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Elastomeric Origami: Programmable Paper-Elastomer Composites as Pneumatic Actuators
Abstract
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.
... However, as a type of metamaterial, the origami structure is a distinguished approach owing to its low cost, lightweight, and simple manufacturing. [36,37] Owing to their various benefits, origami structures have demonstrated great potential for applications in a variety of scenarios, for example, reconfigurable structures, [38][39][40] biomedical robots, [41,42] soft grippers, [43][44][45][46] and crawling robots. [39,47,48] Among various origami structures, the pyramid-shaped bulges in the Miura-ori structure are similar to iguanas' scales. ...
... Moreover, this material is easily achievable, economical, and lightweight. [36] With this composite, a complex structure of pyramid arrays can be made by the manual fabrication process of a well-studied origami structure. [36,37,43] Furthermore, this structure could be integrated with electrical circuits, sensors, controllers, etc., for extensive future applications. ...
... [36] With this composite, a complex structure of pyramid arrays can be made by the manual fabrication process of a well-studied origami structure. [36,37,43] Furthermore, this structure could be integrated with electrical circuits, sensors, controllers, etc., for extensive future applications. [36,37] ...
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.
... The first OSPA were fabricated by Martinez et al. [18] by casting elastomer coated paper composites. They fabricated several paper-elastomer OSPA designs, including an extension actuator that lifted a 1 kg mass. ...
... It is easy to use but is time-consuming due to the number of steps involved and the elastomer curing process. The weakness of the paper-elastomer composites limited the maximum operating pressures used in [18][19][20] to 30 kPa, 20 kPa, and 10 kPa, respectively. Only 50 unloaded pressurization/depressurization cycles were used to test the actuator for fatigue failure in [18]. ...
... The weakness of the paper-elastomer composites limited the maximum operating pressures used in [18][19][20] to 30 kPa, 20 kPa, and 10 kPa, respectively. Only 50 unloaded pressurization/depressurization cycles were used to test the actuator for fatigue failure in [18]. No fatigue test results were reported in [19] or [20]. ...
Soft actuators are essential to soft robots and can also be used with rigid-bodied robots. This paper is focused on methods for improving the applicability of origami-inspired soft pneumatic actuators (OSPA). Our method for rapidly fabricating OSPA is shown to be capable of making a range of actuator sizes out of different materials. The largest OSPA has a force-to-weight ratio of 124, and can lift a 44 kg mass using a −85 kPa supply pressure. Experiments with a smaller OSPA demonstrate that it can perform 150,000 contraction/extension cycles while carrying a 2 kg mass with minimal degradation due to its materials and design. Compared to other OSPAs for which fatigue tests were reported, our accordion pattern OSPA has the best values of work-to-mass ratio, max. force, and fatigue life. A computationally efficient FEA-based constrained optimization method for maximizing an OSPA's work output is then proposed. A 55% improvement in the work output was predicted, while validation experiments with OSPA prototypes showed a 53% improvement. While these improvement percentages are very similar, the values of the predicted stroke and work output are about 16% larger than the experimental values. The optimization requires only~5 h to run on a common laptop.
... There have been some attempts to design robots using Kresling origami [19][20][21][22] . However, they are not specifically designed for rotation actuators or soft actuators [23][24][25][26][27][28][29] . ...
... The maximum rotation angle of the OSPA prototypes made in this work approached 435°, larger than most of the previous soft twist actuators as far as we know [8][9][10][11][12][23][24][25][26][27][28][29] . ...
... The corresponding actuator's rotation ratio (the rotation angle to the aspect ratio) is 136°, about two times higher than the maximum value in the literature 28 . Furthermore, by combining these actuators, we demonstrated the vast applications of the OSPAs in three different robots. ...
Soft actuators have shown great advantages in compliance and morphology matched for manipulation of delicate objects and inspection in a confined space. There is an unmet need for a soft actuator that can provide torsional motion to, for example, enlarge working space and increase degrees of freedom. Toward this goal, we present origami-inspired soft pneumatic actuators (OSPAs) made from silicone. The prototype can output a rotation of more than one revolution (up to 435°), more significant than its counterparts. Its rotation ratio ( = rotation angle/aspect ratio) is more than 136°, about twice the largest one in other literature. We describe the design and fabrication method, build the analytical model and simulation model, and analyze and optimize the parameters. Finally, we demonstrate the potentially extensive utility of the OSPAs through their integration into a gripper capable of simultaneously grasping and lifting fragile or flat objects, a versatile robot arm capable of picking and placing items at the right angle with the twisting actuators, and a soft snake robot capable of changing attitude and directions by torsion of the twisting actuators.
... [29], b) Dielectric elastomer actuators (DEAs) [30], c) Ionic polymer-metal composites (IPMCs) [31], d) Shape memory alloys (SMAs) [32], e) Shape memory polymers (SMPs) [33], f) Soft fluidic actuators (SFAs) [34] Examples of different actuation types in the soft robotics field: a) Surgery robot using a tendon-driven mechanism [35], b) DEA soft gripper [36], c) IPMC gripper for manipulating the object [37], d) SMA spring soft actuator. [38], e) SMP soft gripper [39], f) Soft pneumatic actuator [40] Timeline showing major production advances in the field of SFAs: a) PAM mechanism developed by Suzumori et al. [97], b) OctArm [98], c) PneuNets [99], d) Universal gripper [100], e) Origami soft structure [101], f) VAMPs design [102], and g) HASEL actuator [72] [6], b) Snap-through instabilities mechanism changes by sequential shape changes [117], c) Bistable soft valve in SFA applications [118], d) Large manipulator continuum robot with McKibben's muscles [121], e) Soft pneumatic artificial sleeved muscles [122], f) PneuNets actuator developed by Mosadegh et al. [123], g) Peano-fluidic muscle [124], and h) Peano-HASEL actuator [77] [137], b) Soft multimodulus manipulator for minimally invasive surgery [138], c) Multi-purpose SVFA with jamming-based stiffening [139], d) VAMPS actuator made by Yang et al. [140], e) Soft robot multi-task actuator application [141] [156], b) SFA + Layer jamming mechanism [157] c) Electro adhesion + SPFA [158], d) Gecko adhesion technique +SPFA [159], e) SFA+ hard: changing the bending point and variable stiffness [160], f) Tendon + SFPA [161] [291], b) Using a 3D printer to integrate hydrogel electrodes into silicone as a tactile sensor [292], c) Employing the optoelectronic sensor method as a tactile sensor with SFAs to detect curvature and bending angle [293], d) Embedded magnetic curvature sensor in SFA [294] Table of tables Table 1 ...
... The soft fluidic actuator is one of the most ubiquitous actuation mechanisms in soft robotics due to its many advantages, including simple assembly, cost-effective materials, large deformation, and high generated force [34], [1] (Figure 2.1f). These unique characteristics make them promising candidates for various applications, such as gripping Timeline showing major production advances in the field of SFAs: a) PAM mechanism developed by Suzumori et al. [97], b) OctArm [98], c) PneuNets [99], d) Universal gripper [100], e) Origami soft structure [101], f) VAMPs design [102], and g) HASEL actuator [72]. ...
... In [101], Martinez et al. proposed a wide range of origami soft actuators by combining a stretchable elastomer with a non-stretchable but easily bendable sheet (Figure 2.3e, 6a). ...
This document is a multiple-article format dissertation investigating the design, optimization, and fabrication of soft pneumatic actuators (SFAs) for soft robotic applications. Introduced as a novel technology in recent years, soft robotics broadens new horizons in robotics thanks to promising characteristics such as adaptability, lightweight, less assembly, and low cost to perform complicated configurations in various environments. Even though there is a large diversity of applications for SFAs, many challenges remain in this field, including stiffness and bending shape control. To illustrate the current methodological and theoretical applications of soft robotic systems, the first article presents a systematic review of soft fluidic actuators that tried to address the critical challenges in soft and active materials, processing methods, gripper architectures, sensors, and control methods. Different constitutive models of silicone materials proposed and tested in the literature are regenerated by ABAQUS software to compare the engineering and true strain-stress data from the constitutive models with standard uniaxial tensile test data based on ASTM412. This paper shows that most of these models can predict the material model acceptably in a small range of stress-strain data. But for large strain-stress values, a few of them predict the behavior of the silicone material accurately. The second article presents a novel type of soft finger with a pneumatic-actuated movable joint based on bending point control and variable stiffness. The proposed finger is more flexible than previous solutions in terms of the attainable 3D space and applicable contact forces at the fingertip by changing the position of its joint, and thus, the bending point. The finite element method (FEM) and NSGA-II algorithm are applied to optimize the joint geometry to maximize the bending angle and minimize the joint dimensions. The third article in this dissertation is focused on developing a new type of dexterous soft gripper with three reconfigurable fingers and an active palm enhancing in-hand manipulation capabilities. In each finger, the bending point and the effective manipulation length can be changed and controlled by moving a stiff rod inserted inside the center hole of the finger. The in-hand manipulation capability of this soft robotic gripper is validated by different experimental tests, including rotation, regrasping, and rolling. Therefore, two types of vacuum palms (suction cup and granular particles) are utilized to guarantee a wide range of object manipulation tasks that previously suggested soft grippers cannot completely perform. In the final chapter of this dissertation, the fourth article proposed a low-cost, easy fabrication tactile sensor for soft robot application. It is very flexible and easy use which make it an appropriate choice for soft robot application. Most of the materials (conductive ink, silicone, control board) used in the fabrication of this sensor are inexpensive and can be found easily in the market. The proposed capacitive sensor can detect the position and applied force by measuring the electric charge of the electrodes. Due to the uncertainties and noises, an Artificial neural network is suggested to calibrate the force corresponding to the produced voltage.
