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To improve the adaptability of soft robots to the environment and achieve reliable attachment on various surfaces such as smooth and rough, this study draws inspiration from the collaborative attachment strategy of insects, cats, and other biological claw hooks and foot pads, and designs an actuator with a bionic claw hook-suction cup hybrid structure. The rigid biomimetic pop-up claw hook linkage mechanism is combined with a flexible suction cup of a 'foot pad' to achieve a synergistic adhesion effect between claw hook locking and suction cup adhesion through the deformation control of a soft pneumatic actuator. A pop-up claw hook linkage mechanism based on the principle of cat claw movement was designed, and the attachment mechanism of the biological claw hooks and footpads was analysed. An artificial muscle-spring-reinforced flexible pneumatic actuator (SRFPA) was developed and a kinematic model of the SRFPA was established and analysed using Abaqus. Finally, a prototype of the hybrid actuator was fabricated. The kinematic and mechanical performances of the SRFPA and entire actuator were characterised, and the attachment performance of the hybrid actuator to smooth and rough surfaces was tested. The results indicate that the proposed biomimetic claw hook-suction cup hybrid structure actuator is effective for various types of surface adhesion, object grasping, and robot walking. This study provides new insights for the design of highly adaptable robots and biomimetic attachment devices., (© 2024 IOP Publishing Ltd.)

Purpose: This paper introduces the stiffness-tunable soft actuator (STSA), a novel device that combines a silicone body with a thermoplastic resin structure (TPRS). The STSA's design allows for the variable stiffness of soft robots, significantly increasing their potential for use in medical scenarios such as minimally invasive surgeries (MIS). By adjusting the stiffness of the STSA, it is possible to enhance the robot's dexterity and adaptability, making it a promising tool for performing complex tasks in narrow and delicate spaces., Methods: The stiffness of the STSA can be modulated by altering the temperature of the TPRS, which has been inspired by the helix and is integrated into the soft actuator to achieve a broad range of stiffness modulation while maintaining flexibility. The STSA has been designed with both diagnostic and therapeutic functions in mind, with the hollow area of the TPRS serving as an instrument channel for delivering surgical instruments. Additionally, the STSA features three uniformly arranged pipelines for actuation by air or tendon, and can be expanded with more functional chambers for endoscopy, illumination, water injection, and other purposes., Results: Experimental results show that the STSA can achieve a maximum 30-fold stiffness tuning, providing a significant improvement in load capacity and stability when compared to pure soft actuators (PSAs). Of particular importance, the STSA is capable of achieving stiffness modulation below 45 °C, thereby ensuring a safe entry into the human body and creating an environment conducive to the normal operation of surgical instruments such as endoscope., Conclusion: The experimental findings indicate that the soft actuator with TPRS can achieve a broad range of stiffness modulation while retaining flexibility. Moreover, the STSA can be designed to have a diameter of 8-10 mm, which satisfies the diameter requirements of a bronchoscope. Furthermore, the STSA has the potential to be utilized for clamping and ablation in a laparoscopic scenario, thereby demonstrating its potential for clinical use. Overall, these results suggest that the STSA has significant promise for use in medical applications, particularly in the context of minimally invasive surgeries., (© 2023. CARS.)

Background: Although various endoscopic surgery robots developed in previous studies are versatile and have high lesion accessibility, they have limitations in terms of reaching the target lesion through the curved path in the large intestine and providing a stable tasking environment for the operator., Methods: An endoscopic surgery robot was developed for performing surgery in the large intestine. The robot was easily inserted into the target lesion in the curved colon through the mounted soft actuator and demonstrated high structural stiffness through the insertion of the sigmoidal auxiliary tendons., Results: The robot was able to access the target lesion in the curved colon through teleoperation alone. Further, it was confirmed that the high structural stiffness overtube improved the overall task performance in the user test., Conclusions: The proposed robotic system demonstrated the possibility and potential of performing advanced endoscopic surgery in the large intestine., (© 2022 John Wiley & Sons Ltd.)

Jellyfish have attracted worldwide attention owing to their fantastic moving styles, which also inspired development in soft robotics to meet the demands of underwater surveillance. In this study, a soft robotic jellyfish integrated liquid metal coil, and magnetic field is proposed for the first time to mimic the soft rowing propulsion of oblate jellyfish. The soft robotic jellyfish is actuated by the entirely soft electromagnetic actuators that enabled the gentle motion. Through conceptual experiments and computational fluid dynamics simulations, we systematically interpreted the mechanism of this robotic jellyfish and various factors to dominate its movement behaviors, which involve vortex formation and ascending modalities. Besides, underwater monitoring and bio-friendliness of robotic jellyfish were also demonstrated to illustrate its potential application scenarios and gentle motion characteristics. This study will help to broaden the vistas for liquid metal enabled bionic robotics in a wide range of underwater applications.

