eutectogels with an elongation of 3281%, a toughness of 196 MJ m−3, a fatigue threshold of 1100 J m−2, and ionic conductivity of 5.2 mS cm−1. These appealing characteristics are highly desirable for advanced soft conductors. This study will provide insights into designing next‐generation high‐performance supramolecular materials for flexible electronics is believed. [ABSTRACT FROM AUTHOR]

Four-dimensional (4D) printing adds the dimension of time to 3D-printed specimens, causing movement when external stimuli are applied. This movement enables applications across various fields, including the soft robotics, aerospace, apparel, and automotive industries. Traditionally, 4D printing has utilized special materials such as shape-memory polymers (SMPs) or shape-memory alloys (SMAs) to achieve this movement. This study explores a novel approach to 4D printing by applying microcellular foaming processes (MCPs) to 3D printing. This study primarily aims to design and fabricate patterned specimens using common materials, such as PLA, through 3D printing and to analyze their dynamic behavior under various foaming conditions. To demonstrate the potential applications of this technology, the degree of bending was measured by controlling the patterning and foaming conditions. The 3D-printed specimens with microcellular foaming exhibited predictable deformations owing to the asymmetric expansion caused by differential gas saturation. The results confirm that 4D printing can be realized using conventional materials without the need for smart materials and can introduce foaming processes as a new external stimulus. This study highlights the potential of combining 3D printing with microcellular foaming for advanced 4D printing applications. [ABSTRACT FROM AUTHOR]

Using soft materials in robotic mechanisms has become a common solution to overcome many challenges associated with the rigid bodies frequently used in robotics. Compliant mechanisms allow the robot to adapt to objects and perform a broader range of tasks, unlike rigid bodies that are generally designed for specific applications. However, soft robotics presents its own set of challenges in both design and implementation, particularly in sensing and control. These challenges are abundant when dealing with the force control problem of a compliant gripping mechanism. The ability to effectively regulate the applied force of a gripper is a critical task in many control operations, as it allows the precise manipulation of objects, which drives the need for enhanced force control strategies for soft or flexible grippers. Standard sensing techniques, such as motor current monitoring and strain-based sensors, add complexities and uncertainties when establishing mathematical models of soft grippers to the required gripping forces. In addition, the soft gripper creates a complex non-linear system, compounded by adding an adhesive-type sensor. This work develops a unique visual force sensor trained on synthetic data generated using finite element analysis (FEA) and implemented by integrating a non-linear model reference adaptive controller (MRAC) to control gripping force on a fixed 6-DOF robot. The robot can be placed on a mobile platform to perform various tasks. The virtual FEA sensor and controller, combined, are termed virtual reference adaptive control (VRAC). The VRAC was compared to other methods and achieved comparable control sensing and control performance while reducing the complexity of the sensor requirements and its integration. The VRAC strategy effectively controlled the gripping force by driving the dynamics to match the desired performance after a limited amount of training cycles. The controller proposed in this work was designed to be generally applicable to most objects that the gripper will interact with and easily adaptable to a wide variety of soft grippers. [ABSTRACT FROM AUTHOR]

Biped robots usually adopt feet with a rigid structure that simplifies walking on flat grounds and yet hinders ground adaptation in unstructured environments, thus jeopardizing stability. We recently explored in the SoftFoot the idea of adapting a robotic foot to ground irregularities along the sagittal plane. Building on the previous results, we propose in this paper a novel robotic foot able to adapt both in the sagittal and frontal planes, similarly to the human foot. It features five parallel modules with intrinsic longitudinal adaptability that can be combined in many possible designs through optional rigid or elastic connections. By following a methodological design approach, we narrow down the design space to five candidate foot designs and implement them on a modular system. Prototypes are tested experimentally via controlled application of force, through a robotic arm, onto a sensorized plate endowed with different obstacles. Their performance is compared, using also a rigid foot and the previous SoftFoot as a baseline. Analysis of footprint stability shows that the introduction of the transverse arch, by elastically connecting the five parallel modules, is advantageous for obstacle negotiation, especially when obstacles are located under the forefoot. In addition to biped robots' locomotion, this finding might also benefit lower-limb prostheses design. [ABSTRACT FROM AUTHOR]

