SERS Sensor Chips Based on Nanosphere Lithography on Flexible Platforms for the Detection of Chemicals, Pesticides and Nucleotides

In this paper, we propose an efficient and scalable method for creating high‐performance, flexible surface‐enhanced Raman scattering (SERS) substrates using gap‐tunable nanosphere lithography on flexible substrates such as Kapton and PET. We overcome the natural hydrophobic nature of flexible polymer films by depositing an ultrathin ALD‐SiO 2 interface layer. While we carried out reactive ion etching (RIE) to controllably vary the gaps between the polystyrene nanospheres self‐assembled on the ALD‐SiO 2 coated Kapton and PET films, overcoating of these nanospheres with thin layers of Au or Ag leads to the fabrication of plasmonic nanospheres with sub‐10 nm gaps and intense SERS hotspots. It is observed that while silver is preferable for maximizing SERS signals, gold offers advantages for applications requiring high spectral purity and minimal substrate interference. Mechanical characterization of the flexible SERS sensor chips is carried out, and it demonstrates that the SERS sensor‐chips maintain their spectral integrity during intense cyclic bending and static conformal wrapping. This affirms the appropriateness of these flexible SERS sensor chips for swab‐and‐scan and other point‐of‐care (POC) applications. The applicability of the SERS sensor chips for diverse applications was demonstrated by its ability to detect hazardous pesticide residues and DNA nucleotides with high levels of accuracy.