Movement, artificial muscles

Future direction of gel robots includes polymer robots assisting human with physical interaction muscle suits wrapping around the elders or athletes to support their movements. Artificial muscles will be used for such systems when strength and durability of artificial muscles improve in the future, although existing personal robots and muscle suits are driven by motors or rubber actuators. This study contributes to design and control artificial muscle suits with small numbers of electric wires which enable dexterous and dynamic motions. 

Figure 20. Artificial muscle under work. In reduction (A) electrons are injected into the polymer chains. Positive charges are annihilated. Counter-ions and water molecules are expelled. The polymer shrinks and compaction stress gradients appear at each point of the interface of the two polymers. The free end of the bilayer describes an angular movement toward the left side. (B) Opposite processes and movements occur under oxidation. (Reprinted from T. F. Otero and J. Rodriguez, in Intrinsically Conducting Polymers An Emerging Technology, M. Aldissi, ed., pp. 179-190, Figs. 1,2. Copyright 1993. Reprinted with kind permission of Kluwer Academic Publishers.)...

Figure 25. Movement rate of bilayer devices (along an angle of 90°) with different dimensions (different polypyrrole weights) versus applied electrical current per mass unit (mA mg ). (Reprinted fromT. F. Otero and J. M. Sansinana, Bilayerdimensions and movement of artificial muscles. Bioelectrochem. Bioener-genetics 47, 117, 1997, Fig. 4. Copyright 1997. Reprinted with permission from Elsevier Science.)...

We are able to construct mechanical arms that reproduce movements quite close to those performed by the human arm. The problem in implanting these arms is that movements have to be coordinated with all the other body movements under the brain s direction. There is one possibility for connecting the electronic systems of the artificial arm to the nervous signals (Fig. 33) coming from the brain in order to obtain coordinated movements separate those signals into different components and amplify every component to drive an artificial muscle or electric motor. 

Theoretical models available in the literature consider the electron loss, the counter-ion diffusion, or the nucleation process as the rate-limiting steps they follow traditional electrochemical models and avoid any structural treatment of the electrode. Our approach relies on the electro-chemically stimulated conformational relaxation control of the process. Although these conformational movements179 are present at any moment of the oxidation process (as proved by the experimental determination of the volume change or the continuous movements of artificial muscles), in order to be able to quantify them, we need to isolate them from either the electrons transfers, the counter-ion diffusion, or the solvent interchange we need electrochemical experiments in which the kinetics are under conformational relaxation control. Once the electrochemistry of these structural effects is quantified, we can again include the other components of the electrochemical reaction to obtain a complete description of electrochemical oxidation. 

Rasmussen L (2007) Electrically driven mechanochemical artificial muscle for smooth 3-dimensional movement in robotics and prosthetics. Proc SPIE 6524 652423-1-652423-7. 

T.F. Otero and M.T. Cortes, Artificial muscle movement and position control. Chem. Comm., (3), 284-285 (2004). 

Actuators that generate movements and forces, such as bending, expansion and contraction driven by stimulation of electrical, chemical, thermal and optical energies, are different from rotating machines such as electric motors and internal combustion engines. There are many sorts of soft actuators made of polymers [1-3], gels [4] and nanotubes [5]. Particularly, biomimetic actuators are interesting because of the application to artificial muscles that will be demanded for medical equipment, robotics and replacement of human muscle in the future. 

Otero, T.F., and J.M. Sansinena. 1997. Bilayer dimensions and movement in artificial muscles. Bioelectrochem Bioenerg 42 117. 

Otero, T.E, J.M. Sansinena, H. Grande, and J. Rodriguez. 1995. Artificial muscles Electrical current influence on bilayer movement. Port Electrochim Acta 13 499. 

Otero, T.F. and M.T. Gortes. 2004. Artificial muscles Movement and position control. Chem... 

The oxidation of the CP film promotes the inclusion of electrolyte into the film which causes swelling and anticlockwise bending. The reduction of the film induces the expulsion of electrolyte and therefore the device bends in the clockwise direction. In these systems, a conductive counter electrode is required to allow the current flow and generate electrochemical reaction that causes the volume change of the CPs. Valero et al. describe a PPy-dodecylbenzenesulfonate-qjerchlorate/tape bilayer artificial muscle with reversible movements through subsequent oxidation and reduction of the PPy layer [97]. Figure 13.10 shows pictures of the clockwise movement of this artificial muscle due to PPy oxidation (a) and the counterclockwise movement due to reduction (c). 

FIGURE 13.10 Bilayer artificial muscle with (a) clockwise movement caused by PPy shrinkage during oxidative processes, (b) neutral state of PPy and angle described, and (c) counterclockwise movement caused by PPy expansion during reductive processes. Reprinted with permission from [97]. Copyright 2011 Elsevier. 

Otero, T. R Sansinena, J. M. BUayer dimensions and movement in artificial muscles. Bioelectrvchem. Bioenerg. 1997,42, 117-122. 

Valero, L. Arias-Pardilla, J. Cauich-Rodrfguez, J. Smit, M. A. Otero, T. R Characterization of the movement of polyp5UTole-dodecylbenzenesulfonate-perchlorate/tape artificial muscles. Faradaic control of reactive artificial molecular motors and muscles. Electrochim. Acta 2011,10, 3721-3726. 

Changes in volume occurring in polypyrrole during switching have been applied to the fabrication of microactuators and artificial muscles. These systems act as electrochemopositioning devices, with their movements controlled by the applied electrical potential [194,195]. Films of great structural homogeneity are required for this purpose, in order to enhance conformational movements. 

The intercalation of dopants to conducting polymer chains leads to an increase in volume of up to 30 % [8], This property is used in actuators (polymer-based artificial muscles). Bilayer structure of polypyrrole-based anode and cathode is a simple model. At anode, p-doping of polymer occurs to swell, while the other side shrinks because of the expulsion of counterions. This volume changes promote a bend of the layers. The change of poles cancels the volume changes and gives rise to the movement in the opposite direction. 

The application of muscle to voluntarily control movement and allow locomotion in its various forms is fundamental to animal life and an essential distinguishing feature between animals and plants. One type of animal - humans - seems inherently fascinated by the challenge to emulate nature, and various different types of artificial muscles have been introduced over the past several decades. Some of these different artificial muscle materials can produce muscle-like performances that match, and even exceed in some cases, the performance of natural muscle. As a result of this work, we are getting closer to simultaneously reproducing muscle performance in all of its key attributes force, movement, speed, efficiency, and scalability. 

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