On-Chip Nanoplasmonic Biosensors with Actively Controlled Nanofluidic Surface Delivery

Performances of surface biosensors are often controlled by the analyte delivery rate to the sensing surface instead of sensors intrinsic detection capabilities. In a microfluidic channel, analyte transports diffusively to the biosensor surface severely limiting its performance. At low concentrations, this limitation, commonly known as mass transport problem, causes impractically long detection times extending from days to months. In this proceeding, we propose and demonstrate a hybrid biosensing platform merging nanoplasmonics and nanofluidics. Unlike conventional approaches where the analytes simply stream pass over the sensing surface, our platform enables targeted delivery of analytes to the sensing surface. Our detection platform is based on extraordinary light transmission effect (EOT) in suspended plasmonic nanohole arrays. The subwavelength size nanoholes here act as nanofluidic channels connecting the microfluidic chambers on both sides of the sensors. In order to materialize our detection platform, we also introduce a novel multilayered micro/nanofluidics scheme allowing three dimensional control of the fluidic flow. Using our platform, we show 14-fold improvement in mass transport rate constant appearing in the exponential term. To fabricate these biosensors, we also introduce a lift-off free plasmonic device fabrication technique based on positive resist electron beam lithography. Simplicity of this fabrication technique allows us to fabricate nanostructures with ease, high yield/reproducibility and minimal surface roughness. As a result, we achieve higher refractive index sensitivities. This fabrication technique can find wide range of applications in nanoplasmonics field by eliminating the need for operationally slow and expensive focused ion beam lithography.