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Soft actuators with unique mechanics have gained significant interests for unique capabilities and versatile applications. However, their actuation mechanisms (usually driven by light, heat, or chemical reactions) result in long actuation times. Reported magnetically actuated soft actuators can produce rapid and precise motions, yet their complex manufacturing processes may constrain their range of applications. Here, the “bone-in-flesh” is proposed that constructs combining rigid magnetic structures encapsulated within soft polymers to create untethered magnetic soft actuators. This approach enables these soft, impact-resistant, agile actuators with a significantly simplified fabrication process. As demonstration examples, multiple soft actuators are fabricated and tested, including actuators for auxetic properties, 2D–3D transformations, and multi-stable states. As such, this work offers a promising solution to challenges associated with soft actuators to potentially expand their applications in various domains.

Soft robots have gained significant interest due to their high flexibility and adaptability to various working conditions. Recent advancements in engineering and innovative materials have enabled the design and production of sophisticated soft robotic systems with enhanced capabilities. This study aims to evaluate the fatigue behavior of bellow-type pneumatic soft actuators fabricated through fused filament fabrication (FFF) using thermoplastic polyurethane (TPU), compared to silicone rubber cast actuators. The actuators were equipped with resistive flex sensors to monitor bending motion, and fatigue tests were performed with cycles of inflation and deflation until failure. Results showed that 3D printed TPU actuators could withstand a significant number of cycles before failure, with an average of 6410 cycles at 3 bar pressure, compared to 3439 cycles at 1 bar pressure for the silicone actuators. The study identified a set of fabrication parameters that positively affect the durability of TPU actuators, providing valuable insights for replicating these results. Additionally, the study established a plausible range of utilization for 3D-printed FFF actuators in terms of the number of cycles they can endure, offering critical data for engineers and designers to make informed decisions about the design and application of these actuators in various practical scenarios. The findings demonstrate the potential of FFF for producing durable, long-lasting pneumatic soft actuators. [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]

The present work demonstrates the manufacturing process of a pneumatic bellow actuator with an embedded sensor, utilizing a novel manufacturing approach through the complete use of additive manufacturing techniques, such as direct ink writing (DIW) and traditional fused deposition modeling (FDM) methods. This study is innovative in its integration of a dielectric electroactive polymer (DEAP) structure with sensing electrodes made of conductive carbon grease (CCG), showcasing a unique application of a 3D-printed DEAP with CCG electrodes for combined DEAP sensing and pneumatic actuation. Initial experiments, supported by computational simulations, evaluated the distinct functionality of the DEAP sensor by itself under various pressure conditions. The findings revealed a significant change in capacitance with applied pressure, validating the sensor's performance. After sensor validation, an additive manufacturing process for embedding the DEAP structure into a soft pneumatic actuator was created, exhibiting the system's capability for dual sensing and actuation, as the embedded sensor effectively responded to applied actuation pressure. This dual functionality represents an advancement in soft actuators, especially in applications that require integrated and responsive actuation and sensing capabilities. This work also represents a preliminary step in the development of a 3D-printed dual-modality actuator (pneumatic and electrically activated DEAP) with embedded sensing. [ABSTRACT FROM AUTHOR]

This study investigates the performance enhancement of mandrel-coiled twisted and coiled polymer fibers with a nichrome heater (TCPFLNR) by coating with a solution of graphene–mesoporous carbon–nickel–polyvinyl alcohol. The coating process involved a one-pot synthesis utilizing graphene powder, Ni nanoparticles, mesoporous carbon, and PVA as a binding agent. The coating was performed by manually shaking the TCPFLNR and the subsequent annealing process, which results in improved thermal conductivity and actuation behavior of the TCPFLNR. Experimental results on a 60 mm long actuator demonstrated significant enhancements in actuation displacement and actuation strain (20% to 42%) under various loads with an input current of 0.27 A/power 2.16 W. The blocked stress is ~10 MPa under this 2.16 W power input and the maximum strain is 48% at optimum load of 1.4 MPa. The observed actuation strain correlated directly with the input power. The coated TCPFLNR exhibited better thermal contacts, facilitating enhanced heat transfer, and reducing power consumption by 6% to 9% compared to non-coated actuators. It was found that the nanomaterial coating helps the TCP actuator to be reliable for more than 75,000 actuation cycles at 0.1 Hz in air due to improved thermal conductivity. These findings highlight the potential for further research to optimize electrothermally operated TCP actuators and unlock advancements in this field. [ABSTRACT FROM AUTHOR]

Soft robots present resilient and adaptable systems characterized by deformable bodies inspired by biological systems. In this paper, we comprehensively review existing design methods for soft robots. One unique feature of our review is that we first formulate criteria, which enables us to derive knowledge gaps and suggest future research directions to close these gaps and go further. Another distinctive feature of our review is that we pivot on the general engineering design process for soft robots. As such, we consider three criteria: (1) the availability of design requirements to start with the design of soft robots, (2) the availability of the so-called concept design or architecture design for soft robots, and (3) the systematic process that leads to the final design of soft robots. The review is conducted systematically, especially when searching for and selecting relevant publications in the literature. The main contribution of this review includes (i) identifying knowledge gaps and (ii) suggesting future research directions to close these gaps and go further. [ABSTRACT FROM AUTHOR]

