How the surrounding environment affects the biosensing performance of resonant nanopillars arrays: Under dry conditions or immersed in fluid

Abstract

In this work we demonstrate the advantage of performing the biosensing process of a refractive indexoptical biosensor under dry conditions, in comparison with the biosensing structure immersed in fluid.We developed a biosensing experiment over a specific transducer based on resonant nanopillars (R-NPs)arrays. The optical interrogation to monitor the recognition events was firstly performed with the R-NPsin dry, only in contact with the air, and secondly with the R-NPs immersed in water. We observed asignificant enhance in the sensitivity of the biosensing curve response for the R-NPs in dry conditions,leading an improvement of the Limit of Detection (LoD) in more than one order of magnitude. These resultsare also in good correlation with 3D-Finite difference time domain simulations carried out for both fluidconditions. According to this result, any interferometric optical bio-transducer for in-situ diagnosis willimprove the sensitivity in case it can operate in dry conditions. Moreover, measuring in simple drops ofbiological samples, in dry conditions, will be a relevant issue for Point of Care Devices