... Pneumatic [47,48], Magnetic [49], Electric [50], Motor [51] ...
... Elastomers are key enablers in the creation of soft robot bodies. Despite their highly nonlinear responses, soft origami robots can actuate to accomplish relatively simple types of motions and tasks that are very difficult to accomplish with hard robots and conventional controllers [47,[71][72][73]. In addition, because origami exhibits some plastic deformation, it is difficult to fully recover its basic state. ...
... Elastomers combined with paper are lightweight and easy to fabricate. Additionally, paper can be transformed into a range of complex 3D structures [47]. As a replacement for parts made of silicone rubbers, Lin et al., presented origami "skeletons" using four stacks of 12-layer sandpaper with origami creases in the middle of the four folding faces [73]. ...
Time-dependent shape-transferable soft robots are important for various intelligent applications in flexible electronics and bionics. Four-dimensional (4D) shape changes can offer versatile functional advantages during operations to soft robots that respond to external environmental stimuli, including heat, pH, light, electric, or pneumatic triggers. This review investigates the current advances in multiscale soft robots that can display 4D shape transformations. This review first focuses on material selection to demonstrate 4D origami-driven shape transformations. Second, this review investigates versatile fabrication strategies to form the 4D mechanical structures of soft robots. Third, this review surveys the folding, rolling, bending, and wrinkling mechanisms of soft robots during operation. Fourth, this review highlights the diverse applications of 4D origami-driven soft robots in actuators, sensors, and bionics. Finally, perspectives on future directions and challenges in the development of intelligent soft robots in real operational environments are discussed.
... The integration of origami structures into SPAs has been shown to enhance their off-axis stiffness [33]. The load-carrying capacity of SPAs with origami structures has been improved accordingly; even vertical weight-lifting tasks can be realized [34], [35]. Furthermore, due to their reconfigurable structures, origami chambers can be actuated under lower pressure, and their motion regulated with a higher extension/contraction ratio [35]- [41]. ...
... Besides, aiming at the common weakness of other SPAs, the desirable features of the origami chamber include: large extension/contraction ratio; no radial expansion; low threshold pressure; and ease of fabrication. The Yoshimura pattern [63] is a cylindrical folding origami that has been reportedly used to design soft linear actuators [34], [64], [65]. However, this pattern is actually a solid structure and is discontinuously foldable [66]. ...
Conventional soft pneumatic actuators (SPAs) are made of soft materials that facilitate safe interaction and adaptability. In positioning and loading tasks, however, SPAs demonstrate limited performance. In this article, we extend the current designs of SPAs upon integrating a tendon-driven parallel mechanism into a pneumatic origami chamber, inspired by the performances and structures of vertebrates. The inner rigid/outer soft actuator exploits the advantages of both, parallel mechanisms to achieve precise, versatile motion, and SPAs, to form a compliant, modular structure. With the antagonistic actuation of tendons-pulling and air-pushing, the actuator can exhibit multimode motion, tunable stiffness, and load-carrying maneuvers. Kinematic and quasi-static models are developed to predict the behavior and to control the actuator. Using readily accessible materials and fabrication methods, a prototype was built, on which validation experiments were conducted. The results prove the effectiveness of the model, and demonstrate the motion and stiffness characteristics of the actuator. The design strategy and comprehensive guidelines should expand the capabilities of soft robots for wider applications, and facilitate the development of robots with rigid-soft hybrid structures.
... Compared to their rigid counterparts, soft devices and actuators easily achieve complex motions 2,3 and simplify certain mechanical tasks, such as grasping 4 , navigation 5-8 , and rehabilitation 9,10 . The actuation of soft robots has been demonstrated by pneumatic [11][12][13][14][15][16] or hydraulic 17-23 pressure, tendons 24,25 , or stimuli-responsive materials 2,26-28 , nonetheless pneumatically actuated robots with inflatable elastomeric chambers have drawn considerable attention due to their simple fabrication and actuation 29 . ...
... Compared to their rigid counterparts, soft devices and actuators easily achieve complex motions 2,3 and simplify certain mechanical tasks, such as grasping 4 , navigation [5][6][7][8] , and rehabilitation 9,10 . The actuation of soft robots has been demonstrated by pneumatic [11][12][13][14][15][16] or hydraulic [17][18][19][20][21][22][23] pressure, tendons 24,25 , or stimuli-responsive materials 2,26-28 , nonetheless pneumatically actuated robots with inflatable elastomeric chambers have drawn considerable attention due to their simple fabrication and actuation 29 . ...
Soft inflatable robots are a promising paradigm for applications that benefit from their inherent safety and adaptability. However, for perception, complex connections of rigid electronics both in hardware and software remain the mainstay. Although recent efforts have created soft analogs of individual rigid components, the integration of sensing and control systems is challenging to achieve without compromising the complete softness, form factor, or capabilities. Here, we report a soft self-sensing tensile valve that integrates the functional capabilities of sensors and control valves to directly transform applied tensile strain into distinctive steady-state output pressure states using only a single, constant pressure source. By harnessing a unique mechanism, “helical pinching”, we derive physical sharing of both sensing and control valve structures, achieving all-in-one integration in a compact form factor. We demonstrate programmability and applicability of our platform, illustrating a pathway towards fully soft, electronics-free, untethered, and autonomous robotic systems.
... Wang et al. [23,24] proposed an in-plane method, which first determines the vertices of the "intermediate state"; that is, all vertices are coplanar and then expands the 2D design to the desired state to obtain the 3D folding configuration. Besides, the interconnected inner space and large axial compression ratio make origami tubes widely developed and applied, e.g., space exploration [25], actuators [26,27], energy absorption devices [28], and acoustic metamaterial [29], etc. ...
... where F 1 =F 2 =F 3 =1/3F. Analyzing equations (23) - (26), it can be found that when k 1 ≫k 2 ≫k 3 , the coupling effect of S3's separate drive on S1 and S2 can be ignored, which is also applicable to the bending motion [63][64][65][66]. When the stiffnesses of the three segments are similar, the three steel wires of S3 are differentially controlled, and the steel wires of S1 and S2 have remained relaxed. ...
... Adaptive and extreme changes in shape and configuration are the functional and morphological uniqueness of soft robots that traditional robots have found difficult to achieve. In fact, studies of robot functions accompanied by large deformation corresponding to several times the initial length, such as soft origami designs [24][25][26][27] or vine-like growing robots, [28] have highlighted the cutting-edge branch of the soft robot field. Nevertheless, shape-morphing behaviors based on the predefined and limited coordination between "muscles" and "nerves" identify intrinsic hurdles for versatile uses. ...
... For example, the actuation profiles of the soft pneumatic origami robots, whose crease patterns are closely coupled with embedded fluidic "nerve" networks, produce only preprogrammed folding/ unfolding motions. [25][26][27] In this respect, achieving versatile shape-morphing profiles may require dynamic reconfiguration (i.e., selective and reversible attachment or detachment) of both muscle and nerve parts within the robot body. Modular designs as a potential alternative hold promise for an extensive range of structural reconfiguration for both muscle and nerve parts, DOI: 10.1002/aisy.202300013 ...
Adaptive and extreme changes in shape and configuration are the functional and morphological uniqueness of soft robots, but existing design approaches still rely on the predefined coordination of their “muscle” and “nerve” functions to produce such behaviors. Herein, a strategy is introduced for building modular soft machines that can be innervated in ways that conform to their body extension or shape changes, based on modular soft electronics. The development of soft electronic adhesive interlocking (SEAL) technology allows for instant, robust, and repeatable integration of soft electronic modules that can “innervate” and activate modular soft actuators and machines in a reconfigurable manner. Demonstrations of soft robotic tentacles and their grasping capability show that the robot function can be adapted to or reconfigured within the body with a length extended more than 10 times. The modular strategy presented herein can offer a unique promise to build up future robots with dynamic, reconfigurable functions.
... In this way, various soft actuators with conical [4,5], tapered [6,7], planar [8,9], and doubly curved shell [10] shapes have been developed to perform continuous movements and operate in harsh environments. Recently, cylindrical shapes formed by bellows structures or origami methods have also been proposed [11,12]. Cylindrical shapes can be utilized in the manufacturing of medical devices and biomimetic robots because the shapes ensure that contact with the external environment is minimized, unlike in the case of prismatic shapes, and these shapes can more easily pass through narrow gaps [13][14][15][16]. ...
In this paper, we propose a model for the electrical responses of a soft cylindrical structure with shear deformations using piezoelectric sensors. Specifically, to analyze the cylindrical structure during movement, we assumed that a shear force was applied to the flat surface on the top of the structure. Using this force, we established a model using the Euler–Bernoulli beam theory and estimated the electrical responses of the sensors generated by its deformation. To validate the theoretical analysis, a soft cylindrical structure was fabricated using silicone containing piezoelectric sensors. Moreover, a series of tests were performed by applying a tensile testing machine and vibration exciter to the soft structure. During the experiments, we observed the sensor outputs while generating vibrations in the form of triangular and sinusoidal waves. The experimental outputs demonstrate that the sensors can distinguish the displacements and directions of the structural deformations, similar to our predictive model, through the voltage outputs and phase variations of the sensors. Moreover, parametric studies were performed to investigate the sensor responses under structural deformations affected by four parameters related to the material and external forces: the Young’s modulus, radius, mass density, and frequency of the sinusoidal shear force.
... 874 The properties of the chamber material greatly influence the force transmission and deformation of the fluidic soft actuator. Low-cost and light, semitransparent, or transparent dragon skin, 876 Ecoflex, 877 PDMS, 878 and hydrogel 855,856 are used as chamber materials. Ecoflex, which has a low modulus, shows large deformations even with low-pressure inflow but is more disadvantageous in terms of force transmission. ...
Recent advancements in wearable electronics offer seamless integration with the human body for extracting various biophysical and biochemical information for real-time health monitoring, clinical diagnostics, and augmented reality. Enormous efforts have been dedicated to imparting stretchability/flexibility and softness to electronic devices through materials science and structural modifications that enable stable and comfortable integration of these devices with the curvilinear and soft human body. However, the optical properties of these devices are still in the early stages of consideration. By incorporating transparency, visual information from interfacing biological systems can be preserved and utilized for comprehensive clinical diagnosis with image analysis techniques. Additionally, transparency provides optical imperceptibility, alleviating reluctance to wear the device on exposed skin. This review discusses the recent advancement of transparent wearable electronics in a comprehensive way that includes materials, processing, devices, and applications. Materials for transparent wearable electronics are discussed regarding their characteristics, synthesis, and engineering strategies for property enhancements. We also examine bridging techniques for stable integration with the soft human body. Building blocks for wearable electronic systems, including sensors, energy devices, actuators, and displays, are discussed with their mechanisms and performances. Lastly, we summarize the potential applications and conclude with the remaining challenges and prospects.
... For instance, as the core unit of robots, pneumatically driven soft actuators have utilized such reinforced structures as fibers and rigid skeletons to largely enhance the capabilities of spatial movements and output forces (De Volder et al., 2011;Polygerinos et al., 2015b;Wang et al., 2016;Paterno et al., 2018). Especially, recent developments in soft origami actuators have enabled improved programmable performance (Martinez et al., 2012;Yi et al., 2018a;Yi et al., 2018b;Su et al., 2020;Shen et al., 2021). Based on these fundamental research works, the developments of soft continuum robots have been facilitated by integrating these soft actuators in parallel and longitudinal directions (Bishop-Moser et al., 2012;Chen et al., 2019;Qiao et al., 2019;Chen et al., 2021;Li et al., 2022), presenting individually controllable degrees of freedom for controllable workspace extensibility benefiting from the coordination among soft actuator modules. ...
Introduction: Trunk-like continuum robots have wide applications in manipulation and locomotion. In particular, trunk-like soft arms exhibit high dexterity and adaptability very similar to the creatures of the natural world. However, owing to the continuum and soft bodies, their performance in payload and spatial movements is limited.
Methods: In this paper, we investigate the influence of key design parameters on robotic performance. It is verified that a larger workspace, lateral stiffness, payload, and bending moment could be achieved with adjustments to soft materials’ hardness, the height of module segments, and arrayed radius of actuators.
Results: Especially, a 55% increase in arrayed radius would enhance the lateral stiffness by 25% and a bending moment by 55%. An 80% increase in segment height would enlarge 112% of the elongation range and 70 % of the bending range. Around 200% and 150% increments in the segment’s lateral stiffness and payload forces, respectively, could be obtained by tuning the hardness of soft materials. These relations enable the design customization of trunk-like soft arms, in which this tapering structure ensures stability via the stocky base for an impact reduction of 50% compared to that of the tip and ensures dexterity of the long tip for a relatively larger bending range of over 400% compared to that of the base.
Discussion: The complete methodology of the design concept, analytical models, simulation, and experiments is developed to offer comprehensive guidelines for trunk-like soft robotic design and enable high performance in robotic manipulation.
... Applying a folding structure to a soft actuator can protect it and produce accurate movement. Applying a folding structure to a soft actuator increases its rigidity and anisotropy and reduces its weight [21][22][23]. Efficient folding structures are sometimes inspired by arthropods. Spiders extend their legs using hydraulic pressure instead of muscle pairs, providing a good model for actuator designs. ...
The unique drive principle and strong manipulation ability of spider legs have led to several bionic robot designs. However, some parameters of bionic actuators still need to be improved, such as torque. Inspired by the hydraulic drive principle of spider legs, this paper describes the design of a bionic actuator characterized by the use of air pressure on each surface and its transmittance in the direction of movement, achieving a torque amplification effect. The produced torque is as high as 4.78 N m. In addition, its torque characteristics during folding motions are similar to those during unfolding motions, showing that the bionic actuator has stable bidirectional drive capability.
... As shown in Fig. 3C, α first increases and then decreases as θ increases. When θ = 56°, the HAFMS-TSA shows the maximum α of 401°/cm, which is twice higher than the highest record of twisting angle of existing tubular soft actuators (~189°/cm; Fig. 3D) (21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31). Regulation of fiber winding angles can not only control the direction of deformations (when 0 < θ < θ 2 , shortening; when θ 2 < θ < 90°, elongating) but also enable precise control of the magnitude of the twisting deformations. ...
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.
... Their actuation principle is mainly based on the volume expansion/contraction of actuating parts, producing many mechanical deformations, such as extension, contraction, bending, twisting, or a combination thereof, which are expected to be used in the field of medical rehabilitation. [33,131] By combining soft pneumatic actuators with rigid bodies, the vertical and directional jumping motions can be achieved. [34,132,133] For example, the explosive bursts of gas pressure, resulting from the combustion of hydrocarbons, can contribute to the expansion of microchannels in a silicone elastomer. ...
Drawing inspiration from the jumping motions of living creatures in nature, jumping robots have emerged as a promising research field over the past few decades due to great application potential in interstellar exploration, military reconnaissance, and life rescue missions. Early reviews mainly focused on jumping robots made of lightweight and rigid materials with mechanical components, concentrating on jumping control and stability. Herein, attention is paid to the jumping mechanisms of soft actuators assembled from various soft smarting materials and powered by different stimulus sources. The challenges and prospects of soft jumping actuators are also discussed. It is hoped that this review will contribute to the further development of soft jumping actuators and broaden their practical applications.
... This gripper generates a tip force close to 2 N and is also tendon driven. Martinez et al. propose a composite paper-elastomer origami bellow design for contraction, extension, and bending using positive pressure actuation [17]. Lin et al. propose the use of negative pressure (vacuum) to drive a cube-shaped origami folding structure that can vary its structural stiffness through layer jamming [13]. ...
... New materials and structures made soft robotic fish easy to control and less expensive. For instance, elastomeric polymer is an essential material for soft robotic fish, because of its isotropic stress responses and can be controlled by external actuators (Martinez et al., 2012). Therefore, actuators made of elastic polymers produce a relatively larger range of motion than rigid actuators. ...
Hydraulic drive is one of the main driving methods of traditional bionic fish, which has the disadvantages of high driving pressure and significant radial expansion of the fishtail. In this research, two innovative structures are introduced in the fishtail design to overcome these drawbacks. Firstly, high-flexible origami technology is applied to the fishtail, significantly reducing the unwanted radial expansion of the fishtail and improving energy efficiency. Based on the experiments, the origami-structured fishtail can save up to 92.3% energy compared with the traditional fishtail. Secondly, according to the bionic principles, the hybrid neutral layer of the fishtail which is sandwich-structured with knitting methods was designed. The test results show that this novel hybrid neutral layer could save up to 56.7% energy compared to the fishtail with a rigid neutral layer. A bionic fish in BCF model (Body and/or Caudal Fin propulsion) is fabricated and tested in a water tank. The results prove that the new bionic fish with the innovative fishtail obtain a good straight-line swimming direction and turning ability. This study could provide an important reference for the bionic design to mimic real fish.
... Circular holes are arranged around the top and bottom for connection with the top plate and other actuators. Currently, the existing fabrication methods of soft origami actuators include manual folding [41] or laser cutting [15], [42] paperboard, pouring silica gel [43] on the paper of origami structure, 3D printing with TPE (83A) material [32], and silica gel casting [31]. Casting by polyurethane (PU) was used to fabricate the soft part because the method can achieve wide hardness ranges (20A~90A). ...
A vacuum-driven inclined hexagonal prism soft-rigid hybrid contraction actuator inspired by Kresling origami pattern and with low driving pressure, high contraction ratio, and fast response was proposed. The advantages of soft-rigid hybrid vacuum contraction actuators over conventional positive-type oscillators were investigated. Under 30 kPa vacuum pressure, the actuator can realize a torsional angle of 87°, contraction ratio of 59%, contracting response time of 0.2 s, and restoring response time of 0.42 s. The design and fabrication of the proposed actuator were discussed. A mathematical model treating all creases as a combination of linear and torsion springs, which is firstly considered compared with previously proposed models of Kresling origami-based actuators, was established to predict the output performance. The excellent output force prediction performance of the proposed method was validated experimentally. To investigate the application potential of the proposed modular actuator, six actuators were assembled on a pipe-crawling robot that can crawl in horizontal, vertical, elbow rigid pipes as well as flexible pipes with inner diameters ranging from 55 to 71 mm. The robot achieved a maximum crawling velocity of 34.8 mm/s (0.226 body lengths per second) and maximum load of 1000 g (12.5 times its own weight) in tests. Thus, the excellent application potential of the proposed actuator was validated.
... Among many actuation methods (e.g., electrical, thermal, optical, and magnetic) (12)(13)(14)(15)(16)(17)(18)(19), pneumatic-driven soft actuators have garnered considerable attention for their simple and safe operation features, low cost, and ease of fabrication. These actuators comprise a cephalopod-liked structure entirely constructed from elastomeric materials (e.g., silicone rubber) and come equipped with pneumatic channels that provide various deformation modes upon pressure (20)(21)(22)(23)(24). Although these modes of deformation are dexterous and safe for interaction, their load-bearing and load-carrying capabilities are seriously compromised by the intrinsic stretchability of the rubbery materials. ...
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.
... deformable electronics, [35] and complex actuators. [36] Origamibased deformable electronics could demonstrate the excellent performance of conventional rigid electrical components as well as high 3D deformability levels. The electronic performance in currently existing highly deformable thin-film-based solutions is usually diminished to a high degree due to low areal coverage. ...
Origami structures are a traditional Japanese art which have recently found their way into engineering applications due to their powerful capability to transform flat 2D structures into complex 3D structures along their creases. This has given a rise in their application as designer materials with unprecedented mechanical characteristics, also known as metamaterials. Here, gradient Miura‐ori origami metamaterials are introduced as a method to pre‐program out‐of‐plane curvatures. Nine types of unit cell distributions in the origami lattice structure including checkered, linear gradient, concave radial gradient, convex radial gradient, and striped are considered. The results show that these distributions of Miura‐ori origami can create single‐ or double‐curvatures including twisting, saddling, bending, local inflation, local twisting, local bending, and wavy shapes, when the origami metamaterial is loaded in compression. All the Gaussian curvatures (negative, positive, and zero) can be achieved using the proposed models. Our approach will help tailoring complex pre‐programmed surface geometries by employing linearly varying gradient distributions of Miura‐ori origami. This article is protected by copyright. All rights reserved.
... [4] These features are particularly attractive when targeting medical applications, thanks to the inherent safety of soft materials in interacting with body tissues. [5] Soft materials exist that can be triggered to undergo shape transformation and perform actuation tasks in response to a wide range of stimuli, such as heat, [6] light, [7] chemicals, [8] pressure, [9] or magnetic fields. [10] Out of these stimuli, magnetic triggering and actuation are especially promising due to their wireless nature, safe interaction with tissues, and miniaturization potential. ...
Soft magnetic structures having a non‐uniform magnetization profile can achieve multimodal locomotion that is helpful to operate in confined spaces. However, incorporating such magnetic anisotropy into their body is not straightforward. Existing methods are either limited in the anisotropic profiles they can achieve or too cumbersome and time‐consuming to produce. Herein, a 3D printing method allowing to incorporate magnetic anisotropy directly into the printed soft structure is demonstrated. This offers at the same time a simple and time‐efficient magnetic soft robot prototyping strategy. The proposed process involves orienting the magnetized particles in the magnetic ink used in the 3D printer by a custom electromagnetic coil system acting onto the particles while printing. The resulting structures are extensively characterized to confirm the validity of the process. The extent of orientation is determined to be between 92% and 99%. A few examples of remotely actuated small‐scale soft robots that are printed through this method are also demonstrated. Just like 3D printing gives the freedom to print a large number of variations in shapes, the proposed method also gives the freedom to incorporate an extensive range of magnetic anisotropies.
... Origami has remarkable features such as lightweight and complex folding configurations, which can be transformed into different three-dimensional (3D) shapes [5,6], and these features have attracted researchers to extend its applications [7,8]. Currently, origami is widely used to design various types of robots and other engineering practicalities [9][10][11][12][13][14]. For example, Zhakypov et al. [15] developed a reconfigurable suction cup inspired by origami for picking up objects of variable shapes and sizes. ...
Unlike traditional manipulators with high rigidity and limited degrees of freedom, pneumatic manipulators have significant superiorities such as flexibility, lightweight and cleanliness, and therefore, have been one of the most popular research directions in robotics. However, most existing pneumatic manipulators have disadvantages such as low rigidity and simple functionality. In order to make up for the shortcomings of existing pneumatic manipulators, this paper proposes a new pneumatic flexible manipulator inspired by the concept of origami, which realizes the combination and balance of flexibility and rigidity. Finite element analysis is conducted to study influences of the number of airbags, the angle of main beam, and the width of main beam on the performance of the flexible manipulator. The simulation results are utilized to optimize the structure of the flexible manipulator. A pneumatic control system is designed to realize the automatic control of the pneumatic flexible manipulator. At the same time, a prototype is 3D printed, the experimental platform for pneumatic deformation is built, and the verification experiments of the single-jaw manipulator and the three-jaw manipulator are completed.
... 3 At the same time, they possess higher degrees of freedom, flexibility and adaptability compared to conventional large robots. 4,5 In addition, the micro-robots have multiple drive modes such as electric field drive, 6,7 chemical drive, [8][9][10][11] thermal drive, 12,13 light drive, [14][15][16] pressure drive, 4,17 or magnetic field drive. [18][19][20][21][22][23] In particular, magnetic fields can easily and harmlessly penetrate most biological and synthetic materials and provide a safe and effective actuation method, which endows magnetically controlled flexible micro-robots with great prospects for applications in healthcare and robotics. ...
Magnetically controlled flexible micro-robots can assume desired shapes and motions driven by external magnetic fields, which makes them promising for applications in healthcare and robotics. However, current magnetically controlled flexible micro-robot design methods suffer from size constraints and high manufacturing costs. Here, we report on a composite material based on programmed magnetic powder arrangements that can produce fast, reversible, and programmable shape transformations under magnetic fields. In addition, we investigate this composite's magnetically controlled deformation mechanism through experiments and numerical simulations. With these excellent properties, the composite can be used to design magnetically controlled flexible micro-robots with swimming, transport, and clamping functions.
... 8,9 In principle, folding can be achieved when there is a differentiated volume change and/or variation of elastic moduli, e.g., in a bilayer structure. 10 Accordingly, a wide range of stimuliresponsive soft materials, such as hydrogels, 11 shape memory polymers, 12 liquid crystal polymers (LCPs) 13 including glassy liquid crystal networks (LCNs) and liquid crystal elastomers (LCEs), dielectric elastomers, 14 and pneumatically actuated elastomers, 15 have been investigated to realize the 3D complex folding, triggered by solvent, heat, light, magnetic field, electric field, or pressure. Among them, LCEs and LCNs that have intrinsic anisotropy are attractive because their shape changes can be preprogrammed over multiple length scales by aligning LC mesogens in the networks in certain orientations. ...
Fibrous soft actuators with high molecular anisotropy are of interest for shape morphing from 1D to 2D and 3D in response to external stimuli with high actuation efficiency. Nevertheless, few have fabricated fibrous actuators with controlled molecular orientations and stiffness. Here, we fabricate filaments from liquid crystal networks (LCNs) with segmental crosslinking density and gradient porosity from a mixture of di-acrylate mesogenic monomers and small-molecule nematic or smectic liquid crystals (LCs) filled in a capillary. During photopolymerization, phase separation between the small-molecule LCs and LCN occurs, making one side of the filament considerably denser than the other side. To direct its folding mode (bending or twisting), we control the alignment of LC molecules within the capillary, either along or perpendicular to the filament long axis. We show that the direction of UV exposure can determine the direction of phase separation, which in turn direct the deformation of the filament after removal of the small-molecule LCs. We find that the vertical alignment of LCs within the filament is essential to efficiently direct bending deformation. By photopatterning the filament with segmental crosslinking density, we can induce a reversible folding/unfolding into 2D and 3D geometries triggered by deswelling/swelling in an organic solvent. Moreover, by taking advantage of the large elastic modulus of LCNs and large contrast of the modulus before and after swelling, we show that the self-folded LCP filament could act as a strong gripper.