Purpose: Tracheal intubation is the gold standard of airway protection and constitutes a pivotal life-saving technique frequently employed in emergency medical interventions. Hence, in this paper, a system is designed to execute tracheal intubation tasks automatically, offering a safer and more efficient solution, thereby alleviating the burden on physicians. Methods: The system comprises a tracheal tube with a bendable front end, a drive system, and a tip endoscope. The soft actuator provides two degrees of freedom for precise orientation. It is fabricated with varying-hardness silicone and reinforced with fibers and spiral steel wire for flexibility and safety. The hydraulic actuation system and tube feeding mechanism enable controlled bending and delivery. Object detection of key anatomical features guides the robotic arm and soft actuator. The control strategy involves visual servo control for coordinated robotic arm and soft actuator movements, ensuring accurate and safe tracheal intubation. Results: The kinematics of the soft actuator were established using a constant curvature model, allowing simulation of its workspace. Through experiments, the actuator is capable of 90° bending as well as 20° deflection on the left and right sides. The maximum insertion force of the tube is 2 N. Autonomous tracheal intubation experiments on a training manikin were successful in all 10 trials, with an average insertion time of 45.6 s. Conclusion: Experimental validation on the manikin demonstrated that the robot tracheal intubation system based on a soft actuator was able to perform safe, stable, and automated tracheal intubation. In summary, this paper proposed a safe and automated robot-assisted tracheal intubation system based on a soft actuator, showing considerable potential for clinical applications. [ABSTRACT FROM AUTHOR]

This study introduces a novel modular soft actuator designed for an anthropomorphic robotic finger that addresses the need for adaptive behavior and precise joint-angle control. The key innovation is its modular design, which enables independent pressure regulation in each air chamber, thus achieving superior precision compared to traditional PneuNets soft actuators. A rigid skeleton is integrated to enhance force transmission and measurement capabilities and thus ensure effective force handling and transmission within each module. The versatility of the actuator is demonstrated through its adaptability in various scenarios, and its features include adaptive positional control achieved by modulating the inflation in each air chamber. This research includes kinematic and kinetostatic analyses to ensure precise control of joint angles and forces at the finger's endpoint. Experimental results confirm the actuator's excellent performance and adaptability, providing valuable insights for advancing soft-actuator technology. The findings suggest significant potential for this actuator in diverse applications, emphasizing its role in the future development of precise and adaptable robotic systems. [ABSTRACT FROM AUTHOR]

Stimuli‐responsive patterned photonic actuators, characterized by their patterned nano/microscale structures and capacity to demonstrate synergistic color changes and shape morphing in response to external stimuli, have attracted intense scientific attention. However, traditional patterned photonic actuator systems still face limitations such as cumbersome and time‐consuming preparation processes and small‐scale deformations. Herein, we introduce a facile approach involving an athermal embossing technique to rapidly fabricate patterned photonic actuators based on near‐infrared (NIR) light‐responsive liquid crystal elastomers. The resulting patterned photonic actuators demonstrate remarkable features, including brilliant angle‐dependent structural color, complex three‐dimensional actuation, and good color durability under NIR light stimulation. As illustrative demonstrations of the proof‐of‐concept, we fabricate two light‐fuelled patterned photonic soft actuators: a butterfly‐inspired actuator that can produce wing‐flapping dynamic changes in structural color, and an origami crane‐shaped actuator with shape memory, structural color information storage, and dynamic display properties. This strategy provides distinct insights into the design and fabrication of various patterned photonic soft robotic devices and intelligent actuators. [ABSTRACT FROM AUTHOR]

Soft actuators with embedded fluidic channels are promising for soft robotics, but their continuous nature presents challenges in accurate and efficient modeling. Existing studies on dynamic behavior have shown that both approximate and exact methods have limitations in accurately predicting the deflection of soft actuators. Additionally, conventional methods require experimental parameter extraction for each individual actuator. To address these challenges, we propose a modified analytical method and use finite element analysis as the defined correction functions to improve accuracy and computational efficiency, providing a promising tool for the design and control of soft robotic systems. In this work, we propose a solution methodology for simulating the dynamic behavior of fluidic soft actuators, which are widely used in soft robotics applications. Our approach takes into account the cross-sectional geometry and the number of channels in the actuator's configuration. By scrutinizing various fluidic actuation designs, we can deduce the most suitable cross-sectional configuration for optimal performance. Compared to existing analytical methods, our approach is more accurate and does not require additional calculation time. As the method is adaptable with experimental models, it can be used to design and optimize soft actuators while can be refined and improved through experimental model updating. [ABSTRACT FROM AUTHOR]

Soft actuators belong to a type of actuators made of soft materials which are capable of converting applied energy to mechanical motion. They have been utilized in several fields due to their flexibility, low weight, inexpensiveness and simple fabrication. In this work, iota‐carrageenan (푖C) was chosen as the starting material for a hydrogel‐based actuator. The 푖C hydrogels were fabricated via a simple solvent‐casting technique at various concentrations: 2.4% (v/v), 2.8% (v/v) and 3.2% (v/v). All 푖C hydrogels were characterized for their chemical, thermal, rheological and morphological properties as well as the actuation performances under applied electric field. The 푖C hydrogels showed monotonic increases in the static bending distance and dielectrophoretic force with increasing electric field strength. Above the critical electrical field strengths, the ribbon‐like 푖C hydrogels oscillated back and forth due to the competition between the dielectrophoresis force, the resisting elastic force, the weight and the inertia force. Stability diagrams were constructed for the first time separating static bending from oscillation behavior under constant applied electric fields. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Lab-on-a-chip technology has been developed to streamline biochemical experiments by providing experimental environments in microscopic areas. Due to the difficulty of mixing chemicals in such small channels, various micromixers have been created. Our proposed sidewall-driven micromixer offers easy fabrication and precise control over mixing concentrations. In our previous study, we successfully generated concentration gradients by simultaneously mixing multiple chambers using a single actuator. However, it is not possible to mix different chemicals in each chamber. In this study, we developed a sidewall-driven micromixer that enables independent mixing in each chamber by installing one actuator per chamber. Experimental results showed that different conditions were achieved in each chamber using both microbead-mixture water and colored water. Thus, this mixer can be used to manipulate concentrations regardless of whether the mixing targets are particles or fluids. [ABSTRACT FROM AUTHOR]

