Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

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


The ability to manipulate nanoscopic matter precisely is critical for the development of active nanosystems. Optical tweezers1,2,3,4 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-limited5 systems. Here we present an approach to optofluidic transport that overcomes these limitations, using sub-wavelength liquid-core slot waveguides6. 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 traps7,8, 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.

This is a preview of subscription content

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Nanoscale optofluidic transport.
Figure 2: Trapping and transport of dielectric nanoparticles in a slot waveguide.
Figure 3: Capture and trapping of λ-DNA.
Figure 4: Trapping forces on particles trapped inside and outside the slot waveguide, and analysis of particle release kinetics.


  1. Grier, D. G. A revolution in optical manipulation. Nature 424, 810–816 (2003)

    ADS  CAS  Article  Google Scholar 

  2. Ashkin, A., Dziedzic, J. M., Bjorkholm, J. E. & Chu, S. Observation of a single-beam gradient force optical trap for dielectric particles. Opt. Lett. 11, 288–290 (1986)

    ADS  CAS  Article  Google Scholar 

  3. MacDonald, M. P., Spalding, G. C. & Dholakia, K. Microfluidic sorting in an optical lattice. Nature 426, 421–424 (2003)

    ADS  CAS  Article  Google Scholar 

  4. Grigorenko, A. N., Roberts, N. W., Dickinson, M. R. & Zhang, Y. Nanometric optical tweezers based on nanostructured substrates. Nature Photon. 2, 365–370 (2008)

    ADS  CAS  Article  Google Scholar 

  5. Born, M. & Wolf, E. Principles of Optics (Pergamon, 2003)

    Google Scholar 

  6. Almeida, V. R., Xu, Q. F., Barrios, C. A. & Lipson, M. Guiding and confining light in void nanostructure. Opt. Lett. 29, 1209–1211 (2004)

    ADS  Article  Google Scholar 

  7. Chiu, D. T. & Zare, R. N. Biased diffusion, optical trapping, and manipulation of single molecules in solution. J. Am. Chem. Soc. 118, 6512–6513 (1996)

    CAS  Article  Google Scholar 

  8. Hirano, K. et al. Sizing of single globular DNA molecules by using a circular acceleration technique with laser trapping. Anal. Chem. 80, 5197–5202 (2008)

    CAS  Article  Google Scholar 

  9. Psaltis, D., Quake, S. R. & Yang, C. H. Developing optofluidic technology through the fusion of microfluidics and optics. Nature 442, 381–386 (2006)

    ADS  CAS  Article  Google Scholar 

  10. Monat, C., Domachuk, P. & Eggleton, B. J. Integrated optofluidics: A new river of light. Nature Photon. 1, 106–114 (2007)

    ADS  CAS  Article  Google Scholar 

  11. Neale, S. L., Macdonald, M. P., Dholakia, K. & Krauss, T. F. All-optical control of microfluidic components using form birefringence. Nature Mater. 4, 530–533 (2005)

    ADS  CAS  Article  Google Scholar 

  12. Chiou, P. Y., Ohta, A. T. & Wu, M. C. Massively parallel manipulation of single cells and microparticles using optical images. Nature 436, 370–372 (2005)

    ADS  CAS  Article  Google Scholar 

  13. Liu, G. L., Kim, J., Lu, Y. & Lee, L. P. Optofluidic control using photothermal nanoparticles. Nature Mater. 5, 27–32 (2006)

    ADS  CAS  Article  Google Scholar 

  14. Wang, M. M. et al. Microfluidic sorting of mammalian cells by optical force switching. Nature Biotechnol. 23, 83–87 (2005)

    CAS  Article  Google Scholar 

  15. Sinclair, G. et al. Assembly of 3-dimensional structures using programmable holographic optical tweezers. Opt. Express 12, 5475–5480 (2004)

    ADS  Article  Google Scholar 

  16. Dholakia, K. & Reece, P. J. in Structured Light and Its Applications (ed. Andrews, D. L.) 107–138 (Academic, 2008)

    Book  Google Scholar 

  17. Righini, M., Zelenina, A. S., Girard, C. & Quidant, R. Parallel and selective trapping in a patterned plasmonic landscape. Nature Phys. 3, 477–480 (2007)

    ADS  CAS  Article  Google Scholar 

  18. Marchington, R. F. et al. Optical deflection and sorting of microparticles in a near-field optical geometry. Opt. Express 16, 3712–3726 (2008)

    ADS  CAS  Article  Google Scholar 

  19. Cizmar, T. et al. Optical sorting and detection of submicrometer objects in a motional standing wave. Phys. Rev. B 74, 035105 (2006)

    ADS  Article  Google Scholar 

  20. Schmidt, B. S., Yang, A. H., Erickson, D. & Lipson, M. Optofluidic trapping and transport on solid core waveguides within a microfluidic device. Opt. Express 15, 14322–14334 (2007)

    ADS  CAS  Article  Google Scholar 

  21. Ng, L. N., Luf, B. J., Zervas, M. N. & Wilkinson, J. S. Forces on a Rayleigh particle in the cover region of a planar waveguide. J. Lightwave Technol. 18, 388–400 (2000)

