Techniques for increasing the capture zone in nano and microchannel-based polymer testing structures using concentric arrangements of nanostructures, such as nanopillars are provided. In one aspect, a testing structure for testing polymers is provided that includes a first fluid reservoir and a second fluid reservoir formed in an electrically insulating substrate; at least one channel formed in the insulating substrate that interconnects the first fluid reservoir and the second fluid reservoir; and an arrangement of nanostructures within either the first fluid reservoir or the second fluid reservoir wherein the nanostructures are arranged so as to form multiple concentric circles inside either the first fluid reservoir or the second fluid reservoir with each of the concentric circles being centered at an entry point of the channel. A method of analyzing a polymer using the testing structure is also provided.