Soft continuum robots, characterized by their dexterous and compliant nature, often face limitations due to buckling under small loads. This study explores the enhancement of axial performance in soft robots intrinsically actuated with extensile fluidic artificial muscles (EFAMs) through the incorporation of bio-inspired radial supports, or ossicles. By conducting quasi-static force response experiments under varying pressure conditions (103.4–517.1 kPa), and a modified Euler column buckling model, we demonstrate that ossicles significantly increase the robots' resistance to buckling, thereby extending their application scope in payload-carrying tasks. These findings not only underscore the effectiveness of ossicle reinforcement in improving structural robustness but also pave the way for future research to optimize soft robot design for enhanced performance. [ABSTRACT FROM AUTHOR]

The synthesis of MXene‐cobalt hybrid (MX‐Co) is presented utilizing a molten salt approach, targeting the application in artificial muscle technology. Mxenes possess exceptional electronic conductivity and surface chemistry, making them ideal candidates for electrochemical applications. Cobalt, known for its ferromagnetic qualities, is a good match for MXenes and enhances artificial muscles' mechanical performance. By circumventing hazardous hydrofluoric (HF) acid, a facile and scalable synthesis process for MX‐Co hybrids is demonstrated. Their structural and electrochemical characteristics are revealed through characterization using cutting‐edge spectroscopic and microscopic techniques. When compared to typical PEDOT: PSS electrodes, electrochemical experiments show that MX‐Co electrodes have higher electroactive performance, with enhanced bending deformation under various input conditions. MX‐Co hybrids exhibit a specific capacitance of 77.34 F g−1, 1.6 times higher than PEDOT: PSS, and achieve a substantial enhancement of electrochemical bending displacement, up to 11.72 mm under a low input voltage of 1 V, showcasing their potential for soft actuator applications. [ABSTRACT FROM AUTHOR]

Introduction: Biomimetic soft pneumatic actuators (SPA) with Kresling origami patterns have unique advantages over conventional rigid robots, owing to their adaptability and safety. Objectives: 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. Methods: 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. Results: 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. Conclusion: 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 This study aims to analyze the convection flow of a self-propelled 1-pentanol droplet. The droplets move spontaneously when 1-pentanol droplets are dropped into an aqueous 1-pentanol solution. This self-propulsion is due to the interfacial tension gradient caused by the concentration differences. The shape of the droplet is closely related to its behavior because the shape of the droplet changes the interfacial tension gradient. In this study, an exoskeleton is used to fix the droplet shape. In our preliminary experiments, we observed Marangoni convection in droplets dropped in exoskeleton frames with boomerang and round holes. The results showed that a large difference in surface tension was necessary to control the self-propulsion of the 1-pentanol droplets. Herein, we prepared two exoskeletons with different holes, an elongated symmetrical elliptical shape, and an asymmetrical shape to fix the shape of the droplet. The droplets were then dropped into each exoskeleton, and the droplet behavior, Marangoni convection inside the droplet, and convection in the aqueous phase were analyzed. We found that the direction of the self-propulsion of the droplet was determined by these exoskeletons, particularly in the case of the asymmetrical exoskeleton, and the direction of self-propulsion was fixed in one direction. Marangoni convection was observed in the droplet from the direction of lower surface tension to that of higher surface tension. In the aqueous phase, two convections were generated from the aqueous phase to the droplet because of the diffusion of 1-pentanol. In particular, when an asymmetrical exoskeleton was used, two convections of different sizes and velocities were observed in the aqueous phase. Based on these experimental results, the relationship between droplet behavior and convection is discussed.

In this paper, electrically responsive liquid crystal network (LCN) based soft actuators are presented that can achieve large deformations under an alternating current (AC) electric field. These LCN actuators are prepared by photopolymerization of liquid crystal acrylate monomers with polar end groups, which form polar side chains in the networks. Actuation is initiated by applying a high‐frequency and low‐voltage electric field. When this AC field is applied, the LC mesogens, especially the polar side chains, can oscillate, decreasing the molecular order, and creating free volume in the LCNs, which further results in anisotropic deformation. The formed shapes range from bending to bulging, depending on the programmed molecular alignment. The actuation proceeds fast within 5 s both for activation and for the relaxation to the initial state upon switching the power on and off. This LCN soft actuator exhibits fast response, low power consumption, and high precision, making it a promising candidate for applications in soft robotics, microfluidics, and biomimetic muscles. [ABSTRACT FROM AUTHOR]

Tardigrades are the most resilient biospecies on Earth, capable of surviving extreme conditions including high temperatures, pressures, air deprivation, and exposure to noxious chemicals and radiation. The study here undertakes biomimicry of the remarkable adaptability of tardigrades by designing biomorph soft actuators (BSAs) that can endure these harsh environments. Unlike previous tardigrade‐inspired materials, which lacked a naturalistic interaction with their surroundings, the BSAs replicate the anatomical macrostructures and the non‐monotonic environmental resilience of tardigrades, especially their ability to adapt via dehydration and rehydration. Dual‐layer hydrogel spheres are employed with embedded fluid bubbles, creating cohesive yet non‐monolithic smart BSA structures. These structures exhibit high resilience to compressive, thermal, and radiation stimuli, achieved through thermoresponsive shape morphing driven by fluid balance. Their advanced capabilities are also demonstrated, such as driving a McKibben‐type artificial muscle and rapidly regenerating themselves from a state exposed to hazardous chemicals. Such versatile actuating biomorphs hold great promise for various autonomous applications, including soft robotic operations in aqueous effluents, deserts, polar regions, and outer space. [ABSTRACT FROM AUTHOR]