Thermal actuation is a common actuation method for soft robots. However, a major limitation is the relatively slow actuation speed. Here we report significant increase in the actuation speed of a bimorph thermal actuator by harnessing the snap-through instability. The actuator is made of silver nanowire/polydimethylsiloxane composite. The snap-through instability is enabled by simply applying an offset displacement to part of the actuator structure. The effects of thermal conductivity of the composite, offset displacement, and actuation frequency on the actuator speed are investigated using both experiments and finite element analysis. The actuator yields a bending speed as high as 28.7 cm -1 /s, 10 times that without the snap-through instability. A fast crawling robot with locomotion speed of 1.04 body length per second and a biomimetic Venus flytrap were demonstrated to illustrate the promising potential of the fast bimorph thermal actuators for soft robotic applications.

Helical curling and spiral structure are very common in nature, which inspire researchers to create various forms of helical configurations and actuators. The helically deformable actuators perform asymmetric deformations and show different chirality, which means that they can be left handed or right handed. However, the mechanism of helical curling and especially how the key factors influence the chirality of the actuator have not been systematically explained and well understood. In this study, we focus on the typical double-layer soft actuator composed of an active (expansion) layer and a passive (supporting) layer and investigate the effect of key factors (expansion coefficient, Young's modulus, relative thickness) on the chirality of the helical actuation or morphing by comprehensive finite element analyses. It was found that (i) the anisotropic expansion of the active layer or (ii) the anisotropic Young's modulus of the active or the passive layer is indispensable for helical curling. In Case (i), the actuator curls along the direction of greater expansion of the active layer. In Case (ii), the actuator curls along the direction of closer moduli match of the active and passive layers, and their relative thickness also affects the helical morphing of the actuator. In practice, the above two factors may cooperate or compete with each other, and the dominant one determines the chirality. This work gives the general rules for helical morphing forms and can provide guidance for the design and preparation of spiral actuators and soft robots in the future.

In order to assist patients with finger rehabilitation training and grasping objects, we propose a new type of soft rehabilitation gloves (SRGs), which has both flexion/extension and abduction/adduction movement function for every finger. This paper describes the structure design of the bending actuator and rotating actuator, the fabrication process of the soft actuator, and the implementation of the soft wearable gloves based on a fabric glove. FEM simulation analysis and experiments were conducted to characterize the mechanical behavior and performance of the soft glove in terms of the angle output and force output upon pressurization. To operate this soft wearable glove, we designed the hardware system for SRGs with a flexible strain sensor and force sensor in the loop and introduced a force/position hybrid PID control algorithm to regulate the pressure inputted. Experiment evaluation focused on rehabilitation training gestures; motions and the precise grasping assistance function were executed. The rotating actuator between each finger can supply abduction/adduction motion manner for patients, which will improve rehabilitation effect. The experimental results demonstrated that the developed SRGs have the potential to improve hand movement freedom and the range of grasping successfully.

Background: The hand motor function is lost and activities in daily life (ADLs) are affected due to some illnesses such as stroke and hemiplegia. As a coping way, we present a wearable rehabilitation glove with the bionic actuator for restoring the hand function and the motor control ability lost by stroke patients., Methods: The soft pneumatic bionic actuator (SPBA) is developed on the basis of the research of human hand bone structure and finger joint characteristics and a series of tests are conducted. Besides, we built the rehabilitation glove system based on the proposed SPBAs to verify the availability due to typical gesture, mirror therapy (MT) and grasping experiment for irregular objects., Result: The bending angle of SPBA can reach 260°. The output force of it can reach 5.1N with 0.25 MPa air pressure input. The maximum variance of the bending angle can be concluded at 5.1° in MT. The grasping experiments of the glove worn on the hand or not shows the proposed glove is flexible, the grip force is large and achieve stable grasping of objects., Conclusion: The designed SPBA is satisfied with the requirements of rehabilitation training and the proposed glove restore the normal hand motion of patients in ADLs.

