No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Robotic Tentacles with Three-Dimensional Mobility Based on Flexible Elastomers
Abstract
Soft robotic tentacles that move in three dimensions upon pressurization are fabricated by composing flexible elastomers with different tensile strengths using soft lithographic molding. These actuators are able to grip complex shapes and manipulate delicate objects. Embedding functional components into these actuators (for example, a needle for delivering fluid, a video camera, and a suction cup) extends their capabilities.
... The working air pressure range of the flexible bionic mechanical arm is between 60 and 250 kPa [35][36][37]. The maximum working pressure of the soft hand can reach 70 kPa [38,39]. The working pressure range of the soft quadruped robot [40] is between 150 and 218 kPa. ...
... Martinez et al. [39] Hao et al. [40] Soft Hand Grasp 30-70 ...
This study proposes a novel variable air pressure supply structure based on the electromagnetic effect. This structure can be implemented in various soft robots driven by air pressure, including pneumatic artificial muscles, pneumatic soft grippers, and other soft robots. The structure’s main body comprises a hollow circular tube, a magnetic piston arranged in the tube, and an electromagnetic solenoid nested outside the tube. The electromagnetic solenoid is designed with special winding and power supply access modes, generating either an attractive force or a repulsive force on the magnetic piston. This solenoid conforms with the magnetic piston expectation in the tube by changing the polarity direction. The interior of the whole structure is a closed space. The gas is conveyed to the soft robot by the gas guide hoses at the two ends of the structure, and the expansion energy of the compressed gas is fully utilized. Then, the gas supply pressure is controlled to drive the robot. The mathematical model of the structure is established based on the analysis of the electromagnetic force and gas pressure on the piston. The simulation results show that the structure’s inherent vibration characteristics under various parameters align with expectations. The real-time automatic optimization of the controller parameters is realized by optimizing the incremental proportional-integral-derivative (PID) controller based on a neural network. The simulation results show that the structure can meet the application requirements. The experimental results show that the proposed gas supply structure can provide a continuous pressure supply curve with any frequency in a specific amplitude range and has an excellent tracking effect on the sinusoidal-like pressure curve.
... Soft robots refer to a sort of robots or actuators which do not contain rigid structure. They are made of different materials such as SMA (Shape Memory Alloy), dielectric elastomer (DE), paper and silicone rubber for different purpose of use [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], and applied in fields such as bionics [8,13,14], medical science [15] and even in rescue [16] due to the soft property and ability of forming large deformation. Pneu-Net [17] is one of the most commonly used structural patterns in soft robotics. ...
... The difference in strain between theses layers causes bending deformation. Based on this structure, a series of robots have been proposed including multigait robot [18], chemical reagent transportation robot [19], soft gripper [11,20] and biomimetic fish [13]. However, strong nonlinearity of soft materials combining with pneumatic actuation pattern brings much more challenges in modelling and controlling soft robots compared with traditional motor-driven counterparts. ...
A novel soft robotic tongue is proposed for the purpose of presenting typical tongue movements in speaking, which is pneumatically actuated and supposed to be applied in pronunciation teaching device and humanoid robot to gain verisimilitude. The actuation and control system is mainly composed of solenoid proportional valves (ITV0010, SMC, Japan), DAQ card (PCIe6321, NI, USA) and motion tracking system (OptiTrack, NaturalPoint, USA). A theoretical model based on continuum mechanics is established building the relationship between input air pressure and output deformation. On the basis of the proposed theoretical model and Artificial Neural Network (ANN), an integrated control algorithm is preliminarily raised for different purpose of use in static and dynamic control. A series of verification experiments are carried out based on OptiTrack system in order to test motion controllability and working performance of the robotic tongue. The experimental results indicate that the proposed theoretical model is more suitable for static shape control due to obvious deformation delay compared with input air pressure. High deformation repeatability guarantees the precision of ANN based control method which is more suitable for dynamic motion control. The results of performance test show that actual movements of the robotic tongue generally meet the demand in demonstrating tongue shape when speaking.
... Conventional robots constructed using hard materials have advantages in accuracy, stability, and modeling 1,2 . In recent years, soft robots have been explored to solve problems that are difficult for rigid systems and to broaden the possibilities of the robotics field [1][2][3][4][5][6][7][8][9][10][11] . Soft robots, constructed using soft and flexible materials, exhibit adaptive shape deformation when making contact with objects, making them inherently safer to use in situations where contact with humans and fragile objects occurs. ...
... Figure 3c shows the downward resultant forcef resultant caused by a pair of forcesf existing at an angle θ from the line of force acted on by theF balloon . From Eqs. (8) and (9),f resultant is calculated as follows: ...
Various soft actuators have been investigated to overcome the drawbacks of conventional solid machines and explore the applications of soft robotics. In particular, and because they are expected to be applicable in minimally invasive medicine because of their safety, soft inflatable microactuators using an actuation conversion mechanism from balloon inflation to bending motion have been proposed for high-output bending motion. These microactuators could be applied to create an operation space by safely moving organs and tissues; however, the conversion efficiency could be further improved. This study aimed to improve conversion efficiency by investigating the design of the conversion mechanism. The contact conditions between the inflated balloon and conversion film were examined to improve the contact area for force transmission, with the contact area dependent on the length of the contact arc between the balloon and force conversion mechanism and on the amount of balloon deformation. In addition, surface contact friction between the balloon and film, which affects actuator performance, was also investigated. The generated force of the improved device is 1.21 N at 80 kPa when it bends 10 mm, which is 2.2 times the generated force of the previous design. This improved soft inflatable microactuator is expected to assist in performing operations in a limited space, such as in endoscopic or laparoscopic operations.
... Pneumatic actuation in the form of McKibben artificial muscles [173,198], pneu-nets [203], and other kinds of FEA [174,175,[204][205][206] has shown varying degrees of success, with some examples confined to planar motion [174,203] and others offering more capabilities at the cost of softness Content courtesy of Springer Nature, terms of use apply. Rights reserved. ...
Purpose of Review
This review provides an overview of the state of the art in bioinspired soft robotics by examining advancements in actuation, functionality, modeling, and control.
Recent Findings
Recent research into actuation methods, such as artificial muscles, has expanded the functionality and potential use of bioinspired soft robots. Additionally, the application of finite dimensional models has improved computational efficiency for modeling soft continuum systems, and garnered interest as a basis for controller formulation.
Summary
Bioinspiration in the field of soft robotics has led to diverse approaches to problems in a range of task spaces. In particular, new capabilities in system simplification, miniaturization, and untethering have each contributed to the field’s growth. There is still significant room for improvement in the streamlining of design and manufacturing for these systems, as well as in their control.
... Weather phenomena, animals, plants and other formations can often exhibit patterns that resemble or clearly follow a spiral ( Fig.1-inset) [17]. Classical mechanisms and continuum structures that leverage spiral mechanisms have been designed that take advantage of the energy storage potential of an unwinding motion to exert high forces, manipulate objests, or transverse terrains [18], [10], [19], [20], [21]. However, most of the robots presented by the current literature focus on manipulation or locomotion, tasks that require slowly occurring actuation. ...
For over thirty years optical belt drive configurations are being used in food industries to automatically sort produce in high operating speeds. Despite their benefits, these multi-component assemblies are prone to faults, difficult to clean, and require frequent maintenance that halts the production lines for considerable amount of time. In this paper, we adopt the abundantly occurring spiral motions encountered in nature and translate them to the proof-of-concept design and development of a soft pneumatic actuator (SPA), the SoftER. This novel actuator has the ability to rapidly unwind when pressurized to deliver impact forces. We explore this inherently low-cost and simple design and its potential to replace current systems based on the results of an application case study presented in this paper. Simulation driven optimization methods are leveraged, utilizing quasi-static and dynamic finite element methods models, to create a scalable framework for selecting the best performing design parameters for each application. Using rapid manufacturing processes the optimized actuator is constructed and physical testing validates its high-speed and impact force delivering capabilities.
... Driving methods in the form of power sources for the actuation processes include the fluidic actuation 7,[22][23][24] , the cable actuation 8,[25][26][27][28] , and the shape memory actuation 9,[29][30] . Regarding smart structure designs, soft actuators can perform predefined deformations (e.g., bending) by utilizing the functional driving method providing powers that act on the designed structures and further generate anisotropic mechanical responses (e.g., backbone structures [31][32][33] , tentacles structures [34][35] , and fiberreinforced structures [36][37][38]. ...