This study aims to analyze the convection flow of a self-propelled 1-pentanol droplet. The droplets move spontaneously when 1-pentanol droplets are dropped into an aqueous 1-pentanol solution. This self-propulsion is due to the interfacial tension gradient caused by the concentration differences. The shape of the droplet is closely related to its behavior because the shape of the droplet changes the interfacial tension gradient. In this study, an exoskeleton is used to fix the droplet shape. In our preliminary experiments, we observed Marangoni convection in droplets dropped in exoskeleton frames with boomerang and round holes. The results showed that a large difference in surface tension was necessary to control the self-propulsion of the 1-pentanol droplets. Herein, we prepared two exoskeletons with different holes, an elongated symmetrical elliptical shape, and an asymmetrical shape to fix the shape of the droplet. The droplets were then dropped into each exoskeleton, and the droplet behavior, Marangoni convection inside the droplet, and convection in the aqueous phase were analyzed. We found that the direction of the self-propulsion of the droplet was determined by these exoskeletons, particularly in the case of the asymmetrical exoskeleton, and the direction of self-propulsion was fixed in one direction. Marangoni convection was observed in the droplet from the direction of lower surface tension to that of higher surface tension. In the aqueous phase, two convections were generated from the aqueous phase to the droplet because of the diffusion of 1-pentanol. In particular, when an asymmetrical exoskeleton was used, two convections of different sizes and velocities were observed in the aqueous phase. Based on these experimental results, the relationship between droplet behavior and convection is discussed. [ABSTRACT FROM AUTHOR]

Electro‐ionic artificial muscles, consisting of a configuration where an electrolyte membrane is flanked by two active electrodes, have emerged as transformative components in the field of soft robotics. Despite this, the current actuation performance falls short for many practical applications, because most existing electrode materials exhibit limitations in terms of their properties. Here, a multifunctional active electrode material is reported for an electro‐ionic artificial muscle, employing a triazine framework that incorporates 6,6′‐Dicyano‐2,2′‐bipyridyl (DCB‐TF). The multifunctional DCB‐TF boasts fully conjugated bonds, facilitating fast electron transfer, high porosity for ion accommodation, a substantial surface area of 1800 m2 g−1 for charge storage, numerous active sites for ion interactions, and complete aromatic rings contributing to stability. The application of DCB‐TF to the active electrodes in the electro‐ionic artificial muscles yields remarkable actuation performance, including a substantial bending displacement of 24 mm at 0.5 V and 0.2 Hz, a rapid response time of 2 s, and outstanding durability sustained over 3.4 million continuous cycles. Consequently, these soft actuators have enabled a dragonfly demonstration as a form of kinetic art. [ABSTRACT FROM AUTHOR]

Soft robots, which are often considered safer than rigid robots when interacting with humans due to the reduced risk of injury, have found utility in various medical and industrial fields. Pneumatic artificial muscles (PAMs), one of the most widely used soft actuators, have proven their efficiency in numerous applications, including prosthetic and rehabilitation robots. PAMs are lightweight, responsive, precise, and capable of delivering a high force-to-weight ratio. Their structure comprises a flexible, inflatable membrane reinforced with fibrous twine and fitted with gas-sealing fittings. For the optimal design and integration of these into control systems, it is crucial to develop mathematical models that accurately represent their functioning mechanisms. This paper introduces a general concept of PAM's construction, its various types, and operational mechanisms, along with its key benefits and drawbacks, and also reviews the most common modeling techniques for PAM representation. Most models are grounded in PAM architecture, aiming to calculate the actuator's force across its full axis by correlating pressure, length, and other parameters that influence actuator strength. [ABSTRACT FROM AUTHOR]

This paper presents a motion sensor-based haptic master controller capable of static and dynamic force presentation by the newly invented Finger Band Soft Actuator (FBSA). The master controller operates a surgical assist robot using the $ 6 $ 6 degrees of freedom position and posture data tracked by an optical motion capture. The haptic force presentation can be realized by the pneumatic pressure of FBSA, which can be highly integrated into the controller mechanism to maintain precise manipulability. The FBSA can present a pressing force of 3.7 N for a small-sized finger and 5.1 N for a large-sized finger at an internal pressure of 60 kPa, and there is a monotonically increasing and decreasing relationship between the air pressure and the pressing force. The effectiveness of haptic force presentation by the FBSA was experimentally evaluated in the master-follower operation of a surgical assist robot. Ten subjects performed the task of pulling a suture thread and controlled the manipulation to achieve the directed tension. The experimental result shows that with the four levels of force presentation scheme by the FBSA, the error between suture tension and target operating force is significantly smaller than without force presentation. [ABSTRACT FROM AUTHOR]

Creatures in nature make extensive use of structural color adaptive camouflage to survive. Cholesteric liquid crystals, with nanostructures similar to those of natural organisms, can be combined with actuators to produce bright structural colors in response to a wide range of stimuli. Structural colors modulated by nano-helical structures can continuously and selectively reflect specific wavelengths of light, breaking the limit of colors recognizable by the human eye. In this review, the current state of research on cholesteric liquid crystal photonic actuators and their technological applications is presented. First, the basic concepts of cholesteric liquid crystals and their nanostructural modulation are outlined. Then, the cholesteric liquid crystal photonic actuators responding to different stimuli (mechanical, thermal, electrical, light, humidity, magnetic, pneumatic) are presented. This review describes the practical applications of cholesteric liquid crystal photonic actuators and summarizes the prospects for the development of these advanced structures as well as the challenges and their promising applications. [ABSTRACT FROM AUTHOR]

This article presents a novel bidirectional parallel-chamber soft actuator that improves the end-effector grasping force by adding a row of chambers at both ends of its longitudinal chambers. A mathematical model of the bending behavior of the longitudinal chambers of the actuator is established using the piecewise constant curvature assumption, and the bending properties, gripping force, and contact area of the end wrap were analyzed for the longitudinal and transverse chambers of the actuator. Compared to traditional soft actuators, the proposed bidirectional parallel-chamber actuator provides 1.78 N of grasping force at the end due to longitudinal bending, and 1 N of grasping force at the tail due to transverse bending. To validate the simulation results, a testing platform is built to measure the bending angle and output force of the actuator experimentally. Finally, a two-fingered soft gripper is developed to verify the mathematical model and simulation results, and is tested in grasping objects with diameters ranging from 0 to 250 mm and weights up to 1450 g. [ABSTRACT FROM AUTHOR]

