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A pH-activated Artificial Muscle Using the McKibben-type Braided structure
Abstract
Fluidic McKibben artificial muscle is one of the best biomimetic actuators, exhibiting static and dynamic behaviour in close analogy with skeletal muscle. It is also known that McKibben muscle can combine this analogical behaviour with a high force on mass and on volume ratio. This paper analyses the working possibility of a small-size McKibben muscle for which a chemical activation mode is substituted in place of pneumatic energy, with the hope of deriving an original actuator for new applications in robotics and medicine. A pH activation mode seems particularly well adapted to our approach due to a large availability of pH-sensitive materials and the ease of reversible control by acid and base flows. The use of ion-exchange resins is considered due to their high swelling ability and ball-like microscopic structure favourable to flow circulation through the inner chamber of the McKibben muscle. The paper reports experimental results of artificial muscles 70–100mm in length and 8mm in diameter under isometric and isotonic conditions and against loads between 0.5 and 3kg. A maximum tension of about 100N is generated by the use of 0.1N NaOH/HCl solutions, which corresponds to a maximum stress of approximately 500kN/m2 and is greater than corresponding vertebrate skeletal muscle. We propose adapting the pH-muscle to actuate via ion-exchange in a hydrogel environment in order to overcome the slow response time (>30min), thus addressing one major drawback of their use in biomimetic robotics. Our preliminary results demonstrate the possibility of using synthesized hydrogel powders in order to generate quicker dynamic responses.
... These extreme pH values are motivated by the maximum protonation and deprotonation of the ionizable reactive polymer functional groups. In a previous work we showed how to employ the McKibben-braided structure to construct a compact pH-muscle producing a reversible contraction force with 0.1 M, and even 0.05 M acid-base solutions [10]. ...
... We have detailed in other papers our approach to the McKibben pneumatic artificial muscle [18] and its adaptation to a chemical control approach [10]. Fig. 1 describes the experimental set-up used to test such compact pH-muscles. ...
... In other words, as the pH-muscle must produce an "equivalent" pressure force generator in accordance with pneumatic McKibben artificial muscle theory. In our previous work [10] we demonstrated a maximum contraction ratio of about 15% with a 0.25 kg load. In order to test the dynamic ability of our new control process, in particular its maximum contraction ratio, we designed a longer muscle of l 0 ≈ 170 mm with the same r 0 and˛0 parameters. ...
Reversible swelling and de-swelling of pH reactive polymers are mainly made using strong bases and strong acids, typically with pH equal to 0 or 1 and 14 or 13. As a consequence, pH-artificial muscles are triggered at pH values too extreme to be in contact with living tissues. This report analyses the possibility of using weak base–weak acid buffers to generate the ion circulation necessary for swelling/de-swelling phenomena with a limited pH-range. Further, we describe experiments with ion-exchange resins swelling and de-swelling in response to standard NaHCO3/CH3COOH+CH3COONa weak base–weak acid solutions. The ion-exchange resin is placed inside the inner tube of a McKibben-braided structure whose functioning we have discussed elsewhere in connection with its reliability to define a chemo-mechanical artificial muscle with static and dynamic behaviour close to human skeletal muscle. We experimentally show that a 0.25M buffer solution leads to a maximum isometric force and a contraction time response similar to that obtained with 0.1M NaOH/HCl strong base–strong acid. As a consequence, our McKibben polymeric artificial muscle is now controlled within a lower pH-range with muscle contraction triggered at about 8.3 pH, and muscle relaxation at about 4.5 pH. Finally, we report the dynamic performance of an artificial muscle that is 170mm long/7mm diameter in an isotonic mode with loads between 0.25 and 10kg.
... In a previous work we showed how to employ the McKibben-braided structure to construct a compact pH-muscle producing a reversible contraction force with 0.1 M, and even 0.05 M acid-base solutions. [10] However, when lower concentrations -0.01 M and 0.001 M -are used, the force generated by the artificial muscle dramatically decreases and becomes zero at 0.0001 M concentrations. Other studies also emphasize the use limitation of pH-muscles to very acidic or very basic ranges: for example, PAAM hydrogel actuators have recently appeared to be effective for pH < 3 or pH > 12. [11] Such pH values are not adapted for future medical applications in which the integration of a pH-muscle inside the human body is imagined. ...
... We have detailed in other papers our approach to the McKibben pneumatic artificial muscle [18] and its adaptation to a chemical control approach. [10] Figure 1 synthesizes the experimental set-up used to test such compact pH-muscles. ...
... In other words, as long as the pHmuscle can produce an ''equivalent'' pressure force generator in accordance with pneumatic McKibben artificial muscle theory. In our previous work [10] we demonstrated a maximum contraction ratio of about 15% with a 0.25 kg load. In order to test the dynamic ability of our new control process, and more particularly its maximum contraction ratio, we designed a longer muscle of l 0 % 170mmwith the same r 0 and a 0 parameters. ...
Reversible swelling and de-swelling of pH reactive polymers are mainly made using strong bases and strong acids, typically with pH equal to 0 or 1 and 14 or 13. As a consequence, pH-artificial muscles are triggered off at a pH too high for internal use of such muscles inside the human body. The paper analyses the possibility of using weak base-weak acid buffers to generate the ion circulation necessary for swelling/de-swelling phenomena with a limited pH-range. The paper further reports experiments with ion-exchange resins swelling and de-swelling in response to standard NaHCO3/CH3COOH + CH3COONa weak base-weak acid solutions. The ion exchange resin is placed inside the inner tube of a McKibben-braided structure whose functioning we have discussed elsewhere in connection with its reliability to define a chemo-mechanical artificial muscle with static and dynamic behaviour close to human skeletal muscle. We experimentally show that a 0.25 M buffer solution leads to a maximum isometric force and a contraction time response similar to that obtained with 0.1 M NaOH/HCl strong base-strong acid. As a consequence, our McKibben polymeric artificial muscle is now controlled within a 3.8 pH-range: muscle contraction is triggered at about 8.3 pH, and muscle relaxation at about a 4.5 pH. The dynamic performance of a 170 mm long/7 mm diameter in isotonic mode, with loads between 0.25 kg to 10 kg, is reported.
... A pump is used to pass solutions of differing pH through the actuator, causing swelling and the generation of an internal pressure within the actuator. Depending on the fibre orientation in the weave, swelling will create either an expansion or contraction of the actuator [53][54][55]. This approach to hydrogel control eliminates the issues of electrolysis that occurs with direct electrical control of hydrogels, but does require additional energy input. ...
... The device consists of a hydrogel (a polymer gel that reversibly swells when exposed to differing stimuli in solution) contained within a FMC tube (a cylindrical fibre reinforced composite laminate with an elastomeric matrix). It is a similar concept to the actuators developed by Tondu et al [53][54][55]. ...
Although the actuation mechanisms that drive plant movement have been investigated from a biomimetic perspective, few studies have looked at the wider sensing and control systems that regulate this motion. This paper examines photo-actuation—actuation induced by, and controlled with light—through a review of the sun-tracking functions of the Cornish Mallow. The sun-tracking movement of the Cornish Mallow leaf results from an extraordinarily complex—yet extremely elegant—process of signal perception, generation, filtering and control. Inspired by this process, a concept for a simplified biomimetic analogue of this leaf is proposed: a multifunctional structure employing chemical sensing, signal transmission, and control of composite hydrogel actuators. We present this multifunctional structure, and show that the success of the concept will require improved selection of materials and structural design. This device has application in the solar-tracking of photovoltaic panels for increased energy yield. More broadly it is envisaged that the concept of chemical sensing and control can be expanded beyond photo-actuation to many other stimuli, resulting in new classes of robust solid-state devices.
