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The subject of this book is the current comprehensive research and development of soft actuators, and encompasses interdisciplinary studies of materials science, mechanics, electronics, robotics and bioscience. As an example, the book includes current research on actuators based on biomaterials to provide future perspectives for artificial muscle technology. Readers can obtain detailed, useful information about materials, methods of synthesis, fabrication and measurements. The topics covered here not only promote further research and development of soft actuators but also lead the way to their utilization and industrialization. One outstanding feature of the book is that it contains many color figures, diagrams and photographs clearly describing the mechanism, apparatus and motion of soft actuators. The chapter on modeling is conducive to more extensive design work in materials and devices and is especially useful in the development of practical applications. Readers can acquire the newest technology and information about the basic science and practical applications of flexible, lightweight and noiseless soft actuators, which are quite unlike conventional mechanical engines and electric motors. The new ideas offered in this volume will provide inspiration and encouragement to researchers and developers as they explore new fields of applications for soft actuators.





Chapter 1. Progress and Current Status of Materials and Properties of Soft Actuators

In this chapter, brief history and current status of soft actuators made of various materials driven by different stimuli are described with typical references as milestones of the progress. The soft actuators originated from unique characteristics of cross-linked polymer gels for understanding their physical and chemical properties of dimensional changes and phase transitions induced by various environmental stimuli such as pH, salt, solvent, heat, light, and electric field. The ‘explosion’ of research and development of soft actuators in the 1990s extended over a variety of materials such as conductive polymers, elastomers, carbon nanotubes, and biomaterials, which had driven further progress in soft actuators not only from the fundamental viewpoint of basic science and materials chemistry and physics but also from the engineering viewpoint for the practical applications to light-weight, low-cost, no-noise, less-pollution, and high-efficiency micro- and macro-artificial muscles and soft robotic systems.

Hidenori Okuzaki

Chapter 2. Current Status of Applications and Markets of Soft Actuators

In this chapter, the current status of applications and markets of soft actuators will be described with reference to some published patents in the expected application fields.

Kinji Asaka, Kayo Nakamura

Materials of Soft Actuators: Thermo-Driven Soft Actuators


Chapter 3. Electromagnetic Heating

In this study, we demonstrated the surface modification of carbon microcoil (CMC) with grafting polymers onto the CMC and prepared composite material of poly(


-isopropyl acrylamide) (PNIPAM) gel as thermo-sensitive polymer gels by electromagnetic heating. The properties of the material such as content of carbon micro-coils, swelling ratio, breaking strength, and thermo-sensitivity, and its function as drug carrier were evaluated. The composite gels were shrunken with increase of temperature as well as normal PNIPAM gel and responded to electromagnetic waves with the presence of contained CMCs which absorb electromagnetic waves and generate heat. The surface temperature of composite gel was reached 43 °C within 150 s and changed its shape with squeezed water.

Takeshi Yamauchi

Chapter 4. Thermo-Responsive Nanofiber Mats Fabricated by Electrospinning

Copolymers of


-isopropylacrylamide and stearyl acrylate (PNIPA-SA


) with various SA feed ratios (


 = 1–10 mol%) were synthesized and electrospun into nanofiber mats. It was found that average diameter of nanofibers electrospun at concentration of 25 % and voltage of 30 kV linearly increased from 165 nm (PNIPA) to 497 nm (PNIPA-SA10) with increasing the SA content. The PNIPA-SA




 = 3–10 mol%) nanofiber mats were insoluble in water at 25 °C, in which inter-polymer and inter-fiber physical cross-links were formed through hydrophobic interaction of stearyl side-chains. With increasing the temperature from 25 to 40 °C the PNIPA-SA3 nanofiber mat exhibited significant volume contraction of 66 %, while that of a single nanofiber estimated by AFM measurements was found to be 37 %. The results allowed us to conclude that not only swelling-deswelling but also dissociation-association of the nanofibers via hydrophobic interactions were crucially important for the macroscopic volume changes of the nanofiber mats.