Traditional underwater rigid robots have some shortcomings that limit their applications in the ocean. In contrast, because of their inherent flexibility, soft robots, which have gained popularity recently, offer greater adaptability, efficiency, and safety than rigid robots. Among them, the soft actuator is the core component to power the soft robot. Here, we propose a class of soft electrohydraulic bending actuators suitable for underwater robots, which realize the bending motion of the actuator by squeezing the working liquid with an electric field. The actuator consists of a silicone rubber film, polydimethylsiloxane (PDMS) films, soft electrodes, silicone oils, an acrylic frame, and a soft flipper. When a square wave voltage is applied, the actuator can generate continuous flapping motions. By mimicking Haliclystus auricula, we designed an underwater robot based on six soft electrohydraulic bending actuators and constructed a mechanical model of the robot. Additionally, a high-voltage square wave circuit board was created to achieve the robot's untethered motions and remote control using a smart phone via WiFi. The test results show that 1 Hz was the robot's ideal driving frequency, and the maximum horizontal swimming speed of the robot was 7.3 mm/s. [ABSTRACT FROM AUTHOR]

Actuators based on soft elastomers offer significant advantages to the field of robotics, providing greater adaptability, improving collision resilience, and enabling shape‐morphing. Thus, soft fluidic actuators have seen an expansion in their fields of application. Closed‐cycle hydraulic systems are pressure agnostic, enabling their deployment in extremely high‐pressure conditions, such as deep‐sea environments. However, soft actuators have not been widely adopted on unmanned underwater vehicle control surfaces for deep‐sea exploration due to their unpredictable hydrodynamic behavior when camber‐morphing is applied. This study presents the design and characterization of a soft wing and investigates its feasibility for integration into an underwater glider. It is found that the morphing wing enables the glider to adjust the lift‐to‐drag ratio to adapt to different flow conditions. At the operational angle of attack of 12.5°, the lift‐to‐drag ratio ranges from −70% to +10% compared to a rigid version. Furthermore, it reduces the need for internal moving parts and increases maneuverability. The findings lay the groundwork for the real‐world deployment of soft robotic principles capable of outperforming existing rigid systems. With the herein‐described methods, soft morphing capabilities can be enabled on other vehicles. [ABSTRACT FROM AUTHOR]

Actuators utilizing snap‐through instabilities are widely investigated for high‐performance fast actuators and shape reconfigurable structures owing to their rapid response and limited reliance on continuous energy input. However, prevailing approaches typically involve a combination of multiple bistable actuator units and achieving multistability within a single actuator unit still remains an open challenge. Here, a soft actuator is presented that uses shape memory alloy (SMA) and mixed‐mode elastic instabilities to achieve intrinsically multistable shape reconfiguration. The multistable actuator unit consists of six stable states, including two pure bending states and four bend‐twist states. The actuator is composed of a pre‐stretched elastic membrane placed between two elastomeric frames embedded with SMA coils. By controlling the sequence and duration of SMA activation, the actuator is capable of rapid transition between all six stable states within hundreds of milliseconds. Principles of energy minimization are used to identify actuation sequences for various types of stable state transitions. Bending and twisting angles corresponding to various prestretch ratios are recorded based on parameterizations of the actuator's geometry. To demonstrate its application in practical conditions, the multistable actuator is used to perform visual inspection in a confined space, light source tracking during photovoltaic energy harvesting, and agile crawling. [ABSTRACT FROM AUTHOR]

This paper introduces a soft, cable-driven parallel robot for minimally invasive surgeries. The robot comprises a pneumatic inflatable scaffold, six hydraulic, folded pouch actuators, and a hollow, cylindrical end-effector offering five degrees of freedom. A key development is the design of the pouch actuators, which are small, low-profile, simple structures, capable of a high stroke of 180° angular displacement. The scaffold, actuators, and plastic cables are economically and rapidly fabricated using laser cutting and welding techniques. Constructed primarily from soft plastic materials, the robot can be compactly folded into a cylinder measuring 110 mm in length and 14 mm in diameter. Upon inflation, the scaffold transforms into a hexagonal prism structure with side lengths of 34 mm and edge lengths of 100 mm. The kinematic model of the robot has been developed for workspace calculation and control purposes. A series of tests have been conducted to evaluate the performance of the actuator and the robot. Repeatability tests demonstrate the robot's high repeatability, with mean and root mean square errors of 0.3645 mm and 0.4186 mm, respectively. The direct connection between the end-effector and the actuators theoretically eliminates cable friction, resulting in a hysteresis angle of less than 2°, as confirmed by the tracking results. In addition, simulated surgical tasks have been performed to further demonstrate the robot's performance. [ABSTRACT FROM AUTHOR]

[Display omitted] As ideal and smart stimuli-responsive materials for soft actuators, artificial muscles, etc., liquid crystalline elastomers (LCEs) can respond to external stimuli, including heat, light, electricity, magnetism, humidity, etc., and make corresponding deformations. Among these external stimuli, magnetic stimulus is featured by remote and contactless control, fast, precise, extremely strong penetration, safe, easy tunability, and so on. By doping magnetic nanoparticles into LCEs, their actuation and motion can be triggered by magnetic fields or forces untetheredly, remotely, and highly precisely. Therefore, the magnetic nanoparticles endow LCEs with magneto-responsiveness, opening doors to LCEs for many unique potential uses, such as magnetic read-out, magnetic valves, magnetic switches, and so on. This review summarizes recent advances in magneto-responsive LCE nanocomposites. Their fabrication is comprehensively discussed. New properties of magneto-responsive LCEs brought by magnetic nanoparticles are also thoroughly reviewed. Their promising applications are subsequently summarized and explored. [ABSTRACT FROM AUTHOR]

