Artificial Muscles
“There has been considerable effort to develop human-made actuator materials that can mimic muscle performance. The developmental goal is to generate large mechanical actuation induced by external stimuli such as electric field, temperature, and light. Many materials and approaches have been developed towards this goal including hydrogels, dielectric elastomers, shape memory polymers, conducting polymers, carbon nanotubes, and ferroelectric liquid crystal elastomers. However, there are few that come close to meeting the properties of natural muscle. For instance, hydrogels show a very large volume change. The drawback is a low modulus and speed. On the other hand, electrostrictive materials have demonstrated a very fast response rate, but a high voltage is required.”
(Naciri et of the US Navy, US Patent 7,794,834, 9/14/2010)
Electroactive Polymers
Implants
Medicine
Recent US Patents
9/14/2010
7,794,834
Nematic elastomer fiber with mechanical properties of a muscle
Nacri et al of the US Navy have developed a fiber having a polymeric backbone with a liquid crystalline side group and a crosslinking side group, both bonded to the backbone. Uniaxial contraction of the material can be achieved in the fiber through the nematic to isotropic phase transition. The backbone of the copolymer may be, but is not limited to, polyacrylic, polysiloxane, or polynorbornene. When the fiber is made, the liquid crystalline side groups may have orientational order. When a stimulus such as thermal, electrical, or photo is applied to the fiber, these side groups can become substantially reoriented or disordered. This can have the effect of changing the dimensions of the fiber, such as shortening the length of the fiber. The nematic elastomers can be drawn into well-oriented fibers which can exhibit muscle-like physical properties with an elongation Up to 35% and blocked stress of 450 kPa very similar to that of skeletal muscles. (RDC 11/19/2010)
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