Surface modification techniques that create surfaces capable of killing adherent bacteria are promising solutions to infections associated with implantable medical devices. Antimicrobial peptoid oligomers (ampetoids) that were designed to mimic helical antimicrobial peptides were synthesized with a peptoid spacer chain to allow mobility and an adhesive peptide moiety for easy and robust immobilization onto substrates. TiO2 substrates were modified with the ampetoids and subsequently backfilled with an antifouling polypeptoid polymer in order to create polymer surface coatings composed of both antimicrobial (active) and antifouling (passive) peptoid functionalities. Confocal microscopy images show that the membranes of adherent E. coli were damaged after 2 h exposure to the modified substrates, suggesting that ampetoids retain antimicrobial properties even when immobilized onto substrates.