Electrofluidynamic Patterning of Tailorable Nanostructured Substrates for Surface-Enhanced Raman Scattering.

The unique attributes of surface enhanced Raman spectroscopy (SERS) make it well suited to address the challenges associated with portable diagnostics. However, despite the remarkable progress in this field, where the instrumentation has made great strides forward providing a route to the miniaturization of sensing devices, to date producing three-dimensional low-cost SERS substrates which simultaneously fulfill the multitude of criteria of high sensitivity, reproducibility, tunability, multiplexity, and integratability for rapid sensing has not yet been accomplished. Successful implementation of SERS requires readily fine-tuned nanostructures, which create a high enhancement. Here, an advanced electrofluidynamic patterning (EFDP) technique enables rapid fabrication of SERS active topographic morphologies with high throughput and at a nanoresolution via the spatial and lateral modulation of the dielectric discontinuity due to the high electric field generated across the polymer nanofilm and air gap. The subsequent formation of displacement charges within the nanofilm by coupling to the electric field yield a destabilizing electrostatic pressure and amplification of EFDP instabilities enabling the controllable pattern formation. The top of each gold coated EFDP fabricated pillar generates controllable high SERS enhancement by coupling of surface plasmon modes on top of the pillar, with each nanostructure acting as an individual sensing unit. The absolute enhancement factor depends on the topology as well as the tunable dimensions of the nanostructured units, and these are optimized in the design and engineering of the dedicated EFDP apparatus for reproducible, low-cost fabrication of the three-dimensional nanoarchitectures on macrosurfaces, rendering them for easy integration in further lab-on-a-chip devices. This unique combination of nanomaterials and nanospectroscopic systems lay the platform for a variety of applications in chemical and biological sensing.