Hidenori Okuzaki

Chapter 5. Self-Oscillating Gels

Stimuli-responsive polymer gels and their application to smart materials have been widely studied. On the other hand, as a novel biomimetic gel, we developed gels with an autonomous self-oscillating function like a heart muscle, which was firstly reported in 1996. We designed the self-oscillating gels by utilizing the oscillating reaction, called the Belousov-Zhabotinsky (BZ) reaction which is recognized as a chemical model of the TCA cycle in organisms. The self-oscillating gel is composed of a poly(


-isopropylacrylamide) network in which the metal catalyst for the BZ reaction is covalently bonded. In a closed solution containing the reactants other than the catalyst, the gel undergoes spontaneous cyclic swelling–deswelling changes without any on–off switching of external stimuli. Their potential applications include several kinds of functional material systems, such as biomimetic soft-actuators and autonomous mass transport systems. Here recent progress on the novel polymer gels is introduced.

Ryo Yoshida

Materials of Soft Actuators: Electro-Driven Soft Actuators


Chapter 6. Ionic Conductive Polymers

Electro active polymers (EAPs) are attracting considerable interest due to their special characteristics, including high flexibility and low weight. Ionic conductive polymers have the potential to play a main role in the realization of smart systems for applications such as bio inspired and autonomous robotics, medical devices, and aerospace. Ionic polymer-metal composites (IPMCs) are one of the most promising EAP materials for the artificial muscle-like actuators and sensors. Typical applications of IPMC are soft robotic actuators, since they are suitable for micro actuators in devices used in the human body due to their flexibility and good biological compatibility. In this chapter, the fundamental aspects of the IPMC, i.e., typical fabrication methods, evaluation techniques for testing, recent results of fabrication of miniaturized IPMC, and recent developments of materials of ion conductive polymer actuators are described.

Kunitomo Kikuchi, Shigeki Tsuchitani

Chapter 7. Conducting Polymers

Soft actuators based on conducting polymers are discussed in terms of strain, stress and stability taking the mechanism into consideration. The actuation is generated by the insertion of anions from the electrolyte solution, which is triggered by electrochemical redox reactions. Characteristics of the actuation in polypyrrole, polyaniline, polythiophene, and poly(3,4-ethylenedioxythiophene) (PEDOT) are described. The maximum strain and stress are reported to be 39.9 % and 22 MPa, respectively, in polypyrrole actuator. However, the strain is usually less than 10 %. The stress (contraction force) originates from the elasticity of conducting polymers or Young’s modulus. Creeping under tensile loads, which is intimate issue in soft actuators, is discussed in terms of conformation change of polymer chains and shape memory effect. The actuation generated by sorption and desorption of moisture controlled with electrical heating is also introduced with the mechanism and characteristics.

Keiichi Kaneto

Chapter 8. Humidity-Sensitive Conducting Polymer Actuators

Free-standing films made of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT/PSS) were prepared by casting water dispersion of its colloidal particles. Specific surface area, water vapor sorption, and electro-active polymer actuating behavior of the resulting films were investigated by means of sorption isotherm, and electromechanical analysis. It was found that the non-porous PEDOT/PSS film, having a specific surface area of 0.13 m


/g, sorbed water vapor of 1,080 cm


(STP)/g, corresponding to 87 wt%, at relative water vapor pressure of 0.95. Upon application of 10 V, the film underwent contraction of 2.4 % in air at 50 % relative humidity (RH) which significantly increased to 4.5 % at 90 % RH. The principle lay in desorption of water vapor sorbed in the film due to Joule heating, where electric field was capable of controlling the equilibrium of water vapor sorption. The film generated contractile stress as high as 17 MPa under isometric conditions and work capacity attained 174 kJ/m


, where Young’s modulus of the film increased from 1.8 to 2.6 GPa by application of 6 V at 50 % RH. On the basis of this phenomenon, linear actuators utilizing PEDOT/PSS films were successfully developed and applied to leverage actuator and Braille cell.

