Artificial muscles are man-made materials that try to reproduce the two main characteristics of real muscle fibers, namely, elasticity and contractility. They respond to various external stimulations (ion concentration, electric field, temperature, light etc.) by a significant shape or size change. In addition to classical materials such as piezoelectric ceramics and shape memory alloys, polymer-based artificial muscles have become the most important muscle-like materials since the 1990s [1]. They offer operational similarity to biological muscles in response to external stimulation. They are resilient and damage tolerant and they exhibit large actuation strains (stretching, contraction, or bending). Many new polymer materials/approaches are under active investigation, including ferroelectric polymers, dielectric elastomers, liquid crystal (LC) elastomers and gels, ionic polymer gels, ionomeric polymer-metal composites,

conductive polymers, and carbon nanotubes [1 and references therein]. In addition to the obvious attractiveness of such studies in basic science, artificial muscle systems have many potential applications of great interest, including serving as the materials foundation for fabrication of sensors, microrobots, micropumps, and actuators with combinations of size, weight, and performance parameters beyond those currently achievable. One remarkable advantage of these systems is that they offer the possibility of driving micromachines and nanomachines without the aide of motors and gears.