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[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 objective of this study was to improve the utility of a shape-memory-alloy (SMA) knitted fabric actuator. To that end, we employed a double-sided knitting structure with excellent structural stability and high yarn density and fabricated samples with different total number of courses, wales, and diameters of SMA fibers. These samples were subjected to repeated heating tests during uniaxial elongation along the direction of the wale, and the generated contraction force was measured. Furthermore, by comparing the results of the measurements, the influence of each parameter on the contraction force was evaluated. By including the amount of deformation in the direction of the knitting fabric width and the bending rigidity of the yarn in our analysis, we were able to determine the trend followed by the contraction force generated by SMA double-sided knitted fabrics. The results of this study are expected to be applicable to the development of smart textile products. [ABSTRACT FROM AUTHOR]

Soft bellows-type pneumatic actuators (SBPAs), which consist of two cavities with small chambers embedded in elastomeric structures, are an essential embranchment in the field of soft actuators. However, more analytical modeling and analysis of SBPAs need to be studied. In this article, we first present the structure design, fabrication method, and material property test of the SBPA. Then, based on the plate bending theory, an analytical model and the corresponding design approach for SBPAs are established, which consider both geometric complexity and material nonlinearity. The verification results indicate that the predicted analytical results coincide well with the physical experimental measurement and simulation results. The decision coefficient is R2 = 0.9720. The impacts of geometric dimensions and silicone material characteristics on the bending deformation of SBPAs are also explored. We further demonstrate the bionic utility of SBPAs. Such an approach can be used as a tool for the design optimization of bellows-type actuators and save the designer lots of finite element analysis with its low computational cost. This work provides a detailed investigation of the performance of SBPAs, which can be a basic module for various types of soft robots such as soft snake robots, crawling robots, and robotic arms in the future. [ABSTRACT FROM AUTHOR]

Soft actuators with biomimetic behavior have widely been utilized in intelligent robotics and artificial muscles. Herein, tannic acid (TA) non-covalently modified and γ-methacrylic trimethoxysilane (MPS) covalently modified MXene (MPS-TA-MXene) are incorporated into a poly(n-isopropylacrylamide-polyacrylamide) (PNIPAM-PAM) copolymer hydrogel to yield a light-responsive hydrogel nanocomposite, denoted as MNA. TA effectively preserves the surface characteristics of MXene while the double bonds in MPS form covalent bonding between MXene and PNIPAM-PAM copolymer, ensuring uniform dispersion of MPS-TA-MXene in MNA hydrogel. Under exposure to ultraviolet light, the resulting MNA hydrogel actuators with nematode- or starfish-shaped exhibit not only bending capabilities in various directions and angles but also demonstrate remarkable multiple-freedom rolling behavior in water environments due to their volume shrinkage induced by the phase transition of MNA hydrogel. Overall, the proposed simply assembled MNA hydrogel actuators with multiple and continuous bionic motions, distinguishing them from conventional single soft actuators limited to bending in one specific direction or performing a simple singular action of rolling, look promising for use in underwater exploration. [Display omitted] • UV light-driven MNA hydrogel bionic actuators are prepared for exploration in underwater environments. • MNA hydrogel exhibits ideal tensile strength and elongation with values of 268.5 kPa and 397.5%, respectively. • The MNA hydrogel strain sensor exhibits a quadratic function correspondence between relative resistance change and strain. • The nematode-shaped MNA hydrogel actuator can perform bending, crawling, and hunting by multi-angle UV light. • The starfish-shaped MNA hydrogel actuator can perform biomimetic behaviors such as crawling, rolling, and grasping. [ABSTRACT FROM AUTHOR]

Dynamic behaviour of the pneumatic muscle actuator (PMA) is conventionally modelled as a pressure-based first-order equation under discrete loads, which cannot exactly describe its dynamic features. Considering PMA's nonlinear, time-varying and hysteresis characteristics, we propose a novel high-order modified dynamic model of PMA based on its physical properties and working principle, with coefficients being identified under external dynamic loads. To tackle PMA's nonlinear hysteresis problem in high-frequency movements, a global fast terminal sliding mode controller with the modified model-based radial basis function (RBF) neural network disturbance compensator (RBF-GFTSMC) is designed. Comparison experimental studies are carried on a designed PMA platform that can provide continuously changing loads. Results show that the RBF-GFTSMC has superior trajectory tracking performance and disturbance compensation capability under wide-ranged frequencies and external loads, which can be potentially used to achieve precise control of PMA-actuated robots. • Modified model better describes pneumatic artificial muscle's dynamic behaviour. • Modelling under continuously changing and dynamic load conditions. • Novel controller adapts to high frequency applications with human interaction. • Model-based compensator improves control performance with dynamic external loads. [ABSTRACT FROM AUTHOR]