... A pH-activated McKibben artificial muscle has been developed by Tondu et al. (2009) and Vial et al. (1996). The actuator was filled with an ion-exchange resin. ...
... Many researchers have developed various control approaches to solve this problem. The sliding mode control (SMC) has been applied widely (Aschemann and Schindele, 2008; Cai and Dai, 2003; Cai and Yamaura, 1996; Lilly and Liang, 2005; Shen, 2010; Tondu et al., 2009; Van Damme et al., 2007; Wang et al., 1992; Xing et al., 2010). The fuzzy control approaches (Balasubramanian and Rattan, 2003; Carbonell et al., 2001; Chan et al., 2003; Thongchai et al., 2001; Wu et al., 2009) and the neural network approaches (Ahn and Anh, 2007; Ahn et al., 2005; Hesselroth et al., 1994; Nagaoka et al., 1995; Tian et al., 2004; Van Der Smagt et al., 1996) can also be found. ...
Pressurized artificial muscles are reviewed. These actuators consist of stiff reinforcing fibers surrounding an elastomeric bladder and operate using a pressurized internal fluid. The pressurized artificial muscles, known as McKibben actuators or flexible matrix composite actuators, can be applied to a wide array of applications, including prosthetics/orthotics, robots, morphing wing technologies, and variable stiffness structures. Analytical models for predicting the response behavior have used both virtual work methods and continuum mechanics. Various nonlinear control algorithms have been developed, including sliding mode control (SMC), adaptive control, neural networks, etc. In addition to traditional fluid-driving methods, innovative techniques such as chemical and electrical driving techniques are reviewed. With improved manufacturing techniques, the operational life of pressurized artificial muscles has been significantly extended, thus making them suitable for a vast range of potential applications.
... Ce mouvement d'ion va provoquer la courbure de l'actionneur fait de gel ionique. Ce matériau peut atteindre de grande déformation, jusqu'à plus de 40 % [177], et des forces de plusieurs dizaines de newton [203]. Mais leur interaction chimique avec leur environnement et le besoin d'immerger l'actionneur dans une solution électrolytique rendent leur utilisation peut judicieuse dans un environnement comme le cerveau. ...
L’objectif de ces travaux de thèse est de répondre à la problématique suivante : Suivre des trajectoires courbes dans le cerveau, dans l’objectif de réaliser diverses opérations de neurochirurgie. Pour répondre à cela il est nécessaire de développer un dispositif robotisé capable de progresser dans le cerveau, tout en respectant les contraintes de la neurochirurgie.La première étape consiste à définir les contraintes liées à la neurochirurgie, ainsi que les objectifs à atteindre. Cela amène à la définition d’une liste des exigences. Pour compléter cette liste, il est nécessaire de répondre à une autre problématique, celle de définir la notion de trajectoire courbe en neurochirurgie et de caractériser une trajectoire type désirée.Un algorithme de génération de trajectoire courbe pour la neurochirurgie, basé sur l’utilisation de courbes de Bézier, en intégrant l’opérateur et son savoir dans le tracé, est développé. Une fois la trajectoire type créée et validée par le chirurgien, elle est définie, grâce à des critères que nous avons établis. Ces critères ont ensuite été reportés dans la liste des exigences afin de la compléter.Une étude bibliographique sur les matériaux dits actifs ou intelligents est présentée. La réflexion permettant de choisir le matériau permettant de répondre au mieux à la problématique et aux exigences posées.Une deuxième étude bibliographique sur la fabrication des IPMCs est exposée, et aboutit à la création ainsi qu’à la mise en place du procédé de fabrication. Ce procédé de fabrication se divisent en deux grandes étapes, la mise en forme du polymère par impression 3D et la création des électrodes par electroless plating method. Ce procédé a permis la production de plusieurs actionneurs de formes cylindrique. Des verrous restent à résoudre pour débloquer l’actionnement des IPMCs produits.Même si des verrous sont encore présents, les résultats obtenus sont prometteurs. Une collaboration avec des spécialistes, notamment en chimie, devrait conduire à la production d’actionneurs fonctionnelles et donc du prototype conçu.
... When it comes to precise manipulation or locomotion in limited spaces, soft robots are required to dwindle to a small scale and be powered or actuated externally [7][8][9]. Under such circumstance, magnetic control shows its unique advantage, with contribution in external force actuation research, a number of different external forces are utilized to actuated small-scale robots, including swimming microorganisms and contractile cells [10], steering via taxis behaviors of the microorganisms [11], chemical reaction [12], temperature [13], light [14], pH [15] and remotely delivered magnetic fields [16][17][18]. Among all these external forces, magnetic is of particular importance, for it can provide widezone direct control, allowing for a variety of programming methods. ...
Untethered soft miniature robots are considered to have a wide range of applications in biomedical field. However, researchers today still have not reached a consensus on its configuration design and actuation method. Here, inspired by the tentacles of a certain kind of echinodermata, we propose a soft multi-legged robot with a total weight of 0.26 g capable of multiple locomotion modes. Based on the magnetic field distribution of a square permanent magnet, we qualitatively analyze the motion mechanism of the robot. Finally, we carried out relevant experimental research. The research shows that the robot can move forward, backward, steering and cross obstacles under the control of the magnetic field, and can combine these abilities to navigate the maze.
... Since these performances are comparable to those of biological muscles, the demand for employing these muscles for robotic tools and medical devices is high. Mckibben artificial muscles are simply made of three essential parts: an inner elastomeric bladder, a braided sleeve and the fluid supply system [6]. The inner elastomeric bladder is surrounded by a braided sleeve which is connected to the fluid supply system. ...
... However, this is characteristic only for individual phases of PVDF, which allows, as in the case of alternating excitable and non-excitable tissues and without changing the chemical composition, to manage functionality of PVDF-based implants and sensors. This also allows to move away from the use of PVDF as a "simulator" of biological excitable media-nervous tissue (for example, to create memristors usually opposed in engineering works to both inorganic and purely biopolymer memristors [348][349][350][351][352]) or muscle tissue (for example, in robotic or skin/ subcutaneous implantable artificial muscles, different in action from the teinochemical principle of chemomechanics [353][354][355][356][357][358][359])-to an emergent approach in the development of cooperatively developing bioartificial systems, such as electroactive scaffolds with biologically limited excitation or tissue-guidance structures with reversible activation/inactivation of polymer media, controlled by the biological response upon activation. ...
In this chapter, the basic concepts of ferroelectric polymer-based implantology and regenerative medicine are derived from a comprehensive literature review. Special attention is paid to the main physical and chemical properties of the ferroelectric polymer surface which determine biocompatibility criteria of the implants produced from such polymers. A similarity between the physicochemical properties of ferroelectric polymers and several biological structures is emphasized. The necessity of transition from the passive bioinert implants to the active biomimetic ones is substantiated. The novel applications of poly(vinylidene) fluoride and its copolymers as the basis of the emergent scaffolds for response-controlled histomorphogenesis are proposed.