Hidenori Okuzaki

Chapter 9. Carbon Nanotube/Ionic Liquid Composites

Both carbon nanotubes and ionic liquids are very attractive materials in the present scientific fields. Recently, we combine these two materials into the polymer matrix to make a conductive electrode film which expands and contracts when alternative square voltages are applied. We utilize these interesting phenomena for electroactive polymer actuators (electric-driven soft actuators). In this chapter, we introduce recent studies for electroactive polymer actuators composed of carbon nanotube/ionic liquid composites and their application potential for a thin and light Braille display as well.

Takushi Sugino, Kenji Kiyohara, Kinji Asaka

Chapter 10. Ion Gels for Ionic Polymer Actuators

Ionic polymer actuators are driven by the migration or diffusion of ions and generally exhibit significant deformation (i.e., bending) under low-voltage (<5 V) applications. However, the durability of conventional ionic polymer actuators decreases under open atmosphere owing to the evaporation of solvents, which are essential for the movement of ions, from the actuators. In order to overcome this drawback, ionic polymer actuators that can be operated under open atmosphere and even under vacuum are being developed using ionic liquids (ILs). Combining macromolecules with ILs as additives can result in highly ion-conducting polymer electrolytes (ion gels) suitable for applications in ionic polymer actuators. However, the contribution of polymeric materials to the high performance of IL-based polymer actuators is yet to be elucidated. In this chapter, IL-based polymer electrolytes comprising block copolymers and polyimides are demonstrated to enable easily processable ionic polymer actuators with high performance and durability. The displacement response is also analyzed using our proposed displacement model.

Masayoshi Watanabe, Satoru Imaizumi, Tomohiro Yasuda, Hisashi Kokubo

Chapter 11. Ionic Liquid/Polyurethane/PEDOT:PSS Composite Actuators

The transparent ionic liquid/polyurethane (IL/PU) gels were synthesized by addition reaction of polyol and diisocyanate in the presence of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. With increasing the IL content from 0 to 40 wt%, both ionic conductivity and electric-double-layer capacitance increased from 3.1 × 10


S/cm and 9.6 pF/cm


to 8.8 × 10


S/cm and 277 pF/cm


, respectively, while the compression modulus slightly decreased from 0.49 to 0.44 MPa. The IL/PU/PEDOT:PSS composites were fabricated by sandwiching the IL/PU gel between two conductive polymer films made of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT:PSS) as soft and flexible electrodes. Upon application of an electric field, the IL/PU/PEDOT:PSS composite showed quick and intensive bending toward anode, where the bending displacement attained 3.8 mm at IL = 40 wt% and 2 V, corresponding to the strain of 0.32 %.

Hidenori Okuzaki

Chapter 12. Dielectric Gels

Dielectric gels of various types are recently found electrically active, and can be used for actuators. Polymer gels swollen with large amount of dielectric solvent deformes by applying dc voltage. The deformation is based on the solvent flow (or ion drag) through the polymer network. They shows contractile, bending, and crawling deformation. Advantages are very swift deformation in air, small electric current, and large strain up to over 10 % depending on the degree of crosslinks among the polymer chain. Disadvantages are low durability because of the solvent bleed-out, and relatively high voltage.

Dielectric elastomers (sometime gel-like) can be good candidate when the polymer chains are flexible enough and sensitive enough to the electric field, although flexible polymer chains can not take the rolle of solvents. Similarity to the gel is that the electrically induced asymmetric charge distribution causes the bending deformation. Advantages of this system are low electric current, relatively swift deformation at high voltage, and good durability. Disadvantages of this system are requirement of high voltage, small strain, and basically very limited stress. For attaining large strain, very high voltages are necessary for the actuation such as over 10 kV/mm. We show the cases of polyurethane and poly(methyl methacrylate-b-n-butyl acrylate-b-methyl methacrylate) triblock copolymer.

