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Robotic Tentacles with Three-Dimensional Mobility Based on Flexible Elastomers
Advanced Materials
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.
... Potted plants, for example, are difficult to grasp. To enhance adaptability of grasping, a form of entangled grasping has been proposed for designing soft grippers with straight elongated circular tube actuators (38)(39)(40)(41)(42), which provides an interesting grasping form and has strong shape-adaptive ability. However, this type of grasping tends to be random, with less success in grasping regular objects like spheres (39). ...
... Smooth tendrils are usually used as inspiration for these soft grippers with entangled grasping forms (38)(39)(40)(41)(42). In nature, tendril plants need external support to grow vertically and to get more sunlight (43). ...
... In Darwin's famous paper on the habits of climbing plants, these types of tendrils were described as excellent grapnels, tightly clutching branches like birds perching on them (44). The aforementioned entangled grasping forms of grippers (38)(39)(40)(41)(42) draw inspiration from these tendrils. However, these tendrils quite fail to attach themselves to a brick wall because of their smooth surface, which cannot support their weight on the wall. ...
Existing grippers for unmanned aerial vehicle (UAV) manipulation have persistent challenges, highlighting a need for grippers that are soft, self-adaptive, self-contained, easy to control, and lightweight. Inspired by tendril plants, we propose a class of soft grippers that are voltage driven and based on winding deformation for self-adaptive grasping. We design two types of U-shaped soft eccentric circular tube actuators (UCTAs) and propose using the liquid-gas phase-transition mechanism to actuate UCTAs. Two types of UCTAs are separately cross-arranged to construct two types of soft grippers, forming self-contained systems that can be directly driven by voltage. One gripper inspired by tendril climbers can be used for delicate grasping, and the other gripper inspired by hook climbers can be used for strong grasping. These grippers are ideal for deployment in UAVs because of their self-adaptability, ease of control, and light weight, paving the way for UAVs to achieve powerful manipulation with low positioning accuracy, no complex grasping planning, self-adaptability, and multiple environments.
... Most of the current soft robots are driven by pneumatics, hydraulics or vacuum [1][2][3][4][5][6][7][11][12][13][14]. A soft quadruped robot, driven by pneumatic networks (known as ''Pneu-Nets''), could manage its body posture to avoid obstacles [2], or change its color for active camouflage [3]. ...
... A soft quadruped robot, driven by pneumatic networks (known as ''Pneu-Nets''), could manage its body posture to avoid obstacles [2], or change its color for active camouflage [3]. The soft tentacle-like actuators were capable of achieving 3D mobility and maintaining a complex shape [11]. The pleated pneumatic actuators were resistant to puncture and then self-sealed [12]. ...
... In spite of such impressive progress, soft robotics is still a nascent field with much to be investigated. For example, most of the soft robots are currently tethered with cables connecting to external power supplies and control systems [2,3,7,[11][12][13][14][15][16]19], which greatly limits their functionalities, especially in the applications such as search and rescue operations, undersea/space exploration, and environment monitoring. Much research has been conducted on autonomous robots based on hard materials so far [20]. ...
This paper reports an untethered soft robot using soft electrostatic actuators. The robot consists of a deformable body driven by dielectric elastomer actuators, and two paper-based feet driven by elec-troadhesion actuators. The use of lightweight batteries and small-volume amplifiers contributes to the development of this untethered soft robot. Inspired by inchworms, this untethered soft robot can achieve locomotion through alternate expansion/contraction of its deformable body and adhesion/detachment of its two paper-based feet. The strong electroadhesion ensures a stable locomotion, and the large voltage-induced deformation and fast response of the robotic body leads to a velocity of 0.02 body length/s. This velocity is higher than that of untethered soft crawling robots based on pneumatic actuators or ionic polymer metal composites. The deformation of the robotic body is studied through finite element analysis. Compared to traditional hard robots, soft robots are found to be more susceptible to dissipative processes, including charging/discharging the actuators, dielectric relaxation and viscoelastic effects. These dissipative effects on this untethered soft robot are also investigated in this paper.
... While rigid grippers are commonly preferred in practical applications due to their high output power and precise positioning capabilities, their inherent rigidity limits their performance when dealing with granular materials. In specific conditions, the fluidity and accumulation of such materials can undermine the gripping stability and operational complexity of rigid grippers, making flexible grippers a more suitable alternative [2]. The adaptive and underdriven nature of the flexible gripper is attributed to its infinite curvature point [3]. ...
... The green dashed box is the success boundary. (2) Taking N (number of granules) = 7, the applied pressure is also positively correlated with the success rate at different relative sizes. The green dashed box is the success boundary. ...
The utilization of granular materials for transportation purposes has the potential to mitigate superfluous expenditures associated with the transportation process. Nevertheless, granular materials exhibit distinct flowability characteristics under specific circumstances, which can lead to challenges such as instability maintenance, intricate grasping tactics, and reduced efficiency throughout the grasping process. Hence, the grasping pattern of the trunk of the African elephant (Loxodonta Africana) was observed. Drawing inspiration from the aforementioned concept, this paper put forth a compelling approach centered around an air-powered flexible gripper platform comprising four distinct gripping stages. Our objective is to explore the correlation between the quantity of items and the supplementary pressure required to achieve successful gripping, while considering variations in object dimensions. This study has the potential to provide novel insights for enhancing the efficacy of granular material transportation through improved gripping mechanisms.
... Pneumatic soft actuators, made of compliant materials, require complex geometries to transfer pressure into actuation and stiffening [8][9][10][11]. Actuators are often casted in complex procedures combining several components with multi-stage casting to create the required geometrical structures [8,10,[12][13][14][15][16][17][18]. ...