To improve the calculation accuracy of the contractile force in a shape memory alloy (SMA) knitted fabric actuator, which was developed in a previous study, we measured the Young's modulus, E, and wire diameter, d, of a SMA yarn in unheated (20 °C) and heated (100 °C) environments. Subsequently, the contractile force in the heated environment was calculated in terms of bending rigidity (EI) using the measured values of E and d. The accuracy of the theoretical contractile force, considering contraction and increment in EI, was improved when compared with that in the former one, which only considered contraction of the SMA yarn. Furthermore, to enhance calculation accuracy, we proposed a 2 dimensional stitch model for SMA plain knitted fabric. This model consisted of clothoid curves through four contact points, where each yarn crosses the other stitches and act forces. Further, this model could show the change in the curvature via the contraction of the yarn as well as the increase in its potential energy. Therefore, it was confirmed that this model is useful for calculating the contractile force of the SMA knitted fabric. [ABSTRACT FROM AUTHOR]

Soft robots and actuators are emerging devices providing more capabilities in the field of robotics. More flexibility and compliance attributing to soft functional materials used in the fabrication of these devices make them ideal for delivering delicate tasks in fragile environments, such as food and biomedical sectors. Yet, the intuitive nonlinearity of soft functional materials and their anisotropic actuation in compliant mechanisms constitute an existent challenge in improving their performance. Topology optimization (TO) along with four-dimensional (4D) printing is a powerful digital tool that can be used to obtain optimal internal architectures for the efficient performance of porous soft actuators. This paper employs TO analysis for achieving high bending deflection of a 3D printed polyelectrolyte actuator, which shows bending deformations in response to electrical stimuli in an electrolyte solution. The performance of the actuator is studied in terms of maximum bending and actuation rate compared with a solid, uniformly 3D printed and topology-optimized actuator. The experimental results proved the effectiveness of TO on achieving higher bending deformation and actuation rate against a uniformly 3D printed actuator. [ABSTRACT FROM AUTHOR]

The purpose of this research is to clarify the contractile force mechanism of a shape memory alloy (SMA) knitted fabric actuator. We knitted SMA yarn with plain stitches. We then determined the limit up to which SMA plain knitted fabric can be uniaxially elongated and thereafter the original dimensions can be recovered through its repeated heating. Moreover, the temperature dependence of SMA plain knitted fabric in the case of contractile force is quantitatively evaluated experimentally by heating it and then measuring its tension after it is extended to a certain length and fixed at both ends. The results show that, in its wale direction, the maximum tension by heating exceeds the tension corresponding to the extension. Furthermore, it is confirmed that theoretical calculations for the tensile properties of the knitted fabric of spun yam and filament yarn can be applied to plain knitted fabric of SMA yarn. Using this theoretical calculation, and the flexural rigidity measured by KES system, it is clarified the contractile force of the SMA knitted fabric actuator is affected not only by contraction of SMA yarn but also an increase in its flexural rigidity. [ABSTRACT FROM AUTHOR]

The purpose of this research is to develop a smart textile actuator for clothes. We developed a soft actuator with shape memory alloy wire by using flat knitting technology. It is capable of generating a maximum force of 0.61 N/mm and a maximum contraction of 7.8% when used for compression stockings. It was possible to increase the compression pressure from 10 hPa to 30 hPa in approximately 10 s. We also developed a soft actuator prototype of a flat knitting actuator covered by silicone sheets for a power assist suit. It has a length of 100 mm, a width of 60 mm, and a thickness of 2.3 mm. This actuator is capable of generating a maximum force of 22.7 N, which is more than twice the tension when it is 100% stretched. The data show that the soft actuator can be used for a power assist suit to prevent lumbago. [ABSTRACT FROM AUTHOR]