Achieving both high compliance and stiffness is a key issue in stiffness-tunable soft robots. A wide-range variable-stiffness method keeping pure soft characteristic is proposed by bioinspired design of deep-sea glass sponges adopting thermoplastic starch. The stiffness-tunable mechanism is designed through force analysis and optimization of its bionic cellular structure. It is fabricated with load-weight ratio exceeding 470. Then, a wide-range stiffness-tunable omnidirectional-bending soft actuator (WOSA) is realized, and the bending stiffness model is established. Comparative experiments of stiffness and deformation are conducted on WOSA and a pure soft actuator (PSA) with the same size. Results show that the WOSA can get 92.3 times initial bending and 70.8 times torsional stiffness variation range, of which the flexibility is even better than PSA. A gripper assembled by three WOSAs is verified through stiffness adjustment that it can grasp different weight fragile, soft items from the unshelled fresh egg, boiled egg yolk to grapes. It can even lift a dumbbell weighting 3.32 kg. Finally, a manipulator demonstrated its potential in future minimally invasive surgical applications due to its wide stiffness range and large deformation capacity.

Soft gripping provides the potential for high performance in challenging tasks through morphological computing; however, design explorations are limited by a combination of a difficulty in generating useful models and use of laborious fabrication techniques. We focus on a class of grippers based on granular jamming that are particularly difficult to model and introduce a "one shot" technique that exploits multimaterial three-dimensional (3D) printing to create entire grippers, including membrane and grains, in a single print run. This technique fully supports the de facto physical generate-and-test methodology used for this class of grippers, as entire design iterations can be fitted onto a single print bed and fabricated from Computer-Aided Design (CAD) files in a matter of hours. Initial results demonstrate the approach by rapidly prototyping in materio solutions for two challenging problems in unconventional design spaces; a twisting gripper that uses programmed deformations to reliably pick a coin, and a multifunctional legged robot paw that offers the ability for compliant locomotion over rough terrains, as well as being able to pick objects in cluttered natural environments. The technique also allows us to easily characterize the design space of multimaterial printed jamming grippers and provide some useful design rules. The simplicity of our technique encourages and facilitates creativity and innovation. As such, we see our approach as an enabling tool to make informed principled forays into unconventional design spaces and support the creation of a new breed of novel soft actuators.

Soft robotic gloves were designed to aid the rehabilitation process with hand pathologies and coordination of gripping exercises. The main issue in soft robotic actuators is to design a control strategy to overcome deformation in grasping exercises. In this paper, a new soft robotic actuator is developed to be protected against swell and deformation. This soft robotic glove is equipped with two sensors; these sensors make the robotic glove more intelligent. In the hardware, it was used two sensors in the new closed-loop method which include an air pressure sensor in the figure tip and a flex sensor to measure finger flexion rate. Two closed-loop control system is developed to regulate inlet air pressure and regulate the angle of the fingers for the soft robotic actuator. A Model-Based Design (MBD) method is presented as a very cost-effective, favorable, and robust method. PID programming on an embedded controller is applied by MBD approach. The soft actuator process contains a molded wooden chamber and fiber reinforcement. Experimental results show that the proposed soft robotic has a soft gripping mechanism, accurate gripping against various objects during daily activities., (Copyright © 2021 IPEM. Published by Elsevier Ltd. All rights reserved.)

Beyond a traditional stimuli-responsive soft actuator that shows a single motion by a stimulus, multidirectional actuation reversal with a single stimulus is highly required in applications such as shape morphing sensors and soft robotics. Liquid crystal elastomers (LCEs) are one of the most attractive candidates for the soft actuator due to their capability of stimuli-responsive shape changing in 3D, which is programmable with local orientation of LC mesogens. Here, a simple but effective method to fabricate monolithic LCE actuators that are capable of reversible curvature reversal in bending and twisting deformation by a single stimulus-heat-is reported. The curvature reversal of the LCE film can be programmed by means of asymmetric crosslinking density along the thickness and the orientation of the LC mesogens. The curvature reversal of the monolithic LCE film exhibits highly reversible (more than 100 times) and fast actuation (≈3-5 s) by heating and cooling, allowing new concept of a practical application using LCE material: a self-regulated smart valve that is capable of qualitatively sorting liquids by temperature. It is believed that this system is potentially applied to a self-regulated sorting platform for various endothermic and exothermic chemical or biological reactions., (© 2021 Wiley-VCH GmbH.)