Reconfigurability within hydrogels has emerged as an attractive functionality that can be used in information encryption, cargo/delivery, environmental remediation, soft robotics, and medicine. Here micro‐patterned polymer hydrogels capable of temperature‐dependent reconfigurability are fabricated. For this, the hydrogels are provided with micron‐sized Pickering emulsion droplets stabilized by magnetic particles, which are capable of harnessing energy from external force fields. The droplets can both migrate under magnetic field gradients and heat the environment when laser irradiated. These functions not only affect a single compartment but have higher‐order effects on the mesoscale, thanks to the temperature‐responsiveness of the polymeric network. This double responsiveness is exploited to control the spatial organization of hundreds of droplets within the hydrogel matrix and form predesigned and sophisticated patterns. Furthermore, pattern self‐reconfiguration driven by the droplets themselves upon laser irradiation is induced. Finally, we show that due to their internal liquid phase, the droplets can be used as reservoirs of hydrophobic nutrients for living cells (i.e., Yarrowia lipolytica yeast) in the solid‐like environment of the polymeric network, and demonstrate communication between the droplets and the cells to facilitate nutrient uptake. Altogether, the results provide opportunities for the development of stimuli‐sensitive polymer hydrogels with post‐synthesis reprogrammable response using micro‐compartments as building blocks. [ABSTRACT FROM AUTHOR]

Functionally graded materials (FGMs) have spatial variations in structure or composition that result in gradients in their mechanical, thermal, swelling, or other properties. FGMs have garnered significant research interest because of their extensive applications in areas such as biomedical implants, sensors, and soft robotics. Recently, grayscale photopolymerization 3D printing has emerged as a promising technology for crafting complex and high‐resolution FGMs. This comprehensive work delves into various grayscale photopolymerization 3D printing techniques, offering insights into their ability to precisely control printing exposure energy and polymerization degree, which in turn influence material properties. Furthermore, this work highlights diverse applications of grayscale vat‐photopolymerization 3D printing. Finally, it offers perspectives on ways to enhance grayscale photopolymerization 3D printing, with a focus on improving printing feedstocks and grayscale strategies. [ABSTRACT FROM AUTHOR]

Magnetic miniature robotic systems have attracted broad research interest because of their precise maneuverability in confined spaces and adaptability to diverse environments, holding significant promise for applications in both industrial infrastructures and biomedical fields. However, the predominant construction methodology involves the preprogramming of magnetic components into the system's structure. While this approach allows for intricate shape transformations, it exhibits limited flexibility in terms of reconfiguration and presents challenges when adapting to diverse materials, combining, and decoupling multiple functionalities. Here, we propose a construction strategy that facilitates the on-demand assembly of magnetic components, integrating ferrofluid droplets with the system's structural body. This approach enables the creation of complex solid-droplet robotic systems across a spectrum of length scales, ranging from 0.8 mm to 1.5 cm. It offers a diverse selection of materials and structural configurations, akin to assembling components like building blocks, thus allowing for the seamless integration of various functionalities. Moreover, it incorporates decoupling mechanisms to enable selective control over multiple functions, leveraging the fluidity, fission/fusion, and magneto-responsiveness properties inherent in the ferrofluid. Various solid-droplet systems have validated the feasibility of this strategy. This study advances the complexity and functionality achievable in small-scale magnetic robots, augmenting their potential for future biomedical and other applications. [ABSTRACT FROM AUTHOR]

Highlights This review paper delves into the manufacturing methods, material properties, and applications of polymer‐based composites in the field of advanced manufacturing, offering a detailed explanation of their production through various additive manufacturing (AM) techniques and their diverse applications across multiple industries. Polymer‐based composite materials have emerged as crucial elements in AM due to their enhanced properties and design versatility, enabling the creation of components with unprecedented performance characteristics. The paper comprehensively covers the major AM methods employed for composite materials, including fused filament fabrication, Digital Light Processing/Stereolithography, Direct Ink Writing, and Selective Laser Sintering. Each of these methods is explored in terms of its mechanism, suitability for different composite materials, and the resulting material properties. The review also provides an insightful analysis of how these AM techniques are revolutionizing industries such as soft robotics, mechanical, electrical, and biomedical fields. The paper concludes by discussing the current challenges in this domain and projecting future trends in the development and application of composite materials in advanced manufacturing. This review aims to offer a comprehensive resource for researchers and practitioners in the field, highlighting the transformative impact of polymer‐based composites in AM and their growing significance across various sectors. Comprehensive review and classification of novelties in printing method for polymer based composite material manufacturing. Introduces innovative techniques to create and enhance material properties of composites. Explores interdisciplinary applications in biomedical, electronics, and sensors, demonstrating material versatility. Provides a systematic correlation between manufacturing method, material properties, and applications of novel polymer‐based composites. [ABSTRACT FROM AUTHOR]