There has been a growing need for soft robots operating various force-sensitive tasks due to their environmental adaptability, satisfactory controllability, and nonlinear mobility unique from rigid robots. It is of desire to further study the system instability and strongly nonlinear interaction phenomenon that are the main influence factors to the actuations of lightweight soft actuators. In this study, we present a design principle on lightweight pneumatically elastic backbone structure (PEBS) with the modular construction for soft actuators, which contains a backbone printed as one piece and a common strip balloon. We build a prototype of a lightweight (<80 g) soft actuator, which can perform bending motions with satisfactory output forces (∼20 times self-weight). Experiments are conducted on the bending effects generated by interactions between the hyperelastic inner balloon and the elastic backbone. We investigated the nonlinear interaction and system instability experimentally, numerically, and parametrically. To overcome them, we further derived a theoretical nonlinear model and a numerical model. Satisfactory agreements are obtained between the numerical, theoretical, and experimental results. The accuracy of the numerical model is fully validated. Parametric studies are conducted on the backbone geometry and stiffness, balloon stiffness, thickness, and diameter. The accurate controllability, operation safety, modularization ability, and collaborative ability of the PEBS are validated by designing PEBS into a soft laryngoscope, a modularized PEBS library for a robotic arm, and a PEBS system that can operate remote surgery. The reported work provides a further applicability potential of soft robotics studies.
... Similar to the turgor pressure-induced expansion observed in living plants, pneumatically driven soft actuators have been developed. [104][105][106][107][108][109][110][111][112][113][114] These actuators comprise pneumatic networks of channels in elastomers with the top and bottom walls of different thickness or modulus. When subjected to pneumatic inflation, the different strains between the top and bottom layers causes the pneumatic networks to expand anisotropically, resulting in actuation (Fig. 3e). ...
Natural plant tissues provide potential strategies for the speed regulation of biomimetic actuators, ranging from ultrafast to ultraslow. Feilong Zhang, ABSTRACT Motile plant tissues can control their configurations and regulate their motion speed according to their specific requirement s, which offer various protypes for biomimetic actuators with controlled motion speed. In this perspective, we focus on the speed control of plant tissues and the bioinspired strategies for speed regulation of artificial actuators. We begin with a summary to the strategies and mechanisms of motile plant tissues for controlling motion speed, ranging from ultrafast to ultraslow. We then exemplify the models for fabricating bioinspired artificial actuators and briefly discuss current application scenarios of actuators with varying speeds from ultrafast to ult raslow. Finally, we proposed potential strategies for the speed regulation of actuators.
... However, the unit cost would make the simple arraying and stacking of individually fabricated devices prohibitively expensive if traditional manufacturing was used. As a result, more recent attempts tend to be limited to small devices, such as single-chamber microrobots [16][17][18] and HASEL tentacle actuators [19,20]. Multi-material 3D printing is promising [21][22][23][24], but still in its infancy. ...
Many modern applications, such as undersea drones, exoskeletal suits, all-terrain walker drones, prosthetics, and medical augments, would greatly benefit from artificial muscles. Such may be built through 3D-printed microfluidic devices that mimic biological muscles and actuate electrostatically. Our preliminary results from COMSOL simulations of individual devices and small arrays (2 × 2 × 1) established the basic feasibility of this approach. Herein, we report on the extension of this work to N × N × 10 arrays where Nmax = 13. For each N, parameter sweeps were performed to determine the maximal output force density, which, when plotted vs. N, exhibited saturation behavior for N ≥ 10. This indicates that COMSOL simulations of a 10 × 10 × 10 array of this type are sufficient to predict the behavior of far larger arrays. Also, the saturation force density was ~9 kPa for the 100 μm scale. Both results are very important for the development of 3D-printable artificial muscles and their applications, as they indicate that computationally accessible simulation sizes would provide sufficiently accurate quantitative predictions of the force density output and overall performance of macro-scale arrays of artificial muscle fibers. Hence, simulations of new geometries can be done rapidly and with quantitative results that are directly extendable to full-scale prototypes, thereby accelerating the pace of research and development in the field of actuators.
... The external braided sleeve embedded to solve the undesired module expansion demonstrated to provide effective radial expansion constrains allowing the longitudinal chambers expansion at the same time, but due to a number of undesired effects another solution has to be proposed. Similar examples of constraint can be found in the work by Whitesides et al. who, facing the same ballooning effect [4], developed a manufacturing process which allows the internal patterning of the chambers (PneuNets), reducing the lateral space available to produce outward expansion [5]. A different and simpler approach has been proposed by Brock et al. ...
... As a result, many auxiliary components, such as tethers, valves, connecter, batteries, microprocessors, and pumps (or motors), must be involved to gain actuation and control, which make the robotic system bulky and complicated and thereby difficult to design and fabricate compact, integrated, miniaturized soft robotic system. Whereas our platform shows the capabilities not only to use a single type of entirely soft active LCE materials to achieve the fabrication of tubular soft actuators, offering a feasible solution to overcome a formidable challenge in the materials science community (34,35), but also to enable embedding morphological information inside the material through the helical fiber architecture. The morphing instruction within the material itself via spatial directional-arranged fiber architectures not only largely reduces the required number of active components necessary for complex shape morphing but also saves much time and energy that would otherwise be consumed in signal processing and feedback for morphing control, sharply simplifying fabrication, driving, and control of soft robotic systems (36,37). ...
Biological tubular actuators show diverse deformations, which allow for sophisticated deformations with well-defined degrees of freedom (DOF). Nonetheless, synthetic active tubular soft actuators largely only exhibit few simple deformations with limited and undesignable DOF. Inspired by 3D fibrous architectures of tubular muscular hydrostats, we devised conceptually new helical-artificial fibrous muscle structured tubular soft actuators (HAFMS-TSAs) with locally tunable molecular orientations, materials, mechanics, and actuation via a modular fabrication platform using a programmable filament winding technique. Unprecedentedly, HAFMS-TSAs can be endowed with 11 different morphing modes through programmable regulation of their 3D helical fibrous architectures. We demonstrate a single "living" artificial plant rationally structured by HAFMS-TSAs exhibiting diverse photoresponsive behaviors that enable adaptive omnidirectional reorientation of its hierarchical 3D structures in the response to environmental irradiation, resembling morphing intelligence of living plants in reacting to changing environments. Our methodology would be significantly beneficial for developing sophisticated soft actuators with designable and tunable DOF.
... To further demonstrate our design framework of bellow SPAs for application-driven design, an actuator that matches the shape inspired by the elephant trunk was designed to grasp objects. 31 As shown in Fig. 7A, the spatial curve is divided into two arc segments with a π 2 rotation angle. The upper bound of the applied pressure was set to be 5 kPa because the actuator was expected to be able to take the weight of the object by increasing the pressure after reaching the desired Figure 6. ...
The actuation of a soft robot involves transforming its shape from an initial state to a desired operational state. To achieve task-specific design, it is necessary to map the shape between these two states to the robot's design parameters. This requires both a kinematic model of the soft robot and a shape-matching algorithm. However, existing kinematic models for soft robots are often limited in accuracy and generality due to the robot's flexibility and nonlinearity, and current shape-matching algorithms are not well-suited for 3D cases. To address this challenge, this paper presents a shape-matching design framework for bellow soft pneumatic actuators (SPAs) to expedite the actuator design process. First, a kinematic model of the bellow SPA is developed based on its novel modular design and a surrogate model, which is trained using an Artificial Neural Network and a dataset from Finite Element Method (FEM) simulations. Then, a 3D shape-matching algorithm, composed of a 3D piecewise-constant curvature segmentation and a bi-level Bayesian optimisation algorithm based on the surrogate model, is presented to find the optimal actuator design parameters that match the desired shape. An open-source design toolbox SPADA (Soft Pneumatic Actuator Design frAmework) is also developed to facilitate the use of the proposed design framework, including FEM simulation, shape-matching optimisation based on surrogate modelling, and automatic generation of the ready-to-print CAD file. Experimental results show an averaged root-mean-square error of 2.74 mm, validating the accuracy of the kinematics model. To demonstrate the proposed design framework, actuators are designed to match the predefined shapes in 2D and 3D space.
... These actuators carried maximum impact because of their lightweight, high responsivity, cost-effectiveness, and multi-functional design flexibility [97,98]. As a basic illustration, soft air-pressurized robots made of flexible elastomers can manipulate fragile and uneven items by evenly distributing pressure across huge regions without using complex controls [99,100]. Hamidi and Tadesse [101] printed highly elastic soft robotic elastomeric structures with glass using additive manufacturing techniques. ...
Researchers frequently turn to the adaptable material known as elastomers for various industrial products, including soft robotics, astronautics equipment, vehicles, tissue engineering, self-healing, and constructional materials. The typical lower modulus of popular elastomers is accompanied by weak resistance to chemicals and abrasion. Most commonly, the rubbery polymers are called elastomers and may be readily expanded to lengths several times longer than they were originally. Although the polymeric chains continue to have some mobility, the cross-linkers keep them from wandering indefinitely in relation to one another. The material could become stiff, hard, and more similar in qualities to a thermoset if there were a lot of cross-links. Elastomers have inherent apparent, thermal processing, and mechanical properties, making additive manufacturing (AM) challenging. The advent of additive manufacturing, formerly known as three-dimensional (3D) printing, inspired academic and industrial researchers to combine elastomeric properties with design freedom and the potential for straightforward mass customization. Elastomers are employed in the adhesive industry because they have high adherence qualities. The elastomers may also be utilized extensively in daily applications due to their excellent adherence to various filler kinds and other characteristics. This review article explores current advancements in diverse elastomer types, 3D printing advances, functional elastomers, and applications in several sectors in the context of these developments. The discussions also include the present-day difficulties from the perspective of product development.
