Pauzauskie, P. J. et al. Optical trapping and integration of semiconductor nanowire assemblies in water. Nature Mater. 5, 97-101

Department of Chemistry, University of California, Berkeley, California 94720, USA.
Nature Material (Impact Factor: 36.43). 03/2006; 5(2):97-101. DOI: 10.1038/nmat1563
Source: PubMed

ABSTRACT Semiconductor nanowires have received much attention owing to their potential use as building blocks of miniaturized electrical, nanofluidic and optical devices. Although chemical nanowire synthesis procedures have matured and now yield nanowires with specific compositions and growth directions, the use of these materials in scientific, biomedical and microelectronic applications is greatly restricted owing to a lack of methods to assemble nanowires into complex heterostructures with high spatial and angular precision. Here we show that an infrared single-beam optical trap can be used to individually trap, transfer and assemble high-aspect-ratio semiconductor nanowires into arbitrary structures in a fluid environment. Nanowires with diameters as small as 20 nm and aspect ratios of more than 100 can be trapped and transported in three dimensions, enabling the construction of nanowire architectures that may function as active photonic devices. Moreover, nanowire structures can now be assembled in physiological environments, offering new forms of chemical, mechanical and optical stimulation of living cells.

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Available from: Aleksandra Radenovic, Aug 12, 2015
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    • "Optical manipulation and control of nanoparticles is potentially important in many areas of physical and life sciences [1]. In particular, controlling the position and orientation of elongated objects leads the way towards exciting applications: in nanotechnology, optically trapped semiconducting nanowires have been translated, rotated, cut and fused in order to realize complex nanostructures [2] [3] [4]; in spectroscopy, the composition and morphology of a sample have been probed by scanning optically trapped nanowires [5] and polymer nanofibres [6] over the sample's surface; in biophysics, many bacteria, viruses and macromolecules with rod-like shapes have been optically manipulated and studied [7]. However, optical manipulation of nanoobjects is particularly challenging; in fact, the techniques developed for optical manipulation of microparticles and, in particular, standard threedimensional optical tweezers — i.e., tightly focused laser beams capable of confining microparticles [8] [9] — cannot be straightforwardly scaled down to the nanoscale. "
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    ABSTRACT: We demonstrate that a single sub-wavelength nanoaperture in a metallic thin film can be used to achieve dynamic optical trapping and control of a single dielectric nanowire. A nanoaperture can trap a nanowire, control its orientation when illuminated by a linearly-polarized incident field, and also rotate the nanowire when illuminated by a circularly-polarized incident field. Compared to other designs, this approach has the advantages of a low-power driving field entailing low heating and photodamage.
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    • "DDA and T-Matrix calculations on true ellipsoids and cylinders show that C 0 is stable with very small particles, but perpendicular configurations have been predicted as well [15]. Experiments with nanoribbons by Pauzauskie et al. [10], small rods [19] and with microdisks [20] [21] also indicate that only a dynamical equilibrium may be reached, with the particle constantly oscillating in the laser beam. Below (Section 2) we report on optical levitation of polystyrene ellipsoids of different aspect ratios (k). "
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    ABSTRACT: Radiation pressure forces from a moderately focused vertical laser beam are used to levitate transparent particles, a few micrometers in size. Having recalled basic results about levitation of spheres, and applications to long-working distance trapping, we turn to ellipsoid-shaped particles. Experiments are carried out with polystyrene particles, inside a glass chamber filled with water. The particles are lifted up to contact with the chamber top surface. We examine particle equilibrium in such conditions and show that the system "bifurcates" between static on-axis equilibrium with short ellipsoids, to sustained oscillations with longer ones. A similar Hopf bifurcation is found using a simple ray-optics model of the laser-ellipsoid interaction, providing a qualitative account of the observed oscillations.
    Journal of Quantitative Spectroscopy and Radiative Transfer 09/2013; 126:61-68. DOI:10.1016/j.jqsrt.2012.10.003 · 2.29 Impact Factor
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    • "support optical microrobotics by providing a host of novel synthetic structures for optical trapping and optical manipulation . Optical traps can transport and manipulate nanostructures such as nanoparticles [49] [50], nanowires [51] [52] [53], nanotubes [54] [55], optical probes/tools [56] [57] [58] [59] [60] and building blocks for micro-assembly [62, 63]. However, whereas microstructures are amenable to arbitrary translational and angular positioning in 3D space (the so-called six degree of freedom [6DOF] control), nanostructures are steerable only with limited angular control when using optical traps. "
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    ABSTRACT: Optics is usually integrated into robotics as part of intelligent vision systems. At the microscale, however, optical forces can cause significant acceleration and so optical trapping and optical manipulation can enable the noncontact actuation of microcomponents. Microbeads are ubiquitous optically actuated structures, from Ashkin's pioneering experiments with polystyrene beads to contemporary functionalized beads for biophotonics. However, micro- and nanofabrication technologies are yielding a host of novel synthetic structures that promise alternative functionalities and new exciting applications. Recent works on the actuation of synthetic microstructures using optical trapping and optical manipulation are examined in this review. Extending the optical actuation down to the nanoscale is also presented, which can involve either direct manipulation of nanostructures or structure-mediated approaches where the nanostructures form part of larger structures that are suitable for interfacing with diffraction-limited optical fields.
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