... This issue is addressed to some extent by using alternative techniques to generate the required pressure for actuation. For example, combustion (e.g., butane/oxygen) (24), gas evolution reactions (e.g., hydrogen peroxide with platinum catalyst, consumption of oxygen and hydrogen with a fuel cell to make vacuum, or generating CO 2 from urea with a catalyzer) (25,27), chemically activating swelling/deswelling (e.g., pH-sensitive hydrogels) (28), and phase change materials (e.g., ethanol and paraffin wax) (26,(29)(30)(31) are some of the techniques that have been explored so far. Most combustion and chemical reaction techniques are irreversible; therefore, the fuel should be replenished after several cycles. ...
Pneumatic artificial muscles have been widely used in industry because of their simple and relatively high-performance design. The emerging field of soft robotics has also been using pneumatic actuation mechanisms since its formation. However, these actuators/soft robots often require bulky peripheral components to operate. Here, we report a simple mechanism and design for actuating pneumatic artificial muscles and soft robotic grippers without the use of compressors, valves, or pressurized gas tanks. The actuation mechanism involves a magnetically induced liquid-to-gas phase transition of a liquid that assists the formation of pressure inside the artificial muscle. The volumetric expansion in the liquid-to-gas phase transition develops sufficient pressure inside the muscle for mechanical operations. We integrated this actuation mechanism into a McKibben-type artificial muscle and soft robotic arms. The untethered McKibben artificial muscle generated actuation strains of up to 20% (in 10 seconds) with associated work density of 40 kilojoules/meter ³ , which favorably compares with the peak strain and peak energy density of skeletal muscle. The untethered soft robotic arms demonstrated lifting objects with an input energy supply from only two Li-ion batteries.
... L'espoir de cette dernière solution réside en la promesse de récupération de l'énergie mécanique sous forme d'énergie électrique (fonctionnement inverse de pile à combustible), plutôt que la relâche de l'énergie de pression dans l'atmosphère par ouverture d'une valve. D'autres combinaisons sont rapportées dans la littérature comme la combinaison d'une structure McKibben avec un actionnement généré par un polymère à mémoire de forme [60], ou encore l'utilisation du pH [61][62] Un deuxième défi est l'intégration de capteurs pour mesurer la géométrie déformée de l'actionneur fluidique flexible. Ceci serait très utile pour assurer la navigation d'un cathéter à l'intérieur du corps humain par exemple. ...
... In addition to the more common actuator types listed above there are many other actuation mechanisms, such as electrochemical [16,37,38], electrostatic [39,40], optical [41], magnetic [42], hydraulic [43,44] and pH actuation [45,46]. ...
Smart textiles based on actuator materials are of practical interest, but few types have been commercially exploited. The challenge for researchers has been to bring the concept out of the laboratory by working out how to build these smart materials on an industrial scale and permanently incorporate them into textiles. Smart textiles are considered as the next frontline for electronics. Recent developments in advance technologies have led to the appearance of wearable electronics by fabricating, miniaturizing and embedding flexible conductive materials into textiles. The combination of textiles and smart materials have contributed to the development of new capabilities in fabrics with the potential to change how athletes, patients, soldiers, first responders, and everyday consumers interact with their clothes and other textile products. Actuating textiles in particular, have the potential to provide a breakthrough to the area of smart textiles in many ways. The incorporation of actuating materials in to textiles is a striking approach as a small change in material anisotropy properties can be converted into significant performance enhancements, due to the densely interconnected structures. Herein, the most recent advances in smart materials based on actuating textiles are reviewed. The use of novel emerging twisted synthetic yarns, conducting polymers, hybrid carbon nanotube and spandex yarn actuators, as well as most of the cutting–edge polymeric actuators which are deployed as smart textiles are discussed.
... Therefore, many biomedical applications have been conceived for hydrogels, some of them already exploited at a commercial level [1,2]. For example, hydrogels have been used as artificial muscles [3,4], reservoirs for storage and delivery of cells, drugs or environmental factors in clinical medicine [5,6], as well as artificial ECM in tissue engineering [7]. ...
Magnetorheological (MR) effect is a phenomenon typical of suspensions of magnetizable particles in a liquid carrier, characterized by strong changes of their mechanical properties in response to applied magnetic fields. Its origin is on the migration of magnetized particles and their aggregation into chain-like structures. However, for ferrogels, consisting of dispersions of magnetic particles in a polymer matrix, migration of particles is hindered by the elastic forces of the polymer network, preventing from strong MR effect. Interestingly, in this manuscript, we demonstrate that strong MR effect in robustly cross-linked polymer ferrogels is still possible. Experimental results showed enhancement of the storage modulus of more than one order of magnitude for alginate ferrogels containing less than about 10 vol% of iron particles under moderate magnetic fields. The differential feature of these ferrogels is that, instead of individual particles, the disperse phase consisted of large clusters of iron microparticles homogeneously distributed within the polymer networks. These clusters of magnetic particles were formed at the stage of the preparation of the ferrogels and their presence within the polymer networks had two main consequences. First, the volume fraction of clusters was considerably larger than this of individual particles, resulting in a larger effective volume fraction of solids. Second, since the force of magnetic attraction between magnetic bodies is roughly proportional to the cube of the body size, the existence of such clusters favored inter-cluster interaction under a magnetic field and the appearance of strong MR effect. On this basis, we demonstrated by theoretical modeling that the strong MR effect displayed by the alginate ferrogels of the present work can be quantitatively explained by assuming the existence of large, roughly spherical particle aggregates formed at the stage of the preparation of the ferrogels. Our theoretical model provides a reasonable quantitative prediction of the experimental results.
... Pneumatic Artificial Muscles (PAMs) are interesting actuators that have similar static and dynamic characteristics to the human skeletal muscle and, therefore, have many applications in orthetics and biomimetic systems (Daerden and Lefeber, 2002;Tondu et al., 2009). They are lightweight, easy to fabricate, low cost, compliant and inherits the advantages of pneumatic systems. ...
Pneumatic artificial muscles are soft actuators which resemble human skeletal muscles. They are attractive for many applications where safety, human interaction or biomimetic behavior is required. However, its use is not yet widespread because of the difficulties of working with them, such as high nonlinearities, difficult to model and control accurately. This work proposes a simple method for controlling the pneumatic muscle, which is using a PID controller tuned with a simulated annealing optimization algorithm.
... [5][6][7] McKibben artificial muscles can be operated either hydraulically or pneumatically using pressurized fluids and the actuation system usually requires a compressor/pump as well as a gas/water storage container. [8][9][10] Recently, the pressurized fluids have been substituted with stimuli-responsive materials that exhibit volume changes in response to temperature or chemical species [11][12][13] and these advancements are paving the way for fabricating a lighter McKibben actuation system by eliminating external devices, such as gas/water container and compressor/pump. ...
Fluidic McKibben artificial muscles operate either pneumatically or hydraulically, offering engineering performance similar to those of skeletal muscles. These muscles are normally made of two essential parts: an elastomeric bladder and braided sleeve. To date, the braided sleeves used in manufacturing conventional McKibben artificial muscles are made with industrial braiding machines. In this study, we investigate an alternative method to manufacture braided sleeves using a three-dimensional (3D) printing technique. The 3D printing allows for more versatility in controlling the geometry and the structure of the braids. To this end, two structurally different kinds of braided sleeves with connected and disconnected junction points were manufactured. Both kinds of 3D printed braided sleeves were made with similar geometry. The hydraulic McKibben muscle made using the 3D braided sleeves with disconnected junction points was able to generate isometric forces up to 960 mN (53 kPa), actuation strains up to 6.7%, and power per mass of 0.032 W/kg in ∼1 s at a supply water pressure of 0.66 bar. This unique 3D printing technique is simple, fast, and accurate that can be easily modified to fabricate tools for small robotic systems where custom manufacturing is required.