... Additive manufacturing (AM) and fused filament fabrication (FFF) allows for the fabrication of components by extruding thermoplastic filament into a solidifying geometry [19][20][21]. Availability, simplicity, design flexibility, and affordability have made AM a common soft robotics mold fabrication method for elastomer casting [8,10,[12][13][14][16][17][18]. However, AM and FFF also introduces design freedom compared to casting processes, allowing for single-step fabrication with internal structures, thin walls, minimal volume 2 of 11 compartments, and complex geometries [3,5,22]. ...
Additive manufacturing (AM) offers new possibilities in soft robotics as materials can easily be combined in multi-material designs. Proper sensing is essential for the soft actuators to interact with the surroundings successfully. By fabricating sensors through AM, sensors can be embedded directly into the components during manufacturing. This paper investigates NinjaTek Eels electrical resistance response to strain and the feasibility of using the material to create strain sensors. Strain sensors were 3D-printed out of NinjaTek Eel, a soft conductive TPU, and was tested during cyclic loading. A custom resistance-strain test rig was developed for measuring sensor behavior. The rig was calibrated for electric resistance, able to measure electric resistance as a function of strain. A parabolic response curve was observed during cyclic loading, which led to ambiguous readings. A 10-specimen validation test was conducted, evaluating the statistical variation for the first 100 loading cycles. The validation test showed that the sensor is capable of accurate and predictable readings during single load cases and cyclic loading, with the overall root mean square error being 66.9 Ω. Combining two sensors of different cross-sections gave promising results in terms of calibrating. By monitoring load cycles and strain rates, calibration can also be achieved by machine learning models by the microcontroller used to extract data. The presented work in this article explores the potential of using conductive TPUs as sensors embedded in products such as soft robotics, life monitoring of products with structural, and digital twins for live product to user feedback.
... This facilitates a need to enhance the load capacity of soft grippers for use at sites, such as disaster sites. To realize high load capacity, we focused on a soft gripper that wraps around an object in a helical shape [26] [27] [28]. ...
... If the object is heavy, the gripper wraps around the object while the gripper tip slips on the object. Many pneumatically or hydraulically operated vine-shaped soft grippers [26] [27] [28] grasp objects under pressure. Therefore, it is considered that the gripper may rupture due to stress concentration while grasping an object. ...
Soft robots hold the potential for use in disaster sites where it is difficult to predict the external environment and the manipulation of irregularly shaped heavy objects is required. However, existing soft robots possess the low load capacity. Therefore, we propose a vine-like, power soft gripper that grasps an object by wrapping it, and we fabricated a prototype. The gripper is based on Euler's belt theory, the load capacity increases with the wrap angle and it is demonstrated by load capacity measurements. A grasping experiment demonstrated that the gripper could grasp objects of various shapes. This gripper wraps around an object using the restoring force exerted by the constant-force spring. Hence, the gripper cannot lift heavy objects that tend to rotate during lifting. However, it was confirmed that a twin-gripper with opposite helical directions could grasp such objects. It was also confirmed that twin-gripper could grasp an object weighing 1660 N although its two constant-force springs possess a small load of 43 N. This indicates that the grasping load force surpassed that generated by the spring coiling force. Finally, the gripper was attached to a construction machine robot, and a pick-and-place demonstration was conducted.
... Building soft robots from soft materials makes torque transmission inherently difficult. Materials such as elastomers are commonly used to build soft arms (18,19), but lack the torsional rigidity necessary for exerting torques. Existing flexible torque couplings, such as flex shafts and bellows, have significant limitations. ...
Torque and continuous rotation are fundamental methods of actuation and manipulation in rigid robots. Soft robot arms use soft materials and structures to mimic the passive compliance of biological arms that bend and extend. This use of compliance prevents soft arms from continuously transmitting and exerting torques to interact with their environment. Here, we show how relying on patterning structures instead of inherent material properties allows soft robotic arms to remain compliant while continuously transmitting torque to their environment. We demonstrate a soft robotic arm made from a pair of mechanical metamaterials that act as compliant constant-velocity joints. The joints are up to 52 times stiffer in torsion than bending and can bend up to 45{\deg}. This robot arm can continuously transmit torque while deforming in all other directions. The arm's mechanical design achieves high motion repeatability (0.4 mm and 0.1{\deg}) when tracking trajectories. We then trained a neural network to learn the inverse kinematics, enabling us to program the arm to complete tasks that are challenging for existing soft robots such as installing light bulbs, fastening bolts, and turning valves. The arm's passive compliance makes it safe around humans and provides a source of mechanical intelligence, enabling it to adapt to misalignment when manipulating objects. This work will bridge the gap between hard and soft robotics with applications in human assistance, warehouse automation, and extreme environments.
... DEAs can be arrayed longitudinally to enhance elongation distance and laterally to increase force output. However, the high cost of traditional manufacturing methods limits the scalability of these devices, typically confining them to small applications like single-chamber microrobots [16][17][18] and HASEL tentacle actuators [19,20]. Although multi-material 3D printing holds promise [21][22][23][24], it remains in its early stages. ...