Traditional actuators, such as motors as well as hydraulic or pneumatic artificial muscles, demonstrate excessive noise, a heavy weight, and a large size, which limit their practical application in many areas. Therefore, for many decades, scientists have worked to develop new types of silent, small, and light actuators. In this article, a novel soft actuator (actuator 3 ) with a high load-to-weight ratio from silicone and a low-boiling liquid (ethanol: actuator 3E or water: actuator 3W ) is presented and is compared with two actuators (actuator 1 and actuator 2 ) fabricated according to a method described in the literature. Compared with actuator 1 and actuator 2 , actuator 3 shows a larger volume expansion, output force, and load-to-weight ratio when heated. Owing to the weaker stability and repeatability of actuator 3E , many different kinds of applications based on actuator 3W are proposed, such as robotic hands and underwater rolling robots with color variations. The experimental results demonstrate that the method proposed in this article may be a viable alternative for fabricating low-cost soft actuators with high load-to-weight ratios that can be useful for future applications of soft robots.

Artificial muscles have unique advantages for driving bionic robots because their driving mode is similar to biological muscles. However, there is still a big gap between the existing artificial muscle and biological muscle in performance. The twisted artificial muscles (TAMs) from nylon 6,6 provides a low-cost, high integration, low hysteresis driving method. But as a soft actuator, the control of the TAM is so complex that the advantage of excellent embeddedness has not been brought into play. This work presents a self-sensing control method for the TAM by monitoring the real-time resistance of the heating wire which realizes the accurate controlling of the TAM temperature. The simultaneous control of 18 TAMs is realized by using the self-sensing control method. By using a new step walking method based on the principle of insect bionics, a bionic soft hexapod robot with both multi-motion and load capacity is realized. Besides, due to the excellent environmental adaptability of the TAM, the bionic robot can realize amphibious motion both on land and underwater conditions, and the corresponding maximum load capacities are 300 g and 1 kg, respectively. This work not only provides a reliable self-sensing control method of the TAMs but also promotes the development of bionic soft robots., (© 2021 IOP Publishing Ltd.)

An underwater manipulator is essential for underwater robotic sampling and other service operations. Conventional rigid body underwater manipulators generally required substantial size and weight, leading to hindered general applications. Pioneering soft robotic underwater manipulators have defied this by offering dexterous and lightweight arms and grippers, but still requiring substantial actuation and control components to withstand the water pressure and achieving the desired dynamic performance. In this work, we propose a novel approach to underwater manipulator design and control, exploiting the unique characteristics of soft robots, with a hybrid structure (rigid frame+soft actuator) for improved rigidity and force output, a uniform actuator design allowing one compact hydraulic actuation system to drive all actuators, and a novel fully customizable soft bladder design that improves performances in multiple areas: (1) force output of the actuator is decoupled from the working depth, enabling wide working ranges; (2) all actuators are connected to the main hydraulic line without actuator-specific control loop, resulting in a very compact actuation system especially for high-dexterity cases; (3) dynamic responses were improved significantly compared with the counter system without bladder. A prototype soft manipulator with 4-DOFs, dual bladders, and 15 N payload was developed; the entire system (including actuation, control, and batteries) could be mounted onto a consumer-grade remotely operated vehicle, with depth-independent performances validated by various laboratory and field test results across various climatic and hydrographic conditions. Analytical models and validations of the proposed soft bladder design were also presented as a guideline for other applications.

Dynamics, control, and sensing are still challenges for pneumatically actuated soft actuators. We consider feasible solutions based on a radially contracting actuator to overcome these challenges. The radially contracting actuator was inspired by the movement of the stomach wall. It was capable of achieving radial contraction by inflating its circular air chamber. A quasi-static model that relates the pressure with the deformed wall of the air chamber was proposed and validated. In this article, we conduct a thorough experimental investigation into the contracting dynamics of the actuator with embedded sensing capability. We analyze the kinematics of the actuator at its rest and pressurization states focusing on the midpoint of the deformed wall. The actuator dynamics is characterized under the square wave pressure input by two variables that are the pressure in the air chamber and the trajectories of the midpoint. To achieve the desired contraction, we construct a feed-forward control based on the quasi-static model. It proves that the actuator is capable of tracking a prescribed triangular wave displacement of the midpoint with small deviations. A custom-made soft sensor is integrated into the actuator, which brings in the embedded sensing capability without affecting the actuator compliance. The resistance changes of the sensor versus the controlled contraction are examined, which are used to indicate the amount of radial contraction. The experimental investigation provides a foundation for the closed-loop control and practical applications of the radially contracting actuator developed.