The art of origami has gained traction in various fields such as architecture, the aerospace industry, and soft robotics, owing to the exceptional versatility of flat sheets to exhibit complex shape transformations. Despite the promise that origami robots hold, their use in high-capacity environments has been limited due to the lack of rigidity. This article introduces novel, origami-inspired, self-locking pneumatic modular actuators (SPMAs), enabling them to operate in such environments. Our innovative approach is based on origami patterns that allow for various types of shape morphing, including linear and rotational motion. We have significantly enhanced the stiffness of the actuators by embedding magnets in composite sheets, thus facilitating their application in real-world scenarios. In addition, the embedded self-adjustable valves facilitate the control of sequential origami actuations, making it possible to simplify the pneumatic system for actuating multimodules. With just one actuation source and one solenoid valve, the valves enable efficient control of our SPMAs. The SPMAs can control robotic arms operating in confined spaces, and the entire system can be modularized to accomplish various tasks. Our results demonstrate the potential of origami-inspired designs to achieve more efficient and reliable robotic systems, thus opening up new avenues for the development of robotic systems for various applications.
Three basic deformation modes of an object (bending, twisting, and contraction/extension) along with their various combinations and delicate controls lead to diverse locomotion. As a result, seeking mechanisms to achieve simple to complex deformation modes in a controllable manner is a focal point in related engineering fields. Here, a pneumatic-driven, origami-based deformation unit that offers all-purpose deformation modes, namely, three decoupled basic motion types and four combinations of these three basic types, with seven distinct motion modes in total through one origami module, was created and precisely controlled through various pressurization schemes. These all-purpose origami-based modules can be readily assembled as needed, even during operation, which enables plug-and-play characteristics. These origami modules with all-purpose deformation modes offer unprecedented opportunities for soft robots in performing complex tasks, which were successfully demonstrated in this work.
For mechanical systems where a human–machine interface or interaction is necessary, it is important to consider physical safety. In cases where robots and humans must coexist, these robots must have actuation that is inherently compliant to absorb physical impacts. However, these compliant actuators must possess high performance that is comparable with electro-mechanical actuators. Pneumatic artificial muscles (PAMs) are biologically inspired actuators that possess inherent compliance and are a prime candidate for implementation in future robotic applications. This article reviews several designs of contractile PAMs made from various materials and where the actuator may need to be pressurized, depressurized, or vacuumed to produce mechanical work. Although these PAMs are all physically compliant due to the inherent compressibility of air, their performance varies significantly from one design to the other such that it may be hard to identify a suitable actuator for a given application. This paper covers a broad range of contractile PAM designs and compares their performance based on a few metrics in order to help users determine which actuators have the most potential for future implementations. The paper also identifies a few areas where significant challenges will have to be solved for these new actuators to help pave the way for a world where robots can operate in close proximity to humans.
In this paper, the basic elements of Yoshimura origami patterns are extracted, a discrete splicing construction method to control the circumference of a tubular origami structure based on basic elements is created by summarizing morphological laws, and a construction function and a solution process for the Yoshimura origami pattern tubular structure based on a combination of the basic elements are proposed. A concrete form of the convex polygonal origami structure based on the Yoshimura origami pattern with different numbers of edges is designed by synthesizing the construction function and geometric constraints. This theoretical synthesis approach provides new ideas for the innovative design of origami robots, mechanical metamaterials, and energy-absorbing cushioned structures.
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.
Elementary actuators performing branching or surface swelling are the primary units in the actuator integration system that is leveraged in works requiring a high versatility and complex motion. However, those primary actuator units often lack scalability or compatibility at assembly into a compact form due to the complexity of the structure and the actuation interference between adjacent units. Herein, it is shown that the phase‐change actuator in a simple bilayer structure of a top active layer and a bottom constraint layer achieves 1D surface swelling, such that the closely packed 2D array system of this actuator is easily constructed. Upon resistive heating, the active layer inflates based on the phase change of microliquid droplets embedded in an elastomer body. The inflation along the lateral direction of the actuator is suppressed by controlling the thickness ratio between the active and the constraint layers. The actuation of individual units in the array system is performed independently using a switching device with a microcontroller for the parallel application of resistive heating. The application of 2D shape morphing of the actuator arrays in beam steering and shape displays is investigated.
Soft‐Hard Active‐Passive Embedded Structures (SHAPES) are composites that respond to the environments in which they are embedded. This reaction can be a mechanical actuation, but also an intrinsic computation that yields an adaptation as a result. The actuation capabilities primarily depend on the stiffness combination of the involved materials. Stiffness includes both material parameters (depending on the chosen material model, e.g., the Young's modulus) and geometry parameters (depending on the type of structure, e.g., the beam height). The active properties can be included using the Stimulus Expansion Model, which is based on the analogy of the active reponse to thermal expansion. SHAPES can be designed according to three different behaviors, Case I constrained , Case II combined and Case III free . In the current work, these cases, the modelling and design background, and various examples are presented.
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.
Since the traditional bending theory of bilayers was mainly for linear elastic materials with the assumption of infinitesimal deformation, here we study the bending of a bilayer soft strip with large deformation. The strip under investigation is comprised of an active layer and a passive layer, where only the active layer is assumed to be subjected to an isotropic volumic expansion. A bending theory for the large deformation of the strip is then developed. The subsequent analysis indicates that our theoretical predictions agree well with the finite element simulation, which, however, can significantly diverge from those predicted by the traditional theory under certain circumstances. With our theory, it is also shown that there exists an optimal modulus ratio or thickness ratio for a bilayer strip to achieve a maximal curvature. We suggest that our theory may greatly facilitate the design of soft bilayer strips that can be potentially employed in varied fields.
Soft robots have received much attention due to their impressive capabilities including high flexibility and inherent safety features for humans or unstructured environments compared with hard-bodied robots. Soft actuators are the crucial components of soft robotic systems. Soft robots require dexterous soft actuators to provide the desired deformation for different soft robotic applications. Most of the existing soft actuators have only one or two deformation modes. In this article, a new soft pneumatic actuator (SPA) is proposed taking inspiration from Kirigami. Kirigami-inspired cuts are applied to the actuator design, which enables the SPA to be equipped with multiple deformation modes. The proposed Kirigami-inspired soft pneumatic actuator (KiriSPA) is capable of producing bending motion, stretching motion, contraction motion, combined motion of bending and stretching, and combined motion of bending and contraction. The KiriSPA can be directly manufactured using 3D printers based on the fused deposition modeling technology. Finite element method is used to analyze and predict the deformation modes of the KiriSPA. We also investigated the step response, creep, hysteresis, actuation speed, stroke, workspace, stiffness, power density, and blocked force of the KiriSPA. Moreover, we demonstrated that KiriSPAs can be combined to expand the capabilities of various soft robotic systems including the soft robotic gripper for delicate object manipulation, the soft planar robotic manipulator for picking objects in the confined environment, the quadrupedal soft crawling robot, and the soft robot with the flipping locomotion.
Soft materials enable soft robots to accommodate unstructured working environments robustly. However, they may be easily damaged and destroyed due to their weak mechanical properties. Moreover, most soft materials are not repairable or degradable after being broken or abandoned, resulting in new environmental burdens. Here, a self-healable, recyclable, and degradable soft material (SRDSM) with a network structure formed with gelatin and polyvinyl alcohol (PVA) is reported. The SRDSM exhibits a fracture strength of 3–4 MPa and a stretchability of up to 300 %-400 % by controlling the composition ratio and drying time. Results show that the SRDSM can recover 90 % of its original mechanical strength after healing and 95 % after recycling. An SRDSM-based soft gripper is demonstrated that can be self-healed under thermal cycling after minor damage. It can be recycled and remanufactured to restore its original functionality after severe damage. Furthermore, the soft gripper can decomposes and degrades entirely after contact with water. This research provides an enabling material to develop environmental-friendly and recyclable soft robots, reducing their negative environmental impact.
A large two-dimensional (2D) topological defect array in nematic liquid crystal (NLC) shows a translucent watery hazy texture. The haze is a composition of three optical phenomena: scattering of light, lens imaging and diffraction. The scattering of light causes the milky haze. Vertically aligned NLC cells with pixel electrodes were fabricated to produce the crowded irregular defects. The key parameters are the electrode shape (pad or annulus), the array structure (square or hexagonal) and the pixel size (from 15μm×15μm to 200μm×200μm). Location and topological charge of the defects are identified under a polarised optical microscope. 2D Fourier transform of the defect distribution gives the spatial frequency spectrum, which is the diffraction pattern of light through the defects. Large pad electrodes produce ordered defects and significant diffraction. Crowded irregular defects render the milky translucent haze and a continuous spatial spectrum. The traditional haze measurement is not able to distinguish the scattered and diffracted light. The spatial spectrum can accurately describe the appearance perceived by the viewers. Small annulus electrodes in a hexagonal array produce the messiest defects, the haziest texture and the most comfortable visual experience among the others.
