Systems and methods for measuring nanometer level binding reactions are described herein. In some embodiments, the disclosed subject matter is directed to a device comprising (a) a substrate having a surface and (b) an ordered array of posts, pits, or patches over the surface, wherein the posts, pits, or patches are capable of binding a protein or small molecule ligand, and wherein the pitch between adjacent posts, pits, or patches is less than about 100 nm. In some other embodiments, the disclosed subject matter is also directed to methods for identifying the presence of an analyte in a fluid and to methods for measuring relative binding specificity or affinity between an analyte in a fluid and the posts, pits, or patches, using the device of the disclosed subject matter.