A novel micromachined Fabry-Perot interferometer integrating nano-holes and dielectrophoresis for enhanced biochemical sensing.

Single-layered gold nano-hole arrays lead to extraordinary optical transmission (EOT)-modulated surface plasmonic resonance (SPR) and have seen much progress in biochemical sensing. To further improve the sensing performance, the single-layered structure need to be changed. In this paper, a micromachined Fabry-Perot interferometer (µFPI), featuring two parallel and flat gold-coated mirrors, one of which has sub-wavelength nano-hole arrays, was designed, fabricated, and tested experimentally. Its transmission spectrum was confirmed to have EOT-modulated SPR patterns, and its characteristic peak wavelength was found to have a refractive index sensitivity of 593 nm / RIU and a Q factor up to 128.4, which is 10.2 times its EOT counterparts. By applying AC electric signals across the two gold layers, dielectrophoresis (DEP) induced near the nano-holes was proven to enrich particles significantly. To remove the thermal effects on the transmission spectrum, heat was dissipated by flowing sample during measurement. Biochemical sensing experiments were conducted using BSA protein medium of different low concentrations, demonstrating the detection sensitivity enhancement of ~ 6-fold for 1 pM compared to 100 pM. This novel µFPI presents a new paradigm in EOT-based SPR sensing technology by combining the benefits of µFPI interference, EOT near-field measurement and DEP enrichment of molecules.