Silicone elastomers are extremely attractive materials due to their wide range of possible applications, from biomedical engineering to soft robotics. In this work, an extensive thermo-mechanical characterization of Ecoflex Shore hardness 00-50, a commercially available silicone elastomer, has been carried out to compensate for the lack of relevant literature. The mechanical behaviour of the material has been characterized by performing monotonic and cyclic loading tests. These tests were performed in different deformation states, i.e. uniaxial tension, pure shear and biaxial tension, at different strain rates and temperatures. Experimental findings allowed to highlight the material time-dependent response and quantify the contribution of dissipation deformation phenomena to the overall strain energy. Uniaxial tensile tests performed at different temperatures (between -40°C and 140°C) showed that the material mechanical behaviour is sensitive to temperature in this range: a decrease of the ultimate stress and strain has been observed with increasing temperature. Finally, the data obtained from the latter tests have been used to define a failure envelope, applied for the first time to Ecoflex silicones, and valuable to describe the material ultimate stress and strain at any temperature and strain rate.
Robots that share activity spaces or physically interact with humans typically benefit from appropriate payload capacity, extensible workspace, low weight, safety, and space efficiency. The soft origami design and mechanism can meet many of these beneficial factors; however, achieving a high payload capacity remains challenging. In this study, we developed a soft origami arm module with high variable stiffness (x300) and spatial efficiency (compressed x3.1). The buckling of facets into a cylindrical tube followed by its pressurization enables the arm to be highly stiffened. High-pressure capacity was obtained via the sewing-heat press fabrication process. We used a pneumatic pressure–tendon pair and utilized the frictional force between origami and tendon to prevent unintentional gravity-induced deformation while deploying. An analytical model was developed and compared to the experimental results. With our modular design, we could easily build functional robotic structures. Two robotic demonstrations were performed to examine the expandability of the modules. A variable-length robotic arm that mimics a human arm was built to manipulate typical objects. Additionally, a soft rover, which could carry 14 kg of weight and change its volume 29 times for improved spatial efficiency, was developed. This research suggests a new design methodology for practical soft robotic systems.
Soft pneumatic actuators (SPAs) rely on anisotropic mechanical properties to generate specific motions after inflation. To achieve mechanical anisotropy, additional stiff materials or heterogeneous structures are typically introduced in isotropic base materials. However, the inherent limitations of these strategies may lead to potential interfacial problems or inefficient material usage. Herein, we develop a new strategy for fabricating SPAs based on an aligned liquid crystal elastomer (LCE) by a modified 3D printing technology. A rotating substrate enables the one-step fabrication of tubular LCE-SPAs with designed alignments in three dimensions. The alignment can be precisely programmed through printing, resulting in intrinsic mechanical anisotropy of the LCE. With a specially designed alignment, LCE-SPAs can achieve basic motions-contraction, elongation, bending, and twisting-and accomplish diverse tasks, e.g., grabbing objects and mixing water. This study provides a new perspective for the design and fabrication of SPAs.
Kirigami structures are human-made structures that enable the fabrication of stretchable structures from materials with limited stretching properties through the geometrical re-orientation of their features. But these structures are generally complex in shape with many edges which makes their precise fabrication difficult without the use of engineering manufacturing tools. Building a pneumatic artificial muscle making use of kirigami concepts would be useful as the structure could make use of the re-orientation of its features rather than just relying on the stretching or expansion of the structure, but the structure must remain airtight despite its complex shape which would result in air channels needing to be sealed along each edge of this structure. This work introduces a simple three-step manufacturing method capable of manufacturing inflatable kirigami actuators with networks of air channels with a wide range of shapes. Three novel inflatable kirigami actuators designs are presented making use of this manufacturing process: parallel kirigami actuators, out-of-plane kirigami actuators and spiral kirigami actuators. These actuators are capable of contraction ratios far exceeding those of previous inflatable pneumatic artificial muscles and can be readily implemented as active electronic muscles. This manufacturing method for inflatable kirigami actuators opens the door to a wide range of new inflatable actuator designs and could lead to further optimized designs for wearable uses.
In this work, an experimental investigation of an accordion‐like system with embedded magnetic inclusion is carried out. It is shown that the way that this structure deforms when subjected to an external magnetic field depends on the magnetic moment of the embedded magnets and the length of the arms. Stacking of the accordion‐like system leads to the formation of hexagonal honeycombs that can have a negative, zero, and positive Poisson’s ratio. Variation in the configuration attained depends on the relative positioning of the magnetic inclusion and the applied magnetic field. In particular, one of the hexagonal honeycomb arrangements was able to switch between a conventional and a re‐entrant configuration upon the reversal of the external magnetic field. For all structures considered, the dimensions can be controlled through the external magnetic field allowing for a high degree of turnability. Furthermore, their behaviour can be altered in real time. The practical implications of the results are of interest since they indicate that these structures can be adopted in numerous applications, such in the design of scaffoldings for deployable structures, actuators, variable pored sieves, and sound proofing systems. This article is protected by copyright. All rights reserved.
The unique merits of origami structures and origami metamaterials are the folding-induced shape reconfigurability and the associated evolution of mechanical properties. However, currently, there is a lack of mature solutions on how to achieve active tuning, and the tunability is stuck in static properties. Therefore, this study proposes a pneumatic scheme to overcome the above two bottleneck problems. Specifically, by integrating a pneumatic bladder with a monostable Yoshimura-ori structure, a pneumatic Yoshimura origami (PYO) cell is designed. Compared with the conventional approach making use of the origami multistability, the pressure scheme is simpler in design, more accurate in regulation, and richer in configurations. To exploit the PYO structure for tunable dynamics, the dynamic model is developed via a nonlinear system identification approach, in which the overall system, including the structure itself and the friction contact, is represented as a nonlinear spring-damper element, with the constitutive profile identified via the weighted least square method from the dynamic experimental data. Based on the developed model, the pressure tunability is then explored in a 6-cell PYO structure and a PYO metamaterial. Through comprehensive linear dispersion analyses and numerical simulations, we reveal that pressure could effectively tune the passbands of the 6-cell structure so that the transmission of vibration, at certain frequencies, can be qualitatively switched between amplification and attenuation; from another perspective, pressure could also be tailored for programming the stopbands of the PYO metamaterial to achieve the shift between propagation and prohibition. The results of this investigation could provide useful guidelines for the development of intelligent origami structures/metamaterials with excellent tunability, and meanwhile, open a new perspective of origami dynamics research.
Interest in creating soft active matter that can repeatedly undergo shape morphing and self-sensing in response to external stimuli is growing. Magneto-active soft matter (MASM) with untethered, fast, and reversible shape reconfiguration is highly desirable for diverse applications in biomedical devices, wearable devices, soft robotics. In this work, we develop a heat-assisted magnetic reprogramming strategy for fabricating MASMs capable of reprogrammable shape-morphing and self-sensing functions. The magnetic reprogramming strategy is based on heating thermoplastic matrix above its melting point and reorienting soft-magnetic particle chains by applying magnetic fields during cooling. By reprogramming magnetization profiles through particle chain reconstruction of printed architecture, we demonstrate multiple deformation modes with distinct shape-morphing. This magnetic reprogramming approach enabled multiscale and reprogrammable soft machines with the tunable actuation response, such as adaptive grasping of a soft gripper. In addition, in combining with the unique sensing mechanism of triboelectric skin (tribo-skin), the self-sensing performance of MASMs is realized by using electrical signals to identify the deformation and contact behaviors. We anticipate that the magnetic reprogramming strategy and multimaterial 3D printing-assisted technique can open new avenues for the fabrication of multifunctional MASMs.
Robot-assisted rehabilitation of gait still faces many challenges, one of which is improving physical human-robot interaction. The use of pleated pneumatic artificial muscles to power a step rehabilitation robot has the potential to meet this challenge. This paper reports on the development of a gait rehabilitation exoskeleton with a knee joint powered by pleated pneumatic artificial muscles. It is intended as a platform for the evaluation of design and control concepts in view of improved physical human-robot interaction. The design was focused on the optimal dimensioning of the actuator configuration. Safety being the most important prerequisite, a proxy-based sliding mode controller PSMC was implemented as it combines accurate tracking during normal operation with a smooth, slow and safe recovery from large position errors. Treadmill walking experiments of a healthy subject wearing the powered exoskeleton show the potential of PSMC as a safe robot-in-charge control strategy for robot-assisted gait training.
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.
The increasing demand for physical interaction between humans and robots has led to the development of robots that guarantee safe behavior when human contact occurs. However, attaining established levels of performance while ensuring safety poses formidable challenges in mechanical design, actuation, sens-ing and control. To achieve safety without compromising performance, the human-friendly robotic arm has been developed using the concept of hybrid actuation. The new design employs inherently-safe pneumatic artificial muscles augmented with small electrical actuators, human-bone-inspired robotic links, and newly designed distributed compact pressure regulators with proportional valves. The experimental results show that significant performance improvement that can be achieved with hybrid actuation over a system with pneumatic artificial muscles alone. The pa-per evaluates the safety of the new robot arm and demonstrates that the safety characteristics surpass those of previous human-friendly robots.
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.
