The　key　first　step　in　developing　bacterial　infections　related　to　implants　and　medical　devices　is　the　attachment　of　planktonic　bacterial　cells,　and　subsequent　formation　of　biofilms.　Herein,　it　is　reported　that　graphene,　a　2D　carbon-based　material,　can　be　effectively　used　to　prevent　bacterial　attachment.　The　key　parameter　for　this　effect　is　the　orientation　of　graphene　with　respect　to　the　coated　surface.　Chemical　vapor　deposition　(CVD)　graphene,　deposited　horizontally　on　the　surface,　exhibits　no　antibacterial　effect.　By　contrast,　an　array　of　graphene　flakes　grown　perpendicularly　to　the　surface　by　a　plasma-enhanced　CVD　(PECVD)　process　prevent　biofilm　formation.　Electron　microscopy　reveals　that　the　exposed　edges　of　vertically　aligned　graphene　flakes　penetrate　the　bacterial　membrane　and　drain　the　cytosolic　content.　Bacteria　are　not　able　to　develop　resistance　to　this　killing　mechanism　during　multiple　exposures.　By　keeping　the　height　of　the　vertical　graphene　coating　between　60　and　100　nm,　the　coating　is　able　to　effectively　kill　bacteria,　while　being　completely　harmless　to　mammalian　cells.