... The PneuNet actuator, originally conceived by the renowned Whitesides research group at Harvard University, exemplifies a unique instance where a blend of geometry and material properties can be harnessed to pre-program the bending behaviour of the actuator. [16][17][18] PneuNet comprises a series of channels, each containing an air chamber with thin walls. Upon the application of pressure, the thin lateral walls with the least stiffness expand, resulting in a bend in the structure. ...
PneuNet actuators emulate human finger function and have broad application potential in domestic and industrial settings. To unlock their full potential, enhancing their controlled stiffness is crucial. This study presents the innovative design, fabrication, and evaluation of a cost-effective soft hybrid bending actuator by merging a homogeneous laminar structure, composed of 75 GSM printer paper, with a PneuNet actuator produced through soft lithography techniques. This research also characterizes the ensemble based on its tunable stiffness properties and examines the friction tests on jamming layers, highlighting the stabilization of frictional properties over time, which is critical for achieving consistent tunable stiffness. Experiments revealed that the actuator's resistive force increases due to deformation when subjected to an external load. Furthermore, this linear rise in resistive force can be modulated through the use of an integrated laminar jammer by adjusting the vacuum pressure. Results reveal a negligible stiffness increase beyond -53.33 kPa of vacuum pressure, signifying an ideal vacuum pressure limit for energy conservation during vacuum jamming. A maximum stiffness of 0.116 N was achieved at -80 kPa of vacuum pressure. This study propels the field of soft robotics by offering enhanced tunable stiffness characteristics for diverse applications.
... Nonetheless, full spatial and temporal activation patterns at the individual muscle level, particularly important for decoding the organization of 3D movements, remain inaccessible. Robophysical approaches, despite tremendous progress [17][18][19][20][21][22] , have also struggled to make inroads, stymied by the lack of advanced materials able to replicate the architecture and performance of natural muscular hydrostats. Within this context, in-silico approaches can complement in-vivo and robotic ones, allowing us to computationally explore the functioning of these systems. ...
Muscular hydrostats, such as octopus arms or elephant trunks, lack bones entirely, endowing them with exceptional dexterity and reconfigurability. Key to their unmatched ability to control nearly infinite degrees of freedom is the architecture into which muscle fibers are weaved. Their arrangement is, effectively, the instantiation of a sophisticated mechanical program that mediates, and likely facilitates, the control and realization of complex, dynamic morphological reconfigurations. Here, by combining medical imaging, biomechanical data, live behavioral experiments and numerical simulations, we synthesize a model octopus arm entailing ~200 continuous muscles groups, and begin to unravel its complexity. We show how 3D arm motions can be understood in terms of storage, transport, and conversion of topological quantities, effected by simple muscle activation templates. These, in turn, can be composed into higher-level control strategies that, compounded by the arm's compliance, are demonstrated in a range of object manipulation tasks rendered additionally challenging by the need to appropriately align suckers, to sense and grasp. Overall, our work exposes broad design and algorithmic principles pertinent to muscular hydrostats, robotics, and dynamics, while significantly advancing our ability to model muscular structures from medical imaging, with potential implications for human health and care.
... Bistability, the property of a mechanism or structure reaching a second stable state after undergoing a mechanical instability, has seen a lot of recent interest as a method for improving behaviors and increasing functionalities in soft devices and soft robotics (1)(2)(3). Bistable mechanisms have helped soft robots overcome some of their inherent limitations and help achieve force amplification (4)(5)(6) and high-speed movements (7)(8)(9)(10). Bistability has also allowed soft structures to attain various capabilities, such as energy absorption (11)(12)(13), deployable mechanisms (14,15), sensing (16)(17)(18), logical computation (19)(20)(21)(22)(23), and metamaterial-like mechanisms (24)(25)(26). ...
Mechanical instabilities, especially in the form of bistable and multistable mechanisms, have recently garnered a lot of interest as a mode of improving the capabilities and increasing the functionalities of soft robots, structures, and soft mechanical systems in general. Although bistable mechanisms have shown high tunability through the variation of their material and design variables, they lack the option of modifying their attributes dynamically during operation. Here, we propose a facile approach to overcome this limitation by dispersing magnetically active microparticles throughout the structure of bistable elements and using an external magnetic field to tune their responses. We experimentally demonstrate and numerically verify the predictable and deterministic control of the response of different types of bistable elements under varying magnetic fields. Additionally, we show how this approach can be used to induce bistability in intrinsically monostable structures simply by placing them in a controlled magnetic field. Furthermore, we show the application of this strategy in precisely controlling the features (e.g., velocity and direction) of transition waves propagating in a multistable lattice created by cascading a chain of individual bistable elements. Moreover, we can implement active elements like a transistor (gate controlled by magnetic fields) or magnetically reconfigurable functional elements like binary logic gates for processing mechanical signals. This strategy serves to provide programming and tuning capabilities required to allow more extensive utilization of mechanical instabilities in soft systems with potential functions such as soft robotic locomotion, sensing and triggering elements, mechanical computation, and reconfigurable devices.
... The early curved bending pneumatic soft actuator is cylindrical straight-through elastic actuator [9]. However, this structure will produce a significant balloon effect under the action of pressure, which limits the pressure resistance and external work efficiency of the actuator [10]. The researchers limited the radial expansion of the soft actuator by adding fiber-reinforced and rib-reinforced structures [11][12][13]. ...
Soft robots can accomplish hand rehabilitation training to ensure better safety and compliance for hand rehabilitation. In this study, a wavy non-rotating soft actuator structure was proposed for hand rehabilitation, and an axial stiffener was added to the main structure of the actuator according to the function of the bamboo fiber. A physical model of the actuator was fabricated using a multistep casting molding method, and the performance of the designed soft actuator was tested experimentally. The results showed that the bending angle and contact force gradually increased with increasing pressure. The average maximum bending angle and contact force can reach 286 ± 14.3 degree and 1.04 ± 0.051 N, with a pressure of 72 kPa. Meanwhile, the bending torques of the soft actuator at various joints (MCP, PIP, DIP) were tested, to verify that it can meet the needs of soft actuators for hand applications. Furthermore, the load lifting of the soft actuator with axial stiffeners can increase by 6 mm on average compared with a soft actuator without axial stiffeners under negative pressure. In conclusion, the pneumatic soft actuator can produce two different motion functions under the action of one cavity. In addition, a soft actuator with an axial stiffener can improve the load capacity under negative pressure. By assembling the actuators, a three-finger gripper was manufactured. The gripper could grasp and lift objects. Therefore, this work provides a new route for the development of pneumatic soft actuators and soft robots, which has efficient driving.
... Soft robots (13)(14)(15)(16)(17) made of flexible materials are well tailored to produce continuous deformations and interact with the environment (18)(19)(20). In particular, soft manipulators have shown high compliance and adaptability, enabling the development of grippers capable of grasping in an enveloping (21)(22)(23) or twisting (24)(25)(26)(27) manner. Although there is a growing interest in developing systems that can grasp/manipulate objects through wrapping (28)(29)(30)(31)(32)(33), existing soft robots fail to achieve biologically comparable versatility. ...
Across various species and different scales, certain organisms use their appendages to grasp objects not through clamping but through wrapping. This pattern of movement is found in octopus tentacles, elephant trunks, and chameleon prehensile tails, demonstrating a great versatility to grasp a wide range of objects of various sizes and weights as well as dynamically manipulate them in the 3D space. We observed that the structures of these appendages follow a common pattern - a logarithmic spiral - which is especially challenging for existing robot designs to reproduce. This paper reports the design, fabrication, and operation of a class of cable-driven soft robots that morphologically replicate spiral-shaped wrapping. This amounts to substantially curling in length while actively controlling the curling direction as enabled by two principles: a) the parametric design based on the logarithmic spiral makes it possible to tightly pack to grasp objects that vary in size by more than two orders of magnitude and up to 260 times self-weight and b) asymmetric cable forces allow the swift control of the curling direction for conducting object manipulation. We demonstrate the ability to dynamically operate objects at a sub-second level by exploiting passive compliance. We believe that our study constitutes a step towards engineered systems that wrap to grasp and manipulate, and further sheds some insights into understanding the efficacy of biological spiral-shaped appendages.
... Ruang dan saluran interior ini mengembang di bawah tekanan, menghasilkan gerakan pembengkokan dan ekspansi. Area yang paling sesuai dengan area pneumatik adalah area yang menunjukkan fenomena ekspansi [11]. Studi ini mengeksplorasi penerapan desain yang dijelaskan untuk pembuatan aditif bahan elastomer. ...
