Flexible SERS-based substrates: Challenges and opportunities toward an Army relevant universal sensing platform

Generally the fabrication, assembly and evaluation of plasmonic nanostructures for surface enhanced Raman scattering (SERS) substrates has focused on static rigid substrates such as glass and silicon. However, these static substrates severely limit the application of plasmonic nanostructures as (i) they provide no means to alter the state of assembly of the nanostructures once they are formed or anchored on the surface i.e., not reconfigurable; and (ii) preclude applications which demand non-planar, flexible or conformal surfaces. The above considerations has led to the development of a novel class of SERS substrates based on flexible substrates such paper, polymer membranes and electrospun fibers. These flexible SERS media based on unconventional substrates such as paper offer distinct advantages compared to the conventional SERS substrates in that (i) flexible nature of the substrate enables conformal contact with the surfaces under investigation leading to efficient sample collection; (ii) porous nature of the SERS substrate (interstices between the fibers) provides efficient access to the analytes; (iii) high surface area of the 3D paper substrate results in large dynamic range of the chemical sensors; (iv) intricate network of fibers decorated with metal nanoparticles can provide potentially high density of electromagnetic hotspots; (v) intense light scattering caused by the fibrous structure of the substrate (e.g., paper) enables efficient light-metal interaction; and (vi) facile fabrication leads to efficient, robust, reliable, reusable and cost-effective SERS substrates. In this presentation, we will focus on the Army need for a more flexible (substrate surface and application) SERS substrate for universal sensing. This presentation will leverage from material presented at a flexible SERS (May 2014) workshop hosted by Dr. Srikanth Singamaneni at Washington University.