Dielectrophoresis on nanostructured substrates for enhanced plasmonic biosensing

Abstract

Performance of surface-based plasmonic biosensors 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 the mass transport limitations. A transparent electrode is integrated with the plasmonic substrates that allow dielectrophoresis without interfering with the label-free sensing schemes such as surface plasmon resonance or Raman spectroscopy. Furthermore, by shrinking the gap between gold electrodes to sub-10 nm, we show ultralow-power trapping of nanoparticles and biomolecules. Reducing the operating voltages diminishes Joule heating, bubble formation and electrochemical surface reactions - hurdles associated with traditional electrodes for dielectrophoresis. The ultralow power electronic operation combined with plasmonic detection has potential in high-density on-chip integration and portable biosensing.