Biomimetic flexible SERS substrates replicated from cicada wings for portable in situ detection

Flexible surface-enhanced Raman scattering (SERS) substrate has received great attention because of its unique advantages at fast detection and on-site analysis in practical applications. Here, a biomimetic flexible SERS substrate was fabricated on polydimethylsiloxane (PDMS) film with nanopore arrays which was completely transferred from nanostructures in cicada wings by a replication process, and loaded with uniform silver nanoparticles (Ag NPs) via efficient magnetron sputtering method. By optimizing the deposition time, the optimal biomimetic flexible SERS substrate provided an analytical enhancement factor (4.2 x 10(5)), excellent uniformity and reproducibility with a relative standard deviation (RSD) of 7.3 % and 2.8 %, respectively. Moreover, the biomimetic flexible SERS substrate exhibited excellent mechanical stability, and can obtain high-quality SERS signals under backside illumination. Specifically, malachite green (MG) residues on apple and pear peel can be rapidly and reliably determined using a portable Raman spectrometer, with a minimum detectable concentration of 10(-6) M and a high correlation coefficient (R-2 > 0.99). The proposed biomimetic flexible SERS substrate coupled with a portable Raman spectrometer has great potential to be implemented in point-of-care testing applications.