    ADS  Article  Google Scholar 

  22. Grujic, K., Helleso, O. G., Hole, J. P. & Wilkinson, J. S. Sorting of polystyrene microspheres using a Y-branched optical waveguide. Opt. Express 13, 1–7 (2005)

    ADS  CAS  Article  Google Scholar 

  23. Gaugiran, S., Gétin, S., Fedeli, J. M. & Derouard, J. Polarization and particle size dependence of radiative forces on small metallic particles in evanescent optical fields. Evidences for either repulsive or attractive gradient forces. Opt. Express 15, 8146–8156 (2007)

    ADS  CAS  Article  Google Scholar 

  24. Ng, L. N., Luff, B. J., Zervas, M. N. & Wilkinson, J. S. Propulsion of gold nanoparticles on optical waveguides. Opt. Commun. 208, 117–124 (2002)

    ADS  CAS  Article  Google Scholar 

  25. Gaugiran, S. et al. Optical manipulation of microparticles and cells on silicon nitride waveguides. Opt. Express 13, 6956–6963 (2005)

    ADS  CAS  Article  Google Scholar 

  26. Yang, A. H. J. & Erickson, D. Stability analysis of optofluidic transport on solid-core waveguiding structures. Nanotechnology 19, 045704 (2008)

    ADS  Article  Google Scholar 

  27. Hart, S. J., Terray, A., Leski, T. A., Arnold, J. & Stroud, R. Discovery of a significant optical chromatographic difference between spores of Bacillus anthracis and its close relative, Bacillus thuringiensis . Anal. Chem. 78, 3221–3225 (2006)

    CAS  Article  Google Scholar 

  28. Svoboda, K. & Block, S. M. Optical trapping of metallic Rayleigh particles. Opt. Lett. 19, 930–932 (1994)

    ADS  CAS  Article  Google Scholar 

  29. Braslavsky, I., Hebert, B., Kartalov, E. & Quake, S. R. Sequence information can be obtained from single DNA molecules. Proc. Natl Acad. Sci. USA 100, 3960–3964 (2003)

    ADS  CAS  Article  Google Scholar 

  30. Woolley, A. T., Guillemette, C., Cheung, C. L., Housman, D. E. & Lieber, C. M. Direct haplotyping of kilobase-size DNA using carbon nanotube probes. Nature Biotechnol. 18, 760–763 (2000)

    CAS  Article  Google Scholar 

Download references


We thank A. Stroock for discussions, and A. Nitkowski and S. Manipatruni for technical support. This work was done in part at the Cornell NanoScale Facility, a member of the National Nanotechnology Infrastructure Network, which is supported by the US National Science Foundation. This work was funded by the US National Science Foundation NIRT: Active Nanophotofluidic Systems for Single Molecule/Particle Analysis (award number 0708599).

Author Contributions A.H.J.Y. and S.D.M. were responsible for running the bulk of the trapping experiments and analysing data. A.H.J.Y. carried out the simulation calculations. B.S.S was responsible for running initial experiments and fabrication of the slot waveguide chips. M.K. developed the DNA imaging methods. A.H.J.Y., M.L. and D.E. were responsible for writing the paper. All authors discussed the results and commented on the manuscript.

Author information

Authors and Affiliations


Corresponding author

Correspondence to David Erickson.

Supplementary information

Supplementary Information

This file contains Supplementary Data and Supplementary References (PDF 78 kb)

Supplementary Movie 1

Stable nanoparticle trapping and controlled release by the slot waveguide. This movie demonstrates the high stability, long term trapping of many 75nm polystyrene particles by and optically excited 100nm slot waveguide. In this case, the slot waveguide is excited and particles flowing over it are allowed to accumulate for some time. In the first half of the movie the particles are released by removing the excitation power and in the second half they are released by switching polarity. This capture and release is also shown in Figure 2. (MOV 2065 kb)

Supplementary Movie 2

Nanoparticle capture by the slot waveguide. This movie demonstrates the capture and trapping of two individual 100nm polystyrene particles by an optically excited 120nm slot waveguide. In this movie, the particles are initially flowing from left to right by a microfluidic flow. They are trapped near the stability point and the particle is released when the random thermal energy exceeds the work required to break the trap. (MOV 2740 kb)

Supplementary Movie 3

Optical force transport of a single nanoparticle inside the slot waveguide. In this movie, we demonstrate the optical force transport of a single 100nm particle inside a 120nm slot waveguide. This transport is also shown in Figure 2. (MOV 3979 kb)

Supplementary Movie 4

Biomolecular trapping inside the slot waveguide. In this movie, we demonstrate optical trapping of Yo-Yo tagged lambda-DNA by the slot waveguide. The DNA is initially flowing from left to right in the microchannel and becomes trapped on a 60nm slot waveguide. The DNA is released at the end of the movie when the optical power is removed. Note that when no optical power is applied, no DNA is trapped indicating that the effect is entirely optical, not hydrodynamic. This trapping is also shown in Figure 3. (MOV 10734 kb)

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Yang, A., Moore, S., Schmidt, B. et al. Optical manipulation of nanoparticles and biomolecules in sub-wavelength slot waveguides. Nature 457, 71–75 (2009).

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI:

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing