Surface Acoustic Wave-Driven Active Plasmonicsbased on Dynamic Patterning of Nanoparticles in Microfluidic Channels

The nanoparticles redistribution in a microfluidic channel through a dynamic patterning process will locally change the refractive index of the medium around the nanodisk arrays, as well as the LSPR. The dynamic patterning of nanoparticles was achieved by a standing surface acoustic wave (SSAW), from which the acoustic force generated and force the particles to the pressure nodes. The SSAW were formed through two parallel interdigital transducers (IDTs) on a LiNbO₃ substrate, on which the gold nanodisk arrays were fabricated through a nanosphere lithography. A PDMS microchannel was aligned with the IDTs and bonded with the substrate to cover the nanodisk arrays. A solution of fluorescent polystyrene beads (diameter: 320 nm) was injected into the channel through a pressure driven flow. When SSAW was on, the original peak (lambda=694 nm) is split into two peaks at lambda₁= 662 nm and iquest₂= 746 nm, respectively.