The widespread adoption of dielectric elastomer actuators (DEAs) as compliant artificial muscle is on the horizon after a wide range of prototype demonstrations. The next step is to accelerate the material optimization for specific design requirements. This work proposes a data‐driven framework to predict long‐term DEA energy consumption and efficiency using measurements of initial electrical properties. DEA datasets are generated from 242 pre‐stretched single‐layer actuators and 53 multi‐layer bending actuators actuated for 30–180min. Devices are made with different elastomer and electrode materials, and tested with a novel instrument that can measure multiple aspects of DEA actuation. First, experiments are conducted to develop an empirical understanding of the electro‐mechanical energy conversion mechanism and the impact of material choices during DEA actuation. Second, data‐driven models are applied to the datasets to predict energy consumption and efficiency. Third, the potential generalization of this approach is investigated by using transfer learning strategies to predict energy efficiency at 100 min with as little as 1 min of input data. Moreover, it is found that linear regression can extend the prediction up to 180 min. Additionally, transfer learning is applied to predict energy‐related properties of multi‐layer DEAs using a small dataset. The proposed data‐driven framework can evolve into an intelligent system for accelerating new material discovery by predicting performance and providing device optimization strategies. [ABSTRACT FROM AUTHOR]

Electrically driven soft pumps act as ideal “hearts” for flexible fluidic systems in soft robots and wearable devices. Dielectric elastomers (DEs) are promising for soft pump fabrication owing to their features of fast response, large strain, high energy density, and low power consumption. However, conventional dielectric elastomer actuators (DEAs) using single DE material usually exhibit poor pumping performance due to electromechanical instability or insulating problems. Herein, a multilayer structured heterogeneous dielectric elastomer actuator (H‐DEA) is fabricated based on thin films of processable, high‐performance dielectric elastomer (PHDE) and silicones, and is integrated onto silicone pump body to build a fully soft pump. The pump achieves a flow rate of 3.25 mL min−1 and a blocked pressure of 2.75 kPa with a mass of less than 1 g and a power consumption of 0.21 W. It maintains pumping functions when being bent or stretched and after twisted. It works for viscous liquids and is demonstrated to drive a soft robotic fluidic circuit. [ABSTRACT FROM AUTHOR]

The FinRay soft gripper achieves passive enveloping grasping through its functional flexible structure, adapting to the contact configuration of the object to be grasped. However, variations in beam position and thickness lead to different behaviors, making it important to research the relationship between structure and force. Conventional research using FEM simulations has tested various virtual FinRay models but replicating phenomena such as buckling and slipping has been challenging. While hardware-based methods that involve installing sensors on the gripper and the object to analyze their states have been attempted, no studies have focused on the tangential contact force related to slipping. Therefore, we developed a 16-way object contact force measurement device incorporating two-axis force sensors into each of the 16 segmented objects and compared the normal and tangential components of the enveloping grasping force of the FinRay soft gripper under two types of contact friction conditions. In the first experiment, the proposed device was compared with a device containing a six-axis force sensor in one segmented object, confirming that the proposed device has no issues with measurement performance. In the second experiment, comparisons of the proposed device were made under various conditions: two contact friction states, three object contact positions, and two object motion states. The results demonstrated that the proposed device could decompose and analyze the grasping force into its normal and tangential components for each segmented object. Moreover, low friction conditions result in a wide contact area with lower tangential frictional force and a uniform normal pushing force, achieving effective enveloping grasping. [ABSTRACT FROM AUTHOR]

Recently, most soft grippers rely on complex mechanisms or complicated structures, leading to challenging fabrication and mathematical modeling. This study presents an innovative soft-fingered gripper design with an asymmetric tube that has a variable cross-section, providing a simple yet effective solution for gripping tasks. The proposed mathematical modeling and solutions were successfully developed and experimentally validated to analyze the effects of the robot arm's motion on the gripping capability of the gripper. This innovation represents an improvement over existing designs and has the potential to enhance the design and efficient performance of soft robotic grippers. [ABSTRACT FROM AUTHOR]