... We also highlight that the self-assembling building blocks themselves provide chemical feedback to the driving (master) system by changing the main characteristics of the system (pH maximum, t tr ). The work described here can provide new insight into time-programmed drug release 36,47,48 and artificial muscle 49,50 systems controlled by autonomous stimuli. ...
Dynamic self-assembly is of great interest in the field of chemistry, physics and material science and provides a flexible bottom-up approach to build assemblies at multiscale levels. We propose a method to control the time domain of self-assembling systems in a closed system, from molecular to material level using a driving chemical system: methylene glycolsulfite pH clock reaction coupled to lactone hydrolysis. The time domain of the transient pH state (alkaline) and the time lag between the initialization of the reaction and the pH change can be efficiently fine-tuned by the initial concentration of the reagents and by the chemical composition of lactone. The self-assembly of pH-responsive building blocks can be dynamically driven by this kinetic system, in which the time course of the pH change is coded in the system. This approach provides a flexible and autonomous way to control the self-assembly of pH responsive building blocks in closed chemical systems far from their thermodynamic equilibrium
... The artificial muscle membrane is filled with such resin beads, and by pumping HCl (acid, low pH) or NaOH (base, high pH) solutions through this membrane, the swelling and shrinking of the resin beads changes the lateral expansion of the muscle (Tondu et al. 2009). A precise tuning of the chemical stimuli by a selection of buffer solutions allows to switch such a muscle architecture by slight changes of the pH (Tondu et al. 2010). ...
Stimuli-responsive hydrogels display a variety of interesting features that make them ideal candidates for technological applications. The applicable stimuli range from temperature, pH, and (bio)chemical species to electric fields and light; some materials can even be controlled by multiple stimuli. Hydrogel materials can be synthesized by a single-step free-radical polymerization, and various methods to introduce them into a final system are discussed. This chapter covers applications of smart hydrogels in various (micro-)systems starting from transparent conductors over stimuli-sensitive optical components and drug delivery devices for medical applications. Intensively discussed are microfluidic applications starting from single components as thermostats, chemostats, and valves toward complex integrated systems. Finally, we outline the implications of autonomous microfluidic devices to the field of chemical information processing.
... One approach towards making a more compact and lightweight actuation system is to reduce the need for compressors, pumps and valves by using a volume change material to deform the braided sleeve. Tondu et al. (2009) have shown that pressurized gas/water can be replaced with pH-sensitive hydrogel spheres in McKibben artificial muscles to generate reasonable actuation strain and force. However, there are still some remaining problems that need to be considered, such as the long response time (.10 min) and the required pump for delivering acid/base solutions to the pH-sensitive hydrogel. ...
McKibben artificial muscles are one of the most pragmatic contractile actuators, offering performances similar to skeletal muscles. The McKibben muscles operate by pumping pressurized fluid into a bladder constrained by a stiff braid so that tensile force generated is amplified in comparison to a conventional hydraulic ram. The need for heavy and bulky compressors/pumps makes pneumatic or hydraulic McKibben muscles unsuitable for microactuators, where a highly compact design is required. In an alternative approach, this article describes a new type of McKibben muscle using an expandable guest fill material, such as temperature-sensitive paraffin, to achieve a more compact and lightweight actuation system. Two different types of paraffin-filled McKibben muscles are introduced and compared. In the first system, the paraffin-filled McKibben muscle is simply immersed in a hot water bath and generates isometric forces up to 850 mN and a free contraction strain of 8.3% at 95°C. In the second system, paraffin is heated directly by embedded heating elements and exhibits the maximum isometric force of 2 N and 9% contraction strain. A quantitative model is also developed to predict the actuation performance of these temperature sensitive McKibben muscles as a function of temperature.
... Mechanics engineering, electrical engineering and life sciences require a transplant to increase the connection between these two classes of science. Especially, to make a muscle which is a basic internal body part in animals, materials are needed which do their obligations like a muscle and furthermore its physical shape and method operations are close to the actual muscle [1]- [5]. In recent decades, more researches have been done toward robots that simulate animal's motion [6]- [11]. ...
This paper presents new designing for robot that moves like worm and the structure of this robot is made by the Shape-Memory Alloy (SMA). The smart alloys and the alloys in special kinds of artificial muscles apply motor action to the heat or coldness in the construction of artificial muscles. This robot is controlled by the operator and computer. Imaging, position of detection, smart guidance and environmental factors' estimation such as height and impact are other abilities for this robot.
... A bio-compatible agent is also necessary to generate the "equivalent" fluidic pressure needed for artificial muscle contraction. We have shown elsewhere that ionexchange resins were good candidates for reversible swelling and de-swelling in response to a pHvariation [11]. As also emphasized earlier, the McKibben structure can appear particularly safe as long as it can be ensured that the rubber tube does not explode under pressure. ...
Based on recent experiments made by the present authors on a “pH-muscle” functioning in an admissible physiologically pH-range, a global analysis is developed for a future “artificial muscle implant” both safe and efficient. A scheme of a possible future artificial muscle implant is shown associating our current prototype, whose skeletal muscle-like behaviour is provided by McKibben artificial muscle technology, with the use of a bio-compatible micro-organism, to be specified, which would be able to generate the necessary ionic-strength change to the swelling and de-swelling of the ion-sensitive agent placed inside the McKibben structure. Preliminary experimental results are reported of a 10 cm long artificial muscle and 8 mm external diameter filled with a RCOOH commercial Amberlite resin generating a maximum force of 80 N with buffer solutions of pH between 4.5 and 8.4 in some tens of minutes with the hope of obtaining quicker responses by use of more specific ion-sensitive polymers.
... As a result of the potential benefit offered by the H-FMC concept to hydrogel actuation performance it is believed that the concept will find application in a wide variety of fields, with particular potential for use as soft actuators in robotic devices. A similar actuator concept employing hydrogels contained in McKibben actuator tubes has been developed by Tondu et al for robotic applications [27][28][29][30]. McKibben actuators are similar to FMC based actuators and consist of a internal elastomeric tube constrained externally by an unbonded fibre weave or braid [26]. ...
The underlying theory of a new actuator concept based on hydrogel core flexible matrix composites (H-FMC) is presented. The key principle that underlines the H-FMC actuator operation is that the three-dimensional swelling of a hydrogel is partially constrained in order to improve the amount of useful work done. The partial constraint is applied to the hydrogel by a flexible matrix composite (FMC) that minimizes the hydrogelʼs volume expansion while swelling. This constraint serves to maximize the fixed charge density and resulting osmotic pressure, the driving force behind actuation. In addition, for certain FMC fibre orientations the Poissonʼs ratio of the anisotropic FMC laminate converts previously unused hydrogel swelling in the radial and circumferential directions into useful axial strains. The potential benefit of the H-FMC concept to hydrogel actuator performance is shown through comparison of force–stroke curves and evaluation of improvements in useful actuation work. The model used to achieve this couples chemical and electrical components, represented with the Nernst–Plank and Poisson equations, as well as a linear elastic mechanical material model, encompassing limited geometric nonlinearities. It is found that improvements in useful actuation work in the order of 1500% over bare hydrogel performance are achieved by the H-FMC concept. A parametric study is also undertaken to determine the effect of various FMC design parameters on actuator free strain and blocking stress. A comparison to other actuator concepts is also included.
