Fig. 5
From: Microfluidics for disease diagnostics based on surface-enhanced raman scattering detection
Creation and analysis of the gas sensor. a The schematic diagram for the sensor’s preparation. A nine-dot polystyrene (PS) pattern is initially transferred from a monolayer of PS microspheres to a glass slide using the tape-assisted transfer technique, Subsequently, a PDMS duplicate is obtained through molding. Bimetallic nanocubes are then deposited via a self-assembly approach. Finally, three distinct detection units—UA, UB, and UC—are achieved through customized modification. SEM images of b the patterned PS mold, c the negative PDMS duplicate, d the substrate after nanocube deposition, and e the substrate following Ti3C2Tx Mxene deposition. All scale bars are set at 5 μm. Inserted images include corresponding photographs. (f − i) AFM images corresponding to each step in the preparation process of the array. Inserted images detail the characterization of single micropits, with the color bar indicating height ranging from 0 to 500 nm. j Benzaldehyde mapping results based on SERS intensity at 1004 cm− 1. k stacked image of SERS spectra of benzaldehyde at random regions. l Numerical electromagnetic field simulation in a single pit with bimetallic nanocubes using an excitation wavelength of 632.8 nm. m simulated gas flow field in the microchannel, with a color bar ranging from 0 to 40 mm/s. n Magnified top view of the channel near the entrance and exit of the premixer. o Streamlines near the micropits. p SERS spectra of benzaldehyde obtained on-chip and off-chip. Reprinted with permission from [46]. Copyright 2022 American Chemical Society