Self-healing materials span diverse application fields, including flexible electronics, soft robotics, and energy devices. However, conventional self-healing materials pose a challenge in achieving the delicate balance between flexibility and electrical conductivity. Moreover, they also suffer from prolonged healing times, incomplete healing, and high manufacturing costs. Liquid metals possess excellent self-healing capabilities owing to their unique combination of fluidic and metallic properties, high surface tension, and reversible solid-liquid phase change at room temperature, offering an intriguing material option for addressing the challenges associated with flexibility and electrical conductivity. In this review article, we comprehensively examine the domain of self-healing liquid metals from the standpoint of typical mechanisms underlying self-healing processes, as well as practical strategies employed for achieving such rejuvenation. Additionally, we explore representative applications that showcase the potential of these materials while aiming to provide a valuable reference for advancing and enhancing the field of self-healing materials. Future prospect along this direction is made. [ABSTRACT FROM AUTHOR]

Soft grippers, a rapidly growing subfield of soft robotics, utilize compliant and flexible materials capable of conforming to various shapes. This feature enables them to exert gentle yet, if required, strong gripping forces. In this study, we elaborate on the material selection and fabrication process of gripping fingers based on the dielectric elastomer actuation technique. We study the effects of mixing the silicone elastomer with a silicone thinner on the performance of the actuators. Inspired by nature, where the motion of end-effectors such as soft limbs or fingers is, in many cases, directed by a stiff skeleton, we utilize backbones for translating the planar actuation into a bending motion. Thus, the finger does not need any rigid frame or pre-stretch, as in many other DEA approaches. The idea and function of the backbone strategy are demonstrated by finite element method simulations with COMSOL Multiphysics® 6.5. The paper describes the full methodology from material choice and characterization, design, and simulation to characterization to enable future developments based on our approach. Finally, we present the performance of these actuators in a gripper demonstrator setup. The developed actuators bend up to 68.3° against gravity, and the gripper fingers hold up to 10.3 g against gravity under an actuation voltage of 8 kV. [ABSTRACT FROM AUTHOR]

The research work presents a novel voxel-type soft amphibious robot based on an assembly of origami flexiballs. The geometric and elastic constitutive models of the origami flexiball are theoretically established to elucidate its intricate deformation mechanism. Especially, the zero-energy storage phenomenon and the quasi-zero-stiffness characteristic are revealed to prove that the origami flexiball is suitable for serving as soft robotic components. As a proof of concept, fourteen origami flexiballs are interconnected to form a quadruped robot capable of walking or crawling in both underwater and terrestrial environments, including flat surfaces and sandy terrain. Its adaptability across multiple environments is enhanced by the origami polyhedra-inspired hollow structure, which naturally adjusts to underwater conditions such as hydrostatic pressure and currents, improving stability and performance. Other advantages of the voxel-type soft amphibious quadruped robot include its ease of manufacture using 3D printing with accessible soft elastic materials, ensuring rapid and cost-effective fabrication. We anticipate its potentially versatile applications, including underwater pipeline inspections, offshore maintenance, seabed exploration, ecological monitoring, and marine sample collection. By leveraging metamaterial features embodied in the origami polyhedra, the presented voxel-type soft robot exemplifies an innovative approach to achieving complex functionalities in soft robotics. [ABSTRACT FROM AUTHOR]

This paper considers the design, manufacture, and testing of a prototype "soft–stiff" worm-inspired robot referred to herein, as the PneumaticallyActuated PeristaLtic Advancing Modular (PALAM) robot. The robot has a modular structure, mimicking the segmented nature of earthworms, and each segment is individually actuated by a set of three pneumatic artificial muscles (PAMs). The PAMs contract when inflated by pressurised air, generating a pulling force and fulfilling the role of biological muscles in the robot. The PAMs are made from the elastomer silicone rubber, which affords the robot flexibility and enables a wide range of real-life applications. A control-system is designed which can inflate any PAM on demand, and hence replicate the peristaltic motion of earthworms in the PALAM robot. Finally, this paper discusses a successful, low-cost, and widely accessible approach for the manufacture of the PAMs utilised herein. The PAMs can be scaled dimensionally and made from different materials with varying mechanical properties and behaviours, meaning that they are suitable for use in a wide range of robotics applications. [ABSTRACT FROM AUTHOR]

