structure (1) comprising an antimicrobial surface (2) on a substrate (3), the antimicrobial surface comprising a plurality of nanostructures (4), each nanostructure (4) comprising:i. a nanopillar (5) on the substrate, the nanopillar (5) having a height (H), andii. a head (6) covering a distal end (7) and at least part of the height (H) of the nanopillar (5).