... Polymer network change their volume in response to external stimuli such as changes in solvent composition [1], pH [2][3][4], temperature [5], electric field [6,7], and light irradiation [8], they have many potential uses in various fields of biotechnology [9], medicine [10,11], robotics [12], and pharmaceutical applications, including controlled drug delivery [13], and their practical applications will be further extended if their microscopic structures can be controlled. An acrylate polymer belongs to a group of polymers, also commonly known as acrylics or polyacrylates, which could be referred to generally as plastics. ...
... A pH-sensitive actuator was designed using an ion-exchange resin that swells under controlled acid/base flow. Acidic or basic solutions are delivered to the RMA through narrow channels [20]. Similarly, the system proposed in the following work could be fueled by a liquid reactant distributed to actuation sites by capillary forces. ...
A biologically inspired pneumatic pressure source was designed and sized to supply high pressure CO2(g) to power a rubber muscle actuator. The enzyme urease served to catalyze the hydrolysis of urea, producing CO2(g) that flowed into the actuator. The actuator’s power envelope was quantified by testing actuator response on a custom-built linear-motion rig. Reaction kinetics and available work density were determined by replacing the actuator with a double-action piston and measuring volumetric gas generation against a fixed pressure on the opposing piston. Under the conditions investigated, urease catalyzed the generation of up to 0.81 MPa (117 psi) of CO2(g) in the reactor headspace within 18 min, and the evolved gas produced a maximum work density of 0.65 J ml⁻¹.
Pneumatic artificial muscles have been widely used in the field of robotics because of their large output force and fast actuation, however, the accompanying bulky compressors and pumps limit their miniaturized applications. Despite current untethered pneumatic artificial muscles can be driven by adjusting the internal pressure, it is challenging to structurally mimic natural muscles with high water content. Here, we propose untethered pneumatic artificial muscles comprising a hydrogel actuator with snap-through instability and an air storage chamber. These hydrogel actuators can realize the conversion from hydrophobic association of octyl acrylate moieties to host-guest interaction between β-cyclodextrin and octyl acrylate under thermal stimuli, leading to the decrease of their moduli. The inflated hydrogel actuators exhibit rapid actuation with a radial expansion speed of 200% s⁻¹, which are powered by snap-through instability, thermal expansion of the gas inside the hydrogel actuator, and evaporation of water on its internal surface. With the pneumatic artificial muscles miniaturized, we demonstrate diving and rolling robots, exemplifying bionic robots able to adapt to and modify the environment. We expect that the design of hydrogel actuator in miniaturized pneumatic artificial muscles will facilitate rapid locomotion for future bionic robotic platforms.
Tardigrades are the most resilient biospecies on Earth, capable of surviving extreme conditions including high temperatures, pressures, air deprivation, and exposure to noxious chemicals and radiation. The study here undertakes biomimicry of the remarkable adaptability of tardigrades by designing biomorph soft actuators (BSAs) that can endure these harsh environments. Unlike previous tardigrade‐inspired materials, which lacked a naturalistic interaction with their surroundings, the BSAs replicate the anatomical macrostructures and the non‐monotonic environmental resilience of tardigrades, especially their ability to adapt via dehydration and rehydration. Dual‐layer hydrogel spheres are employed with embedded fluid bubbles, creating cohesive yet non‐monolithic smart BSA structures. These structures exhibit high resilience to compressive, thermal, and radiation stimuli, achieved through thermoresponsive shape morphing driven by fluid balance. Their advanced capabilities are also demonstrated, such as driving a McKibben‐type artificial muscle and rapidly regenerating themselves from a state exposed to hazardous chemicals. Such versatile actuating biomorphs hold great promise for various autonomous applications, including soft robotic operations in aqueous effluents, deserts, polar regions, and outer space.
The physics of soft matter can contribute to the revolution in robotics and medical prostheses. These two fields require the development of artificial muscles with behavior close to biological muscles. Today, artificial muscles rely mostly on active materials, which can deform reversibly. Nevertheless transport kinetics is the major limit for all of these materials. These actuators are only made of a thin layer of active material and using a large thickness dramatically reduces the actuation time. In this article, we demonstrate that a porous material reduces the limit of transport and enables the use of a large volume of active material. We synthesize a new active material: a macroporous gel, which is based on polyacrylic acid. This gel shows very large swelling when we increase the pH and the macroporosity dramatically reduces the swelling time of centimetric samples from one day to 100 s. We characterize the mechanical properties and swelling kinetics of this new material. This material is well adapted for soft robotics because of its large swelling ratio (300%) and its capacity to apply a pressure of 150 mbar during swelling. We demonstrate finally that this material can be used in a McKibben muscle producing linear contraction, which is particularly adapted for robotics. The muscle contracts by 9% of its initial length within 100 s, which corresponds to the gel swelling time.
Stimuli‐responsive materials have been lately employed in soft robotics enabling new classes of robots that can emulate biological systems. The untethered operation of soft materials with high power light, magnetic field, and electric field has been previously demonstrated. While electric and magnetic fields can be stimulants for untethered actuation, their rapid decay as a function of distance limits their efficacy for long‐range operations. In contrast, light—in the form of sunlight or collimated from an artificial source (e.g., laser, Xenon lamps)—does not decay rapidly, making it suitable for long‐range excitation of untethered soft robots. In this work, an approach to harnessing sunlight for the untethered operation of soft robots is presented. By employing a selective solar absorber film and a low‐boiling point (34 °C) fluid, light‐operated soft robotic grippers are demonstrated, grasping and lifting objects almost 25 times the mass of the fluid in a controllable fashion. The method addresses one of the salient challenges in the field of untethered soft robotics. It precludes the use of bulky peripheral components (e.g., compressors, valves, or pressurized gas tank) and enables the untethered long‐range operation of soft robots. While offering immense potential for disruptive applications, pneumatically driven soft robots require bulky, heavy, and pricy peripherals, such as gas tanks, compressors, and valves, to operate. Here, a technique to fabricate untethered soft robots that are directly powered by solar energy is presented.
Soft wearable actuators can help connect machines and humans, providing a personalized, ergonomic, and cooperative physical interface between people and their world. Until now, the torque of these interfaces has been limited, restricting their ability to assist the completely paralyzed. This article presents a method for realizing a soft structure that stably and comfortably applies a knee extension torque to the body that is sufficient for sit-to-stand (STS). The structure, the pleated pneumatic interference actuator (PPIA), is based on pleated inflatables; is lightweight, collapsible, and clothing integratable; and generates torque from buckling of a constrained fabric-reinforced rubber tube. Multiple PPIAs were integrated into a soft orthosis, the soft lift assister for the knee (SLAK). The SLAK was inflated to a pressure of 320 kPa, and it produced a maximum 324 Nm torque at a flexion angle of 82°. This exceeds the peak 180 Nm torque required for STS and torques required for other everyday tasks. The SLAK met the torque requirement for STS, which is more than 93% of the STS motion when worn by a test leg. Worn by a human, it shows potential for complete support, which is more than 100% of the motion. The PPIA's theoretical model overestimated torque at low to moderate flexion angles and underestimated PPIA torque at high flexion angles. Further development of the PPIA will focus on testing the SLAK with human subjects; increasing the PPIA's speed and flexibility; reducing the PPIA's bulk; and improving the PPIA's model accuracy.