A Dielectric Elastomer Actuator (DEA) consists of electrodes with a dielectric layer between them. By controlling the design of the electrodes, voltage, and frequency, the operating range and speed of the DEA can be adjusted. These DEAs find applications in biomimetic robots, artificial muscles, and similar fields. When voltage is applied to the DEA, the dielectric layer undergoes compression and expansion due to electrostatic forces, which can lead to electrical breakdown. This phenomenon is closely related to the performance and lifespan of the DEA. To enhance stability and improve dielectric properties, a DEA Reservoir layer is introduced. Here, stability refers to the ability of the DEA to perform its functions even as the applied voltage increases. The Reservoir layer delays electrical breakdown and enhances stability due to its enhanced thickness. The proposed DEA in this paper is composed of a Reservoir layer and electrode layer. The Reservoir layer is placed between the electrode layers and is independently configured, not subjected to applied voltage like the electrode layers. The performance of the DEA was evaluated by varying the number of polymer layers in the Reservoir and electrode designs. Introducing the Reservoir layer improved the dielectric properties of the DEA and delayed electrical breakdown. Increasing the dielectric constant through the DEA Reservoir can enhance output characteristics in response to electrical signals. This approach can be utilized in various applications in wearable devices, artificial muscles, and other fields. [ABSTRACT FROM AUTHOR]

The hygroscopic motion of plants has inspired the development of moisture‐activated soft actuators. These actuators driven by ambient moisture sources are of great research interest in robotics and self‐regulating textiles. However, these actuators often have slow motion and can only perform bending and twisting motions. Herein, a cellulose film‐based fast‐morphing and motion‐programmable soft actuator is presented that can generate caterpillar‐like movement. The cellophane films reported here bend almost instantaneously under changing humidity, with a large bending curvature, high repeatability, and negligible hysteresis. Different actuation modes are studied using both coated and uncoated cellophane films. The uncoated cellophane film can continuously move on a moist substrate through autonomous bending–rolling–flipping (or oscillating) cycles. A facile strategy is used here to control the rolling direction and facilitate the flipping motion by offsetting its center of gravity during deformation by adding appropriate weights on the end of the actuator. The coated cellophane film is used to fabricate motion‐programmable actuators through heat‐laminating. Several actuator structures are designed and fabricated and their diverse moisture‐induced motions are demonstrated. [ABSTRACT FROM AUTHOR]

A porous actuator is prepared using a liquid crystal elastomer (LCE) loaded with metal‐organic framework (MOF) nanoparticles (MIL‐88A). While the swellable MOF additive endows the LCE actuator with nanoscale pores, after its removal by chemical etching, macroporous LCE actuator is obtained. This LCE‐MOF actuator displays several interesting features. 1) Selective etching allows the actuator in water to curl in one direction and then reverse the curling direction owing to differential water absorption of the nano‐ and macroporous layers. 2) The stretching‐induced alignment of mesogens in the actuator is little affected by the presence of MOF and substantially retained after water uptake, so that an actuation deformation can be generated either by water absorption or thermally induced order‐disorder phase transition. 3) Assisted by the UV irradiation used for polymer cross‐linking, magnetic iron oxide FeO appears to be formed after chemical etching, which allows the actuator to gain the ability to move on water surface guided by a magnet. 4) The in situ formation of magnetic iron oxide in the macroporous actuator also provides an enhanced photothermal effect, making light‐driven locomotion of the actuator more effective. The use of active porogen like MOF opens a new way to explore porous LCE actuators. [ABSTRACT FROM AUTHOR]

In this study, we demonstrate the development of a fast-response soft composite actuator fabricated by mechanical mixing of silicone elastomer (matrix) and ethanol (as phase-change fluid). Joule heating generated by electrical actuation causes a liquid-vapor transition of ethanol embedded in silicone microcapsules; provides the required pressure for mimicking the natural movements. We discuss the critical design variables to improve the temperature response, chemical composition, mechanical properties, force generated, and microstructure of soft actuator. Our soft actuator produces a high load-to-weight ratio (1000 times greater than its own) using a low-voltage source (˂20V). The stability of the soft actuator under multiple working cycles would bring the application to different robotic areas. The actuator using the mechanism presented here is easy to manufacture, automate, and recyclable. It can be used in a range of robotic applications. [ABSTRACT FROM AUTHOR]

Soft robots require soft actuators for mobility and functionality. To integrate multiple functions in a limited space, researchers are developing multifunctional soft actuators with several functions integrated in one device. This study successfully demonstrates an electroluminescent (EL) soft actuator, a single device with both light‐emitting and actuating capabilities, using liquid dielectric and uniformly dispersed EL phosphor particles. EL phosphor particles are copper‐doped zinc sulfide (ZnS) particles doped with copper. The work is able to disperse the ZnS particles uniformly in the oil by coating the ZnS particles with silica, ensuring consistent luminescence across the device's active area. The performance of the soft actuator is notable, with a strain of 25% and a maximum EL intensity of 23 cd m−2 for a single actuator. When stacking multiple actuators, the intensity exceeds 29 cd m−2. The findings suggest that EL actuator devices will be valuable smart components for soft robots and interactive sensors. They can effectively represent external stimuli through color signals, expanding the capabilities of these systems. [ABSTRACT FROM AUTHOR]

This paper focuses on soft actuators that utilize fluid power to drive soft robots and describes their features and applications. First, it discusses how soft actuators function as elemental technology in robots. This is followed by an introduction to the driving principle and features of fluid-driven soft actuators. It also classifies these soft actuators based on the fluid power source and the active mode of operation. Furthermore, an overview is provided on the materials employed in soft actuators and the control and evaluation methods for them. Finally, currently reported applications of these soft actuators, such as wearable devices, grippers, and bio-inspired robots, are presented. [ABSTRACT FROM AUTHOR]

