Regular paper

Performance and flow dynamics studies of polymeric optofluidic SERS sensors

¹ VTT Technical Research Centre of Finland, Kaitoväylä 1, 90590 Oulu, Finland
² University of Oulu, Pentti Kaiteran katu 1, 90014 Oulu, Finland
³ Nanocomp Oy Ltd, Ensolantie 6, 80710 Lehmo, Finland

^* Sanna.uusitalo@vtt.fi

Received: 30 June 2015
Revised: 17 August 2015

Abstract

We present a polymer-based optofluidic surface enhanced Raman scattering chip for biomolecule detection, serving as a disposable sensor choice with cost-effective production. The SERS substrate is fabricated by using industrial roll-to-roll UV-nanoimprinting equipment and integrated with adhesive-based polymeric microfluidics. The functioning of the SERS detection on-chip is confirmed and the effect of the polymer lid on the obtainable Raman spectra is analysed. Rhodamine 6G is used as a model analyte to demonstrate continuous flow measurements on a planar SERS substrate in a microchannel. The relation between the temporal response of the sensors and sample flow dynamics is studied with varied flow velocities, using SERS and fluorescence detection. The response time of the surface-dependent SERS signal is longer than the response time of the fluorescence signal of the bulk flow. This observation revealed the effect of convection on the temporal SERS responses at 25 µl/min to 1000 µl/min flow velocities. The diffusion of analyte molecules from the bulk concentration into the sensing surface induces about a 40-second lag time in the SERS detection. This lag time, and its rising trend with slower flow velocities, has to be taken into account in future trials of the optofluidic SERS sensor, with active analyte binding on the sensing surface.