Plasticized polymer system provides another possibility, and we think at this moment the best candidate from the viewpoint of easy processing and variable possibilities. Polymers with large content of plasticizer (we call this category as “polymer gel” in stead of plasticized polymer) shows peculiar deformation such as amoeba-like creep deformation. In some cases, we investigated the gels show high power, high toughness, very low current, and variable application possibilities. The characteristics comes out from the very large dielectric constant from the cooperative interaction between the polymer and plasticizer both of which have very low dielectric constant. By applying the characteristic properties, not only the electro-mechanical function but also the electro-optical functions and mechano-electric functions are found.

Through these investigations, we could conclude the dielectric gels have great possibilities as novel type of electro-active materials.

Toshihiro Hirai

Chapter 13. Dielectric Elastomers

Electroactive polymer transducers have many features that are desirable for various devices. An especially attractive type of electroactive polymer is dielectric elastomer.

Dielectric elstomer, based on the field-induced deformation of elastomeric polymers with compliant electrodes, can produce a large strain response, a fast response time and high electromechanical efficiency. This unique performance, combined with other factors such as low cost, suggests many potential applications, a wide range of which are under investigation. Applications that effectively exploit the properties of dielectric elastomers include artificial muscle actuators for robots; low-cost, lightweight linear actuators; solid-state optical devices; diaphragm actuators for pumps and smart skins; acoustic actuators; and rotary motors. Dielectric elastomers may also be used to generate electrical power from mechanical deformation.

Seiki Chiba

Chapter 14. Development of Actuators Using Slide Ring Materials and Their Various Applications

Recently, the driving source with excellent lightweight properties and silence is requested. Therefore, a variety of polymer actuator is actively researched and developed. Polymer dielectric actuator shows an excellent characteristic in the response and the energy efficiency in these actuator. However,dielectric actuator has the fault with high drive voltage. To overcome this fault, a novel polymeric material (slideringmaterial) was adopted. Moreover,we made the artificial arm that moved with dielectric actuator.

Hiromitsu Takeuchi

Chapter 15. Piezoelectric Polymers

The study of the piezoelectric polymers has advanced in the last few decades, and their practical application to sensor and actuator devices has progressed. The piezoelectric polymers in practical use are divided into the following classes with different piezoelectric characteristics: chiral polymers (optically active polymers), ferroelectric polymers, and cellular electrets. The piezoelectricity of a chiral polymer is in response to shear strain, that of a ferroelectric polymer is in response to tensile strain, and that of cellular electrets is in response to strain perpendicular to film surface. In this chapter, the fundamental properties and applications of these different types of polymers are systematically discussed.

Yoshiro Tajitsu

Materials of Soft Actuators: Light-Driven Soft Actuators


Chapter 16. Spiropyran-Functionalized Hydrogels

Photoresponsive actuators composed of a hydrogel functionalized with spiropyran are described. The hydrogel exhibits drastic shrinking in rapid response to blue light irradiation in acidic aqueous systems, and is examined for the application of several photoresponsive actuator systems. Rod-like hydrogel bends drastically after 1 s light irradiation, and microrelief is formed instantly on the hydrogel sheet by the micropatterned light irradiation. Based on these characteristics of the hydrogel, a photo-controllable microfluidic system is constructed with a hydrogel sheet, and the microchannels with arbitrary width, height and pathway are formed instantly by the micropatterned light irradiation. Also independent and parallel control of microvalve array by local light irradiation is demonstrated for a similar microfluidic system combined with fixed microchannel.

Kimio Sumaru, Toshiyuki Takagi, Shinji Sugiura, Toshiyuki Kanamori

Chapter 17. Photomechanical Energy Conversion with Cross-Linked Liquid-Crystalline Polymers

Cross-linked liquid-crystalline (LC) polymers with a photochromic moiety show photoinduced deformation with change in molecular shape and alignment of photochromic compounds. Molecular-level photoisomerization of the photochromic moieties can give rise to macroscopic deformation of the materials, allowing one to convert light energy directly into mechanical work. The photomechanical effects extend the applicability of azobenzene-containing polymers towards light-driven actuators and artificial muscles. Recently, the effect of structure–property relationships and crosslinking density on the photomechanical property of photochromic polymers was investigated. Various motions based on the photoinduced deformation of the LC polymers were achieved by forming the polymer materials. This chapter summarizes the recent progress in photoinduced movements and light-driven actuation property of the LC polymers, in particular cross-linked LC polymers with a photochromic property.

