Artificial muscle electrically activated

The model of electric field-controlled artificial muscles has been described in 1972 [5], Fragala et al. fabricated an electrically activated artificial muscle system which uses a weakly acidic contractile polymer gel sensitive to pH changes. The pH changes are produced through electrodialysis of a solution. The response of the muscle as a function of pH, solution concentration, compartment size, certain cations, and gel fabrication has been studied. The relative change in length was about 10%, and the tensile force was 1 g/0.0025 cm2 under an applied electric field of 1.8 V and 10 mA/cm2. It took 10 min for the gel to shrink. 

Hirai T., Zheng J., Watanabe M., Electrically active polymer materials - application of non-ionic polymer gel and elastomers for artificial muscles in Tao X. (ed.) Smart Fibres, Fabrics and Clothing, Woodhead Publishing, Cambridge. 2001. 

Today the number of electroactive polymers has grown substantially. There currently exists a wide variety of such materials, ranging from rigid carbon-nanotubes to soft dielectric elastomers. A number of reviews and overviews have been prepared on these and other materials for use as artificial muscles and other applications [1, 2, 7, 10, 11, 13-28]. The next section will provide a survey of the most common electrically activated EAP technologies and provide some pertinent performance values. The remainder of the paper will focus specifically on dielectric elastomers. Several actuation properties for these materials are summarized in Table 1.1 along with other actuation technologies including mammalian muscle. It is important to note that data was recorded for different materials under different conditions so the information provided in the table should only be used as a qualitative comparison tool. 

Perhaps the most transparent (to the user) artificial arms are the ones that use electrical activity generated by the muscles remaining in the stump to control the actions of the elbow, wrist and hand [Stein et al., 1988]. This electrical activity is known as myoelectricity, and is produced as the muscle contraction spreads through the muscle. Note that these muscles, if intact, would have controlled at least... 

Boyack, J., Enos, J., Lalone, A., Fragala, A. Development of an Electrically Activated Artificial Muscle System (1970)... 

Schreyer, H., Gebhart, N., Kim, K. and Shahinpoor, M. (2000) Electrical activation of artificial muscles containing polyacrylonitrile gel fibers. Biomacromolecules, 1, 642-7. 

Mojarrad have been experimenting with various chemically active as well as electrically active ionic polymers and their metal composites as artificial muscle actuators. 

Shahinpoor, M. "Active Polyelectrolyte Gels as Electrically-Controllable Artificial Muscles and Intelligent Network Structures,", Book Paper, in Active Structures, Devices and Systems, edited by H.S. Tzou, G.L. Anderson and M.C. Natori, World Science Publishing, Lexington, Ky., (1995)... 

Electrically active polymer materials -application of non-ionic polymer gel and elastomers for artificial muscles... 

Shahinpoor, M. In Electrically-Activated Artificial Muscles Made with Liquid Crystal Elastomers-, BarCohen, Y., Ed. Smart Structures and Materials 2000 Conterence, Newport Beach, CA, 05-09 March 2000 SPIE-International Society tor Optical Engineering Newport Beach, CA pp 187-192. 

Practical inputs typically come from muscular activity, (1) directly, (2) indirectly through joints, and (3) indirectly from by-products of muscular contraction (myoelectricity, myoacoustics, muscle bulge, and mechanical/electrical impedance). Although signals can be obtained from brain waves, voice, feet, eyes, and other places, these sources of control have not been shown to be practical for artificial limb control (Childress 1992). 

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