Salah satu bidang robotika yang menjadi fokus dibanyak negara saat ini adalah robotika lunak. Robotika lunak memiliki potensi besar untuk menggerakkan dan menjadi manipulator baru dalam aplikasi industri dan medis. Dalam sistem kontrol canggih yang cerdas, karena karakteristik fisik tekanan udara yang sangat nonlinier dan bervariasi waktu, sulit untuk menyesuaikan aktuator pneumatik untuk kontrol gerakan yang tepat. Namun, negara-negara maju seperti Eropa, Amerika dan Jepang telah berhasil mengembangkan sejumlah aktuator pneumatik lunak. Pengaplikasian aktuator lunak dapat digunakan secara luas di bidang operasi medis, keperawatan, teknik rehabilitasi, industri dan biomedis. Namun kerugiannya adalah strukturnya kompleks dan relatif mahal, dan topik penelitian terkait saat ini membahas mode perilaku dinamis dari kebebasan satu dimensi.
Pada penelitian ini kami mengusulkan metode Fused Deposition Modelling (FDM) dalam pencetakan 3D untuk perancangan sebuah aktuator lunak yang dapat dikontrol menggunakan sistem pneumatik. Penelitian ini menggunakan filamen TPU (thermoplastic polyurethane) yang merupakan material elastomer termoplastik. Filamen ini memiliki tingkat Shore rendah, sehingga mudah ditekuk, lembut dan fleksibel. Hasil dari penelitian ini yaitu proses pencetakan aktuator lunak berbasis sistem pneumatic dapat dilakukan menggunakan mesin 3D Printing. Aktuator lunak memiliki bentuk seperti jari manusia. Tekanan maksimum dari aktuator untuk menghasilkan tekukan 90° adalah 400 KPa.
... Kulkarni [17] and Martinez et al. [18] designed several soft actuators that can perform active bending and twisting. Heung et al. [19] developed an earthworm-like robot that can perform active bending and forward movements. ...
In recent years, soft pipeline robot, as a new concept, is proposed to adapt to tunnel. The soft pipeline robots are made of soft materials such as rubber or silicone. These materials have good elasticity, which enhance the adaptability of the soft pipeline robot. Therefore, the soft pipeline robot has better performance on deformability than rigid robot. However, the structure of tunnel is complex and varied that brought challenges on design structure of soft pipeline robot. In this paper, we propose soft pipeline robot with simple structure and easy fabrication, which can be realized straight, turning motion in a variety of tunnels with different diameters. The soft pipeline robot composed of two types of structure, which are expansion part and deformation part. Front and rear deformation part for bending and position fixation, and middle expansion part for elongation, so the pipeline soft robot can be moved in various structures of tunnels. Moreover, the locomotion ability and adaptability in tunnel are verified by simulating on software. The structure of chamber proposed in this paper can guide the design method of soft pipeline robot.
... There are mainly three categories of grippers inspired by nature: muscular hydrostats, spinal grippers, and manual grippers [2]. The muscular hydrostats inspired by octopus arms typically have infinite degrees of freedom and rely on a soft body to passively adapt to the shape and size of the grasped object [3][4][5], while the suction cups designed on the surface enhance the grasping ability [6]. Similarly, the skeletal joints in spinal grippers are shorter towards the tips, and the geometric shape can be effectively adapted to the objects [7,8]. ...
The core capabilities of soft grippers/soft robotic hands are grasping and manipulation. At present, most related research often improves the grasping and manipulation performance by structural design. When soft grippers rely on compressive force and friction to achieve grasping, the influence of the surface microstructure is also significant. Three types of fingerprint-inspired textures with relatively regular patterns were prepared on a silicone rubber surface via mold casting by imitating the three basic shapes of fingerprint patterns (i.e., whorls, loops, and arches). Tribological experiments and tip pinch tests were performed using fingerprint-like silicone rubber films rubbing against glass in dry and lubricated conditions to examine their performance. In addition to the textured surface, a smooth silicone rubber surface was used as a control. The results indicated that the coefficient of friction (COF) of the smooth surface was much higher than that of films with fingerprint-like textures in dry and water-lubricated conditions. The surface with fingerprint-inspired textures achieved a higher COF in oil-lubricated conditions. Adding the fingerprint-like films to the soft robotic fingers improved the tip pinch gripping performance of the soft robotic hand in lubricated conditions. This study demonstrated that the surface texture design provided an effective method for regulating the grasping capability of humanoid robotic hands.
... Thus, studies of soft actuators with high strain rates such as sPNs do not quantitatively compare FEM and experimental data. These studies either: (a) only present experimental data with no FEM modeling [20], [21], or (b) only present FEM modeling with no experimental data [22], [23], [24], or (c) only qualitatively compare the FEM and experimental data, and so the accuracy of their FEM models is not validated [19], [25], [26]. ...
Soft actuators have attracted a great deal of interest in the context of rehabilitative and assistive robots for increasing safety and lowering costs as compared to rigid-body robotic systems. During actuation, soft actuators experience high levels of deformation, which can lead to microscale fractures in their elastomeric structure, which fatigues the system over time and eventually leads to macroscale damages and eventually failure. This paper reports finite element modeling (FEM) of pneu-nets at high angles, along with repetitive experimentation at high deformation rates, in order to study the effect and behavior of fatigue in soft robotic actuators, which would result in deviation from the ideal behavior. Comparing the FEM model and experimental data, we show that FEM can model the performance of the actuator before fatigue to a bending angle of 167 degrees with ~96% accuracy. We also show that the FEM model performance will drop to 80% due to fatigue after repetitive high-angle bending. The results of this paper objectively highlight the emergence of fatigue over cyclic activation of the system and the resulting deviation from the computational FEM model. Such behavior can be considered in future controllers to adapt the system with time-variable and non-autonomous response dynamics of soft robots.
... Significant progress has been made in the design and construction of bio-integrated and flexible wearable devices using software materials, but improvements in the field of actuators have not been very encouraging [20][21][22][23][24][25][26]. Currently, hard materials are still used for the main material composition of the actuator. ...
An actuator built with flexible material has the advantage of smaller size and can withstand certain collisions better than actuators with rigid material. This paper proposes a crawling actuator model driven by dielectric elastomer (DE), which uses the electrically induced deformation of the DE membrane to drive the motion of the actuator. When the dielectric elastomer in the actuator is at higher voltage, the DE material produces higher deformation, and the deformation is transmitted to the ground through the friction foot thus driving the motion of the actuator. An interpolation fitting estimation algorithm (IFEA) was constructed based on the relevant material properties and principles. The pre-stretch length of the DE membrane was determined and verified through experiment; the verified results showed that the actuator has better driving performance when the membrane pre-stretching ratio is equal to 3. The crawling actuator can achieve a speed of about 50 mm/s at 4 kv and can reach 11 mm/s when loaded with four times its weight. The new crawling actuator achieved an excellent turning ability of 8.2°/s at 60% duty cycle and 32 Hz frequency. Compared with other types of crawling actuators, the actuator presented in this work has better load capacity and crawling performance.
... Additionally, a soft gripper with less control and sensory ability was proposed that is able to manipulate objects without knowing their precise position, shape, or size, including unscrewing caps and sorting snacks [156]. In addition, various hardware facilities can be combined to expand the application of soft robots [157], and grippers assembled on mechanical arms could be used in various industrial tasks. ...
Compared with traditional rigid robots, soft robots have high flexibility, low stiffness, and adaptability to unstructured environments, and as such have great application potential in scenarios such as fragile object grasping and human machine interaction. Similar to biological muscles, the soft actuator is one of the most important parts in soft robots, and can be activated by fluid, thermal, electricity, magnet, light, humidity, and chemical reaction. In this paper, existing principles and methods for actuation are reviewed. We summarize the preprogrammed and reprogrammed structures under different stimuli to achieve motions such as bending, linear, torsional, spiral. and composite motions, which could provide a guideline for new soft actuator designs. In addition, predominant manufacturing methods and application fields are introduced, and the challenges and future directions of soft actuators are discussed.
... The deformation rate can be tuned by controlling the amplitude and duration of the internal fluidic pressure in each cavity. The inflatable cavities and surrounding structure can have different designs and segment morphologies, such as cylindrical (13), pleated (14), and ribbed (15), depending on the intended robotic operations (16). Their design determines a soft robot's actuation speed. ...
Soft robots’ flexibility and compliance give them the potential to outperform traditional rigid-bodied robots while performing multiple tasks in unexpectedly changing environments and conditions. However, soft robots have not yet revealed their full potential since nature is still far more advanced in several areas, such as locomotion and manipulation. To understand what limits their performance and hinders their transition from laboratory to real-world conditions, future studies should focus on understanding the principles behind the design and operation of soft robots. Such studies should also consider the major challenges with regard to complex materials, accurate modeling, advanced control, and intelligent behaviors. As a starting point for such studies, this review provides a current overview of the field by examining the working mechanisms of advanced actuation and sensing modalities, modeling techniques, control strategies, and learning architectures for soft robots. Next, we summarize how these approaches can be applied to create sophisticated soft robots and examine their application areas. Finally, we provide future perspectives on what key challenges should be tackled first to advance soft robotics to truly add value to our society.
