Journal Article

Optical manipulation of nanoparticles and biomolecules in sub-wavelength slot waveguides

Klug, Matthew, Erickson, David, Moore, Sean D., Yang, Allen H. J., Schmidt, Bradley S., Lipson, Michal

2009

Overview

Trapping and transport in an optical nanochannel One of the obstacles to the development of active nanosystems is the ability to controllably deliver nanoscopic matter to and within nanostructures. This paper describes the combination of near-field optical forces (such as those used in optical traps) to confine nanoscopic matter inside a liquid core-slot waveguide and photon scattering forces to transport them. The waveguide overcomes the diffraction limits of conventional optical trapping systems to manipulate objects down to tens of nanometres in scale. As the waveguide is linear, it can also manipulate extended biomolecules demonstrated by trapping and transporting DNA molecules. This paper describes the combination of near-field optical forces (such as those used in optical traps) to confine nanoscopic matter inside a liquid core-slot waveguide and photon scattering forces to transport them. The waveguide overcomes the diffraction limits of conventional optical trapping systems to manipulate objects down to tens of nanometres in scale. As the waveguide is linear, it can also manipulate extended biomolecules demonstrated by trapping and transporting DNA molecules. The ability to manipulate nanoscopic matter precisely is critical for the development of active nanosystems. Optical tweezers 1 , 2 , 3 , 4 are excellent tools for transporting particles ranging in size from several micrometres to a few hundred nanometres. Manipulation of dielectric objects with much smaller diameters, however, requires stronger optical confinement and higher intensities than can be provided by these diffraction-limited 5 systems. Here we present an approach to optofluidic transport that overcomes these limitations, using sub-wavelength liquid-core slot waveguides 6 . The technique simultaneously makes use of near-field optical forces to confine matter inside the waveguide and scattering/adsorption forces to transport it. The ability of the slot waveguide to condense the accessible electromagnetic energy to scales as small as 60 nm allows us also to overcome the fundamental diffraction problem. We apply the approach here to the trapping and transport of 75-nm dielectric nanoparticles and λ-DNA molecules. Because trapping occurs along a line, rather than at a point as with traditional point traps 7 , 8 , the method provides the ability to handle extended biomolecules directly. We also carry out a detailed numerical analysis that relates the near-field optical forces to release kinetics. We believe that the architecture demonstrated here will help to bridge the gap between optical manipulation and nanofluidics.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: Atoms & subatomic particles / Bacteriophage lambda - genetics / Biological and medical sciences / Biomolecules / Diffraction / DNA, Viral - analysis / Electric fields / Electrons / Exact sciences and technology / Experiments / Fundamental and applied biological sciences. Psychology / Fundamental areas of phenomenology (including applications) / General aspects / Humanities and Social Sciences / Instrumentation. Materials. Reagents. Research laboratory organization / Kinetics / Laser trapping / letter / Manipulation / Mechanical effects of light on atoms, molecules, electrons, and ions / Methods / Microfluidics / Micromanipulation - instrumentation / Micromanipulation - methods / multidisciplinary / Nanocomposites / Nanomaterials / Nanoparticles / Nanoparticles - analysis / Nanostructure / Numerical analysis / Optical properties / Optical Tweezers / Optics / Optics and Photonics - instrumentation / Optics and Photonics - methods / Physics / Plasma etching / Quantum optics / Science / Science (multidisciplinary) / Transport / Trapping / Wave power / Waveguides