Ionic polymer–metal composites (IPMCs) are synthetic composite nanomaterials that display artificial muscle behavior under an applied voltage or electric field. IPMCs are composed of an ionic polymer like Nafion or Flemion whose surfaces are chemically plated or physically coated with conductors such as platinum or gold. Under an applied voltage, ion migration and redistribution due to the imposed voltage across a strip of IPMCs result in a bending deformation. Also, IPMCs can be ionic hydrogel which is being immersed in an electrolyte solution and connected to the electric field indirectly.