Stimuli-responsive hydrogels display a variety of interesting features that make them ideal candidates for technological applications. The applicable stimuli range from temperature, pH, and (bio)chemical species to electric fields and light; some materials can even be controlled by multiple stimuli. Hydrogel materials can be synthesized by a single-step free-radical polymerization, and various methods to introduce them into a final system are discussed. This chapter covers applications of smart hydrogels in various (micro-)systems starting from transparent conductors over stimuli-sensitive optical components and drug delivery devices for medical applications. Intensively discussed are microfluidic applications starting from single components as thermostats, chemostats, and valves toward complex integrated systems. Finally, we outline the implications of autonomous microfluidic devices to the field of chemical information processing.
To implant an active artificial muscle inside the human body is still a dream due to the extreme difficulty of replicating natural muscular tissue. Present-day development of chemo-mechanical artificial muscles for robots could help to specify first prototypes of such active implants. Based on recent experiments made by the present authors on a "pH-muscle" functioning in an admissible physiologically pH-range, a global analysis is developed for a future "artificial muscle implant" both safe and efficient. A scheme of a possible future artificial muscle implant is shown associating our current prototype, whose skeletal muscle-like behaviour is provided by McKibben artificial muscle technology, with the use of a bio-compatible micro-organism, to be specified, which would be able to generate the necessary ionic-strength change to the swelling-deswelling of the ion-sensitive agent placed inside the McKibben structure. Preliminary experimental results are reported of a 10 cm long artificial muscle and 8 mm external diameter filled with a RCOOH commercial Amberlite resin generating a maximum force of 80 N with buffer solutions of pH between 4.5 and 8.4 in some tens of minutes with the hope of obtaining quicker responses by use of more specific ion-sensitive polymers.
Recently, the smart or intelligent polymers are synthesized and modified by gamma-rays;they have showngreat potential in advanced materials. In this chapter, the smart polymers were reviewed from their preparation, properties and potential applications. The combination of smart polymers and drug delivery systems provides specific characteristics for intelligent materials and might be encouraged to hold enormous chances in biotechnology applications. Graft copolymers and hydrogels were modified by gamma radiation of pH and thermo sensitive monomers. The effects of the absorbed dose, monomer concentration and reaction time were discussed in this chapter. The surface chemistry of smart materials was analyzed by FTIR-ATR spectroscopy, while their thermal properties were analyzed by TGA and DSC. The stimuli-responsive behavior was studied by swelling and contact angle in water, as well as by DSC. Sensitive films presented a critical pH and LCST.
As a way to protect against dermal exposure to chemical and biological hazards, barrier materials have been designed to be used in protective clothing. However, several problems remain; for example, breathability, functionality, performance and durability. Smart membranes based on technologies such as nanomaterials, electrospinning, graft polymerization, N-halamine compounds, etc. offer some promising solutions to these needs; in particular, in providing responsive and self-decontaminating capabilities. Yet numerous challenges still exist before getting to the ultimate goal - an adaptive membrane that rapidly adjusts in a reversible way to environmental conditions and threat intensity.
This paper provides a review on various methods and designs developed for the precise actuation control of shape memory alloys, which can be in different physical forms. Shape memory alloy (SMA) is the class of smart materials, which generates large force when an external stimulus is
provided. Nitinol (NiTi) wire is the most commonly used forms of SMA actuator, whose length alters when the current is varied through the wire. Some of the advantages of using SMA actuators in working systems are due to their light weight, compact size, can be easily integrated with existing
systems, simple, frictionless and respond to temperature change with low energy consumption. In the past few years, SMAs have been used in a wide range of applications where actuation is desired and where fine position control is a requisite such as in medical, aeronautics, industries, surgical
tools, robotics, and so on. Many factors must be taken into consideration, including the desired range of motion, the amount of force required and the useful lifetime of the device. However, the shape memory alloys exhibit the hysteresis effect. In this review work, various controlling schemes
developed in the past few years and their applications in present scenario have been reviewed, which also include adaptive and nonlinear control schemes like variable structure control, time slicing, fuzzy logic control etc., in order to minimize the hysteresis effect of SMA actuator. The
objective of the present study is to assist researchers and students to attain the requisite knowledge on recent improvements in the methods for controlling of SMA actuators and ongoing applications of SMA actuators in various fields.
This paper presents a flexible artificial muscle actuator using coiled shape memory alloy (SMA) wires. The actuator mainly consisted of flexible materials and SMA wires and the fabrication was based on molding of silicon rubber. The actuator was also characterized by the motion with the body in flexion. We measured several characteristics to investigate a relationship between the bending angle of its body and the actuation. As the results, we confirmed that it was possible to actuate with the body in flexion.
Traditional dynamic hydrogels have been designed to respond to changes in physicochemical inputs, such as pH and temperature, for a wide range of biomedical applications. An emerging strategy that may allow for more specific “bio-responsiveness” in synthetic hydrogels involves mimicking or exploiting nature's dynamic proteins. Hundreds of proteins are known to undergo pronounced conformational changes in response to specific biochemical triggers, and these responses represent a potentially attractive toolkit for design of dynamic materials. This “emerging area” review focuses on the use of protein motions as a new paradigm for design of dynamic hydrogels. In particular, the review emphasizes early examples of dynamic hydrogels that harness well-known protein motions. These examples then serve as templates to discuss challenges and suggest emerging directions in the field. Successful early examples of this approach, coupled with the fundamental properties of nature's protein motions, suggest that protein-based materials may ultimately achieve specific, multiplexed responses to a range of biochemical triggers. Applications of this new class of materials include drug delivery, biosensing, bioactuation, and tissue engineering.
Although the technological and scientific importance of functional polymers has been well established over the last few decades, the most recent focus that has attracted much attention has been on stimuli-responsive polymers. This group of materials is of particular interest due to its ability to respond to internal and/or external chemico-physical stimuli, which is often manifested as large macroscopic responses. Aside from scientific challenges of designing stimuli-responsive polymers, the main technological interest lies in their numerous applications ranging from catalysis through microsystem technology and chemomechanical actuators to sensors that have been extensively explored. Since the phase transition phenomenon of hydrogels is theoretically well understood advanced materials based on the predictions can be prepared. Since the volume phase transition of hydrogels is a diffusion-limited process the size of the synthesized hydrogels is an important factor. Consistent downscaling of the gel size will result in fast smart gels with sufficient response times. In order to apply smart gels in microsystems and sensors, new preparation techniques for hydrogels have to be developed. For the up-coming nanotechnology, nano-sized gels as actuating materials would be of great interest.
A number of materials have been explored for their use as artificial muscles. Among these, dielectric elastomers (DEs) appear to provide the best combination of properties for true muscle‐like actuation. DEs behave as compliant capacitors, expanding in area and shrinking in thickness when a voltage is applied. Materials combining very high energy densities, strains, and efficiencies have been known for some time. To date, however, the widespread adoption of DEs has been hindered by premature breakdown and the requirement for high voltages and bulky support frames. Recent advances seem poised to remove these restrictions and allow for the production of highly reliable, high‐performance transducers for artificial muscle applications.
