While surface enhanced Raman spectroscopy (SERS) may not compete with the standard central lab approaches for chemical and biological sensing, SERS may have the potential to provide unique capabilities for analytics away from the central lab. Raman spectrometers have evolved from benchtop systems to high-performing handheld instruments that are compatible with analysis of samples in the field. However, for SERS to truly succeed as a “point-of-sample” analytical technique, the SERS sensor must fit the needs of analysis in the field, including little or no sample preparation, minimal peripheral equipment, and ease of use. Traditional plasmonically-active rigid devices do not meet these requirements. Even microfluidic SERS devices generally are not compatible with point-of-sample analysis, as the "world-to-chip" interface presents challenges, and peripheral equipment is generally required. In this review we will discuss the advances in plasmonic substrates fabricated on porous membranes, leading to SERS sensors that can collect samples via swabbing or dipping, clean up samples through separation, concentrate analytes by lateral flow focusing, and avoid the need for peripheral equipment. In particular, we will focus on inkjet-fabricated devices, which may present the best opportunity for scale-up via roll-to-roll manufacturing. We will also discuss the directions that flexible SERS sensors are moving the field, such as simple fabrication techniques, new support materials, SERS swabs, and SERS-active tapes and films.
|