This paper illustrates an experimental activity for the closed-loop position control of an actuator made using shape memory alloy (SMA) wire. A solution with the self-sensing effect was implemented to miniaturize the systems, i.e., without external sensors. A proportional control algorithm was initially used, demonstrating the idea's feasibility; the wire can behave simultaneously as an actuator and sensor. An experimental investigation was subsequently conducted for the optimization of the developed actuator. As for the material, a Flexinol wire, Ni-Ti alloy, with a diameter of 0.150 mm and a length of 200 mm, was used. Preliminarily, characterization of the SMA wire at constant and variable loads was carried out; the characteristics detected were elongation vs. electric current and elongation vs. electrical resistance. The control system is PC based with a data acquisition card (DAQ). A drive board was designed and built to read the wire's electrical resistance and power it by pulse width modulation (PWM). A notable result is that the actuator works with good precision and in dynamic conditions, even when it is called to support a load up to 65% different from that for which the electrical resistance–length correlation has previously been experimentally obtained, on which the control is based. This opens up the possibility of using the actuator in a counteracting configuration with a spring, which makes hardware implementation and control management simple. [ABSTRACT FROM AUTHOR]

Microrobots powered by multi-physics fields are becoming a hotspot for micro–nano manufacturing. Due to the small size of microrobots, they can easily enter small spaces that are difficult for ordinary robots to reach and perform a variety of special tasks. This gives microrobots a broad application prospect in many fields. This paper describes the materials, structures, and driving principles of microrobots in detail and analyzes the advantages and limitations of their driving methods in depth. In addition, the paper discusses the detailed categorization of the action forms of microrobots and explores their diversified motion modes and their applicable scenarios. Finally, the article highlights the wide range of applications of microrobots in the fields of biomedicine and environmental protection, emphasizing their great potential for solving real-world problems and advancing scientific progress. [ABSTRACT FROM AUTHOR]

Soft actuators are gaining attention as flexible components for soft robotics. Responsive materials that respond to external stimuli such as light are often used as the driving part of the soft actuator. For example, thermoresponsive soft actuators are fabricated by bilayer polymer films of different thermal expansion coefficients. Heating of such bilayer polymer films by plasmon heating enables the soft actuators to be driven remotely by light. In the present study, we report the fabrication of plasmonic heating driven responsive soft actuators by using metal-organic framework (MOF) thin films as supports of plasmonic nanoparticles. The thin films of Cu2(bpydc)2 (bpydc = 2,2’-bipyridine-5,5’-dicarboxylate) of which metal ion adsorption capacity is high were fabricated on Cu2(bpdc)2 (bpdc = 4,4’-biphenyldicarboxylate) which grown on ceramics precursor, Cu(OH)2. The actuating was operated by plasmon heating of Ag nanoparticles contained in MOF thin films inserted in between the two polymers, PDMS (poly(dimethylsiloxane)) and PVDC (poly(vinylidene chloride)). Two polymers have different thermal expansion coefficient so that they work as soft actuators by plasmon heating. Such fabrication process of soft actuators would pave the way for development of advanced devices in the field of soft robotics. [ABSTRACT FROM AUTHOR]

In this review, 4D printing (4DP) is delved into through fused filament fabrication (FFF) and its implications for human–material interaction (HMI). FFF 4DP's emergence in HMI represents a nascent and evolving concept worthy of deeper exploration. In this article, FFF 4DP's fundamental principles, methodologies, materials, and associated benefits and challenges are introduced. Herein, the primary focus is the intersection between FFF 4DP and HMI, investigating the potential of employing FFF 4D‐printed objects as interactive interfaces. Various HMI scenarios are examined, including applications in soft actuators, smart toys, household devices, smart consumer products, 4D textiles, and customizable wood‐based items. Moreover, in this article, the current state of the art and development in the field are discussed, highlighting notable projects that integrate FFF 4DP into HMI to advance environmental sustainability. Also, key challenges/limitations requiring attention for the widespread adoption of 4DP in HMI applications are identified. In this work, an in‐depth analysis of FFF 4DP within the HMI context is offered, underscoring its potential to transform human interactions with machines and smart devices. Innovative features for dynamic and adaptable interfaces are introduced, promising to revolutionize user experiences. The article serves as a valuable resource for researchers, practitioners, and designers interested in exploring the exciting possibilities of FFF 4DP in the realm of HMI. [ABSTRACT FROM AUTHOR]

In recent years, there has been a growing demand for wearable actuators, that can be worn on individual body parts. This demand is dynamically increasing due to the numerous potential applications such as rehabilitation and enhancing load-bearing capabilities. Exoskeletons are mechanical structures that supplement or facilitate human movements and increase the body parts natural capabilities. Despite their wide range of applications, rigid exoskeletons have several deficiencies that required further developments. Soft actuators have been developed to address these deficiencies, forming one of the main categories of easily wearable exoskeletons. The two categories - rigid and soft exoskeletons - complement each other in their structures during applications. Soft robotic elements enable precise and delicate movements while providing adequate flexibility during use and rigid units are responsible for the stable frame structure and fixation. Their combined use is applied for rehabilitation, occupational safety, and enhancing work performance purposes. The aim of this article is to physically realize a device that has a legitimate purpose in the field of human hand rehabilitation. The goal was to design, manufacture, and functionally test the elements of a device capable of assisting in the rehabilitation of fingers using completely flexible actuators. [ABSTRACT FROM AUTHOR]

Present paper deals with my thoughts in my mind, which can be connected with human health. In this study I show what are the main problems with all of the technological developments all around the globe. There are so many publications which discuss the main problems and they trie to show the solutions, but these are the most difficult problems because the human do not want to leave comfortable solutions of their life nowadays. It is enough to mention that the uses of bicycle instead of the cars especially ever since the European Union finished the all-around development of bicycle ways in the area of and between the cities in European countries. It is important to know, that there are so many talented students in University of Miskolc, at Faculty of Healthcare, for example at Health-visitor and prevention professionals, who interested in in multi-and interdisciplinary borderlines of professionalism between science of health and law and technological science. I have to mention that this study is a begin of a new trend in this Faculty. [ABSTRACT FROM AUTHOR]