[Display omitted] 4D printing combines the typical 3D printing with "smart materials", allowing 3D printed materials to undergo a structural change over time. Since its original concept was first introduced in 2013, 4D printing became an innovative research that has received more attention from scientists in different fields. This review summarizes the progress achieved in 4D printing technologies and their associated materials. First, the technology and process of 4D printing are overviewed, and then the structure and properties of smart materials utilized in 4D printing are analyzed in depth, including metamaterials, shape memory materials, hydrogels, and self-healing polymers. We systematically illustrate the morphing mechanisms of the 4D printed smart materials, and then critically discuss the stimuli that can trigger transformation in the 4D printed smart materials, including heat, light, moisture, pH, electric current, and magnetic field. For 4D printed smart materials, all the changes programmed in the materials follow a mathematical model that allows scientists to predict and design the desired behaviors of the structures, using parameters such as the material distribution and the spatial gradients of the metric tensor. We finally conclude with the discussion of future challenges and opportunities for this ever-growing technology. Overall, 4D printing can create dynamic structures programmed to be responsive to external stimuli in the environment, widening its use in a myriad of applications such as rapid prototyping, electronics, biomedicine, soft robotics, self-assembly structures, smart sensors, and dynamic actuators. [ABSTRACT FROM AUTHOR]

Conductive hydrogels, known for their flexibility, biocompatibility, and conductivity, have found extensive applications in fields such as healthcare, environmental monitoring, and soft robotics. Recent advancements in 3D printing technologies have transformed the fabrication of conductive hydrogels, creating new opportunities for sensing applications. This review provides a comprehensive overview of the advancements in the fabrication and application of 3D-printed conductive hydrogel sensors. First, the basic principles and fabrication techniques of conductive hydrogels are briefly reviewed. We then explore various 3D printing methods for conductive hydrogels, discussing their respective strengths and limitations. The review also summarizes the applications of 3D-printed conductive hydrogel-based sensors. In addition, perspectives on 3D-printed conductive hydrogel sensors are highlighted. This review aims to equip researchers and engineers with insights into the current landscape of 3D-printed conductive hydrogel sensors and to inspire future innovations in this promising field. [ABSTRACT FROM AUTHOR]

Electrical and mechanical integration approaches are essential for emerging hybrid electronics that must robustly bond rigid electrical components with flexible circuits and substrates. However, flexible polymeric substrates and circuits cannot withstand the high temperatures used in traditional electronic processing. This constraint requires new strategies to create flexible materials that simultaneously achieve high electrical conductivity, strong adhesion, and processibility at low temperature. Here, an electrically conductive adhesive is introduced that is flexible, electrically conductive (up to 3.25×105 S m−1) without sintering or high temperature post‐processing, and strongly adhesive to various materials common to flexible and stretchable circuits (fracture energy 350

Liquid‐metal embedded elastomers (LMEEs) have been demonstrated to show a variety of excellent properties, including high toughness, dielectric constant, and thermal conductivity, with applications across soft electronics and robotics. However, within this scope of use cases, operation in extreme environments – such as high‐temperature conditions – may lead to material degradation. While prior works highlight the functionality of LMEEs, there is limited insight on the thermal stability of these soft materials and how the effects of liquid metal (LM) inclusions depend on temperature. Here, the effects on thermal stability, including mechanical and electrical properties, of LMEEs are introduced. Effects are characterized for both fluoroelastomer and other elastomer‐based composites at temperature exposures up to 325 °C, where it is shown that embedding LM can offer improvements in thermo‐mechanical stability. Compared to elastomer like silicone rubber that has been previously used for LMEEs, a fluoroelastomer matrix offers a higher dielectric constant and significant improvement in thermo‐mechanical stability without sacrificing room temperature properties, such as thermal conductivity and modulus. Fluoroelastomer‐LM composites offer a promising soft, multi‐functional material for high‐temperature applications, which is demonstrated here with a printed, soft heat sink and an endoscopic sensor capable of wireless sensing of high temperatures. [ABSTRACT FROM AUTHOR]

