An optofluidic chip based on a multilayered photonic crystal structure is employed for an efficient beaming of the emitted radiation in a fluorescent microarray assay. Upon a near-field coupling of fluorescent emitters to surface modes sustained by the photonic crystal, a significant portion of radiated energy is diffracted out-of-plane towards the collection optics. The improvement in fluorescence collection is experimentally demonstrated in an antibody-antigene immunoassay. As a result, a decrease of the limit of detection for labelled antigenes by a factor of about 40 is demonstrated to occur in a robust and reproducible way, with little or no optical alignment issues. (C) 2015 Elsevier B.V. All rights reserved.