Continuum robotics has rapidly become a rich and diverse area of research, with many designs and applications demonstrated. Despite this diversity in form and purpose, there exists remarkable similarity in the fundamental simplified kinematic models that have been applied to continuum robots. However, this can easily be obscured, especially to a newcomer to the field, by the different applications, coordinate frame choices, and analytical formalisms employed. In this paper we review several modeling approaches in a common frame and notational convention, illustrating that for piecewise constant curvature, they produce identical results. This discussion elucidates what has been articulated in different ways by a number of researchers in the past several years, namely that constant-curvature kinematics can be considered as consisting of two separate submappings: one that is general and applies to all continuum robots, and another that is robot-specific. These mappings are then developed both for the single-section and for the multi-section case. Similarly, we discuss the decomposition of differential kinematics (the robot’s Jacobian) into robot-specific and robot-independent portions. The paper concludes with a perspective on several of the themes of current research that are shaping the future of continuum robotics.
Airborne chemical sensing with mobile robots has been an active research areasince the beginning of the 1990s. This article presents a review of research work in this field,including gas distribution mapping, trail guidance, and the different subtasks of gas sourcelocalisation. Due to the difficulty of modelling gas distribution in a real world environmentwith currently available simulation techniques, we focus largely on experimental work and donot consider publications that are purely based on simulations.
Bolted-down robots labor in our factories, performing the same task over and over again. Where are the robots that run and jump? Equaling human performance is very difficult for many reasons, including the basic challenge of demonstrating motors and transmissions that efficiently match the power per unit mass of muscle. In order to exceed animal agility, new actuators are needed. Materials that change dimension in response to applied voltage, so-called artificial muscle technologies, outperform muscle in most respects and so provide a promising means of improving robots. In the longer term, robots powered by atomically perfect fibers will outrun us all.
This paper presents an introduction to ionic polymer-metal composites and some mathematical modeling pertaining to them. It further discusses a number of recent findings in connection with ion-exchange polymer-metal composites (IPMCS) as biomimetic sensors and actuators. Strips of these composites can undergo large bending and flapping displacement if an electric field is imposed across their thickness. Thus, in this sense they are large motion actuators. Conversely by bending the composite strip, either quasi-statically or dynamically, a voltage is produced across the thickness of the strip. Thus, they are also large motion sensors. The output voltage can be calibrated for a standard size sensor and correlated to the applied loads or stresses. They can be manufactured and cut in any size and shape. In this paper first the sensing capability of these materials is reported. The preliminary results show the existence of a linear relationship between the output voltage and the imposed displacement for almost all cases. Furthermore, the ability of these IPMCs as large motion actuators and robotic manipulators is presented. Several muscle configurations are constructed to demonstrate the capabilities of these IPMC actuators. This paper further identifies key parameters involving the vibrational and resonance characteristics of sensors and actuators made with IPMCS. When the applied signal frequency varies, so does the displacement up to a critical frequency called the resonant frequency where maximum deformation is observed, beyond which the actuator response is diminished. A data acquisition system was used to measure the parameters involved and record the results in real time basis. Also the load characterizations of the IPMCs were measured and it was shown that these actuators exhibit good force to weight characteristics in the presence of low applied voltages. Finally reported are the cryogenic properties of these muscles for potential utilization in an outer space environment of a few Torrs and temperatures of the order of - 140 degrees Celsius. These muscles are shown to work quite well in such harsh cryogenic environments and thus present a great potential as sensors and actuators that can operate at cryogenic temperatures.
By integrating a number of different disciplines, rapid prototyping and manufacturing technology (RPM) is capable of forming parts with complicated structures and non-homogeneous materials. RPM techniques are mainly used as prototypes in such product invention process as stereo lithography, 3D printing, laminated object manufacturing and fused deposition modeling. So far, many new RPM techniques emerged out and have been already applied in such fields as rapid tooling/moulding, direct formed usable part, nano-/micro-RPM and biomanufacturing. The flexible digital manufacturing method will have a bright prospect.
<<<Please do not ask me for the full text to this book! The book is under copyright to the publishers and I cannot give out the full text!!>>>
Are you tired of picking up a book that claims to be on "practical" finite element analysis only to find that it is full of the same old theory rehashed and contains no advice to help you plan your analysis? If so then this book is for you! The emphasis of this book is on doing FEA, not writing a FE code. A method is provided to help you plan your analysis and a chapter is devoted to each choice you have to make when building your model giving you clear and specific advice. Finally nine case studies are provided which illustrate the points made in the main text and take you slowly through your first finite element analyses. The book is written in such a way that it is not specific to any particular FE software so it doesn't matter which FE software you use, this book can help you!
The 2nd Edition of this very popular finite element analysis guide:
1)Emphasises practical finite element analysis with commercially available finite element software packages
2)Is written in a generic way so it is not specific to any particular software but clearly shows the methodology required for successful FEA
3)Is focused entirely on structural stress analysis
4)Offers specific advice on which element types to use, which material model to pick, which type of analysis to use and which type of results to look for
5)Provides specific, no nonsense advice on how to fix problems in the analysis
6)Contains over 300 illustrations
7)Provides nine detailed case studies which specifically show you how to perform various types of analysis 8)Does not weigh you down with unnecessary theory, but provides you with the minimum theory needed to understand the methods
9)Is an invaluable guide and reference for engineering students and practising engineers.
Dynamic effects are very important in improving the design and study of the micro-robot. In the paper, our preliminary work in using ICPF to develop a novel tortoise-like flexible micro-robot with four legs and one tail is reported, which can crawl and swim underwater. ICPF is the abbreviation of Ionic Conducting Polymer gel Film which is a kind of smart film and can give large and fast bending displacement in the presence of a low applied voltage in wet condition. For controlling and analyzing easily the robot, we establish the micro-robot's tail dynamic model by applying Pseudo-Rigid-Body-Dynamic-Model (PRBDM). The model is established by considering the dynamic effect of the robot's tail, which is based on statics and kinematics. Then, the frequency analysis of a micro-robot based on PRBDM is investigated. Based on the PRBDM, the relation between the robot's tail angle displacement and the electrical voltage's frequency omega is theoretically derived and the simulation result for the tail's angle displacement is performed.
Small and lightweight actuators that generate high force and high energy are strongly required for realizing powerful robots and tools. By applying ultra-high-strength p-phenylene-2,6-benzobisoxazole fiber sleeves to McKibben artificial muscles, new hydraulic artificial muscles have been developed. While conventional McKibben muscles are driven by a maximum pneumatic pressure of 0.7 MPa, the newly developed muscles are driven by a maximum water hydraulic of pressure of 4 MPa, resulting in very high force capability. This paper presents the materials and structure of the new artificial muscle and the experimental results. The developed muscles are evaluated by four parameters — force density per volume (FDV), force density per mass (FDM), energy density per volume (EDV) and energy density per mass (EDM) — for comparisons with other conventional linear actuators. The prototype artificial muscle, which is 40 mm in diameter and 700 mm in length, can achieve a maximum contracting force of 28 kN, FDV of 32.3 × 10 N/mm, FDM of 9.44 × 10 N/kg, EDV of 2600 × 10 J/mm and EDM of 762 × 10 J/kg. These values are 1.7 to 33 times larger than those of the typical conventional actuators. As the result, a high force artificial muscle of 40 mm in diameter that generates 28-kN contracting force has been developed successfully.
An artificial muscle is one of the key technologies for soft robots. This paper describes design, fabrication, and characterization of an artificial muscle cell using an electro-conjugate fluid (ECF) and integration of the cells. The ECF is a kind of dielectric and functional fluid, which generates a powerful jet flow or ECF jet under an electrostatic field applied with an electrode pair. It is experimentally clarified that the smaller electrodes generate a more powerful ECF jet with constant voltage applied. The authors propose in this study a new type of micro artificial muscle cell using electro-conjugate fluid (ECF micro artificial muscle cell). This soft actuator having a power source inside is compact enough for integration. By integrating a large number of cells, we can realize a macro-sized artificial muscle. In this paper, we fabricate a prototype of ECF micro artificial muscle cell (Ø 12.5 mm × 13 mm), and integrate four cells into a 2 × 2 ECF artificial muscle actuator showing larger stroke and force. The maximum stroke and force are 1.56 mm and 320.5 mN with a single cell, and they are increased to be 2.8 mm and 504.1 mN with the 2 × 2 ECF artificial muscle actuator.
