Fig. 1. Schematic of the preparation methods and applications of SERS detection integrated microfluidic chips

Fig. 2. Electromagnetic enhancement and chemical enhancement in SERS^[9-10]. (a) A gold nanoparticle acts as a nanoantenna by excitation of a dipolar localized surface plasmon resonance (LSPR); (b) both the “incoming” field (ωinc) and the “

Fig. 3. Femtosecond laser direct writing on glass substrate to prepare microfluidic channel with three-dimensional configuration and high aspect ratio^[23]. (a) Schematic of femtosecond laser three-dimensional fabrication system and flow chart of microfluidic channel fabrication procedure; (b) direct laser writing in mesoporous glass; (c) post-processing; (d) optical microscopy images of three-dimensional spiral microchannels embedded in consolidated glas

Fig. 4. Schematic illustration of the preparation procedure of Ag nanoparticle film and the integration of microfluidic channels^[25]. (a) Ag nanoparticles deposition and parylene cladding process; (b) fabrication of microfluidic channels; (c) system integration

Fig. 5. Whole procedure of the synthesis of NP-AgMS^[44]. (a) On-chip synthesis was performed using a flow-focusing microfluidic device composed of 3 inlets and 1 outlet, the channel dimensions were 300μm wide and 100μm deep;(b)(c) images of AgCl microstructures synthesized within a microchannel were taken using a microscope and a scanning electron microscope

Fig. 6. Femtosecond laser direct writing enabled integration of Ag/Pd SERS substrates inside the microfluidic channels^[58]. (a) Ag/Pd alloy nanostructures with various compositions could be fabricated through femtosecond laser induced reduction; (b)--(f) surface morphology of Ag/Pd alloy substrates composed of different metal molar ratios, and the scale bar is 1μm; (g)--(k) locally magnified images, and the scale bar is 1μm

Fig. 7. Schematics of TBLI fabrication of RGO gratings and subsequent silver coating toward the development of SERS substrates^[67]. (a) TBLI treatment of GO films; (b) light intensity distribution of two interfered laser beams; (c) RGO grating; (d) Ag-RGO grating as SERS substrate

Fig. 8. Fabrication of AgNPs@RGO biochip^[71]. (a) Schematic of the fabrication procedure of an AgNPs@RGO SERS biochip; (b) the mechanism of AgNPs growth onto graphene sheets under UV irradiation; (c) programmable patterning of various AgNPs@RGO SERS substrates for biochip assembly, and the scale bar is 500μm; (d) photograph of the as-prepared AgNPs@RGO SERS biochip, and the scale bar is 1cm

Fig. 9. Working principle of electrochemially assisted SERS-based detection^[86]. (a) Showing the variations of surface charges on the Au-capped nanopillar SERS substrates and the suggested interaction of the surface with melamine; (b) illustration of the custom-made electrochemical-SERS platform and its respective system interfacing; (c) photo of the assembled chip and SEM image of Au-capped nanopillar structures for SERS detection, and the scale bar is

Fig. 10. Preparation of multifunctional integrated chip for in-situ chemical catalysis and SERS detection^[88].(a) High resolution SEM image of AgNPs@RGO layer; (b) low magnification of SEM image of AgNPs@RGO layer, and the scale bar is 20μm; (c) schematic of the strategy for SERS monitoring catalytic chip; (d) SERS monitoring results of flow rate above and below V_th normalized by feature peak 473cm^-1

Fig. 11. Schematics of SERS based immunoassay with digital microfluidic technology^[87].(a) Schematic of DMF-SERS method and DMF chip baseplate;(b) the two characteristic Raman peaks of 4-MBA are respectively located at 1071cm^-1 and 1580cm^-1; (c) side view of the DMF chip, which contains droplets with magnetic beads; (d) immune complexes functionalized with SERS tags on magnetic beads; (e) SERS spectra of different concentrations of H

Fig. 12. Workflow of SERS microfluidic platform for single cell encapsulation and simultaneous detection of three metabolites produced by single cell^[91]. (a) Schematic of the composite materials synthesis and injection location of composite materials in chip; (b)(d) internal enlarged diagram of single cell and its analyte; (c) droplet formed at the beginning; (e) droplet after forming for 90min; (f) Fe₃O₄@AgNPs nanocomposites are us