Substrates having nucleic acid polymers attached at varying surface densities and methods for creating substrates having nucleic acid polymers attached at varying surface densities are provided. Methods according to embodiments of the invention are adapted to the rapid synthesis of arrays of DNA polymers on a substrate surface. In embodiments of the invention an array of DNA molecules on a substrate comprises a plurality of DNA polymers attached to a trifunctional linker such that at least two DNA polymers are attached to one trifunctional linker that is attached to the surface of the substrate. By coupling trifunctional linkers to trifunctional linkers that are attached to a substrate surface, the density of DNA polymers on a substrate surface is increased.