Jun-ichi Mamiya

Chapter 18. Photoredox Reaction

A photoelectrochemical actuator based on poly(acrylic acid) gel loaded with TiO


nanoparticles and copper(II) ions swells in a water-ethanol mixed solution under ultraviolet (UV) light due to photocatalytic reduction of copper(II) to copper(0) nanoparticles and oxidation of ethanol. After removal of UV light, the hydrogel gradually shrinks again due to aerobic oxidation of copper nanoparticles to copper(II) ions. A photoelectrochemical actuator based on poly(acrylic acid) gel loaded with TiO


nanoparticles and silver(I) ions also swells in water under UV light due to photocatalytic reduction of silver(I) to silver(0) nanoparticles and oxidation of water. The hydrogel shrinks again under visible light due to re-oxidation of silver nanoparticles to silver(I) ions and reduction of oxygen molecules by the plasmon-induced charge separation. Partial swelling and shrinking of the hydrogel are also possible.

Tetsu Tatsuma

Materials of Soft Actuators: Magneto-Driven Soft Actuators


Chapter 19. Magnetic Fluid Composite Gels

Polymer gels in which magnetic fluid is immobilized have been considered as a possible candidate of useful actuators or sensors. Particularly, remote actuation is possible without any harmful damage to the body in medical actuation. This means the system can also be applied for energy harvesting system, too. In this chapter the author summarize the some characteristics of magnetid fluid (or ferrofluid) which implies super paramagnetic property. Then the immobilization of these material in polymer gels, and the structural changes induced in the magnetic gels by applying magnetic field or gradient of magnetic field. Some applications of these gels are introduced in the last section.

Toshihiro Hirai

Chapter 20. Magnetic Particle Composite Gels

Magnetic soft materials containing solid state magnetic particles demonstrate various motions and magnetorheological behavior in response to magnetic fields. When a rotational magnetic field is applied to magnetic gels containing with magnetized particles, the magnetic gels exhibit rotational motion. When a non-uniform magnetic field is applied to magnetic gels, the elongation of magnetic gels is observed. The rotational motion of magnetic gels can be applied to a fluid pump that delivers water in straight and spiral tubes. A bead of magnetic gels loaded with drugs undergoes accelerated drug release depending on the rotation rates. The elongational motion of magnetic gels can be applied to an elongation-contraction actuator or a microvalve. Under uniform magnetic fields, the magnetic gels show variable viscoelastic behavior depending on the field-strength, which is called the magnetorheological effect. The dynamic modulus of magnetic hydrogels increases by two orders of magnitude synchronized with magnetic fields. The magnetorheological effect of magnetic gels can be applied to haptic devices or intelligent dampers. Actuators and magnetorheological effects of magnetic soft materials consisting of solid state magnetic particles are described.

Tetsu Mitsumata



Chapter 21. Molecular Mechanism of Electrically Induced Volume Change of Porous Electrodes

Electroactive soft actuators that make use of the volume change of porous electrodes on applying voltage are recently drawing attention. We discuss the mechanism of the volume change of the porous electrodes on applying voltage by using the Monte Carlo simulation. We show that, when the pore size of the electrode is so small that it is comparable to the size of the electrolyte ions, slight change in the molecular structure or in the external field can drastically change the thermodynamic properties in porous electrodes. The pressure exerted inside the porous electrodes can be two or three orders of magnitude larger than the atmospheric pressure. Those behaviors are explained by the balance between the volume exclusion interaction and the electrostatic interaction.