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Braided pneumatic artificial muscles, and in particular the better known type with a double helical braid usually called the McKibben muscle, seem to be at present the best means for motorizing robot-arms with artificial muscles. Their ability to develop high maximum force associated with lightness and a compact cylindrical shape, as well as their analogical behavior with natural skeletal muscle were very well emphasized in the 1980s by the development of the Bridgestone “soft robot” actuated by “rubbertuators”. Recent publications have presented ways for modeling McKibben artificial muscle as well as controlling its highly non-linear dynamic behavior. However, fewer studies have concentrated on analyzing the integration of artificial muscles with robot-arm architectures since the first Bridgestone prototypes were designed. In this paper we present the design of a 7R anthropomorphic robot-arm entirely actuated by antagonistic McKibben artificial muscle pairs. The validation of the robot-arm architecture was performed in a teleoperation mode.
The design and analysis of a series of linear actuators based on polymer hydrogel is presented. The actuators use arrays of pH sensitive gel fibers together with a fluid irrigation system to locally and rapidly regulate the composition of the solution. A dynamic model is constructed for one of the linear actuators, which includes the polymer gel, fluidic system, and transmission mechanics. Emphasis in the design and mechanical modeling of the actuators is placed on the com plete system including not only the polymer gel, but also on the containment system, irrigation scheme, and servo valving system.
Actuators, the prime drive unit in any system (biological or mechanical), are responsible for transferring energy in its many forms into mechanical motion that permits interaction with the external environment. The complexity of the organic mechanism has traditionally precluded its emulation, but a demand in robotic and other mechatronic systems for closer human interaction involving safety, redundancy, self-repair and affinity, has highlighted the potential benefits of softness, both in terms of functional and physical behaviour. This is prompting a shift in the traditional design paradigm based on motors–gears–bearings–links to a novel bio-mimetic schema based on muscle–tendon–joint–bone. Among the most fundamental features of actuators designed around this format will be a desire to emulate the performance of natural muscle in forming a safe and natural interaction medium, while still possessing the beneficial attributes of conventional engineering actuators, i.e. high power to weight/volume, high force weight/volume and good positional and force control. In this paper a study has been undertaken of two novel forms of actuators (polymeric and pneumatic Muscle), that have characteristics that can be broadly classified as giving them a range of bio-mimetic functions.The work considers the production, modelling and performance testing of these two forms of bio-mimetic actuators. Enhancements to the performance of both systems are explored to show their capacity for bio-emulation. For the pneumatic Muscle Actuator a practical example is briefly explored to show the potential for real world applications of this technology. Finally a comparison of the relative merits of the ‘muscles’ are made with references to required enhancements, improvements or developments needed for viable future exploitation.
The functioning of natural skeletal muscle is based on microscopic phenomena that no technology is at present able to reproduce. The notion of artificial muscle is as a consequence mainly founded on a macroscopic model of the skeletal muscle. The mimicking of both tension-length and tension-velocity characteristics is aimed at giving future humanoid robots touch ability which is so fundamental in the `relational life' of human beings. No definitive technology has as yet emerged in the design of artificial muscle. It is, however, interesting to note that the most promising ones are based on the use of polymers whose physical properties (responses to chemical or physical agents, elasticity, etc.) mimic some dynamic properties of animal tissues. In particular pH, temperature or electric field are now currently used to produce and control the shape changes of polymer fibres or polymer-based composite materials. These results are generally obtained on a small scale ? typically a mm2-section scale ? and the application of these technologies to macroscopic skeletal muscle scales ? typically a cm2-section scale ? generally induces a performance loose in power-to-volume and power-to-mass. Today the integration of artificial muscles to anthropomorphic limbs on a human-scale in volume and mass, necessitates power-to-mass and power-to-volume very close to human skeletal muscle.. Pneumatic artificial muscles, in the form of McKibben artificial muscles or alternative types such as pleated artificial muscles, are at present able to mimic these natural muscle dynamic properties. As a consequence, we consider that their use is interesting to test control
Braided pneumatic artificial muscles, and in particular the better known type with a double helical braid usually called the McKibben muscle, seem to be at present the best means for motorizing robot- arms with artificial muscles. Their ability to develop high maximum force associated with lightness and a compact cylindrical shape, as well as their analogical behavior with natural skeletal muscle were very well emphasized in the 1980s by the development of the Bridge- stone "soft robot" actuated by "rubbertuators". Recent publica- tions have presented ways for modeling McKibben artificial muscle as well as controlling its highly non-linear dynamic behavior. How- ever, fewer studies have concentrated on analyzing the integration of artificial muscles with robot-arm architectures since the first Bridge- stone prototypes were designed. In this paper we present the design of a 7R anthropomorphic robot-arm entirely actuated by antagonis- tic McKibben artificial muscle pairs. The validation of the robot-arm architecture was performed in a teleoperation mode. KEY WORDS—anthropomorphic robot-arm, artificial mus- cle, McKibben muscle
The increasing understanding of the advantages offered by fish and insect-like locomotion is creating a demand for muscle-like materials capable of mimicking nature's mechanisms. Actuator materials that employ voltage, field, light, or temperature driven dimensional changes to produce forces and displacements are suggesting new approaches to propulsion and maneuverability. Fundamental properties of these new materials are presented, and examples of potential undersea applications are examined in order to assist those involved in device design and in actuator research to evaluate the current status and the developing potential of these artificial muscle technologies. Technologies described are based on newly explored materials developed over the past decade, and also on older materials whose properties are not widely known. The materials are dielectric elastomers, ferroelectric polymers, liquid crystal elastomers, thermal and ferroelectric shape memory alloys, ionic polymer/metal composites, conducting polymers, and carbon nanotubes. Relative merits and challenges associated with the artificial muscle technologies are elucidated in two case studies. A summary table provides a quick guide to all technologies that are discussed.
The McKibben artificial muscle is a pneumatic device characterized
by its high level of functional analogy with human skeletal muscle.
While maintaining a globally cylindrical shape, the McKibben muscle
produces a contraction force decreasing with its contraction ratio, as
does skeletal muscle. The maximum force-to-weight ratio can be
surprisingly high for a limited radial dimension and for a conventional
pressure range. A 50 g McKibben muscle can easily develop more than 1000
N under 5 bar pressure for an external radius varying from about 1.5 to
3 cm. Thus, robotics specialists are interested in this well-adapted
artificial muscle for motorizing powerful yet compact robot arms. The
basic McKibben muscle static modeling developed in the paper, which is
based on the three main parameters (i.e., initial braid angle, initial
muscle length, and initial muscle radius) and includes a three-parameter
friction model of the thread against itself, has shown its efficiency in
both isometric and isotonic contraction
Problems with the control and compliance of pneumatic systems have
prevented their widespread use in advanced robotics. However, their
compactness, power/weight ratio, and simplicity are factors that could
potentially be exploited in sophisticated dextrous manipulator designs.
This paper considers the development of a new high power/weight and
power/volume braided pneumatic muscle actuator (PMA) having considerable
power output potential, combined with controllable motion and inherent
compliance to prevent damage to handled objects. Control of these
muscles is explored via adaptive pole-placement controllers.
Experimental results indicate that accurate position control of 1°
is feasible, with power/weight outputs in excess of 1kW/kg at 200kPa
By chemically stimulating a polyelectrolyte gel (PVA-PAA copolymer) dilation/contraction responses are produced which mimic the actions of natural muscle. This report investigates an artificial muscle pair composed of a flexor and an extensor which under controlled stimulus can provide power for a robot gripper. The response rates of this system are at present slow relative to animal muscle, but scope exists for substantial improvement and with force/area values comparable with natural muscle a new linear direct drive actuator with excellent power/weight ratios is a realistic longterm possibility.