This review summarizes the controllable flow and manipulation of gallium‐based liquid metals (e.g., eutectic gallium indium, EGaIn). There are generally only a few ways to handle fluids, but liquid metals offer versatile control due to their properties: 1) excellent fluidity, 2) adjustable surface tension, 3) electrically and chemically controllable surface oxides, 4) metallic electrical and thermal conductivity, and 5) the ability to alloy with other metals (e.g., magnetic particles). These all‐in‐one properties empower liquid metals to exhibit controllable flow in confined microchannels (steerable flow) and from nozzles (printable flow), and make liquid metals susceptible to various energy fields, including electric, magnetic, electromagnetic, wave, and light fields. Consequently, the flow and manipulation of liquid metals enable intriguing morphological changes (e.g., formation of droplets/plugs, jets, fibers) and controllable motion (e.g., jumping, bouncing, directional locomotion, rotation) of liquid metals with new fluidic phenomena and practical applications such as soft electronics and robotics. This review aims to present a selective framework and provide an insightful understanding for controlling and shaping liquid metals, thereby stimulating further research and generating increased interest in this topic. [ABSTRACT FROM AUTHOR]

Recent advances in composite hydrogels achieve material enhancement or specialized stimuli‐responsive functionalities by pairing with a functional filler. Liquid metals (LM) offer a unique combination of chemical, electrical, and mechanical properties that show great potential in hydrogel composites. Polymerization of hydrogels with LM microdroplets as initiators is a particularly interesting phenomenon that remains in its early stage of development. In this work, an LM‐hydrogel composite is introduced, in which LM microdroplets dispersed inside the hydrogel matrix have dual functions as a polymerization initiator for a polyacrylic acid‐poly vinyl alcohol (PAA/PVA) network and, once polymerized, as passive inclusion to influence its material and stimuli‐responsive characteristics. It is demonstrated that LM microdroplets enable ultra‐fast polymerization in ≈1 min, compared to several hours by conventional polymerization techniques. The results show several mechanical enhancements to the PAA/PVA hydrogels with LM‐initiated polymerization. It is found that LM ratios strongly influence stimuli‐responsive behaviors in the hydrogels, including swelling and ionic bending, where higher LM ratios are found to enhance ionic actuation performance. The dual roles of LM in this composite are analyzed using the experimental characterization results. These LM‐hydrogel composites, which are biocompatible, open up new opportunities in future soft robotics and biomedical applications. [ABSTRACT FROM AUTHOR]

Liquid metal composites are promising soft conductors for applications in soft electronics, sensors, and soft robotics. Existing liquid metal composites usually have a high‐volume fraction of liquid metal, which not only increases the density but also the material cost. Future applications in soft electronics and robotics highly demand liquid metal composites with low density and high conductivity for large‐scale, low‐cost, lightweight, and more sustainable applications. In this work, lightweight and highly conductive composites embedded with liquid metal fiber networks are synthesized. This new paradigm of liquid metal composites consists of an interconnected liquid metal fiber network embedded in a compliant rubber matrix. The liquid metal fiber network serves as an ultra‐lightweight conductive pathway for electrons. Experiments indicate that this soft conductive composite also possesses nearly strain‐insensitive conductance and superior cyclic stability. Potential applications of the composite films as stretchable interconnects, electrodes, and sensors are demonstrated. [ABSTRACT FROM AUTHOR]

The design of robotic soft matter capable of emulating the complex movements of living organisms such as mechanical actuation, shape transformation, and autonomous translation remains a grand challenge in soft materials science. Functionalized hydrogels are excellent candidates for such materials since they can operate in water and are highly responsive to their environment, but their response times can be slow. This work investigates fast photoactuation of hybrid bonding hydrogels composed of peptide amphiphile (PA) supramolecular nanofibers bonded covalently to merocyanine‐based (MCH+) photoresponsive networks. By incorporating ionizable acrylic acid (AA) co‐monomers in these networks, photoactuation at nearly neutral pH is observed, which in turn enables a new mechanism to accelerate the response by triggering the bundling of supramolecular nanofibers by rapid proton exchange reactions. Furthermore, this rapid response and its consequent large shape transformations lead to hydrogels capable of spontaneously tracking external light sources inspired by pedicellariae, defensive organs present in echinoderms like the starfish and the sea urchin. This work suggests that hybrid bonding polymers (HBPs), which leverage the interplay between supramolecular assemblies and covalent networks, offer novel strategies to design rapidly actuating soft robotic materials. [ABSTRACT FROM AUTHOR]