This paper presents a novel approach to enhancing the performance of artificial muscle fibers by incorporating air gaps within the bulk dielectric material. Building on previous models, the COMSOL simulation was developed to investigate the effects of varying the inner ligament width (‘w3’) and air gap width (‘w2’) on force production. Results indicated that an air gap width of 50 µm is optimal, balancing improved force output with manufacturability constraints. A longitudinal array sweep was conducted to determine force density saturation in long fiber arrays, comparing the gap model with a traditional non-gap model. The gap model demonstrated superior performance, achieving higher force densities and better energy efficiency. The inclusion of air gaps reduced overall weight, enhanced flexibility, and improved the force-to-weight ratio, making the design particularly suitable for applications in prosthetics, exoskeletons, and soft robotics. These findings suggest that the air gap design represents a significant advancement in artificial muscle technology, offering a practical and efficient solution for various biomedical and robotic applications.
... 1 Currently, soft robots, powered by pneumatic actuators made of soft materials, typically silicone rubber, have been extensively explored. 2 They have been demonstrated in various applications such as locomotion, [3][4][5] manipulation, [6][7][8] and wearable 9,10 and biomedical devices 11,12 for their lightweight design, simplicity of operation, and safety. However, early work in soft pneumatic actuators heavily relied on elastomeric architectures, which typically exhibit inflatable deformations in all directions upon air actuation. ...
Pneumatic soft robotics are highly desirable for interacting with humans and navigating uncertain environments. However, it remains a great challenge to simultaneously achieve high actuation efficiency, programmable deformations, real-time feedback, and robustness. Herein, a textile engineering approach is harnessed to integrate multifunctionality into woven actuators by tailoring yarn groupings using all-in-one industrial weaving technologies. The unique nearly zero Poisson’s ratio inflatable deformation of the actuators contributes to a large bending strain (2,250° m−1), a high output force (30 N MPa−1), and robust mechanical performance. Bilateral bending actuators with negative, zero, and positive curvatures are realized by hierarchical shape transformations of the woven layers. The embedded sensing yarns provide facile and effective methods to proprioceptively sense actuation deformation without compromising actuation performance. Moreover, this manufacturing method is cost efficient and highly scalable, which expands practical applications of soft actuators in healthcare and offers a new perspective on the structure design of customized soft actuators.
... The most common gas is air. Actuation of these soft robots require different actuators than rigid link robots like pneumatic actuation [7], [8], [9], tendon-driven actuation [6] and actuation based on shape memory alloy (SMA) [10]. The majority of popular systems rely on pneumatic action utilizing compressed gas. ...
The present work aims to design a soft, hyper redundant robotic gripper inspired by natural tendrils. The development of automation also requires extensive study in the field of biomimetic robotics. Most robotic systems are generally built using traditional rigid materials, such as hard plastics and metals. Creating accurate robotic systems necessitates the assembly of firm components connected at specific joints. Nonetheless, crafting a robotic system modeled after natural systems, comprising continuous deformable materials, is anticipated to match or exceed the capabilities of rigid robotic systems. Soft and highly redundant robotic grippers offer nearly limitless degrees of freedom (DOF) and elevated levels of kinematic redundancy. In the present work, a soft robotic gripper is proposed, inspired by plant tendrils that deform helically to hold the object on actuation. The work describes the initial design, material selection, method, important design parameters, an actuation mechanism and the simulation and analysis of the soft gripper. Such studies will be useful to industries and researchers in automation and biomimetic robotic systems.
... Alternatively, the soft actuators themselves, a major contributor to the weight of soft robotic systems, are a target for weight reduction. Pneumatic network actuators (pneu-nets) are one common design of soft actuators (20)(21)(22)(23)(24)(25). Various embodiments of pneu-nets-such as fiber-reinforced (26)(27)(28)(29)(30)(31), multimaterial (32)(33)(34), buckling (35,36), origami-inspired (37)(38)(39)(40), and fabric/textile (41)(42)(43) soft actuators-are noteworthy in this context. ...
This paper introduces an approach to fabricating lightweight, untethered soft robots capable of diverse biomimetic locomotion. Untethering soft robotics from electrical or pneumatic power remains one of the prominent challenges within the field. The development of functional untethered soft robotic systems hinges heavily on mitigating their weight; however, the conventional weight of pneumatic network actuators (pneu-nets) in soft robots has hindered untethered operations. To address this challenge, we developed film-balloon (FiBa) modules that drastically reduced the weight of soft actuators. FiBa modules combine transversely curved polymer thin films and three-dimensionally printed pneumatic balloons to achieve varied locomotion modes. These lightweight FiBa modules serve as building blocks to create untethered soft robots mimicking natural movement strategies. These modules substantially reduce overall robot weight, allowing the integration of components such as pumps, valves, batteries, and control boards, thereby enabling untethered operation. FiBa modules integrated with electronic components demonstrated four bioinspired modes of locomotion, including turtle-inspired crawling, inchworm-inspired climbing, bat-inspired perching, and ladybug-inspired flying. Overall, our study offers an alternative tool for designing and customizing lightweight, untethered soft robots with advanced functionalities. The reduction of the weight of soft robots enabled by our approach opens doors to a wide range of applications, including disaster relief, space exploration, remote sensing, and search and rescue operations, where lightweight, untethered soft robotic systems are essential.
... Currently, a wide variety of investigations have primarily concentrated on the design, fabrication, and grasping experiments of different SPGs tailored for some specific tasks. Representative examples include a starfish-like SPG [7], an octopus-shaped tentacle [8], a five-finger anthropomorphic SPG [9], a four-finger SPG [10][11][12], a three-finger SPG [13], and other SPGs [14][15][16][17][18]. However, how to model and simulate grasping motion of these SPGs remain a topic worthy of exploration. ...
