Novel plasmonic biosensors molding the flow of light and fluidics at subdiffraction limit

We introduce a novel hybrid platform merging label free nanoplasmonic biosensing with actively controlled nanofluidic analyte delivery to overcome mass transport limitations. We show 14-fold improvement in mass transport rate constants appearing in the exponentials. Performances of the surface biosensors are often controlled by the analyte delivery rate to the sensing surface instead of the sensors intrinsic detection capabilities. In a microfluidic channel, diffusive analyte transport to the biosensor surface severely limits the analyte delivery as a result the biosensors performance. At low concentrations, this limitation, which is commonly known as mass transport problem, causes impractically long detection times extending from days to months for nano-sensors. Although an extensive work has been done on the subject, previous approaches based on stirring and various mixing strategies seem to result in moderate enhancements in mass transport efficiencies. One of the main conceptual constraints in these approaches was that microfluidics and biosensing are always considered as different parts of a sensor platform completing each other but not a fully merged single entity. In this article, we demonstrate a hybrid biosensing platform merging nanoplasmonics and nanofluidics. Unlike conventional approaches where the analytes simply stream pass over the surface, our platform enables targeted delivery to the sensing surface. Using our platform, we show 14-fold improvement in mass transport rate constant appearing in the exponential terms. Such an improvement means superior analyte delivery to the biosensor surface at low concentrations. Our detection platform is based on extraordinary light transmission effect (EOT) in suspended plasmonic nanohole arrays. The nanoholes here act as nanofluidic channels connecting the fluidic chambers on both sides of the sensors (Fig. 1c). As a result, unlike convectional approaches, our platform enables targeted delivery of the analytes to the sensor surface.