Expected final online publication date for the Annual Review of Control, Robotics, and Autonomous Systems, Volume 14 is May 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
The autonomous manipulation of objects by robotic grippers has made significant strides in enhancing both human daily life and various industries. Within a brief span, a multitude of research endeavours and gripper designs have emerged, drawing inspiration primarily from biological mechanisms. It is within this context that our study takes centre stage, with the aim of conducting a meticulous review of bioinspired grippers. This exploration involved a nuanced classification framework encompassing a range of parameters, including operating principles, material compositions, actuation methods, design intricacies, fabrication techniques, and the multifaceted applications into which these grippers seamlessly integrate. Our comprehensive investigation unveiled gripper designs that brim with a depth of intricacy, rendering them indispensable across a spectrum of real-world scenarios. These bioinspired grippers with a predominant emphasis on animal-inspired solutions have become pivotal tools that not only mirror nature’s genius but also significantly enrich various domains through their versatility.
A shape estimation method that utilizes two sensing modalities of a customized fiber Bragg grating (FBG) sensor and a commercial air pressure sensor for a pneumatically driven soft finger with an extensive bending angle range based on an artificial neural network model is proposed. The proposed FBG sensor utilizes two tiny nitinol rods as a backbone to attach the long‐grating FBG element fiber, enabling high strain transfer, shape sensing for large bending deformation, and preventing chirping failure and fiber sliding when bending. Its distal end is set free to slide and synchronizes with the extended length and reflects shapes for large bending deformation (up to 320° with a linearity of 99.96%), while its proximal end is fixed. The small packaged sensor unit enables modular design, easy assembly, and high repeatability with negligible effects on the soft finger's bending performances. The artificial neural network model is utilized to process the input of two sensing modalities, reducing errors from material nonlinearity, fabrication, and assembly of soft fingers while improving shape estimation's accuracy and transferability with average errors of 0.90 mm (0.69%) and 1.55 mm (1.19%) for whole shape and distal end position, respectively. Preliminary experiments also verify the potential for pressing force prediction and hardness recognition.
Octopus vulgaris has become an important model for motor control studies in soft robotics, due to its highly developed neural system and complexity in motion. For the past ten years, research on octopus arm motor system has provided advancements in understanding the control system of these hyper-redundant and flexible structures with further implementation in the field of soft robotics. In this work, we performed a correlation study of the sucker size and structure with their pattern of “attachment and detachment” using morphological and in-vivo behavior observational approaches.Three main patterns of sucker attachment and detachment were identified and coded as ‘Contraction Attachment/Detachment‘ (CA/CD), ‘Orientation-Contraction Attachment‘ (OCA), and ‘Wave-Like Attachment/Detachment’ (WLA/WLD). The first two were more frequently used in attachment and the third one in detachment. Suckers involved in these motions showed a similar morphology and no correlation between the use of a specific strategy and their size was found.We interestingly found indications of a possible association between the sucker strategy of attachment/detachment and overall arm movement. This suggests that the control of the sucker motion pattern may be linked to the suckers’ functional use and interpreted within the framework of the animal behavior.KeywordsSuckerOctopusAttachmentDetachmentSoft roboticsBehaviorMotionNeural control
Robots are becoming more and important and can support humans in all possible areas of life. Due to their inherent compliance, soft robots are ideal for human-machine interaction. In contrast to their material compliance, soft robots such as walkers are often still powered and controlled by rigid and bulky electronics. In this study, we show a walking compliant robot, which is 3D printed by FDM printers, controlled by soft, pneumatic logic gates, and powered only by a source of constant pressurized air. The robots form and gait are inspired by the stick insect (Carausius morosus). To mimic the walking gait in fast walking on horizontal planes and the interdependency of the legs, we developed bioinspired pneumatic actuators functioning as legs and implemented a novel pneumatic logic circuit. In this circuit, one pair of legs can only transition from stance to swing when the other pair of legs has touched the ground. Our results demonstrate how the field of soft robotics can advance with critical technology such as soft, pneumatic logic gates being printed on FDM printers. We envision that our system will continue to evolve with the incorporation of even more advanced control circuits, enabling the robot to operate at even higher speed. The lifting capacity has the potential to be further optimized and an on-board pressure supply system can be implemented, allowing for more efficient and effective performance. This will ultimately lead to a fully autonomous soft machine.Keywordssoft valvesoft robotinsect locomotionbiomimetics
Although natural continuum structures, such as the boneless elephant trunk, provide inspiration for new versatile grippers, highly deformable, jointless, and multidimensional actuation has still not been achieved. The challenging pivotal requisites are to avoid sudden changes in stiffness, combined with the capability of providing reliable large deformations in different directions. This research addresses these two challenges by harnessing porosity at two levels: material and design. Based on the extraordinary extensibility and compressibility of volumetrically tessellated structures with microporous elastic polymer walls, monolithic soft actuators are fabricated by 3D printing unique polymerizable emulsions. The resulting monolithic pneumatic actuators are printed in a single process and are capable of bidirectional movements with just one actuation source. The proposed approach is demonstrated by two proof‐of‐concepts: a three‐fingered gripper, and the first ever soft continuum actuator that encodes biaxial motion and bidirectional bending. The results open up new design paradigms for continuum soft robots with bioinspired behavior based on reliable and robust multidimensional motions.
Integrated control circuits with multiple computation functions are essential for soft robots to achieve diverse complex real tasks. However, designing compliant yet simple circuits to embed multiple computation functions in soft electronic systems above the centimeter scale is still a tough challenge. Herein, utilizing smooth cyclic motions of magnetic liquid metal droplets (MLMD) in specially designed and surface‐modified circulating channels, a soft reconfigurable circulator (SRC) consisting of three simple and reconfigurable basic modules is described. Through these modules, MLMD can utilize their conductivity and extreme deformation capabilities to transfer their simple cyclic motions as input signals to programmable electrical output signals carrying computing information. The obtained SRCs make it possible for soft robots to perform complex computing tasks, such as logic, programming, and self‐adaptive control (a combination of programming and feedback control). Following, a digital logic‐based grasping function diagnosis, a locomotion reprogrammable soft car, and a self‐adaptive control‐based soft sorting gripper are demonstrated to verify SRCs’ capabilities. The unique attributes of MLMD allow complex computations based on simple configurations and inputs, which provide new ways to enhance soft robots' computing capabilities.
Soft robots have gained significant attention in recent years owing to their high safety in human–machine interactions and exceptional adaptability to unpredictable environments. Despite great advances, achieving continuous rotation with tunable stepping angle in soft robots remains a challenge. Herein, inspired by the stepping rotation strategy of the flagellum, an artificial soft rotary motor capable of bidirectional continuous rotation and tunable stepping angles is presented. The motor features a wide range of stepping angles (−72.5° to 73.4°), enabling it to rotate to any angle position with high resolution. The soft motor also exhibits high rotation speed (18.23 r min ⁻¹ ), zero‐energy position‐holding, and excellent durability. Furthermore, the potential applications of the soft rotary motors, including tuning the grasping direction of a soft gripper and adjusting the winding direction of a soft tentacle is demonstrated. This work offers a universal soft fluidic component for soft robots, endowing them with enhanced agility and movement capabilities.
The aim of this article is to propose a bio-inspired morphological classification for soft robots based on an extended review process. The morphology of living beings that inspire soft robotics was analyzed; we found coincidences between animal kingdom morphological structures and soft robot structures. A classification is proposed and depicted through experiments. Additionally, many soft robot platforms present in the literature are classified using it. This classification allows for order and coherence in the area of soft robotics and provides enough freedom to expand soft robotics research.
Soft pneumatic gripping strategies are often based on pressurized actuation of structures made of soft elastomeric materials, which limits designs in terms of size, weight, achievable forces, and ease of fabrication. In contrast, fabric‐based inflatable structures offer high stiffness‐to‐weight ratio solutions for soft robotics, but their actuation has been little explored. Herein, a new class of pneumatic soft grippers is presented that exploits the in‐plane overcurvature effect of inextensible fabric flat balloons upon inflation. A star‐shaped gripper contracts radially under pressure producing a gripping force on the object whose intensity can be modulated by the pressure input. First, the kinematics and mechanics of a single V‐shaped actuator are studied through experiments, finite element simulations, and analytical models. Then, these results are leveraged to predict the mechanical response of the entire star, optimize its geometry, and maximize contraction and stiffness. It is shown that the gripping performance can be improved by stacking several stars with silicon‐coated corners. It is expected that the flexibility, robustness, scalability, and ease of fabrication of this methodology will lead to a new generation of lighter and larger actuators capable of developing higher forces and moving delicate and irregularly shaped objects while maintaining reasonable complexity.
