Facile fabrication of integrated microfluidic SERS substrate by femtosecond laser sintering of silver nano particles

Surface Enhanced Raman Scattering (SERS) has emerged as a very powerful analytical tool due to its unique capability of molecular fingerprint detection. Integration of SERS onto microfluidic platforms will enable the study of liquid samples especially for point-of-care medical diagnostics and Biology. Fabrication of uniform, reproducible and large area microfluidic SERS substrates are essential in order to get consistent results especially while dealing with samples in liquid form. Femtosecond Laser Micromachining as a tool is being extensively used in various fields as it gives consistent and reproducible results. In the present work, we integrated SERS substrate onto a fused silica based microfluidic channel by employing Femtosecond Laser Sintering of Silver Nano Particles. Due to the inherent advantages of Femtosecond Laser Micromachining, uniform and large area SERS substrates were fabricated to study the SERS of liquids. The parameters suitable for fabrication of SERS substrates in a microfluidic channel are discussed. The Average Enhancement Factor of the SERS signals is correlated with the Femtosecond Laser Sintering parameters. As a proof of concept, we have demonstrated the SERS studies of 1 mM Rhodamine-6G (in water) solution. Reproducibility of the SERS results was verified and an Average Enhancement Factor of 104 is achieved. This facile fabrication add nuances to the glass based microfluidic channels to perform SERS measurements.