Fabric muscle is important for wearable robots that are soft, compliant, and silent with high contractility and high force. This study presents a novel shape memory alloy (SMA) spring-based fabric muscle (SFM). The SFM is manufactured by bundling SMA springs with proven performance as artificial muscle. The SFM generates high contractility and high force, and is soft, flexible, and light because it is covered with fabric used to make actual clothes. The SFM is contracted by heat and shows a contraction strain of 50% at a heating temperature of 70°C while generating 100 N force or higher. Furthermore, it generates a maximum contraction strain of 67% under no load. To drive it with the optimum voltage and current, the SFM is designed by optimizing the serial and parallel connection methods for the embedded SMA springs. We propose herein design and manufacturing methods for the SFM and verify the usability of the SFM as a soft actuator through a performance evaluation. The SFM as a soft actuator with a simple structure-like fabric is easily applicable to soft wearable robots that can support muscle power by simply being attached to usual suits. The SFM has a soft touch, and is lightweight; hence, it has the potential for wide applications to new-concept soft wearable robots that can be comfortably worn anytime and anywhere like usual clothes.

Soft robots exhibit many exciting properties due to their softness and body compliance. However, to interact with the environment safely and to perform a task effectively, a soft robot faces a series of challenges such as dexterous motion, proprioceptive sensing, and robust control of its deformable bodies. To address these issues, this article presents a method for fabrication and dynamic modeling of a novel bidirectional bending soft pneumatic actuator that embeds a curvature proprioceptive sensor. The bidirectional bending deformation was generated by two similar chambers with a sinusoidal shape for reducing the internal dampness during bending deformation. An optical waveguide made from flexible poly (methyl methacrylate) material that is immune to the inlet pressure was embedded into the actuator body to measure its bending angle. A dynamic modeling framework based on step response and parameter fitting was proposed to establish a simple differential equation that can describe the nonlinear behavior of the soft actuator. Hence, a sliding mode controller is designed based on this differential equation and the Taylor expansion. The proposed dynamical model and the sliding mode controller were validated by trajectory tracking experiments. The performance of the bidirectional bending soft actuator, such as the linear output of the curvature sensor in different inflating patterns, the proprioceptive sensitiveness to the external environment, the output force, and large bending range under relatively small pressure, was evaluated by relevant experimental paradigms. Prototypes from the novel design and fabrication process demonstrated the soft actuator's potential applications in industrial grasping and hand rehabilitation.

We present the design and development of the fluid-driven, wearable, Soft Poly-Limb (SPL), from the Greek word polys, meaning many. The SPL utilizes the numerous traits of soft robotics to enable a novel approach in providing safe and compliant mobile manipulation assistance to healthy and impaired users. This wearable system equips the user with a controllable additional limb that is capable of complex three-dimensional motion in space. Similar to an elephant trunk, the SPL is able to manipulate objects using a variety of end effectors, such as suction adhesion or a soft grasper, as well as its entire soft body to conform around an object, able to lift 2.35 times its own weight. To develop these highly articulated soft robotic limbs, we provide a novel set of systematic design rules, obtained through varying geometrical parameters of the SPL through experimentally verified finite element method models. We investigate performance of the limb by testing the lifetime of the new SPL actuators, evaluating its payload capacity, operational workspace, and capability of interacting close to a user through a spatial mobility test. Furthermore, we are able to demonstrate limb controllability through multiple user-intent detection modalities. Finally, we explore the limb's ability to assist in multitasking and pick and place scenarios with varying mounting locations of the SPL around the user's body. Our results highlight the SPL's ability to safely interact with the user while demonstrating promising performance in assisting with a wide variety of tasks, in both work and general living settings.

Substantial device mass and control complexity can hinder the impact of wearable robotic technologies, such as exoskeletons. Thus, despite promising previous research, the development of a simple, lightweight actuator for these systems has not yet been fully realized. The purpose of this study was to derive and demonstrate a proof-of-concept for a pneumatic interference actuator (PIA)-a lightweight, soft actuator able to produce torque by the self-intersection of a fabric balloon that arises from changes in physical geometry. General closed-form equations are derived to express the expected actuator torque and mechanical work as functions of the balloon geometry, pressure, and deflection angle. Hard and soft cylindrical physical prototypes were constructed to assess the accuracy of the mathematical models. The proposed mathematical model was found to agree with the pressure-volume relationship and successfully predict the maximum torque as a function of geometry, pressure, and deflection at nonzero deflection angles. Peak powers up to 122.1 ± 10.0 W (mean ± standard deviation), with a resting internal pressure of 158.0 ± 0.2 kPa, were observed from the hard actuator prototype. For the soft actuator prototype, peak powers of 97.9 ± 21.1 W were observed at a resting pressure of 166.8 kPa. The work performed was within 3.2% ± 3.4% and 14.4% ± 8.2% of theoretical values across all trials, and within 19.1% ± 4.4% of theoretical values when compared to the torque-angle relationship. This study highlights the promise of utilizing the self-intersection of a PIA to perform human-scale mechanical work, and future research will focus on implementations for wearable robotic systems.

