Stable Light-Trapping SERS Substrates with Bioinspired Arrays for Biochemical Sensing

In Raman spectroscopy, the optimal signal is obtained when the sample is irradiated by a laser at normal incidence. Ensuring both signal stability and high sensitivity for capturing analyte molecules on nonflat or tilted substrates remains difficult, especially in the process of rapid testing. Here, 3D hemispherical polydimethylsiloxane (PDMS) substrate with bioinspired compound-eye structure was fabricated by utilizing the liquid–liquid interface self-assembly and transfer technique. Using Au monolayer films decorated PDMS substrate as a surface-enhanced Raman scattering (SERS) substrate. The rotational symmetry of the bioinspired SERS substrate architecture enables stable SERS performance even under substrate tilting from 0 to 75°, demonstrating excellent suitability for field-based detection applications. The hemispherical SERS substrate demonstrated a minimum detectable urea concentration of 10–5 M, which is significantly lower than the minimum urea level (10–3 M) in the tear fluid of the body.