Metamaterialsareartificialcompositematerialsengineeredtohavepropertiesthatmaynotbefoundinnature.Byexploringlocallyresonanteffectofthebuildingunits,elasticmetamaterialsareabletopossessnegativevaluesofeffectivemass,effectivebulkorshearmodulus.Mass-springandcontinuummaterialversionsoftheseelasticmetamaterialsarereportedandthephysicalmechanismsofnegativeeffectiveparametersaredemonstrated.Applicationsofmetamaterialstoacousticcloakingandsuperlensingarealsodiscussed.