Soft pneumatic robotic grippers have found extensive applications across various engineering domains, which prompts active research due to their splendid compliance, high flexibility, and safe human-robot interaction over conventional stiff counterparts. Previously simplified rod-based models principally focused on clarifying overall large deformation and bending postures of soft grippers from static or quasi-static perspectives, whereas it is challenging to elaborate grasping characteristics of soft grippers without considering contact interaction and nonlinear large deformation behaviors. To address this, based on absolute nodal coordinate formulation (ANCF), comprehensively allowing for structural complexity, geometric, material and boundary nonlinearities, and incorporating Coulomb’ friction law with a multiple-point contact method, we put forward an effective nonlinear dynamic modeling approach for exploring grasping capability of soft gripper. Moreover, we solved the established dynamic equations using Generalized-α scheme, and conducted thorough numerical simulation analysis on a three-jaw soft pneumatic gripper (SPG) in terms of grasping configurations, displacements and contact forces. The proposed dynamic approach can accurately both describe complicated deformed configurations along with stress distribution and provide a feasible solution to simulate grasping targets, whose effectiveness and precision were analyzed theoretically and verified experimentally, which may shed new light on devising and optimizing other multifunctional SPGs.
... Nevertheless, this manufacturing process is complicated (Ma et al. 2021;Xiang et al. 2020a, b), and costly (Xiang et al. 2020b), with limited extensibility, low durability, and less scalability to be manufactured as an inhibitor in many applications (Xu et al. 2017;Xiang et al. 2020a). The strain sensors as the feedback system are used to detect an electrical shift in mechanical changes so that they can be used in soft robotics health monitoring (Xu et al. 2017;Levi et al. 2013;Martinez et al. 2013;Nawroth et al. 2012;Shepherd et al. 2011), wearable electronics (Kim et al. 2009(Kim et al. , 2011Pang et al. 2012;Xu et al. 2014), human-machine interface Ko et al. 2008), and other areas (Cotton et al. 2009;Keplinger et al. 2013;Khang et al. 2006;Kim et al. 2008;Lu et al. 2012;Rosset et al. 2009;Sekitani et al. 2009;Someya et al. 2005;Sun et al. 2006). ...
Strain sensors and soft pneumatic actuators are required to make sensorized soft pneumatic actuators. Conventionally, the strain sensors and soft pneumatic actuators are fabricated separately and then embedded afterward. The process was time- and resource-consuming. Fabricating a Sensorized Soft Pneumatic Actuator efficiently, cheaply, and relatively quickly becomes a desirable theme. The fabrication process can overcome these desires by developing Fused Deposition Modeling (FDM) technology. Many studies have been conducted, but the FDM process of fabricating sensorized soft pneumatic actuators is rarely discussed. Many literature reviews on strain sensors and soft pneumatic actuators are available, yet they are in separate resources. Meanwhile, the process of making a sensorized soft pneumatic actuator requires both. A literature review of the application of FDM to both strain sensors and soft pneumatic actuators has never been carried out. Yet, it is necessary to investigate the research gaps and opportunities for further development. This way, the downstream process of the sensorized soft pneumatic actuator-based products can be immediately developed and utilized by relevant parties. Using the systematical literature review, 53 studies were investigated regarding material, shape, characteristics, and applications. The investigation indicates that the topic leaves opportunities for further development, such as for commercial purposes. It is also possible to explore the parameters and the product’s characteristics.
... Thus, the large deformation of the soft actuator under external stimulation will affect the accuracy of sensor measurements and may potentially compromise or damage the device [37,38]. Currently, there are several methods to realize the integration of soft actuators and functional devices [39][40][41][42][43]. For example, a variety of ion conduction and fluid characteristics can be integrated into the soft drive system using embedded 3D printing technology to prepare an effective soft-sensing actuator [44]. ...
Soft robots with good deformability and adaptability have important prospects in the bionics and intelligence field. However, current research into soft robots is primarily limited to the study of actuators and ignores the integrated use of functional devices and actuators. To enrich the functions of soft robots and expand their application fields, it is necessary to integrate various functional electronic devices into soft robots to perform diverse functions during dynamic deformation. Therefore, this paper discusses methods and strategies to manufacture optical stimuli-responsive soft actuators and integrate them into functional devices for soft robots. Specifically, laser cutting allows us to fabricate an optically responsive actuator structure, e.g., the curling direction can be controlled by adjusting the direction of the cutting line. Actuators with different bending curvatures, including nonbending, can be obtained by adjusting the cutting depth, cutting width, and the spacing of the cutting line, which makes it easy to obtain a folded structure. Thus, various actuators with complex shape patterns can be obtained. In addition, we demonstrate a fabrication scheme for a worm-like soft robot integrated with functional devices (LEDs are used in this paper). The local nonbending design provides an asymmetric structure that provides driving power and avoids damage to the functional circuit caused by the large deformation during movement. The integration of drive and function provides a new path for the application of soft robots in the intelligence and bionics field.
... For example, soft robots enable compliance to highly confined spaces or self-locomotion on complex terrain [1][2][3]. In recent years, soft robots have evolved from traditional one-dimensional open-loop retractable actuators to three-dimensional closed-loop powerful execution devices [1,3,4]. For a soft robot to interact with its external environment, the perception ability of its own deformations via the sensors is essential. ...