Table of Contents Introduction Building Blocks Elephant Design Traditional Bases Folding Instructions Stealth Fighter. Snail. Valentine. Ruby-Throated Hummingbird. Baby. Splitting Points Folding Instructions Pteranodon. Goatfish. Grafting Folding Instructions Songbird 1. KNL Dragon. Lizard. Tree Frog. Dancing Crane. Pattern Grafting Folding Instructions Turtle. Western Pond Turtle. Koi. Tiling Folding Instructions Pegasus Circle Packing Folding Instructions Emu. Songbird 2. Molecules Folding Instructions Orchid Blossom. Silverfish. Tree Theory Folding Instructions Alamo Stallion. Roosevelt Elk. Box Pleating Folding Instructions Organist. Black Forest Cuckoo Clock. Uniaxial Box Pleating Folding Instructions Bull Moose Polygon Packing Crease Patterns Flying Walking Stick. Salt Creek Tiger Beetle. Longhorn Beetle. Camel Spider. Water Strider. Scarab Beetle. Cicada Nymph. Scarab HP. Cyclomatus metallifer. Scorpion HP. Euthysanius Beetle. Spur-Legged Dung Beetle. Hybrid Bases Folding Instructions African Elephant References Glossary of Terms Index
Many 4-DOF exoskeleton type robot devices have been widely developed for the gait rehabilitation of post-stroke patients. However, most systems run with purely position control not allowing voluntary active movements of the subject. The lack of intelligent control strategies for variable gait patterns has been a clinical concern of such kind exoskeleton man–machine systems. In this work, we establish a 5-link model for the usual 4-DOF gait rehabilitation exoskeleton type man–machine system and propose a gait trajectory adaption control strategy. A 4-DOF gait rehabilitation exoskeleton prototype is developed as a platform for the evaluation of design concepts and control strategies in the view of improved physical human–robot interaction. The experimental results with eight healthy volunteers and three stroke patients are encouraging.
A novel transducer concept based on an organic electrochemical transistor is described. Its function as an integral part of an air humidity sensor, in which the proton conductor Nafion acts as sensitivity layer has been realised. The resulting electrochemical sensor–transistor, based on the conducting polymer PEDOT:PSS, operates at low voltages, on the order of 1 V. The sensor response, measured as the drain–source current of the electrochemical transistor, versus air humidity, has a close to exponential behaviour. The sensor can be realised using exclusively printing and coating fabrication techniques. Here, we demonstrate devices realised on plastic foils and on ordinary coated fine paper substrates. This organic electrochemical transducer promise future applications such as all-integrated low-cost sensor tags for single-use chemical sensors.
Did you know that any straight-line drawing on paper can be folded so that the complete drawing can be cut out with one straight scissors cut? That there is a planar linkage that can trace out any algebraic curve, or even ‘sign your name’? Or that a ‘Latin cross’ unfolding of a cube can be refolded to 23 different convex polyhedra? Over the past decade, there has been a surge of interest in such problems, with applications ranging from robotics to protein folding. With an emphasis on algorithmic or computational aspects, this treatment gives hundreds of results and over 60 unsolved ‘open problems’ to inspire further research. The authors cover one-dimensional (1D) objects (linkages), 2D objects (paper), and 3D objects (polyhedra). Aimed at advanced undergraduate and graduate students in mathematics or computer science, this lavishly illustrated book will fascinate a broad audience, from school students to researchers.
This paper discusses a method for controlling a hyper-redundant arm to manipulate an object on a plane. The hyper-redundant arm can perform simple whole-arm manipulation by coiling or wrapping around the object and then pulling the object toward the goal position. The process of object manipulation can be separated into two steps: encircling the object and transporting the object. In the process of encircling the object, the arm is controlled by a set of virtual constraints that guide the arm to reach around the object and encircle it, keeping the arm within a specified bound to ensure the circular shape around the object. In the process of transporting the object, a simplified desired shape is generated from a Bézier curve according to a given goal position and the arm geometry. Then, the gradient descent method is used to update the joint angles of the arm at each step to move the arm toward the desired shape until the object reaches its target position. The proposed method has been tested in both simulation and real experiments.
This paper presents a three-dimensional (3-D) dynamic model for a self-propelled, multilink dolphin-like robot to predict the dynamic behaviors of the bio-inspired artificial dolphin system within the framework of multibody dynamics. The propulsive structure mimicking dorsoventral motion includes a multilink tail and a flexibly oscillating fluke moving in coordination, as well as a pair of mechanical flippers performing flapping movements. This configuration can practically be simplified as an open-chain, tree-like multibody with a mobile base. The Schiehlen method is then employed to formulate the equations of motion based on the well-integrated kinematic and dynamic analyses of propulsive elements. Several locomotor behaviors, via coordinated control of the propulsors, can be principally replicated and numerically evaluated. Comparative results between simulations and experiments on forward swimming and combined motions are shown to demonstrate the effectiveness of the created model and locomotion control methods for dolphin-like swimming.
An electro-conjugate fluid (ECF) is a type of dielectric and functional fluid that generates a powerful jet flow when subjected to high DC voltage. Although a high voltage is needed to generate the jet flow, the current is quite low at several microamperes, resulting in a total power consumption of several milliwatts. Using this smart fluid, we can develop micro fluid-driven mechanical components without any bulky pumps. Also, it is clarified that the power density of the ECF jet is higher when the electrode pair is miniaturized; therefore, it is suitable for micro actuators. Here, we propose and fabricate three types of soft actuators with an antagonistic configuration: (i) micro artificial muscle cells, (ii) a McKibben-type micro artificial muscle actuator using the ECF effect and (iii) a micro finger actuator with two chambers to bend. The actuators basically consist of a silicone rubber tube covered with a fiber sleeve and a micro pressure source using the ECF effect. Next, we apply and integrate these actuators into a micro robot hand, driven with ECF jets. The driving characteristics of the micro artificial muscle actuator and the integrated micro ECF hand with ECF fingers were fabricated and experimentally investigated. The experimental results show that this ECF jet actuation is effective for driving soft micro hands.
Abstract Human muscular skeleton structure plays an important role for adaptive locomotion. Understanding of its mechanism is expected
to be used for realizing adaptive locomotion of a humanoid robot as well. In this paper, a jumping robot driven by pneumatic
artificial muscles is designed to duplicate human leg structure and function. It has three joints and nine muscles, three
of them are biarticular muscles. For controlling such a redundant robot, we take biomechanical findings into account: biarticular
muscles mainly contribute to joint coordination whereas monoarticular muscles contribute to provide power. Through experiments,
we find (1) the biarticular muscles realize coordinated movement of joints when knee and/or hip is extended, (2) the extension
of the ankle does not lead to coordinated movement, and (3) we can superpose extension of the knee with that of the hip without
losing the joint coordination. The obtained knowledge can be used not only for robots, but may also contribute to understanding
of adaptive human mechanism.
This paper proposes a method to generate novel motions of mollusk-type deformable robots made of electro-active polymer gel. Simulation and experimental results show that large transformations can be obtained with multiple electrodes in a planar configuration. We have designed a starfish-shaped gel robot that can turn over using spatially varying electric fields.
This paper describes the development of MEMS force sensors constructed using paper as the structural material. The working principle on which these paper-based sensors are based is the piezoresistive effect generated by conductive materials patterned on a paper substrate. The device is inexpensive (∼$0.04 per device for materials), simple to fabricate, lightweight, and disposable. Paper can be readily folded into three-dimensional structures to increase the stiffness of the sensor while keeping it light in weight. The entire fabrication process can be completed within one hour without expensive cleanroom facilities using simple tools (e.g., a paper cutter and a painting knife). We demonstrated that the paper-based sensor can measure forces with moderate performance (i.e., resolution: 120 μN, measurement range: ±16 mN, and sensitivity: 0.84 mV mN(-1)). We applied this sensor to characterizing the mechanical properties of a soft material. Leveraging the same sensing concept, we also developed a paper-based balance with a measurement range of 15 g, and a resolution of 0.39 g.
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).
This paper presents an innovative wormlike robot controlled by cellular neural networks (CNNs) and made of an ionic polymer-metal composite (IPMC) self-actuated skeleton. The IPMC actuators, from which it is made of, are new materials that behave similarly to biological muscles. The idea that inspired the work is the possibility of using IPMCs to design autonomous moving structures. CNNs have already demonstrated their powerfulness as new structures for bio-inspired locomotion generation and control. The control scheme for the proposed IPMC moving structure is based on CNNs. The wormlike robot is totally made of IPMCs, and each actuator has to carry its own weight. All the actuators are connected together without using any other additional part, thereby constituting the robot structure itself. Worm locomotion is performed by bending the actuators sequentially from "tail" to "head," imitating the traveling wave observed in real-world undulatory locomotion. The activation signals are generated by a CNN. In the authors' opinion, the proposed strategy represents a promising solution in the field of autonomous and light structures that are capable of reconfiguring and moving in line with spatial-temporal dynamics generated by CNNs.
A biological paradigm of versatile locomotion and effective motion control is provided by the polychaete annelid worms, whose motion adapts to a large variety of unstructured environmental conditions (sand, mud, sediment, water, etc.), and could thus be of interest to replicate by robotic analogs. Their locomotion is characterized by the combination of a unique form of tail-to-head body undulations (opposite to snakes and eels), with the rowing-like action of numerous lateral appendages distributed along their long segmented body. Focusing on the former aspect of polychaete locomotion, computational models of crawling and swimming by such tail-to-head body undulations have been developed in this paper. These are based on the Lagrangian dynamics of the system and on resistive models of its interaction with the environment, and are used for simulation studies demonstrating the generation of undulatory gaits. Several biomimetic robotic prototypes have been developed, whose undulatory actuation achieves propulsion on sand and other granular unstructured environments. Extensive experimental studies demonstrate the feasibility of robot propulsion by tail-to-head body undulations in such environments, as well as the agreement of its qualitative and quantitative characteristics to the predictions of the corresponding computational models.
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