The following protocol describes the experimental steps used to prepare arrayable and label-free biological sensors that are based on the fluorescence unquenching of DNA hairpins immobilized on metal surfaces. This two-part protocol describes both the creation of gold-coated substrates and the oligonucleotide surface self-assembly process that transforms the substrates into reporters for detecting DNA. Using this procedure, one can create sensors for oligonucleotides that are highly sensitive and have demonstrated an exceptional specificity to single nucleotide polymorphisms. From start to finish, the entire procedure can be accomplished in 24–30 h.