In recent years, soft robotic sensors have rapidly advanced to endow robots with the ability to interact with the external environment. Here, we propose a polymer optical fiber (POF) sensor with sensitive and stable detection performance for strain, bending, twisting, and pressing. Thus, we can map the real-time output light intensity of POF sensors to the spatial morphology of the elastomer. By leveraging the intrinsic correlations of neighboring sensors and machine learning algorithms, we realize the spatially resolved detection of the pressing and multi-dimensional deformation of elastomers. Specifically, the developed intelligent sensing system can effectively recognize the two-dimensional indentation position with a prediction accuracy as large as ~99.17%. The average prediction accuracy of combined strain and twist is ~98.4% using the random forest algorithm. In addition, we demonstrate an integrated intelligent glove for the recognition of hand gestures with a high recognition accuracy of 99.38%. Our work holds promise for applications in soft robots for interactive tasks in complex environments, providing robots with multidimensional proprioceptive perception. And it also can be applied in smart wearable sensing, human prosthetics, and human–machine interaction interfaces.
... Unlike traditional rigid actuators, their soft counterparts are crafted from hyperelastic materials and possess infinite degrees of freedom (DoF). Such inherent flexibility offers enhanced safety and sensitivity independent of the control algorithm [3,4], with the potential showcased in diverse areas like locomotion, manipulation, and wearable and biomedical devices [5][6][7][8][9][10][11][12]. Even though actuation techniques such as thermal, optical, magnetic, and electrical have been introduced [13][14][15][16], soft pneumatic actuators (SPAs) continue to gain traction for their affordability, straightforward actuation, user safety, and uncomplicated creation process. ...
Soft grippers due to their highly compliant material and self-adaptive structures attract more attention to safe and versatile grasping tasks compared to traditional rigid grippers. However, those flexible characteristics limit the strength and the manipulation capacity of soft grippers. In this paper, we introduce a hybrid-driven gripper design utilizing origami finger structures, to offer adjustable finger stiffness and variable grasping range. This gripper is actuated via pneumatic and cables, which allows the origami structure to be controlled precisely for contraction and extension, thus achieving different finger lengths and stiffness by adjusting the cable lengths and the input pressure. A kinematic model of the origami finger is further developed, enabling precise control of its bending angle for effective grasping of diverse objects and facilitating in-hand manipulation. Our proposed design method enriches the field of soft grippers, offering a simple yet effective approach to achieve safe, powerful, and highly adaptive grasping and in-hand manipulation capabilities.
This chapter discusses origami robotics, that is, robots that are fabricated as 2D sheets and folded into their 3D form. Folding is an elegant solution to assembly wherein thin sheets morph to produce a wide variety of structures with complex geometry, kinematics, and mechanical response. By incorporating actuators, sensing, and computation directly into the sheet, full robots can be fabricated, self-assembled, and deployed in a single uniform process. Moving joints are fabricated in exactly the same way as static, structural elements, opening opportunities for end-to-end manufacturing of multi-functional robotic devices with fully embedded behaviors and control. We discuss methods for modeling, designing, controlling, and fabricating origami robots, and we highlight how these principles have been applied in a wide variety of applications, including manipulation, locomotion, self-reconfiguration, and human-robot interaction.
In this chapter, we discuss some practical issues in deploying soft robots. Specifically, we describe the practical advantages and problems arising from the conversion of industrial concrete hoses into soft continuum hose robots, for 3D printing of cement in the construction industry. “Robotizing” the inherent flexibility and maneuverability of hoses offers the potential for the creation and high fidelity repair of more complex structures than currently feasible. However, the inherent softness present in the hose structures presents practical problems. Hose compression can reduce the accuracy of the concrete print. We discuss this phenomenon, along with practical measures taken to address the issue.
The excellent flexibility and plasticity of a flexible robotic hand enable it to grip objects of various shapes and sizes. Currently, most of the flexible robotic hand fingers on the market use pneumatic drives. However, the unstable power of the pneumatic drive can cause the object gripped by the finger to slip. Additionally, the pneumatic pump can create noise pollution. To address these issues, a flexible end-effector is designed using an electromagnetic coil as the power source. The electromagnetic-driven end-effector has high precision and fast response, without the need for external devices. It only requires controlling the current to control the magnetic force of the electromagnet, thereby controlling the degree of end-effector bending. The finite element simulation is used to analyze the impact of the structural parameters of the end-effector on bending degree. And the optimal basic parameters of the end-effector are determined. Under the same intensity of the current, when the bottom layer thickness is 5 mm, end-effector knuckle spacing is 4 mm, the maximum angle of end-effector bending is reached.
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, an octopus-inspired arm made of ∼ 200 continuous muscle groups is synthesized, exposing “mechanically intelligent” design and control principles broadly pertinent to dynamics and robotics. Such principles are mathematically understood in terms of storage, transport, and conversion of topological quantities, effected into complex 3D motions via simple muscle activation templates. These are in turn composed into higher-level control strategies that, compounded by the arm’s compliance, are demonstrated across challenging manipulation tasks, revealing surprising simplicity and robustness.
Biomedical devices are indispensable in modern healthcare, significantly enhancing patients’ quality of life. Recently, there has been drastically increasing innovations in the fabrication of biomedical devices. Amongst these fabrication methods, the thermal drawing process emerged as a versatile and scalable process for developing advanced biomedical devices. By thermally drawing a macroscopic preform, which is meticulously designed and integrated with functional materials, hundreds-of-meters of multifunctional fibers are produced. These scalable flexible multifunctional fibers are embedded with functionalities such as electrochemical sensing, drug delivery, light delivery, temperature sensing, chemical sensing, pressure sensing, etc. In this review, we summarize the fabrication method of thermally drawn multifunctional fibers and highlight recent developments in thermally drawn fibers for modern biomedical application, including neural interfacing, chemical sensing, tissue engineering, cancer treatment, soft robotics, and smart wearables. Finally, we discuss the existing challenges and future directions of this rapidly growing field.