Kenji Kiyohara, Takushi Sugino, Kinji Asaka

Chapter 22. Material Modeling

Attention has been focused on ionic conducting polymer-metal composites (IPMCs) as intelligent materials for artificial muscles and robotics for recent years. The two-dimensional finite element formulation based on the Galerkin method is conducted for the basic field equations governing electrochemical response of IPMC beams with two pairs of electrodes upon applied electric field. The three-dimensional finite element analysis is conducted for the deformation of IPMC beams due to water redistribution in the beams associated with the electrochemical response. Some numerical studies are carried out in order to show the validity of the present formulation. A computational modeling is also established for the electrochemical-poroelastic behavior of conducting polymers such as polypyrrole. The three-dimensional continuum modeling given by Della Santa et al. for the passive, poroelastic behavior of conducting polymers is extended to the formulation for the active, electrochemical-poroelastic formulation according to Onsager-like laws, which is combined with the one-dimensional equation for ionic transportation. The validity of the finite element formulation for these governing equations has been demonstrated by numerical studies for the passive and active responses of polypyrrole membranes.

Yutaka Toi

Chapter 23. Distributed Parameter System Modeling

This chapter discusses a distributed parameter system modeling of ionic polymer-metal composite actuators based on modified Yamaue’s electro-stress diffusion coupling model. The lowest order linear time invariant state equation with the spatial variable is derived to carry out the simulation. An introductory method for simulation based on the state space model is also shown. The results of the simulation demonstrate the effectiveness of the derived model by showing the differences of the responses for the different cation species.

Kentaro Takagi, Gou Nishida, Bernhard Maschke, Kinji Asaka

Chapter 24. Modeling and Feedback Control of Electro-Active Polymer Actuators

Electro-active polymers (EAPs) are functional polymeric materials which respond to electrical stimuli with shape change. Since EAPs can be activated by the electric field, driving equipments and implementation of control are easily achievable. However, a modeling and a feedback control are needed for practical applications such as a positioning control or a force control with high speed and high precision. In this chapter, we will show the basics of modeling and feedback control methods for ionic polymer-metal composites (IPMCs) from a viewpoint of control engineering. First, general modeling and actuation methods are briefly explained. Then, feedback control methods for output force or deformation are illustrated such as a PID controller, a feed-forward and feedback controller based on an identified model, a servo controller, and a robust PID controller considering uncertainty of the actuator.

Norihiro Kamamichi, Kentaro Takagi, Shigenori Sano

Chapter 25. Motion Design-A Gel Robot Approach

The main focus of this chapter is to propose methods for motion design of deformable machines, using a particular electroactive polymer gel. They are deformable like mollusk that can locomote dynamically or manipulate things softly. Such a machine has been a dream in the past but is now experimentally possible. Mechanisms consisting of the gel, hereafter called ‘gel robots’, were designed, developed, and controlled experimentally. It includes: (1) a mathematical model of the gel to be applied for design and control of distributed mechanisms, (2) gel robots driving systems, (3) control of gel robots for dynamic deformations. This chapter overviews a gel robot approach based on agent model for motion design of deformable robots utilizing electroactive polymers with simulation and experimental results.

Mihoko Otake

Chapter 26. Motion Control

Poly vinyl chloride (PVC) gel actuators show great potential because of such positive characteristics as movement in the air, large deformation, and being lightweight. We propose a configuration of a contraction type actuator and investigate its various characteristics. The contraction strain is 10–15 %, the response frequency is 3–7 Hz and the applied voltage 200–600 V. The generating stress is proportional to the number of layers, and the stress is then about 10 kPa when the actuator height is 10 mm. To use this actuator as a control element, we develop a mathematical model. Based on these results, we develop a position feedback control technique for the actuator and investigate the validity of the control method. The control law included a feed forward term to compensate for the elastic characteristic of the PVC gel actuator. The control method had good performance.