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]

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]

Nonskeletal animals such as worms achieve locomotion via crawling. We consider them as an inspiration to design robots that help underline the mechanisms of crawling. In this paper, we aim to identify an approach with the simplest structure and actuators. Our robots consist of cut-and-fold bodies equipped with pneumatically-driven soft actuators. We have developed fabrication techniques for coin-sized robots. Experiments showed that our robots can move up to 4.5 mm/s with straight motion (i.e., 0.1 body lengths per second) and perform cornering and U-turns. We have also studied the friction characteristics of our robots with the ground to develop a multistate model with stick–slip contact conversions. Our theoretical analyses depict comparable results to experiments demonstrating that simple and straightforward techniques can illustrate the crawling mechanism. Considering the minimal robots' structure, this result is a critical step towards developing miniature crawling robots successfully. [ABSTRACT FROM AUTHOR]

Pneumatic soft actuators possess relatively fast response, inherent high flexibility, and achieve extraordinary shape morphing under large deformations. Conventionally, the entire body of soft pneumatic robots needs to be designed for specific applications. Herein, a soft pneumatic actuator design with structured fabrics as actuator skins, which has high bending stiffness variation that can accomplish multiple tasks and different deformation modes in a single body, is proposed. By adjusting the structured skin, the developed soft actuator can be tailored to achieve various deformations. It is experimentally shown that the bending stiffness of the actuator can be adjusted from 108 to 5654 N m−1. The blocking force of the actuator in bending is comparable with that of conventional fabric‐reinforced pneumatic actuators, while the actuator skins are reusable and programmable. In application, the actuators are used to construct a bionic soft gripper with multiple degrees of freedom. By switching between three grasping modes, the gripper successfully fulfills a series of tasks including lifting weights up to 1 kg and grasping objects ranging from a grain of grape to a large iron basin. This work opens up an avenue for designing structured skins for pneumatic robots with programmable deformation modes and versatile functions. [ABSTRACT FROM AUTHOR]

Soft pneumatic biomimetic robotic systems excel at the specific application they are designed for, often to interact or navigate unstructured environments safely. However, redeployment to new purposes requires substantial resources, from redesign to revalidation. Despite most pneumatic artificial muscles surpassing the power and contraction performance of natural muscles, natural muscles largely remain unmatched in terms of their versatility and complex performance. This is likely due to artificial muscle's low effective strain and high radial expansion, limiting parallel operating efficiencies. To address these challenges, a class of compact versatile pneumatic actuators, called multilayer artificial muscle (MAM), that are capable of deployment to different applications through configurable modularity, is presented. The MAMs are biomimetically inspired by the sarcomere, the building block for natural muscle architecture. Similarly, MAM can extend and contract as well as be rearranged to mimic muscle‐like actions and functions, such as a caterpillar locomotion robot and an entire robotic arm. The MAMs are fabricated through multilayer, multimaterial, low‐cost additive manufacturing, which offers certain advantages such as higher extension, contraction force, and durability. MAMs have the potential to provide a crucial fundamental building block toward future versatile reconfigurable architecture. [ABSTRACT FROM AUTHOR]

Nonskeletal animals such as worms achieve locomotion via crawling. We consider them as an inspiration to design robots that help underline the mechanisms of crawling. In this paper, we aim to identify an approach with the simplest structure and actuators. Our robots consist of cut-and-fold bodies equipped with pneumatically-driven soft actuators. We have developed fabrication techniques for coin-sized robots. Experiments showed that our robots can move up to 4.5 mm/s with straight motion (i.e., 0.1 body lengths per second) and perform cornering and U-turns. We have also studied the friction characteristics of our robots with the ground to develop a multistate model with stick–slip contact conversions. Our theoretical analyses depict comparable results to experiments demonstrating that simple and straightforward techniques can illustrate the crawling mechanism. Considering the minimal robots’ structure, this result is a critical step towards developing miniature crawling robots successfully.