Aiming to endow natural minerals with fast, high-sensitivity, and controllable smart light, humidity, solvent and temperature responsiveness, a novel ceramic clay and cucurbituril (CB) guest-host system (MVCB) inspired by nature was self-assembled and rearranged via an ingenious and simple design successfully. For the first time, the multi-functional MVCB not only displayed a high intelligent multi-stimuli responsiveness as light, humidity, solvent, and temperature switches, but also had multiple selective molecular recognition responses because of different organic vapor with CB and asymmetrical bilayer clay. For instance, due to the factors of guest-host and slow release, the average response speed of self-assembled shuffling the MVCB in methanol was as high as 108°/s compared with bilayer film without CB (20°/s). Besides, the MVCB exhibited controllable swift movement and was bending for grabbing three times its own weight. Moreover, the ultra-wide operating temperature of the MVCB from was ranging −196 to 300 °C under extreme condition. More interestingly, the MVCB presented a unique and compliable self-driven, smart switch, shape memory, environmental awareness and soft robotic gripper owing to the asymmetrical swelling and supramolecular of the CB. This work not only brings a simple, cost-effective, large-scale, and efficient strategy for multi-functionalized natural minerals materials, but also opens potential applications for intelligent response, extremely resistant substances, energy conversion and soft robotics. [ABSTRACT FROM AUTHOR]

3D bioprinting is an advanced technology combining cells and bioactive molecules within a single bioscaffold; however, this scaffold cannot change, modify or grow in response to a dynamic implemented environment. Lately, a new era of smart polymers and hydrogels has emerged, which can add another dimension, e.g., time to 3D bioprinting, to address some of the current approaches' limitations. This concept is indicated as 4D bioprinting. This approach may assist in fabricating tissue-like structures with a configuration and function that mimic the natural tissue. These scaffolds can change and reform as the tissue are transformed with the potential of specific drug or biomolecules released for various biomedical applications, such as biosensing, wound healing, soft robotics, drug delivery, and tissue engineering, though 4D bioprinting is still in its early stages and more works are required to advance it. In this review article, the critical challenge in the field of 4D bioprinting and transformations from 3D bioprinting to 4D phases is reviewed. Also, the mechanistic aspects from the chemistry and material science point of view are discussed too. [ABSTRACT FROM AUTHOR]

This article presents a bibliometric analysis of the current research landscape and future prospects in the field of elastomeric soft pneumatic actuators (ESPAs) inspired by the human hand. Drawing inspiration from the intricate mechanisms of the human hand, the study maps out the research landscape in the field of ESPAs, highlighting recent advancements and emerging trends. By analyzing the leading countries, institutions, authors, journals, funding bodies, citation patterns and intellectual structures, the article identifies emerging themes and research directions, shedding light on the evolution of human hand inspired ESPAs. Finally, the literature analysis is synthesized in the form of a list of research topics which could further extend the horizons of research on ESPAs. The findings of this bibliometric analysis offer valuable guidance for researchers, practitioners, and policymakers in understanding the current state of ESPA research and charting future research agendas. By synthesizing and visualizing the research landscape, the article aims to foster collaboration, innovation, and interdisciplinary exchange in the field of soft robotics and human-machine interaction. [ABSTRACT FROM AUTHOR]

This paper presents the computational design, fabrication, and control of a novel 3-degrees-of-freedom (DOF) soft parallel robot. The design is inspired by a delta robot structure. It is engineered to overcome the limitations of traditional soft serial robot arms, which are typically low in structural stiffness and blocking force. Soft robotic systems are becoming increasingly popular due to their inherent compliance match to that of human body, making them an efficient solution for applications requiring direct contact with humans. The proposed soft robot consists of three soft closed-loop kinematic chains, each of which includes a soft actuator and a compliant four-bar arm. The complex nonlinear dynamics of the soft robot are numerically modeled, and the model is validated experimentally using a 6-DOF electromagnetic position sensor. This research contributes to the growing body of literature in the field of soft robotics, providing insights into the computational design, fabrication, and control of soft parallel robots for use in a variety of complex applications. [ABSTRACT FROM AUTHOR]

