A sensitive and precise microfluidic platform for SERS
The application of microfluidic tools for surface-enhanced Raman spectroscopy (SERS) has received increasing attention in recent years due to their high sensitivity and spatial precision. Semih Sevim and coworkers from the deMello group have developed a novel microfluidic approach for in-situ fabrication of SERS substrates and the detection of analytes using SERS with high regional control whilst successfully avoiding on-chip cross-contamination. This novel microfluidic technology allows the detection of analytes at concentration as low as 10 fM and is designed to be reconfigurable and reusable.
SERS is a detection technique which employs nanostructured metallic surfaces (SERS substrates) to enhance the phenomena of inelastic light scattering of adsorbed molecules (Raman scattering) by several orders of magnitude. While microfluidic approaches show great advantages over other SERS platforms, their use is still underdeveloped, as they often lack reusability, suffer cross-contamination, and struggle with precise analyte localization.
Semih’s work, carried out under the supervision of Dr. Josep Puigmartí-Luis, describes an advanced microfluidic chip equipped with nitrogen inlets, which leave an open and unperturbed channel when unpressurized and cause a partial deformation of the membrane towards the glass substrate when pressurized. The shielding features of these pneumatic clamps together with laminar flow is used to guide SERS substrates and samples to specific locations, with customized washing steps to avoid cross-contamination. To demonstrate application in SERS, a nanostructured Ag line is deposited in the chip, which upon a post-experimental etching, can be cleaned and thus recycled. A uniformity of the signal along the Ag substrate is demonstrated, as well as high spatial control allowing multiple Ag lines underneath of a single clamp, and multiple sample depositions on a single Ag line. The Ag substrate was labeled with crystal violet as a test probe molecule, by injection over 4 min at a flow rate of 50 μL/min, which allowed detection at analyte concentrations down to the 10 fM level.
The developed method allows for high spatial control, reusability and high detection sensitivity of multiple analytes in a single microfluidic channel and may play an ongoing role in research for the regioselective functionalization of metallic nanostructures.