Polelectrolyte gels are synthesized as a structural material for a chemically stimulated muscle-like actuator to be used in a robotic arm. This investigation is undertaken to determine the feasibility of producing a new power system with an excellent power/weight ratio. The static and dynamic mechanical properties of the polymer are studied, especially those affected by crosslinking, component ratio and environmental conditions. Control of the muscular, and circulatory responses under chemical stimulus is investigated and options considered.Comparisons of the relative abilities of natural and artificial muscle are made, with special reference to those properties having a bearing on the use of this type of actuator in robotic applications.
Polyacrylonitrile (PAN) fibers were investigated for their use as “artificial muscle” linear actuators. Basic properties and characteristics of PAN fiber gel were investigated using a single strand (yarn) to define the material as an actuator. Properties of interest include force generation, force–strain behavior, and chemical reactions. Diameter and volume changes were observed as greater than 100% and greater than 1000%, respectively for pH activated systems. For the electrically induced systems the diameter and volume changes were similar though the response time was longer. For the elongated state the mechanical properties were not as strong as those in the contracted state, while also having a decreased flexible elasticity. Also, the amount of H+ present affected the shrinking of the fibers as well as the response time, though the effect decreased after the concentration reached a critical value. Profiles of force development for both the pH driven and electrically actuation systems indicate that single PAN strand fibers of a 100mm length produced an approximate force of 0.1N for both activation methods. Also, a plot of actuation stress versus actuation strain is constructed to map the current PAN actuator technology against other competing actuator technologies.
Stimuli-responsive polyampholyte hydrogels were synthesized by the copolymerization of dimethylaminoethyl methacrylate (DMAA) and acrylic acid (AAc) or itaconic acid (IAc) by UV-irradiation. Temperature and pH responsiveness of these hydrogels were studied. The temperature responsiveness of poly-(DMAA-co-AAc, IAc) hydrogels shown in change of water content became dull compared to that of DMAA homo-polymer hydrogel. The water content of the poly-(DMAA-co-AAc, IAc) hydrogels showed a minimum at pH 8, and increased in more acidic and alkaline regions. This fact can be attributed to the coexistence of anions and cations in the poly-(DMAA-co-AAc, IAc) hydrogels. The poly-(DMAA-co-AAc, IAc) hydrogels were polyampholyte having both temperature responsiveness and pH responsiveness.
Electroelastomers (also called dielectric elastomer artificial muscles) have been shown to exhibit up to 380% electrically-driven strain. Their elastic energy density and power output compare favorably with natural muscles. A variety of actuator configurations have been developed for a variety of important applications including linear actuation, fluidic control, and flat panel speakers. In particular, spring rolls are compact, have a potentially high electroelastomer-to-structure weight ratio, and can be configured to actuate in several ways, including axial extension, bending, and as multiple degree-of-freedom actuators. They combine load bearing, actuation, and sensing functions. Simulation and robot fabrication have produced six-legged robots, using a spring roll as each of the robots' legs, that can run and clear obstacle.
Graft copolymerization of mixtures of acrylic acid (AA) and acrylamide (AAm) onto chitosan was carried out by using potassium persulfate (KPS) as a free radical initiator in the presence of methylenebisacrylamide (MBA) as a crosslinker. The effect of reaction variables, such as MBA concentration and AA/AAm ratio on the water absorbency capacity have been investigated. The polymer structures were confirmed by FTIR spectroscopy. Water absorbencies were compared for the hydrogels before and after alkaline hydrolysis. In the non-hydrolyzed hydrogel, enhanced water absorbency was obtained with increasing AA in monomer feed. However, after saponification, the sample with high AAm ratio exhibited more water absorbency. These behaviors were discussed according to structural parameters. The swelling kinetics of the superabsorbing hydrogels was studied as well. The hydrogels exhibited ampholytic and reversible pH-responsiveness characteristics. The swelling variations were explained according to swelling theory based on the hydrogel chemical structure. The hydrogels exhibited salt-sensitivity and cation exchange properties. The pH-reversibility and on–off switching properties of the hydrogels make the intelligent polymers as good candidates for considering as potential carriers for bioactive agents, e.g. drugs.
A novel natural polymer blend, namely, a semi-interpenetrating polymer network (semi-IPN) composed of crosslinked chitosan with glutaraldehyde and silk fibroin was prepared. The FTIR spectra of the semi-IPN manifested that the chitosan and silk fibroin had a strong hydrogen-bond interaction and formed an interpolymer complex. The semi-IPN showed good pH sensitivity and ion sensitivity. According to the different swelling ratios of the semi-IPN in the buffer solution with different pH values or the AlCl3 aqueous solution with different concentrations, the semi-IPN could swell and shrink while being put alternately into different pH buffer solutions or AlCl3 aqueous with different concentrations. The semi-IPN could also act as an ''artificial muscle'' because its swelling-shrinking behavior exhibited a fine reversibility. q 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2257-2262, 1997
Le gonflement et d??gonflement rapide et accentu?? des copolymers de l'acide m??thacrylique et du divinyl benz??ne dans des solutions aqueuses alcalines et acides ont ??t?? ??tudi??s.
Les ph??nom??nes ressemblent aux contractions et dilatations des syst??mes biologiques.
L'interpr??tation donn??e est bas??e sur l'effet du redressement des cha??nes mol??culaires sous l'influence de la r??pulsion ??lectrostatique des groupes carboxyliques ionis??s, qui se contractent lors de la neutralisation des charges.
Polyvinylalcohol (PVA) hydrogel containing both polyacrylic acids
(PAA) and polyallylamines (PAlAm) has been investigated for some time.
In this report the performances of two kinds of improved materials are
shown. One was made with a very narrow gap mold, and the other by
applying uniaxial stretching during gelation to realize an anisotropic
hydrogel. As a result, thin films of 10-μm thickness have been
realized. These films are able to contract within 0.2 s under loading
from 0 to 2 kg/cm2. The contraction ratio varies depending on
the load from 25% (no load) to 10% (2 kg/cm2). The effect of
anisotropy was found to increase the contraction ratio about 15% in this
case
`Artificial' actuator technologies under development include shape
memory alloys, piezoelectric actuators, magnetostrictive actuators,
contractile polymers and electrostatic actuators. The relevant
properties of muscle are outlined and compared with a variety of
artificial actuators. These and other actuators, such as regular and
superconducting electromagnetic motors, internal combustion engines,
hydraulic motors, pneumatic actuators, are reviewed and compared with
muscle elsewhere (see Hunter, 1990; Hollerbach et al., 1991)
This paper reports mechanical testing and modeling results for the McKibben artificial muscle pneumatic actuator. This device, first developed in the 1950's, contains an expanding tube surrounded by braided cords. We report static and dynamic length-tension testing results and derive a linearized model of these properties for three different models. The results are briefly compared with human muscle properties to evaluate the suitability of McKibben actuators for human muscle emulation in biologically based robot arms.
Artificial muscles for humanoid robots, chap. 5, in: Humanoid Robots-Human like Machines
- B Tondu
B. Tondu, Artificial muscles for humanoid robots, chap. 5, in: Humanoid Robots-Human like Machines, Advanced Robotics Books, Vienna, Austria, 2007, pp.
90-122.
Reflections on Muscle
- A F Huxley
A.F. Huxley, Reflections on Muscle, Princeton University Press, Princeton, NJ,
USA, 1980.
pH sensitivity and ion sensitivity of hydrogels based on complex-forming chitosan/silk fibroin interpenetrating polymer network
- Chen