Capillary optofluidics by high-aspect-ratio photonic crystals

In this work, vertical, silicon/air one-dimensional photonic crystals (1DPhCs) are proposed as sensing elements for capillary optofluidics. As proof-of-concept, a drop-and-measure optofluidic platform that integrates a 1DPhC operating in the near-infrared region into a simple capillary microfluidic network is reported. The platform is fabricated by silicon electrochemical micromachining (ECM) technology and is optically characterized by measuring the shift of 1DPhC refelctivity upon capillary infiltration of liquids with different refractive indices into the PhC air-gaps. Experimental measures highlight that high reproducibility, good linearity, high sensitivity, and good limit of detection are achieved under capillary operation, thus foreseeing a novel generation of drop-and-measure platforms for refractometry/chemical analysis making use of PhCs.