Soft structures and actuation allow robots, conventionally consisting of rigid components, to perform more compliant, adaptive interactions similar to living creatures. Although numerous functions of these types of actuators have been demonstrated in the literature, their hyperelastic designs generally suffer from limited workspaces and load-carrying capabilities primarily due to their structural stretchability factor. Here, we describe a series of pneumatic actuators based on soft but less stretchable fabric that can simultaneously perform tunable workspace and bear a high payload. The motion mode of the actuator is programmable, combinable, and predictable and is informed by rapid response to low input pressure. A robotic gripper using three fabric actuators is also presented. The gripper demonstrates a grasping force of over 150 N and a grasping range from 70 to 350 millimeters. The design concept and comprehensive guidelines presented would provide design and analysis foundations for applying less stretchable yet soft materials in soft robots to further enhance their practicality.
The design of soft actuators is often focused on achieving target trajectories or delivering specific forces and torques, rather than controlling the impedance of the actuator. This article outlines a new soft, tunable pneumatic impedance module based on an antagonistic actuator setup of textile-based pneumatic actuators intended to deliver bidirectional torques about a joint. Through mechanical programming of the actuators (select tuning of geometric parameters), the baseline torque to angle relationship of the module can be tuned. A high bandwidth fluidic controller that can rapidly modulate the pressure at up to 8 Hz in each antagonistic actuator was also developed to enable tunable impedance modulation. This high bandwidth was achieved through the characterization and modeling of the proportional valves used, derivation of a fluidic model, and derivation of control equations. The resulting impedance module was capable of modulating its stiffness from 0 to 100 Nm/rad, at velocities up to 120°/s and emulating asymmetric and nonlinear stiffness profiles, typical in wearable robotic applications.
To improve the grasping power of soft robots, inspired by the scene of intertwined and interdependent vine branches safely clinging to habitats in a violent storm and the phenomenon of large grasping force after being entangled by aquatic plants, this paper proposes a soft robotic gripper with multi-stem twining. The proposed robotic gripper can realize a larger contact area of surrounding or containing object and more layers of a twining object than the current twining gripping methods. It not only retains the adaptive advantages of twining grasping but also improves the grasping force. First, based on the mechanical characteristics of the multi-stem twining of the gripper, the twining grasping model is developed. Then, the force on the fiber is deduced by using the twining theory, and the axial force of the gripper is analyzed based on the equivalent model of the rubber ring. Finally, the torsion experiments of fibers and the grasping experiments of the gripper are designed and conducted. The torsion experiment of fibers verifies the influence of a different number of fiber ropes and fiber torque on the grasping force, and the grasping experiment reflects the large load of the gripper and the high adaptability and practicability under different tasks.
Soft and flexible magnetic robots have gained significant attention in the past decade. These robots are fabricated using magnetically-active elastomers, are capable of large deformations, and are actuated remotely thus allowing for small robot size. This combination of properties is appealing to the minimally invasive surgical community, potentially allowing navigation to regions of the anatomy previously deemed inaccessible. Due to the low forces involved, one particular challenge is functionalizing such magnetic devices. To address this limitation we introduce a proof-of-concept variable stiffness robot controlled by remote magnetic actuation, capable of grasping objects of varying sizes. We demonstrate a controlled and reversible high deformation coiling action induced via a transient homogeneous magnetic field and a synchronized sliding nitinol backbone. Our soft magnetic coiling grasper is visually tracked and controlled during three experimental demonstrations. We exhibit a maximum coiling deformation angle of 400
$^{\circ }$
.
Programming inflatable systems to deform to desired 3D shapes opens up multifarious applications in robotics, morphing architecture, and interventional medicine. This work elicits complex deformations by attaching discrete strain limiters to cylindrical hyperelastic inflatables. Using this system, a method is presented to solve the inverse problem of programming myriad 3D centerline curves upon inflation. The method entails two steps: first, a reduced‐order model generates a conceptual solution giving coarse indications of strain limiter placement on the undeformed cylindrical inflatable. This low‐fidelity solution then seeds a finite element simulation nested within an optimization loop to further tune strain limiter parameters. We leverage this framework to achieve functionality through a priori programmed deformations of cylindrical inflatables, including 3D curve matching, self‐tying knotting, and manipulation. The results hold broad significance for the emerging computational design of inflatable systems.
Soft actuators that operate with overpressure have been successfully implemented as soft robotic grippers. Naturally, as these pneumatic devices are prone to cuts, self-healing properties are attractive. Here, we prepared a gripper that operates based on the liquid-gas phase transition of ethanol within its hollow structure. The gripping surface of the device is coated with a self-healing polymer that heals with heat. This gripper also includes a stainless steel wire along the device that heats the entire structure through resistive heating. This design results in a soft robotic gripper that actuates and heals in parallel driven by the same practical stimulus, that is, electricity. Compared to other self-healing soft grippers, this approach has the advantage of being simple and having autonomous self-healing. However, there remain fundamental drawbacks that limit its implementation. The current work critically assesses this overpressure approach and concludes with a broad perspective regarding self-healing soft robotic grippers.
Rigidity and softness are essential for robot motion and manipulation in various complex scenarios. To integrate these two contrary features, several variable‐stiffness structures are investigated while requiring a longer processing time and more energy for switching from a stiffer to softer status, with only one status at a specific point in time. Inspired by the combined softness–rigidity hybrid property of desert iguanas’ skin, the concept of an anisotropic stiffness structure is developed, which simultaneously possesses rigidity and softness properties in different directions, leading to the development of novel soft robots. This anisotropic stiffness structure comprises a silicone–paper composite with multiple superimposed origami patterns and has high stiffness and softness properties. The anisotropic stiffness structure is then constructed by developing three novel soft robots: a crawling robot capable of extending and contracting with a payload of 117 times its own weight, a multifunctional prosthetic hand capable of grasping fragile items with its soft side and lifting and crushing items with its hard side, and a snake robot capable of traveling with the soft side and extruding out with over 75% of its body length with the stiffer side. Inspired by the desert iguanas’ skin, an origami anisotropic stiffness structure (OASS) is proposed, which coexists with rigidity and softness states in different directions. Then, the OASS is constructed to develop three novel soft robots: a crawling robot moving under an ultraheavy payload; a prosthetic hand grasping fragile items and lifting or crushing items; a snake‐shaped robot traveling and extruding out.
Soft shells are ubiquitous in soft devices, e.g., soft robots, wearable sensors, and soft medial replicas. However, previous widely accepted methods, such as mold casting, dip coating, and additive manufacturing, are limited to thick shells due to the mold assembly and the large friction during demolding, long processing time for mold dissolution, and poor scalability, respectively. Here, a facile, robust, and scalable manufacturing technique, named flow casting, to create soft shells with complex geometries and multifunctionalities is proposed. The method involves a flow‐governed layer casting process and a peel‐dominated demolding process. A one‐dimensional soft shell is first made with controllable thicknesses (100–400 µm) and fabricated various soft shells of intricate geometries, including three‐branched, circular‐shaped, and exquisite microstructures such as papillae and microgrooves on curved surfaces, with the resolution of feature sizes on the order of 100 µm. Furthermore, the versatility of this method is demonstrated with a 3D vascular phantom model for a magnetic robot transporting, microstructured cubic sleeves for enhancing the grasping ability of rigid grippers, and a stretchable optical waveguide capable of color changing by external mechanical stimuli. The authors harness a flow‐governed layer casting process and a peel‐dominated demolding process for complex monolithic soft‐shell fabrication, named flow casting. Theoretical models have been built to control thickness in soft shells and rationalize the demolding process. Both complex 3D geometries and delicate microstructures of soft shells are replicated and employed to enhance the multifunctionalities of versatile soft devices.
Developing large, soft grippers with high omnidirectional load (above 40 kg) has always been challenging. We address this challenge by developing a powerful soft gripper that can grasp the human body based on a soft-enclosed grasping structure and a soft-rigid coupling structure. The envelope size of the proposed soft gripper is 611.6 mm × 559 mm × 490.7 mm, the maximum grasping size is 417 mm, and the payload on the human body is more than 90 kg, which has exceeded most existing soft grippers. Furthermore, the grasping force prediction of the gripper is achieved through theoretical modeling. The primary contribution of this work is to overcome the size and payload limits of current soft grippers and implement a human-grasping experiment based on the soft-grasping method.
A multifunctional molecule DTPCZTZ was synthesized, which can not only realize high efficiency nondoped deep blue device, but also achieve high efficiency phosphorescent devices.
Pneumatic-powered actuators are receiving increasing attention due to their widespread applications. However, their inherent low stiffness makes them incompetent in tasks requiring high load capacity or high force output. On the other hand, soft pneumatic actuators are susceptible to damage caused by over-pressuring or punctures by sharp objects. In this work, we designed and synthesized a coordination adaptable network (PETMP-AIM-Cu) with high mechanical rigidity (Young's modulus of 1.9 GPa and elongation <2% before fracturing) as well as excellent variable stiffness property (soft-rigid switching ability σ as high as 3 268 000 when ΔT = 90 °C). Combining PETMP-AIM-Cu with a self-healing elastomer based on dynamic disulfide bonds (LP-PDMS), we fabricated a new pneumatic actuator which shows high load capacity at room temperature, but can also easily deform upon heating and thus can be actuated pneumatically. Benefiting from the excellent self-healing ability of PETMP-AIM-Cu and LP-PDMS, the entire pneumatic actuator can still be actuated after being cut and healed. Such a variable-stiffness and healable pneumatic actuator would be useful for complex environmental applications.
