Micromachines

2014

• Driving corrugated donut rotors with Laguerre-Gauss beams

  Loke, V. L. Y., Asavei, T., Stilgoe, A. B., Nieminen, T. A., & Rubinsztein-Dunlop, H. (2014). Optics Express, 22(16), 19692. https://doi.org/10.1364/oe.22.019692'

  Abstract BibTex Source

  Tightly-focused laser beams that carry angular momentum have been used to trap and rotate microrotors. In particular, a Laguerre-Gauss mode laser beam can be used to transfer its orbital angular momentum to drive microrotors. We increase the torque efficiency by a factor of about 2 by designing the rotor such that its geometry is compatible with the driving beam, when driving the rotation with the optimum beam, rather than beams of higher or lower orbital angular momentum. Based on Floquet’s theorem, the order of discrete rotational symmetry of the rotor can be made to couple with the azimuthal mode of the Laguerre-Gauss beam. We design corrugated donut rotors, that have a flat disc-like profile, with the help of the discrete dipole approximation and the T-matrix methods in parallel with experimental demonstrations of stable trapping and torque measurement. We produce and test such a rotor using two-photon photopolymerization. With a rotor that has 8-fold discrete rotational symmetry, an outer radius of 1.85 \mum and a hollow core radius of 0.5 \mum, we were able to transfer approximately 0.3 h per photon of the orbital angular momentum from an LG04 beam. \textcopyright 2014 Optical Society of America.

  @article{Loke2014,
    author = {Loke, Vincent L. Y. and Asavei, Theodor and Stilgoe, Alexander B. and Nieminen, Timo A. and Rubinsztein-Dunlop, Halina},
    doi = {10.1364/oe.22.019692},
    issn = {1094-4087},
    journal = {Optics Express},
    mendeley-groups = {Optical Tweezers/UQOMG},
    month = aug,
    number = {16},
    pages = {19692},
    publisher = {The Optical Society},
    title = {{Driving corrugated donut rotors with Laguerre-Gauss beams}},
    volume = {22},
    year = {2014}
  }
  

2013

• Optically trapped and driven paddle-wheel

  Asavei, T., Nieminen, T. A., Loke, V. L. Y., Stilgoe, A. B., Bowman, R., Preece, D., Padgett, M. J., Heckenberg, N. R., & Rubinsztein-Dunlop, H. (2013). New Journal of Physics, 15. https://doi.org/10.1088/1367-2630/15/6/063016'

  Abstract BibTex Source

  We demonstrate the control and rotation of an optically trapped object, an optical paddle-wheel, with the rotation direction normal to the beam axis. This is in contrast to the usual situation where the rotation is about the beam axis. The paddle-wheel can be optically driven and moved to any position in the field of view of the microscope, which can be of interest for various biological applications where controlled application of a fluid flow is needed in a particular location and in a specific direction. This is of particular interest in signal transduction studies in cells, especially when a cell is flat and spread out on a surface. \textcopyright IOP Publishing and Deutsche Physikalische Gesellschaft.

  @article{Asavei2013,
    author = {Asavei, Theodor and Nieminen, Timo A. and Loke, Vincent L.Y. and Stilgoe, Alexander B. and Bowman, Richard and Preece, Daryl and Padgett, Miles J. and Heckenberg, Norman R. and Rubinsztein-Dunlop, Halina},
    doi = {10.1088/1367-2630/15/6/063016},
    issn = {13672630},
    journal = {New Journal of Physics},
    mendeley-groups = {Optical Tweezers/UQOMG},
    month = jun,
    title = {{Optically trapped and driven paddle-wheel}},
    volume = {15},
    year = {2013}
  }
  

2009

• Optical angular momentum transfer to microrotors fabricated by two-photon photopolymerization

  Asavei, T., Loke, V. L. Y., Barbieri, M., Nieminen, T. A., Heckenberg, N. R., & Rubinsztein-Dunlop, H. (2009). New Journal of Physics, 11. https://doi.org/10.1088/1367-2630/11/9/093021'

  Abstract BibTex Source

  We design, fabricate and test optically driven microrotors a few microns in size. The rotors are trapped and rotated in optical tweezers using an LG 02 Laguerre-Gaussian laser beam. We verify that we can accurately measure the total optical torque by measuring the spin angular momentum transfer for three different polarizations, by comparing the optical torque with the optical torque calculated using computational electrodynamics and the viscous drag torque determined from the rotation rate and computational fluid dynamics. The torque agrees with that expected from the design principles and electromagnetic modelling of the torque within the optical trap. \textcopyright IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

  @article{Asavei2009,
    author = {Asavei, Theodor and Loke, Vincent L.Y. and Barbieri, Marco and Nieminen, Timo A. and Heckenberg, Norman R. and Rubinsztein-Dunlop, Halina},
    doi = {10.1088/1367-2630/11/9/093021},
    issn = {13672630},
    journal = {New Journal of Physics},
    mendeley-groups = {Optical Tweezers/UQOMG},
    month = sep,
    title = {{Optical angular momentum transfer to microrotors fabricated by two-photon photopolymerization}},
    volume = {11},
    year = {2009}
  }