a method of manufacturing nanostructures on a surface of a metal substrate is provided . the method includes forming the nanostructures by a forming step , which includes subsequently performing at least once the steps of anodizing the surface at a second voltage for forming at the surface a second oxidized metal layer comprising second pores , and performing an etching step on the surface for modifying the dimensions of the second pores . prior to the forming step , the method comprises a substrate preparation step for enabling the forming a mix of different sized nanostructures during the forming step , the preparation step including the steps of anodizing the surface at a first voltage for forming at the surface an first oxidized metal layer comprising first pores , selectively etching the surface for extending the first pores into the metal underneath the first oxidized metal layer , and removing the first oxidized metal layer .