Microfluidic Platform for Integrated Plasmonic Detection in Laminal Flow.

In this work, we propose a novel approach to design robust microfluidic devices with integrated plasmonic transducers allowing portability, reduced analysis time through dynamic measurements and high sensitivity. Specifically, the strategy we apply involves two steps: i) the controlled deposition of gold bipyramidal nanoparticles (AuBPs) onto a functionalized solid glass substrate and ii) the integration of the as-fabricated plasmonic substrate into a polydimethylsiloxane (PDMS) microfluidic circuit. The localized Surface Plasmon Resonance (LSPR) sensitivity of the plasmonic-microfluidic device was evaluated by monitoring the optical responses at refractive index changes proving a bulk sensitivity of 243 RIU/nm for the longitudinal LSPR band of isolated AuBPs and 150 RIU/nm for the band assigned to end-to-end linked nanoparticles. A strong electric field generated in the gaps between AuBPs - due to the generation of the so-called 'hot-spots' - was subsequently proved by the SERS detection of molecules in continuous flow conditions by loading the analyte into the microfluidic channel via a syringe pump. In conclusion, our miniaturized portable microfluidic system aims to detect and identify in real-time with high specificity and accuracy analyte molecules in laminal flow, providing thus a groundwork for further complex biosensing applications.