In recent years, a proliferation of soft actuators tailored for hand rehabilitation has been observed. In particular, modular soft actuators have garnered particular interest due to their capacity for individual customization and joint-specific support, a feature often lacking in whole-finger soft actuators. Despite these advancements, a significant limitation persists: the majority of these actuators facilitate only finger flexion, neglecting the equally vital extension movements required for comprehensive hand rehabilitation. Traditional approaches to achieving multi-degree-of-freedom or bidirectional motion have relied on the integration of multiple chambers within soft actuators. However, this strategy has proven impractical for modular soft actuators, primarily due to spatial constraints within the finger joint. To address this challenge, we introduce a foldable pouch actuator (FPA). Designed as a flat, foldable structure composed of a single sheet, the FPA expands solely upon pressurization, generating the requisite force for finger extension. Notably, the FPA seamlessly integrates with existing modular soft actuators without compromising their structural integrity or functional capabilities, thereby enabling bidirectional support for individual joints. Evaluations using a synthetic finger model achieved a joint flexion torque of 0.17 Nm and estimated an overall extension torque of 0.12 Nm. These advancements were accomplished without compromising the traditional flexion functionality, adding individual joint extension support to the existing capabilities. This study constitutes a substantive leap forward in the utilization of soft actuators for clinical hand rehabilitation applications.

Soft actuators developed for hand rehabilitation show promise, but their practical application requires addressing individual differences and establishing suitable design rules. While joint modular soft actuators offer flexibility for diverse hand dimensions, existing performance validations have only examined a limited number of actuator sizes and neglected crucial factors like joint alignment. Customization efforts have lacked standardization, relying on a trial-and-error approach. Therefore, this study systematically evaluates the impact of actuator design parameters (size and mounting position) on joint range of motion (ROM) and torque, proposing novel design rules based on linear optimization. Experimental assessments, conducted on dummy fingers emulating human biomechanics, provide profound insights into the intricate interplay of design parameters and support performance. The findings strongly advocate maintaining a reference position for stable support, irrespective of actuator size, emphasizing the need to align the actuator with the joint center. The proposed design rules incorporate user-specific finger information, offering customized design rules. Proportionate actuator lengths to single-phalangeal length (PsPL), Proportionate actuator lengths to multi-phalangeal length (PmPL), Proportionate actuator lengths to Range of Motion (PROM), and the Traditional Method are systematically compared. Assistive performances (ROM and torque) and trajectory analysis reveal that the PsPL-designed actuator exhibits the most stable and natural assistive performance. This study emphasizes the importance of understanding actuator deformations for personalized adaptation, providing valuable insights for advancements in assistive and rehabilitative technologies.

To optimize the performance of the soft actuator, numerical simulation and regression analysis of the multi-structure parameter are presented based on the numerical calculation method. Firstly, numerical simulation and regression analysis were performed on the parameters of different driving channel shapes, including equilateral triangle, square, regular pentagon, regular hexagon, and circle, to determine the driving performance under different channel cross-sections. Secondly, numerical simulation and regression analysis were conducted on the parameters of fiber winding diameter and winding angle of the soft actuator, and qualitative analysis was performed on the failure states of the numerical calculations. Lastly, numerical simulation and regression analysis were carried out on the parameters of wall thickness and driving channel length of the soft actuator to determine the influence of these parameters on the driving performance. Through the numerical simulation and regression analysis, this study provides a necessary theoretical foundation for the optimization design of soft actuator, effectively improving the development efficiency and dynamic performance of soft actuators.

Air cylinders are actuators that slide a piston inside cylinders by applying air pressure. We propose an air-cylinder-type artificial muscle that can be flexibly bent by using a flexible tube for the cylindrical part. The actuator output was a string connected to a piston. When the air-cylinder-type artificial muscle bends, the inner wall of the tube and the string come into contact, causing output fluctuations owing to friction. In this study, we investigated the output when an artificial muscle was bent. After describing the structure of the air-cylinder-type artificial muscle, the measurement results of the resistance force at each part of the actuator are presented. A theoretical output inspired by the capstan equation was derived, and its validity was verified by comparison with experimental results. [ABSTRACT FROM AUTHOR]

Soft Actuator Based on a Novel Variable Stiffness Compound Extensor Bending-Pneumatic Artificial Muscle (CEB-PAM): Design and Mathematical Model [ABSTRACT FROM AUTHOR]

Soft actuators have played an indispensable part in the field of biosensors and soft robotics as such systems offer solutions that cannot be addressed with rigid actuators due to the lack of both flexibility and sensitivity. However, soft actuators have certain limitations when it comes to their durability and longevity. In recent years, quite a few versatile fabrication techniques and innovative solutions have been developed that have played an essential role in the development of soft robotics. An exemplary innovation involves the integration of nanomaterials into polymers that act as a host in the fabrication of inorganic/organic actuators. These actuators have shown significant enhancement both in their physical and chemical properties. Consequently, it paves the way for the development of sophisticated soft actuator-based devices that can find broader applications in the field of biomedical sciences. However, biocompatibility has been a matter of concern for inorganic/organic soft actuators. Addressing this issue, studies on the development of biomaterial-based soft actuators that incorporate nanomaterials have been conducted for biohybrid robots. This review aims to provide a comprehensive understanding of diverse stimulus-trigger actuation alongside exploring the influence of nanomaterials in inorganic/organic actuators. Further, it gives valuable insights into the implication of biomaterials in soft actuators for the development of biohybrid robot. [ABSTRACT FROM AUTHOR]