Pneumatically driven soft actuators with sensors have been developing rapidly these years. They can perceive external stimulus and be applied to different scenarios. In this study, we present a novel soft robotic finger with sensorized finger pulp based on sealing a flexible fabric piezoresistive film called Velostat into a pre-charged air bag, which can perceive the contact force with an object based on changes in resistance value of the sensor. The soft sensor mimics human finger pulp and deforms passively according to the shape of objects during grasping, so that it can firmly contact with objects and as such improves the gripper’s grasping stability. Moreover, based on force feedback, the actuator can reduce or increase the input pressure to hold the object and control the contact force precisely. The sensor exhibits a sensitivity of up to 0.328 kPa⁻¹ and can measure pressures ranging from 0 to over 10 kPa. The sensor's measurement range and sensitivity can be pre-adjusted by regulating the pre-charged pressure during fabrication for different grasping tasks. The response/recovery time of the sensor is 80/60 ms on average. Experiments show that the finger with sensorized pulp can be applied for object softness and size detection, object transport minitoring as well as force control grasping. The proposed soft robotic finger has potential for applications in scenarios that require safe contact and closed-loop control.
Commercial suction cups offer versatile solutions for adhering to a variety of objects through their good adhesion capabilities, compliance to object features, and ease of use. This has made them a practical solution for a variety of applications, and they have become ubiquitous across diverse industries. However, they are limited in their ability to adhere to objects at an angle from their main axis due to the limited passive compliance of their structure. This study introduces morphing suction cups that use cavities within the walls of the suction cups to enable them to bend and lengthen while still allowing the suction cup to adhere to objects. The morphing suction was able to lengthen by 42.7% of its initial length and bend at an angle of up to 67°. This allowed to adhere to objects at an angle of up to 70° from the axis of the suction cup. A multi-directional morphing suction cup was also presented which can bend bidirectionally. The proposed morphing suction cup has the potential to increase the versatility of suction cups for unstructured environments.
Soft grippers, generating movement immediately, are generally based on flexible materials actuated by air pressure and comprised of bulky parts, including valves, compressors/pumps, motors, and tubes. In this work, a compact soft gripper with the ability to actuate with a low boiling point liquid (acetone) is presented. SolidWorks 2021 software and 3D printing technology are used to design and manufacture the gripper molds, respectively. The constitutive material of the soft gripper body is highly flexible Ecoflex. A silver‐coated nylon fabric (SCNF) heater reinforced with stainless steel yarn (SSY) covering the external surface of the gripper is designed and manufactured using Autocad 2021 and a laser cutting machine, respectively. The idea is inspired by floating the gripper in warm water to provide smooth heat over a large surface area. The available commercial software Abaqus2021 is used to simulate the mechanical deformation of the gripper, and its results are verified with experimental results. The parameter's effect including the voltage and low boiling liquid volume on achievable force and actuating time are investigated. The relation between the electrical, thermal, and mechanical properties of the presented gripper is discussed in detail.
Somatic design is crucial for soft grippers to emulate the embodied intelligence of their biological counterparts, due to the blurry boundaries among material, structure and function. There are five critical parts in somatic design, including morphology, material, fabrication, actuation, and variable stiffness. The strong nonlinear coupling among these factors often leads to mutual influence and functional compromise after integration. Existing excellent reviews about soft grippers tend to focus more on summarizing and discussing the partial factors of somatic design, and ignore the importance of somatic‐part collaborative design. In this review, a systematic somatic design guide that covers all five parts while investigating their functional synergy is provided. The remaining challenges and the future development directions of soft grippers for organism‐like intelligence and wide‐range applications are discussed. image © 2024 WILEY‐VCH GmbH
Soft actuators have recently attracted considerable attention owing to their inherent flexibility and adaptability. Nevertheless, for a soft robot to successfully engage with its surroundings and perform tasks with optimal effectiveness, it encounters a range of obstacles, including the need for precise and skillful movement, the capacity to perceive its own position and motion, and the ability to effectively regulate its flexible structures. Researchers have developed techniques to integrate curvature sensors onto flexible devices, enabling them to detect and react to their positions. However, the integration of curvature sensors into flexible structures presents a substantial challenge in the structural manufacturing process. To address these concerns, this article presents a technique for designing, dynamic modeling, and controlling the bending angle of foldable soft actuator without the need for curvature sensors. An optimal design for the geometric dimensions of the soft structure utilizing origami concepts to guarantee the requisite bending properties is suggested. A model-based control method that considers both the motion dynamic and the air dynamic is proposed for controlling the angular bending of the actuator. The motion dynamic was developed using the constant volume principle of the elastomer material and the neo-Hookean hyperelastic theory to establish the correlation between the applied pressure and bending angle. This dynamic model incorporates both the hyperelastic material characteristics of silicone rubber and the geometry of the actuator. Soft actuators have variations in the air chamber's volume during operation, and accurately measuring this variation is challenging. In order to tackle this problem, the fuzzy active disturbance rejection controller is used to predict these variations. The controller possesses exceptional position-tracking capability. This control strategy exhibited excellent responsiveness throughout the range of steady-state error values from approximately 1o to 2o. Removing the curvature sensor increases the longevity of this soft actuator and promotes the efficiency of the manufacturing process, hence enhancing the practical application possibilities for the soft actuator made from super elastic material.
