An apparatus and method for making coiled and buckled electrospun fiber including (a) providing a solution of a polymer in an organic solvent and a device for electrospinning fiber; b) subjecting the polymer solution to an electric field such that at least one fiber is electrospun; (c) subjecting the so formed fiber to electrical bending and mechanical buckling instability to hereby form a coiled and buckled fiber; (d) collecting the at least one fiber on a collector, such that a fiber structure is produced.