(464c) Biomolecular Optical Transport in Nanoscale Slot Waveguides

One of the roadblocks to development of active nanosystems is the ability to controllably deliver nanoscopic matter to and within nanostructures. Optically-driven transport enabled by the integration of rectangular dielectric waveguides with microfluidic devices exploits radiation pressure and gradient forces to trap and propel particles along the waveguide structures. We recently demonstrated an optofluidic device for the trapping and transport of microparticles in the evanescent field of a polymer solid-core waveguide. To the best of our knowledge, researchers have not been able to exploit such waveguide based structures for the trapping and transport of nanoscopic matter, as it would require stronger optical confinement than currently available to overcome random thermal diffusion. Here we demonstrate a new paradigm for nanoscopic transport using sub-wavelength scale planar photonic ?slot waveguides?. The slot waveguide generates high confinement liquid-core optical modes, creating the necessary optical intensity for nanoparticle trapping. Demonstrated here is the trapping and transport of 75 and 100 nm polystyrene beads flowing in an overlaying microfluidic channel for slots ranging in width from 100 nm to 160 nm. Furthermore, we show that we can trap and transport partially extended λ-DNA in 60 nm slot waveguides. We validate our observations by characterizing the trapping stability using a modified Polanyi-Wigner equation. The architecture demonstrated here is the first step towards an optical nanochannel, bridging the gap between microfluidics and nanofluidics.

Keywords: Optofluidics, DNA trapping, waveguide