Due to a shortage of labor, the harvesting of fruits and vegetables faces significant challenges. Soft robotic hands, adaptable to variable environments due to their high-curvature bending and twisting, have garnered widespread attention and usage. However, their application in Sichuan pepper picking remains largely unexplored. Therefore, this study proposes a picking soft robotic hand composed of a rigid skeleton and flexible skin for pepper harvesting. Through analyzing the characteristics of peppers, the structure of the robotic hand is determined. Inflatable airbags are employed to drive finger bending, utilizing a rotating–twisting method for Sichuan pepper picking. Structural parameters influencing the bending angle of the airbags were determined through theoretical analysis and validated via simulation. Optimal parameter combinations for the airbags were obtained through response surface experiments to establish the robotic hand model. To assess the feasibility of the robotic hand's movement, dynamic simulations were conducted using R D (RecurDyn V9R2) software. Subsequently, a discrete element model of Sichuan pepper clusters was established and coupled with the simulation of the Sichuan pepper picking process. The results indicate that the robotic hand does not cause damage to the Sichuan peppers during picking. Finally, field tests were conducted in pepper orchards to validate the success rate of the robotic hand in picking, yielding an 85% success rate and a 0.3% damage rate. [ABSTRACT FROM AUTHOR]

Soft tissues, such as muscle could autonomously grow through re‐alignment and/or ‐combination of collagen nanofibrils upon the mechanical training. This adaptive capability is highly expected in artificial materials, particularly in hydrogel actuator. In order to avoid the failure for devices by suffering from the accumulated mechanical loading, in this work, a double layered thermo‐responsive hydrogel actuator capable of self‐strengthening was successfully prepared. In the bilayer, PVA nanocrystals with different particle sizes were uniformly distributed in each monolayer matrix, giving rise to the asymmetric structure and the resultant differentiated de‐swelling behaviors. Thus, the obtained hydrogel actuator with the semi‐interpenetrating network of P(NIPAM‐co‐NMA) can display diverse programmable transformations by varying the temperatures. The existence of PVA nanocrystals in both layers not only can enhance the mechanical strength, dramatically minimizing the collapse of hydrogel actuator in service due to the imbalance of the mechanical properties for bilayer structure, but also was greatly involved in the self‐reinforcing behavior. After repetitive tensile training with 80% strain, the tensile strength and fracture strain increased from 29.6 to 45.8 kPa and 95% to 104%, respectively. The experimental results indicated that the anisotropic orientation and strain‐induced‐crystallization for PVA crystalline domains readily occurred along the tensile direction, finally leading to the synchronous enhancement in mechanical strength for both layers. This work provides a new strategy for designing smart and robust biomimetic hydrogel systems that can be further used as the intelligent soft robotics in various fields. [ABSTRACT FROM AUTHOR]

The development of fast-responding electrically conductive polymers as actuators activated by low electrical current is now regarded as an urgent matter. Due to their limited electrical conductivity, actuators based on polymeric hydrogels must be activated using a high voltage (up to 200 V) and frequency (up to 500 Hz) when employing AC power. In this work, to improve the electrical conductivity of the hydrogel and decrease the required activation voltage of the hydrogel actuators, lithium chloride (LiCL) was added as a conductive filler to the polymer matrix of polyvinyl alcohol (PVA). In order to ascertain the deformation of actuators, activation and relaxation times, actuator efficiencies, and generated force under the conditions of activation, linear actuators that can be activated by extension/contraction (swelling/shrinking) cycles were prepared and investigated depending on the LiCl content, applied voltage, and frequency. Under a load of approximately 20 kPa and using a 90 V AC power at a 50 Hz frequency with a 30 wt.% LiCl content, it was found that the actuators' total contraction, reinforced by a woven mesh braided material, was about 20% with a ~2.2 s activation time, while the actuators' total extension, reinforced by a spiral weave material, was about 52% with a ~2.5 s activation time, after applying a 110 V AC at a 50 Hz frequency with a 10 wt.% LiCl content. Furthermore, as the lowest voltage, a 20 V AC power can operate these actuators by increasing the LiCl weight content to the same PVA mass content. Moreover, the PVA/LiCl hydrogels' activation force can be greater than 0.5 MPa. The actuators that have been developed have broad applications in soft robotics, artificial muscles, medicine, and aerospace fields. [ABSTRACT FROM AUTHOR]