Transfer printing for preparing nanostructured PDMS film as flexible SERS active substrate

Flexible surface enhanced Raman scattering (SERS) substrate would offer a highly sensitive and rapid means for detecting ultra-low concentration of analytes on an irregular surface, enabling its arising applications in wearable and wipeable devices. In this study, we launched a transfer printing method to fabricate a flexible and low cost SERS substrate with an ordered nanostructure. When polydimethylsiloxane (PDMS) is being applied onto self-assembled polystyrene (PS) nanoparticles (NPs) template, the flowability of PDMS solution during the curing process may better align the spacing among the PS NPs to form a closer packing, an outcome which provides a highly ordered nanostructure on the PDMS film. We developed a strategy for prompting a uniform Au nanoparticles (NPs) coating on the PDMS surface for further growing an Ag NPs layer. We successfully fabricated a flexible SERS substrate for testing analytes on a curved object to achieve high detection capability with enhancement factors at the order of ∼107 and well-posed reproducibility with deviation less than 13%. Our study could effectively implement flexible SERS practice and could be extended for future applications in flexible sensors and actuators.