Engineering systems that leverage the flexibility and softness of soft materials have been fostering revolutionary progress and broad interest across various applications. The inherently flexible mechanical properties of these materials lay the groundwork for engineering systems that can adapt comparably to biological organisms, enabling them to adjust to unpredictable environments effectively. However, alongside the positive benefits of softness, these systems face challenges such as low durability, continuous energy demands, and compromised task performance due to the inherently low stiffness of soft materials. These limitations pose significant obstacles to the practical impact of soft engineering systems in the real world beyond innovative concepts. This review presents a strategy that employs materials with variable stiffness to balance adaptability advantages with the challenge of low rigidity. The developments are summarized in materials capable of stiffness modulation alongside their applications in electronics, robotics, and biomedical fields. This focus on stiffness modulation at the material unit level is a critical step toward enabling the practical application of soft engineering systems in real‐world scenarios.
Herein, the design, modeling, and validation of high‐flow, fluid‐driven, membrane valves tailored specifically for applications in soft robotic systems are described. Targeting the piping problem in hyper‐actuated soft robots, two fluid‐driven membrane valve designs that can admit flows of up to 871 mg s−1 while weighing less than 20 gfalse are introduced. A mathematical model to predict fluid flow by representing the displacement of the membrane as a scalar quantity influenced by the balance of pressures applied across the valve's ports is established. The model incorporates six parameters with direct physical relevance, enhancing its usefulness in valve design and system integration. In an experimental validation, flow rates with deviations within 4% are predicted and the onset of flow is correctly identified with an error rate of less than 1%. In addition, applications of these valves for flow amplification and for the creation of a fluid‐driven oscillator are experimentally demonstrated. This research contributes to the advancement of soft robotics by providing a tool for designing, optimizing, and controlling fluid‐driven systems and it lays the groundwork for the future development of embedded, fluid‐controlled valve networks that can be used to realize hyper‐actuated soft robotic systems.
Shape display devices composed of actuation pixels enable dynamic rendering of surface morphological features, which have important roles in virtual reality and metaverse applications. The traditional pin-array solution produces sidestep-like structures between neighboring pins and normally relies on high-density pins to obtain curved surfaces. It remains a challenge to achieve continuous curved surfaces using a small number of actuated units. To address the challenge, we resort to the concept of surface continuity in computational geometry and develop a C0-continuity shape display device with trichamber fiber-reinforced soft actuators. Each trichamber unit produces three-dimensional (3D) deformation consisting of elongation, pitch, and yaw rotation, thus ensuring rendered surface continuity using low-resolution actuation units. Inspired by human tactile discrimination threshold on height and angle gradients between adjacent units, we proposed the mathematical criteria of C0-continuity shape display and compared the maximal number of distinguishable shapes using the proposed device in comparison with typical pin-array. We then established a shape control model considering the nonlinearity of soft materials to characterize and control the soft device to display C0-continuity shapes. Experimental results showed that the proposed device with nine trichamber units could render typical sets of distinguishable C0-continuity shape sequence changes. We envision that the concept of C0-continuity shape display with 3D deformation capability could improve the fidelity of the rendered shapes in many metaverse scenarios such as touching human organs in medical palpation simulations.
The soft actuators of smart materials have attracted significant attention in recent years due to their unique functions and distinctive characteristics. The actuators are composed of smart materials that can demonstrate substantial alterations in their dimensions, shape, or mechanical characteristics when subjected to external stimuli, including but not limited to temperature, light, electricity, or magnetic fields. These aforementioned characteristics render them highly advantageous for various applications, including tissue engineering, prosthetics, surgical robots, drug delivery, and soft robotics. A deeper understanding of the principles of the actuators is crucial for their development and application expansion. This article provides a comprehensive analysis of soft actuators made from smart materials, explaining their underlying concepts, operational mechanisms, material composition, production techniques, and the diverse range of applications across various fields, including tissue engineering, prosthetics, surgical robotics, drug delivery systems, and the emerging field of soft robotics. This review further highlights the current challenges and prospects to address these problems to enable their ability to revolutionize into a variety of different technical fields.
Stiffness regulation strategies endow soft machines with stronger functionality to cope with diverse application requirements, for example manipulating heavy items by improving structural stiffness. However, most programmable stiffness strategies usually struggle to preserve the inherent compliant interaction capabilities following an enhancement in structural stiffness. In this study, inspired by the musculocutaneous system, we propose a soft stimuli‐responsive material (SRM) by combining shape memory alloy into compliant materials. By characterizing the mechanical performance, the flexural modulus increases from 6.6 to 142.4 MPa under the action of active stimuli, crossing two orders of magnitude, while Young's modulus stays at 2.2 MPa during programming structural stiffness. This comparative result indicates that our SRMs can keep a lower contact stiffness for compliant interaction although structural stiffness increases. Then, we develop three diverse soft machines to show the application potential of this smart material, such as robotic grippers, wearable devices, and deployable mechanisms. By applying our materials, these machines possess stronger load‐bearing capabilities. Meanwhile, these demonstrations also illustrate the efficacy of this paradigm in regulating the structural stiffness of soft machines while maintaining their compliant interaction capabilities.