A series of liquid crystal elastomer-based printed electronic devices has been innovatively crafted through modifying screen-printing patterns. [Display omitted] • A printed liquid crystal elastomer soft actuator with multi-stimuli responsiveness and self-sensing capabilities is achieved. • A printed liquid crystal elastomer near-infrared light array sensor is fabricated. • A series of printed functional devices are fabricated through simple modifications of the printing patterns. Liquid crystal elastomers (LCEs) are valuable in soft actuators, sensors and other emerging fields. However, it is still a huge challenge to build high-performance LCE-based functional devices in a simple and fast way to achieve the orderly and patterned integration of multiple functional layers and LCE. Herein, screen-printing technology is used to realize the multi-layer pattern deposition of silver fractal dendrites conductive ink (with excellent Joule heating effect and strain-sensing function) and carbon black conductive ink (with photothermal conversion ability) on the surface of LCE. A series of LCE-based electronic devices are prepared through customized printing patterns. The as-obtained actuator possesses excellent electric actuating performance (bending angle of 102° at 200 mA) and self-sensing function (maximum relative resistance changes of −55.0%), and also exhibits NIR light-driven self-sensing bending actuation behavior (bending angle of 81° at 1.43 W/cm2), which can be used to control the robotic arm. The as-printed NIR light sensing array system can accurately sense the intensity, spot size and position of NIR light, showing good application potential in the field of unmanned aerial vehicle flight safety. This work provides a new strategy for the efficient preparation of LCEs-based flexible electronics. [ABSTRACT FROM AUTHOR]

Soft robotics is projected to have a significant impact on healthcare, industry, and the military to deliver assistance in rehabilitation, daily living activities, repetitive motion tasks, and human performance augmentation. Many attempts have been made for application-specific robotic joints, robots, and exoskeletons using various actuator types, materials, and designs. The progress of creating soft robotic systems can be accelerated if a set of actuators with defined characteristics were developed, similar to conventional robotic actuators, which can be assembled to create desired systems including exoskeletons and end effectors. This work presents the design methodology of such a modular actuator, created with a novel corrugated diaphragm that can apply linear displacement, angular displacement, and force. This modular actuator approach allows for creating various robotic joints by arranging them into different configurations. The modular corrugated diaphragm actuator concept was validated through numerical simulation, fabrication, and testing. Linear displacement, angular displacement, and force characteristics were shown for a single module and in multi-module assemblies. Actuator assemblies that are configured in a serial and parallel manner were investigated to demonstrate the applicability and versatility of the concept of the modular corrugated diaphragm actuator for creating single and multi-degree-of-freedom joints. [ABSTRACT FROM AUTHOR]

The flexible soft actuators of conducting polymers can directly convert electrical stimulus into mechanical motions, which can be used for robotics and biomimetic applications. Herein, an electro-responsive membrane actuator based on poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate), functionalized single-walled carbon nanotube was fabricated using solution casting method with poly(vinyl alcohol) as a base intermediate polymer membrane. The poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) was evenly ornamented onto the single-walled carbon nanotube/poly(vinyl alcohol) membrane (single-walled carbon nanotube/ poly(vinyl alcohol)/ poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate)) surfaces through dip coating and verified by scanning electron and transmission electron microscopy analysis. The desirable bending response of the fabricated single-walled carbon nanotube/ poly(vinyl alcohol)/poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) membrane with time at different voltages and generated tip force makes it a promising material as a new-generation conductive polymer-based soft actuator. A permutation of the electrical conductivity, more surface area, and admirable electromechanical properties of the single-walled carbon nanotube/poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) components consequences in the composite electrode exhibited excellent actuation performance compared to the ionic polymer-metal composite actuators with Pt electrodes surface. The fabricated actuator membrane can be employed for artificial muscles, robotics, and other bio-mimetic applications. [ABSTRACT FROM AUTHOR]

Soft contraction actuators are becoming important elements particularly for human-friendly robotic applications. However, it is challenging to achieve both a large operating distance while generating practical force. Hence, we present a new soft contraction actuator capable of realizing a high ratio contraction by pneumatic power. It can be easily fabricated using soft materials, including rubber tubes, one-way extensible cloth, and inextensible wire. Its initial shape is tubular but it can curve and coil to a helix shape owing to its different extensibilities on two sides when pressurized. A maximum contraction ratio of 78% and a 23 N contraction force can be achieved with an 11.6 mm initial outer diameter tube under 0.3 MPa. The effect of the tilt angle of a one-way extensible cloth on the helical shape is investigated, and a mathematical model illustrating the relationship between the contraction ratio and force is derived. Our experimental results suggest that this helical actuator has a much higher contraction ratio than a McKibben actuator under the same conditions. Finally, we discuss the potential application of the proposed actuator to a wearable device, i.e., for assisting the dorsiflexion of an ankle joint requiring a wide range of motion. [ABSTRACT FROM AUTHOR]