Minoru Hashimoto



Chapter 27. Application of Nano-Carbon Actuator to Braille Display

Ionic electro-active polymer(EAP) actuators based on nano-carbon electrodes, which are comprised of materials such as carbon nano-tubes, ionic liquid and polymer are characterized by their thin, light and low-voltage properties. Alps had developed an ultra-thin and ultra-light Braille display for vision-impaired people utilizing this technology, in collaboration with AIST, Tokyo Univ., and Keio Univ. from fiscal 2009 to 2010, with the support of Ministry of Heath, Labor and Welfare (MLHW), Japan.. In addition, for the purpose of improving the readability of display on the part of vision-impaired people who lost vision later in life, or those with finger paralysis, we developed a Braille display with a latching mechanism to move Braille dots.

Isao Takahashi, Tomomasa Takatsuka, Munemitsu Abe

Chapter 28. Underwater Soft Robots

Two underwater soft robots using ionic polymer-metal composites (IPMCs), a ray-like robot and a quadruped robot, are introduced. For autonomous operation of the ray-like robot, miniaturized electrical devices are developed. A simple traveling wave input is employed to generate the motion of the fin. The propulsion speed of the robot is able to be controlled by the parameters of the traveling wave. In the experiment we observed that the amplitude of the fin increased toward the backward in spite of the uniform control input. This phenomenon may be the key to achieve the energy-efficient swimming of underwater robots by utilizing the elasticity of the actuator. The underwater quadruped robot is developed from a sheet of IPMC of which electrode is segmented into some parts to be controlled independently. We demonstrate the electro-discharge machining (EDM) method is useful to segment the electrode with the minimum damage to the polymer. In the experiment we found by accident that the deformation of the IPMC became gradually large by ion exchange with the copper electrode contact. Finally we show the gait of turtle is effective to control the developed quadruped robot.

Kentaro Takagi, Zhi-Wei Luo, Kinji Asaka

Chapter 29. IPMC Actuator-Based Multifunctional Underwater Microrobots

A variety of microrobots have commonly been used in the fields of biomedical engineering and underwater operations during the last few years. Due to their compact structure, low driving power, and simple control systems, microrobots can complete a variety of underwater monitoring operations, even in restricted underwater environments. Generally speaking, compact structure, multi-functionality, flexibility and precise positioning are considered incompatible characteristics for underwater microrobots. Nevertheless, we have designed several novel types of bio-inspired locomotion, using ionic polymer metal composite (IPMC) and shape memory alloy (SMA) actuators. We reviewed a number of previously developed underwater microrobot prototypes that were constructed to demonstrate the feasibility of these types of biomimetic locomotion. Based on these prototypes, we summarized the implemented techniques and available results for efficient and precise underwater locomotion. In order to combine compact structure, multi-functionality, flexibility and precise positioning, we constructed a prototype of a new lobster-like microrobot and carried out a series of experiments to evaluate its walking, rotating, floating and grasping motions. Diving/surfacing experiments were performed by electrolyzing the water around the surfaces of the actuators. Three proximity sensors were installed on the microrobot to detect an object or avoid an obstacle while walking.

Shuxiang Guo, Liwei Shi

Chapter 30. Medical Applications

Current applications of soft actuators in medical fields are discussed. Included here are polymer, elastomer, and gel actuators along with biocompatibility issues. The applications expands to a wide range of medical devices: artificial muscles, muscle alternatives, prosthetic devices, catheters, stents and surgical instruments. With the nature of medical applications, shown here are not only from articles but from many patent documents.

Tadashi Ihara

Chapter 31. Micro Pump Driven by a Pair of Conducting Polymer Soft Actuators

Micro pumps are regarded as key components of many MEMS devices. They are widely used in the fluid operations systems of fields ranging from chemistry and biotechnology to mechanical engineering. The micro pumps developed to present generally incorporate piezoelectric-element, thermopneumatic, electrostatic, electromagnetic, electroosmotic, electromagnetic-fluid, and various other drives, but along with their reduced size they have increased in component number and structural complexity. The conducting polymer soft actuator based on polypyrrole opens widely and closes completely as a result of electrochemical oxidation and reduction, respectively. The opening and closing movement of the soft actuator, inside which the cation-driven layer is arranged, becomes large because the anion-driven layer that is arranged outside is the predominant driver. We developed a micro pump that is driven by a pair of conducting polymer soft actuator based on polypyrrole and clarified the fundamental characteristics and transport mechanism of the micro pump. The proposed micro pump can transport fluids unidirectionally without backflow by means of a pair of conducting polymer soft actuators that open and close. Furthermore, a wider range of flow rates and a greater maximum delivery head was obtained with the proposed micro pump. The energy consumption rate of the proposed micro pump is dramatically lower than the energy consumption rates of conventional micro pumps because the conducting polymer soft actuator can be driven with a low voltage.

