Enhanced Plasmonic Detection With Dielectrophoretic Concentration

Performance of surface-based plasmonic sensors is often plagued by diffusion-limited transport, which complicates detection from low-concentration analytes. By harnessing gradient forces available from the sharp metallic edges, tips, or gaps that are often found in the plasmonic sensors, it is possible to combine a dielectrophoretic concentration approach to overcome mass transport limitations. A transparent electrode is combined with the plasmonic substrates that allow dielectrophoresis without interfering with the optical detection. Detection from pM-level protein solution is expedited by more than 1000 times as compared to the case of diffusion. Also, enhanced Raman spectroscopic detection is demonstrated using carbon nanotubes and biological particles. Finally, to improve the performance of dielectrophoresis, the gap between the electrodes is reduced to sub-10 nm and ultralow voltage trapping experiments are shown. The ultralow power electronic operation combined with plasmonic detection can enable high-density on-chip integration and portable biosensing.