Soft robots are envisioned as the next generation of safe biomedical devices in minimally invasive procedures. Yet, the difficulty of processing soft materials currently limits the size, aspect‐ratio, manufacturing throughput, as well as, the design complexity and hence capabilities of soft robots. Multi‐material thermal drawing is introduced as a material and processing platform to create soft robotic fibers imparted with multiple actuations and sensing modalities. Several thermoplastic and elastomeric material options for the fibers are presented, which all exhibit the rheological processing attributes for thermal drawing but varying mechanical properties, resulting in adaptable actuation performance. Moreover, numerous different fiber designs with intricate internal architectures, outer diameters of 700 µm, aspect ratios of 10³, and a fabrication at a scale of 10s of meters of length are demonstrated. A modular tendon‐driven mechanism enables 3‐dimensional (3D) motion, and embedded optical guides, electrical wires, and microfluidic channels give rise to multifunctionality. The fibers can perceive and autonomously adapt to their environments, as well as, probe electrical properties, and deliver fluids and mechanical tools to spatially distributed targets.
Unlike most animals, plants fail to move bodily at will. However, movements also occur in every single part of plants out of energy and nutrients needs, spanning from milliseconds to hours on a time scale. And with the growing understanding of plant movement in the academic community, bionic soft robots based on plant movement principles are increasingly studied and are considered by scientists as a source of inspiration for innovative engineering solutions. In this paper, through the study of the biological morphology, microstructure, and motion mechanism of the flytrap, we developed chambered design rules, and designed and fabricated a gas-driven bionic flytrap blade, intending to investigate its feasibility of performing complex bending deformation. The experimental result shows that the bionic flytrap blade can achieve multi-dimensional bending deformation, and complete the bending and closing action within 2 s. The performance of the bionic flytrap blade fabricated is in high agreement with the real flytrap blade in terms of bending and deformation, achieving an excellent bionic design effect. In this study, the chambered design rules of the bionic flytrap blade were proposed and developed, and the possibility of its deformation was investigated. The effects of different chamber types and different flow channel design precepts on the bending deformation of the bionic flytrap blade were revealed, together with the relationship between the response time and flow rate of the bionic flytrap blade. At last, this study provides new ideas for the study of plant blade motion mechanism in a hope to expand the application fields of bionic robots, especially hope to offer solutions for plant-type robotics.
Inspired by the observation that many naturally occurring adhesives arise as tex- tured thin films, we consider the displacement-controlled peeling of a flexible plate from an incision-patterned thin adhesive elastic layer. We find that crack initiation from an incision on the film occurs at a load much higher than that required to propagate it on a smooth adhesive surface; multiple incisions thus cause the crack to propagate intermittently. Microscopically, this mode of crack initiation and prop- agation in geometrically confined thin adhesive films is related to the nucleation of cavitation bubbles behind the incision which must grow and coalesce before a viable crack propagates. Our theoretical analysis allows us to rationalize these experimental observations qualitatively and quantitatively and suggests a simple design criterion for increasing the interfacial fracture toughness of adhesive films.
Evolution has resolved many of nature's challenges leading to lasting solutions with maximal performance and effective use of resources. Nature's inventions have always inspired human achievements leading to effective materials, structures, tools, mechanisms, processes, algorithms, methods, systems and many other benefits. The field of mimicking nature is known as Biomimetics and one of its topics includes electroactive polymers that gain the moniker artificial muscles. Integrating EAP with embedded sensors, self-repair and many other capabilities that are used in composite materials can add greatly to the capability of smart biomimetic systems. Such development would enable fascinating possibilities potentially turning science fiction ideas into engineering reality.
Based on the sulfonated poly (styrene-b-ethylene-co-butylene-b-styrene) ionic membrane, a novel electro-active polymer, which can be used as sensors and actuators, was developed through the electroless plating procedure. The surface and cross-sectional morphologies of the SSEBS actuator were disclosed by using scanning electron microscope and transmission electron microscopy. The electromechanical results of the SSEBS actuators show high-speed bending actuation under constant voltages and also give excellent harmonic responses under sinusoidal excitation. In the voltage–current test, the electrical current is almost synchronous with the applied voltages, while the mechanical displacement shows high phase shift from the voltage signals. The SSEBS-based ionic polymer-metal composite can be a promising smart material and may possibly be used to implement biomimetic motion.
Traditional robots have rigid underlying structures that limit their ability to interact with their environment. For example, conventional robot manipulators have rigid links and can manipulate objects using only their specialised end effectors. These robots often encounter difficulties operating in unstructured and highly congested environments. A variety of animals and plants exhibit complex movement with soft structures devoid of rigid components. Muscular hydrostats (e.g. octopus arms and elephant trunks) are almost entirely composed of muscle and connective tissue and plant cells can change shape when pressurised by osmosis. Researchers have been inspired by biology to design and build soft robots. With a soft structure and redundant degrees of freedom, these robots can be used for delicate tasks in cluttered and/or unstructured environments. This paper discusses the novel capabilities of soft robots, describes examples from nature that provide biological inspiration, surveys the state of the art and outlines existing challenges in soft robot design, modelling, fabrication and control.
This manuscript describes a unique class of locomotive robot: A soft robot, composed exclusively of soft materials (elastomeric polymers), which is inspired by animals (e.g., squid, starfish, worms) that do not have hard internal skeletons. Soft lithography was used to fabricate a pneumatically actuated robot capable of sophisticated locomotion (e.g., fluid movement of limbs and multiple gaits). This robot is quadrupedal; it uses no sensors, only five actuators, and a simple pneumatic valving system that operates at low pressures (< 10 psi). A combination of crawling and undulation gaits allowed this robot to navigate a difficult obstacle. This demonstration illustrates an advantage of soft robotics: They are systems in which simple types of actuation produce complex motion.
Animals with rigid skeletons can rely on several mechanisms to simplify motor control--for example, they have skeletal joints that reduce the number of variables and degrees of freedom that need to be controlled. Here we show that when the octopus uses one of its long and highly flexible arms to transfer an object from one place to another, it employs a vertebrate-like strategy, temporarily reconfiguring its arm into a stiffened, articulated, quasi-jointed structure. This indicates that an articulated limb may provide an optimal solution for achieving precise, point-to-point movements.
Using a simple constitutive law for elastic behavior that includes the feature of a maximum allowable strain,1 equations are derived for inflation pressure as a function of the amount of inflation for three rubber shells: a thin-walled spherical balloon, a small spherical cavity in a large rubber block, and a thin-walled cylindrical tube. The results are compared with those obtained using the neo-Hookean constitutive law. Uniform expansion is generally predicted to become unstable at a modest degree of inflation but the new relations give a second stable inflation state, in accord with experience.
The development of soft pneumatic actuators based on composites consisting of elastomers with embedded sheet or fiber structures (e.g., paper or fabric) that are flexible but not extensible is described. On pneumatic inflation, these actuators move anisotropically, based on the motions accessible by their composite structures. They are inexpensive, simple to fabricate, light in weight, and easy to actuate. This class of structure is versatile: the same principles of design lead to actuators that respond to pressurization with a wide range of motions (bending, extension, contraction, twisting, and others). Paper, when used to introduce anisotropy into elastomers, can be readily folded into 3D structures following the principles of origami; these folded structures increase the stiffness and anisotropy of the elastomeric actuators, while being light in weight. These soft actuators can manipulate objects with moderate performance; for example, they can lift loads up to 120 times their weight. They can also be combined with other components, for example, electrical components, to increase their functionality.
"Why do you shift from walking to running at a particular speed? How can we predict transition speeds for animals of different sizes? Why must the flexible elastic of arterial walls behave differently than a rubber tube or balloon? How do leaves manage to expose a broad expanse of surface while suffering only a small fraction of the drag of flags in high winds?. The field of biomechanics--how living things move and work--hasn't seen a new general textbook in more than two decades. Here a leading investigator and teacher lays out the key concepts of biomechanics using examples drawn from throughout the plant and animal kingdoms. Up-to-date and comprehensive, this is also the only book to give thorough coverage to both major subfields of biomechanics: fluid and solid mechanics.
The first arm wrestling match between a human arm and a robotic arm
driven by electroactive polymers (EAP) was held at the EAPAD conference
in 2005. The primary objective was to demonstrate the potential of the
EAP actuator technology for applications in the field of robotics and
bioengineering. The Swiss Federal Laboratories for Materials Testing and
Research (Empa) was one of the three organizations participating in this
competition. The robot presented by Empa was driven by a system of
rolled dielectric elastomer (DE) actuators. Based on the calculated
stress condition in the rolled actuator, a low number of pre-strained DE
film wrappings were found to be preferential for achieving the best
actuator performance. Because of the limited space inside the robot
body, more than 250 rolled actuators with small diameters were arranged
in two groups according to the human agonist-antagonist muscle
configuration in order to achieve an arm-like bidirectional rotation
movement. The robot was powered by a computer-controlled high voltage
amplifier. The rotary motion of the arm was activated and deactivated
electrically by corresponding actuator groups. The entire development
process of the robot is presented in this paper where the design of the
DE actuators is of primary interest. Although the robot lost the arm
wrestling contest against the human opponent, the DE actuators have
demonstrated very promising performance as artificial muscles. The
scientific knowledge gained during the development process of the robot
has pointed out the challenges to be addressed for future improvement in
the performance of rolled dielectric elastomer actuators.
