Methods and systems for nanopillar sensors are described. Nanopillars can be defined on a substrate, and metal deposited on the nanopillars. A thermal treatment can reflow the metal on the nanopillars forming metallic bulbs on the top end of the nanopillars. These structures can have enhanced optical detection when functionalized with biological agents, or can detect gases, particles and liquids through interaction with the metal layer on the nanopillars.