Elastomers with hyperelastic deformation bring prosperity to soft robotics, especially in constituting fluidic actuators, largely due to the merit of large deformation and airtightness. However, the large (typically 0.5-1.5 strain) in-plane stretching of such materials concurrent to motion generation inevitably causes energy loss, hinders force output and accuracy. Particularly, the high nonlinearity of the low-durometer (typically 10A to 30A Shore) hyperelastic elastomers makes the modeling and control of actuators a well-known challenge. In this work, we proposed an alternative approach of using semi-rigid elastomer of significantly larger durometer (70A to 100A) to create the typical fluidic soft actuator with axial translation, by utilizing small-strain folding to generate motion. Deformation constraints and property programming are combined into a single-piece body, enabling easy fabrication by Selective Laser Sintering 3D-printing and post-treatment for origami patterned structure. Systematic analyses on the principles, modeling and design are presented. The long lifespan (over 1 million cycles), superior output linearity, high energy efficiency (more than 60% increase), and drastically improved force output (more than 98% increase) were validated experimentally, showing high potentials in enabling high-performance soft actuators that are easy to design, fabricate and drive, strong to use, and accurate to control, towards even wider applications.
Deformable, elastic materials that buckle in response to external stimuli can display “snap-through”, which involves a transition between different, stable buckled states. Snap-through produces a quick release of stored potential...
Soft pneumatic actuators (SPAs) that can perform three-dimensional movements are being developed to perform more diverse tasks beyond simple bending. The conventional PneuNet actuators have expansion limit layers, which can obtain more tip force by limiting the expansion of the bottom. However, the presence of the expansion limit layer impedes other motions, such as rotation, when configured with multiple channels. In this study, we propose a two-chamber PneuNet actuator (TPA) to which the expansion limit line (ELLINE) is applied to obtain a force gain without a limitation on rotational motion due to the expansion limit layer. We perform a finite element analysis (FEA) on three designs that can rotate and bend using twochamber to find the optimal design. The effects on twisting, bending, and tip force according to the width of the ELLINE on the selected design were then verified through an FEA. After measuring rotation and bending for the fabricated actuator with and without the ELLINE. In the case of the fabricated TPA with the ELLINE, the bending decreased by 19.8%. However, rotation increased by 22.8%, tip force increased by 1.53 times (with the ELLINE the force is 2.77 N in 70 kPa; without the ELLINE it is 1.8 N in 70 kPa), and grasping force increased by 5 times (with the ELLINE the force is 500 gf in 70 kPa, without the ELLINE it is 100 gf in 70 kPa). Furthermore, we fabricated a gripper using three actuators, capable of holding a weight of 505 g and objects of various shapes.
Soft pneumatic actuators (SPAs) hold great promise for simple and effective actuation of soft robots. Multi‐degree‐of‐freedom SPAs are highly desired as they enable diverse motion forms and improve possibility for soft robots to navigate challenging environments and perform complex tasks. Herein, this study proposes two novel origami‐based SPAs (O‐SPAs), namely the Flasher origami‐inspired SPA (FO‐SPA) and the Kresling origami‐inspired SPA (KO‐SPA), which are fabricated entirely from soft silicone without any rigid supports. A finite element model is developed to predict the deformation behavior of O‐SPAs and the deformability and dynamic response of O‐SPAs are characterized through performance tests. Simulation experiments are carried out to investigate the impact of different structural parameters on their performance. These O‐SPAs are highly sensitive to low negative pressure, exhibiting 80% of maximum deformation at −4 kPa. Based on the Flasher and Kresling origami pattern, the actuators are capable of generating compound motions including contraction, twisting, and radial motions. These motions can be used as “building blocks” for the rapid reconfiguration of various soft robots. The study has successfully enriched the types of existing SPAs by providing important multiple motions through origami, with great potential to facilitate the rapid and low‐cost design of soft robots.
Elephant trunks are capable of complex, multimodal deformations, allowing them to perform task‐oriented high‐degree‐of‐freedom (DOF) movements pertinent to the field of soft actuators. Despite recent advances, most soft actuators can only achieve one or two deformation modes, limiting their motion range and applications. Inspired by the elephant trunk musculature, a liquid crystal elastomer (LCE)‐based multi‐fiber design strategy is proposed for soft robotic arms in which a discrete number of artificial muscle fibers can be selectively actuated, achieving multimodal deformations and transitions between modes for continuous movements. Through experiments, finite element analysis (FEA), and a theoretical model, the influence of LCE fiber design on the achievable deformations, movements, and reachability of trunk‐inspired robotic arms is studied. Fiber geometry is parametrically investigated for 2‐fiber robotic arms and the tilting and bending of these arms is characterized. A 3‐fiber robotic arm is additionally studied with a simplified fiber arrangement analogous to that of an actual elephant trunk. The remarkably broad range of deformations and the reachability of the arm are discussed, alongside transitions between deformation modes for functional movements. It is anticipated that this design and actuation strategy will serve as a robust method to realize high‐DOF soft actuators for various engineering applications.
Pipeline inspection is a part of the pipeline integrity management for keeping the pipeline in good condition. The pipeline internal inspection is normally carried out through nondestructive testing techniques and technologies such as magnetic-flux leakage technology inn axial and circumferential, ultrasound technologies, eddy-current technologies and in-pipe inspection robot. Traditional in-pipe navigation robots are of rigid type with some limitations in terms of adaptability to different pipe diameters. This paper describes the development of a soft in-pipe navigation robot which can hop and crawl for maneuverability in horizontal and vertical pipes for pipe inspection. The robot consists of four motors, cables, elastic ribbons and cable-driven soft artificial muscles. The elastic ribbons control the contraction and elongation of the robot for propulsion, while the artificial muscles anchor the robot to provide a strong grip in a pipeline. The buckling and releasing characteristics of the artificial muscle and elastic ribbons are studied based on the performance of the robot. These findings can aid in navigations and inspection inside pipelines with corners and different pipe diameters.
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
Rus presented at 15th Int
- C D Onal
- X Chen
- G M Whitesides