Robot assistants and wearable devices are highly useful; however, these artificial systems are susceptible to hackers. In this article, two sets of experiments were conducted. The first part of this study simulated a malicious attack on a prosthetic arm system to adversely affect the operation of the prosthetic system, while the perception of 10 human subjects was surveyed. These 10 able-bodied subjects controlled the prosthetic arm and hand with electromyogram signals, while an artificial sensation of touch was conveyed to their arms as they operated the system, which enabled them to feel what the prosthetic hand was grasping as they were asked to transport an object from one location to another. This haptic feedback was provided in both the normal and abnormal operational modes but was disabled in the extremely abnormal mode. The electromyogram control signals for the arm were reversed in both the abnormal and extremely abnormal modes. Results from the simulated malicious attack on a prosthetic arm system showed that the subjects found the haptic feedback helpful in both the normal and abnormal modes of operation. Both the abnormal and extremely abnormal modes of operation negatively impacted the self-reported levels of trust, satisfaction, and frustration with the prosthetic system as the subjects grasped and transported an object. While these metrics were negatively impacted by system malfunctions resembling a malicious attack on the control functionality, it was possible to rebuild them to their former higher levels after the functionality of the prosthetic system was restored. A parallel study in this article involved simulating a malicious attack on a robot assistant to unfavorably affect the delivery operation modes, while the perception of 20 human subjects was surveyed. Results showed that the simulated malfunctions unfavorably impacted the perception of trust, satisfaction, and frustration, but it was possible to restore these metrics in two different ways as the device functionality was restored. [ABSTRACT FROM AUTHOR]

This work presents a novel soft actuator with a 3D-printed elastic body based on a fused-deposition-modeling technique and with tendon actuation based on flexible shafts, which allow push, pull, and twist torque transmissions. The combination of the soft body and flexible shaft furnishes an easy-making, modular and functional unit that possesses softness and enables three degrees of freedom. We derive the kinematics and statics of the actuator based on the assumption of piecewise constant curvature, and identify the parameters experimentally. To understand the performance of the soft actuator in different design and fabrication settings, extensive experiments are performed to compare different shapes of cross sections, infill densities, infill patterns, dentation structures and moment arms in terms of generating forces under the same pulling forces. In addition, experimental validations are performed to characterize other properties such as workspace, hysteresis, pushing force, transmitted torque, and tip force under both bending and twisting. Finally, three potential applications, i.e., a soft robotic hand, a multisegment continuum robot, and a miniaturized drilling device, are prototyped and presented experimentally where the flexibility endowed by the shafts is demonstrated and highlighted. The scalability and modularity are also showcased in the three applications. [ABSTRACT FROM AUTHOR]

The output force of high-power electrostatic motors is defined by an internal electric field, and a strong electric field can cause air discharge unless the motors are operated within a dielectric liquid. Previous studies evaluated how the viscosity of a dielectric liquid can impact the output performance of a motor. While the viscous drag resistance increases with viscosity, the degradation of the output force was found to be negligible. However, the reason for this behavior was not clarified in those studies. This work clarifies the reason for the output behavior through numerical simulations and experiments. In the simulation, motion trajectories and motor output were analyzed for different operation speeds in different liquid viscosities. The results revealed that the existence of peaks in the force characteristics of the motor is the key to understanding a motor's unique behavior within a viscous liquid. In a viscous liquid, the trajectories change such that the peak force is generated to compensate for the drag resistance. The simulations also revealed that the behavior only appears in one of the two types tested in the simulation, which differ in the smoothness of their force characteristics. The simulation results were verified in experiments. The experimental results reconfirmed the results of previous studies, and verified the findings of the simulations of this work. [Display omitted] • Electrostatic motor output did not decrease in viscous insulating liquid. • The insulating liquid in the motor was not actuated by the electric field. • Viscous drag in electrostatic motor is compensated by force peaks. • Use of force peaks is possible due to motion delay, caused by viscous drag. [ABSTRACT FROM AUTHOR]