Masaki Fuchiwaki

Chapter 32. Elastomer Transducers

Dielectric elastomers, transducers that couple the deformation of a rubbery polymer film to an applied electric field, show particular promise with features such as simple fabrication in a variety of size scales, high strain and energy density, high efficiency and fast speed of response, and inherent flexibility, environmental tolerance, and ruggedness. A variety of actuator configurations has been demonstrated at various size scales including rolled “artificial muscle” actuators, framed and bending beam actuators for efficient opto-mechanical switches, and diaphragm and thickness mode actuators for pumps and valves. The performance benefits of dielectric elastomers can allow for new generations of devices in microrobotics, communications, and biotechnology.

Dielectric elastomer has also been shown to operate in reverse as a generator. It has several characteristics make it potentially well suited for power takeoff systems using wave, water current, wind, human motion, etc.

Mikio Waki, Seiki Chiba

Next-Generation Bio-Actuators


Chapter 33. Tissue Engineering Approach to Making Soft Actuators

Recent innovation in the tissue engineering makes it real to construct the biological organ and tissue in vitro using proteins and living cells. This technology is not only for the regeneration of patients’ organ and tissue but also for the actuation of any artificial machine. The living muscles driven by the activation of actin-myosin molecular motors transform biochemical energy of ATP into mechanical energy. They have excellent characteristics of lightweight, high flexibility, and remarkable efficiency for energy conversion compared to the mechanical actuators that require electricity as a power source. Therefore, a muscle cell-based bio-hybrid actuator termed bio-actuator has the potential of being flexible and highly efficient on a micro to macro scale. The aim of this chapter is to describe the bio-actuator made of cultured skeletal muscle cells in vitro based on our investigation. There are still several issues to be solved for getting large and powerful bio-actuator which works long term with proven reliability, however it must be done in the near future by intensive studies of vigorous tissue-engineers.

Toshia Fujisato, Shunya Takagi, Tomohiro Nakamura, Hiroshi Tsutsui

Chapter 34. ATP-Driven Bio-machine

Biomolecular motor systems

microtubule/kinesin, actin/myosin are constituent components of biological power unit, which can perform mechanical work by converting chemical energy obtained from hydrolysis of adenosine triphosphate (ATP). The biomolecular motors are organized into highly complex and ordered structures as observed in muscle, stress fiber, contractile ring which exhibit various functions. Performance of these natural machines are much attractive compared to man-made machine. Therefore, to utilize the advantage of these natural machines biological motors have been proposed as the building blocks of



driven bio



. In this chapter, different methodologies for designing biomolecular motor based bio-machines through non-equilibrium self-organization process are described.

Daisuke Inoue, Arif Md. Rashedul Kabir, Kazuki Sada, Jian Ping Gong, Akira Kakugo

Chapter 35. Employing Cytoskeletal Treadmilling in Bio-Actuator

In this chapter, we describe treadmilling bio-actuators. The principle of treadmilling actuator is, filamentous protein complex formation by actin or tubulin accompanying a sequence of nucleotide triphosphate hydrolysis is to alter the critical concentration of polymerization at the two ends of the filament. Recently, we have succeeded in the creation of hydrogels which autonomously oscillate owing to the treadmilling of actin or tubulin. These hydrogels have great potential as bio-actuators because they are easy to make on a centimeter scale.

Ken-Ichi Sano, Ryuzo Kawamura, Yoshihito Osada


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