Inspired by common patterns of biological movement, a series of near-infrared (NIR) laser-driven bionic intelligent hydrogel actuators were successfully fabricated via the combination of infiltration method (entirety infiltration and locality infiltration), structure design and material characteristics. The controllable distribution of graphene oxide (GO) particles in a hydrogel matrix resulting from the infiltration method led to abundant bionic deformations with multiple degrees of freedom and flexibility. In addition to the highest response speed of 187.7°/s, the hydrogel actuators underwent accurate and repeatable static deformations and efficient and stabilized dynamic locomotion, demonstrated, for example, through the assembly of origami, the deformation of fingers and palm, the closing and blooming of a chrysanthemum and the crawling of an inchworm. This study opens a new path for practical bionic applications of NIR-triggered hydrogel actuators in self-assembly biosensor, targeted drug delivery and minimally invasive surgery. [ABSTRACT FROM AUTHOR]

Stimuli-responsive soft actuators, which are expected to supplement or replace traditional rigid actuators, have attracted enormous research and developed rapidly since their discovery. Among them, the most representative light and electrical stimulus-responsive actuators have been extensively studied, but the mechanism and performance of the photoelectric synergistic stimulus response of actuators are rarely studied. Herein, through vacuum-assisted filtration and hot pressing, a Ti 3 C 2 T x MXene-CNT/PDMS bilayer actuator is designed and manufactured to realize the photoelectric synergistic stimulus strategy based on photothermal and electrothermal actuation. The photoelectric synergistic mechanism is clearly stated, the equivalence relation for the photoelectric synergistic response is summarized, and the order-independence rule that the input order of stimuli does not affect the response angle is found. Moreover, a soft mechanism is devised to drive the reciprocating motion of the slider to broaden the application of the soft actuator. This study opens a new insight into the soft actuator field and provides reliable guidance for dispersing and reducing the energy of stimuli. [Display omitted] • A Ti 3 C 2 T x MXene-CNT/PDMS bilayer actuator that can respond to NIR light and electrical stimuli is shown. • The photoelectric synergistic mechanism is stated and an equivalence relation A S − half Δ = A L (A E) is excavated. • Bending angles under different ratios of photoelectric synergistic stimulus are always small. • The order-independence rule that the input order of the stimuli does not affect the response angle is found. [ABSTRACT FROM AUTHOR]

Abstract: In soft actuators, the creep under tensile loads is a serious problem for the positioning. The creep during electrochemical cycle (electrochemical creep) in conducting polymers is remarkable compared with the static creep under tensile loads. Correlation between the electrochemical creep and the actuating strain in polypyrrole films doped with docecylbenzene sulfonic (DBS) anion has been studied in NaCl aqueous electrolyte. It has been found that chemical cross-link in polypyrrole with di-pyrrole alkanes suppressed the creep, however, the actuator strain also decreased. The creep in crossliked PPy saturated after several cycles, keeping the strain of actuation constant. The result indicates the creep can be minimized by idling before use. Scan rate dependences of the electrochemical creep and actuation were also examined to find the ways to depress the creep. [Copyright &y& Elsevier]

Soft actuators with accurate and real-time motion perception are of great importance for flexible machines and artificial intelligence robotics to enable an autonomic response to surroundings. To enhance the sensing-signal reliability and calibration, synchronous motion perception with multiplex feedback signals is desired but has not been sufficiently explored. Herein, we present a soft bimorph actuator that has electrical and visual dual channel signal feedback functions for real-time multiplex motion perception. Cellulose paper and polyimide tape were assembled together as bimorph actuation layers on which an MXene/graphene bilayer was coated for electrothermal function and electrical signal feedback and a thermochromic interlayer was used for real-time visual signal feedback. Based on the proposed actuators, three kinds of bionic robotics and an electro-puppetry robot, " Wu Song Fights the Tiger ", with motion-programmable features are demonstrated, revealing the broad application prospects of the present soft actuators in bionic soft robotics with real-time multiplexing motion perception. Here, we have developed a soft bimorph actuator which has thermochromic and self-sensing dual functionalities for real-time multiplex motion perception. Image 1 • A soft bimorph actuator that has thermochromic and self-sensing dual functionalities is proposed. • The resulting bimorph actuators have been proven to have excellent actuating performances. • The obtained actuator can realize real-time multiplex motion perception via colour shifting and output resistance. • The actuator can be used in the fabrication of bionic robotics with motion-programmable features. [ABSTRACT FROM AUTHOR]