Soft robotic manipulators, unlike their rigid-linked counterparts, deform continuously along their lengths similar to elephant trunks and octopus arms. Their excellent dexterity enables them to navigate through unstructured and cluttered environments and handle fragile objects using whole arm manipulation. Soft robotic manipulator design involves the specification of air muscle actuators and the number, length and configuration of sections that maximize dexterity and load capacity for a given maximum actuation pressure. This paper uses nonlinear models of the actuators and arm structure to optimally design soft robotic manipulators. The manipulator model is based on Cosserat rod theory, accounts for large curvatures, extensions, and shear strains, and is coupled to nonlinear Mooney-Rivlin actuator model. Given a dexterity constraint for each section, a genetic algorithm-based optimizer maximizes the arm load capacity by varying the actuator and section dimensions. The method generates design rules that simplify the optimization process. These rules are then applied to the design of pneumatically and hydraulically actuated soft robotic manipulators, using 100 psi and 1000 psi maximum pressure, respectively.
Two examples illustrate the propagation of instability modes under quasi-static, steady-state conditions. The first is the inflation of a long cylindrical party balloon in which a bulge propagates down the length of the balloon. The second is the collapse of a long pipe under external pressure as a result of buckle propagation. In each example, there is a substantial barrier to the initiation of the instability mode. Once initiated, however, the mode will not arrest if the pressure is in excess of the quasi-static, steady-state propagation pressure. It is this critical pressure that is determined in this paper for each of the two examples.
Purpose
The paper describes a pipe repair conducted in August 2004 using two types of snake‐arm robot. The pipe was located 5 m below the reactor core of Ringhals 1 nuclear reactor.
Design/methodology/approach
The two types of robot worked co‐operatively to replace a section of critical pipe. The 23‐degree of freedom arm snaked around obstructing pipes to positions cameras in a humanly unreachable location in order to give the ideal view of the work site. The more substantial second arm used 13 degrees of freedom to deliver fixtures, cutting tools, gas shields, inspection equipment and also conducted both tack welding and continuous welding.
Findings
The leaking pipe was repaired manually during the 2004 outage. The robots successfully completed the externally assessed Factory Acceptance Tests which involved copying the complete procedure on a purpose built mock‐up. The robots are now on standby for 2005 and beyond.
Practical implications
The successful completion of this extremely difficult task indicates that snake‐arm robots are now a viable solution to a variety of complex access tasks in all industries including aerospace, pharmaceuticals, the miltary sector and nuclear industries.
Originality/value
The paper describes a procedure that has never been attempted before using two completely new designs of redundant snake‐arm robot.
Polymers are highly attractive for their inherent properties of mechanical flexibility, light weight, and easy processing. In addition, some polymers exhibit large property changes in response to electrical stimulation, much beyond what is achievable by inorganic materials. This adds significant benefit to their potential applications.
The focus of this issue of MRS Bulletin is on polymers that are electromechanically responsive, which are also known as electroactive polymers (EAPs). These polymers respond to electric field or current with strain and stress, and some of them also exhibit the reverse effect of converting mechanical motion to an electrical signal.
There are many types of known polymers that respond electromechanically, and they can be divided according to their activation mechanism into field-activated and ionic EAPs. The articles in this issue cover the key material types used in these two groups, review the mechanisms that drive them, and provide examples of applications and current challenges. Recent advances in the development of these materials have led to improvement in the induced strain and force and the further application of EAPs as actuators for mimicking biologic systems and sensors. As described in this issue, the use of these actuators is enabling exciting applications that would be considered impossible otherwise.
This paper presents some problems dealing with the transportation of bulk and liquid materials. The robotization of the transport process by an elastic manipulator of an elephant trunk type is proposed. The design of an experimental stand and some results of statical and dynamical analysis are presented. In conclusion, some proposals describing the possibilities of utilising elastic manipulators for transport purposes are given.
Shape-memory polymers (SMPs) have been one of the most popular subjects under intensive investigation in recent years, due to their many novel properties and great potential. These so-called SMPs by far surpass shape-memory alloys and shape-memory ceramics in many properties, e.g., easy manufacture, programming, high shape recovery ratio and low cost, and so on. However, they have not fully reached their technological potential, largely due to that the actuation of shape recovery in thermal-responsive SMPs is normally only driven by external heat. Thus, electro-activate SMP has been figured out and its significance is increasing in years to come. This review focuses on the progress of electro-activate SMP composites. Special emphases are given on the filler types that affect the conductive properties of these composites. Then, the mechanisms of electric conduction are addressed.
Soft robots: A methodology based on embedded pneumatic networks (PneuNets) is described that enables large-amplitude actuations in soft elastomers by pressurizing embedded channels. Examples include a structure that can change its curvature from convex to concave, and devices that act as compliant grippers for handling fragile objects (e.g., a chicken egg).
This protocol provides an introduction to soft lithography--a collection of techniques based on printing, molding and embossing with an elastomeric stamp. Soft lithography provides access to three-dimensional and curved structures, tolerates a wide variety of materials, generates well-defined and controllable surface chemistries, and is generally compatible with biological applications. It is also low in cost, experimentally convenient and has emerged as a technology useful for a number of applications that include cell biology, microfluidics, lab-on-a-chip, microelectromechanical systems and flexible electronics/photonics. As examples, here we focus on three of the commonly used soft lithographic techniques: (i) microcontact printing of alkanethiols and proteins on gold-coated and glass substrates; (ii) replica molding for fabrication of microfluidic devices in poly(dimethyl siloxane), and of nanostructures in polyurethane or epoxy; and (iii) solvent-assisted micromolding of nanostructures in poly(methyl methacrylate).
The area of tentacle and trunk type biological manipulation is not new, but there has been little progress in the development and application of a physical device to simulate these types of manipulation. Our research in this area is based on using an 'elephant trunk' robot. In this paper, we review the construction of the robot and how it compares to biological manipulators. We then apply our previously designed kinematic model to describe the kinematics of the robot. We finish by providing some examples of motion planning and intelligent manipulation using the robot.
The flexible microactuator (FMA) is a novel pneumatic rubber
actuator developed for use in microrobots. This paper reports on its
miniaturization and integration using a stereo lithography method, also
known as a photo-forming. First, two key technical issues arising in the
application of stereo lithography to FMA fabrication are discussed. One
issue is the development of a new FFIA design, which we call a
“restraint beam” FMA. This design makes it possible to
fabricate FMAs from a single material, allowing lithography to be used.
The other issue is related to materials. While conventional materials
used in stereo lithography are rigid plastics, new investigations of
rubber-like materials are necessary. In this report, we show
experimentally that appropriate compound coloring of a resin enables us
to control its side-forming and elastic properties. Later in the paper,
several examples of fabrication and experiments on prototype FMAs are
reported; we discuss the fabrication equipment, the bending motions of
“restraint beam” FMAs, the integration of pneumatic
circuits, and a 5×5 FMA array. The 5×5 array was
successfully able to move a glass plate placed on it
Unlike traditional rigid linked robots, soft robotic manipulators can bend into a wide variety of complex shapes due to control inputs and gravitational loading. This paper presents a new approach for modeling soft robotic manipulators that incorporates the effect of material nonlinearities and distributed weight and payload. The model is geometrically exact for the large curvature, shear, torsion, and extension that often occur in these manipulators. The model is based on the geometrically exact Cosserat rod theory and a fiber reinforced model of the air muscle actuators. The model is validated experimentally on the OctArm V manipulator, showing less than 5% average error for a wide range of actuation pressures and base orientations as compared to almost 50% average error for the constant-curvature model previously used by researchers. Workspace plots generated from the model show the significant effects of self-weight on OctArm V.
Continuum or hyper-redundant robot manipulators can exhibit behavior similar to biological trunks, tentacles, or snakes. Unlike traditional rigid-link robot manipulators, continuum robot manipulators do not have rigid joints, hence these manipulators are extremely dexterous, compliant, and are capable of dynamic adaptive manipulation in unstructured environments. However, the development of high-performance control algorithms for these manipulators is quite a challenge, due to their unique design and the high degree of uncertainty in their dynamic models. In this paper, a controller for continuum robots, which utilizes a neural network feedforward component to compensate for dynamic uncertainties is presented. Experimental results using the OCTARM, which is a soft extensible continuum manipulator, are provided to illustrate that the addition of the neural network feedforward component to the controller provides improved performance.
- Ilievski